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For conversion of Si metric units to U.S./British customary units of measurement consult ASTM Standard E380, Metric Practice Guide, published by the American Society for Testing and Materi­ als, 1916 Race St., Philadelphia, Pa. 19103. BUREAU OF RECLAMATION DENVER LIBRARY 92071918 ,\ 92071918 CRREL Report 80-6

Maximum thickness and subsequent decay of lake, river and fast sea ice in Canada and Alaska

Michael A. B ile llo

February 1980

UNITED STATES ARMY CORPS OF ENGINEERS COLD REGIONS RESEARCH AND ENGINEERING LABORATORY HANOVER, NEW HAMPSHIRE, U S A.

Approved for public release; distribution unlimited. Unclassified SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) READ INSTRUCTIONS REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM 1, R E P O R T N U M B E R 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER CRREL fceport 80-6

4. T I T L E (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED

MAXIMUM THICKNESS AND SUBSEQUENT DECAY OF LAKE, RIVER AND FAST SEA ICE IN CANADA AND ALASKA 6. PERFORMING ORG. REPORT NUMBER

7. A U T H O R ^ 8. CONTRACT OR GRANT NUMBER(s)

Michael A. Bilello

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK AREA & WORK UNIT NUMBERS

U.S. Army Cold Regions Research and Engineering Laboratory DA Project 4A161101A91D Hanover, New Hampshire 03755

11. CONTROLLING OFFICE NAME AND ADDRESS 12. R E P O R T D A T E February 1980 U.S. Army Cold Regions Research and Engineering Laboratory 13. N U M B E R O F PA G E S Hanover, New Hampshire 03755 165 14. MONITORING AGENCY NAME & ADDRESSfff different from Controlling Office) 15. S E C U R IT Y C l ASS. (of this report) Unclassified

15a. DECLASSIFICATION/DOWNGRADING SCHEDULE

16. DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, it different from Report)

18. SUPPLEMENTARY NOTES

Additional funding was provided by DA Project 4A762730AT42, Technical Area A1, Work Unit 002

19. K E Y WORDS (Continue on reverse aide if necessary and identify by block number) Air temperature Ice thickness Alaska Canada Ice decay Ice reporting 2Qv A B S T R A C T (Continue am reversa aids ff neceeeary and. identity by block number) Weekly measurements of the thickness of lake, river and fast sea ice made over a.period of 10 to 15 years at 66 loca­ tions in Canada and Alaska are analyzed, and the portion of the data relating to maximum ice thickness and decay (i.e. the decrease in ice thickness) is examined. Ice thickness curves revealed individual patterns of ice decay, and comparisons between locations disclosed major contrasts in the amount of ice accretion and the times of maximum ice and ice clearance. Although many factors affect the ice decay process, this study investigates in detail the effect of thawing temperatures. Concurrent measurements of the air temperature at each location made it possible to analyze the relationship between accumulated thawing degree-days (ATDD) and ice cover decay. Other factors affecting ice ablation and breakup, such as snow-ice formation, snow cover depth, solar radiation and wind are also discussed.

D D , ^ * * 7 3 147 3 E D m o N O F * Mov es ,s o b s o l e t e Unclassified SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) PREFACE

This report was prepared by Michael A. Bilello, Meteorologist, of the Snow and Ice Branch, Research Division, U.S. Army Cold Regions Research and Engineering Laboratory. Funding for this research was primarily provided by DA Project 4A161101A91 D, In-House Laboratory Independent Research, with additional sup­ port from DA Project 4A762730AT42, Design, Construction and Operations Technology for Cold Regions, Technical Area A1, Ice and Snow Technology, Work Unit 002, Snow and Ice Predictions in Winter Environments. This report was technically reviewed by Dr. Anthony Gow and Lawrence Gatto of CRREL. The encouragement to pursue this study received from Dr. George Ashton, Chief of the Snow and Ice Branch, and the suggestions received from a number of colleagues at CRREL, including Drs. Wilford Weeks and Donald Nevel, proved invaluable. Without the efforts and cooperation received from many known and unknown individuals this investigation could not have been conducted. The more than 8,000 ice measurements incorporated in the study, often made under adverse winter conditions, were provided by countless U.S. and Canadian observers. Their contribution and dedicated service merits special recognition. Subsequent assistance in the retrieval and tabulation of the data was provided by several CRREL employees, including Eiazel Sanborn, Ruth Barrup and Pamela Sirois. Further aid in the calculations and plotting of the data and preparation of the figures was given by Mary-Lynn Brown, Dennis Thomas and Matthew Pacillo. Considerable help in the statistical and computer portions of this study was pro­ vided by Raymond Sweeney. Editorial reviews of the text and appendices per­ formed by members of the Technical Information Branch are much appreciated. The contents of this report are not to be used for advertising or promotional purposes. Citation of brand names does not constitute an official endorsement or approval of the use of such commercial products.

ii CONTENTS

Page A bstract...... i P re fa ce ...... ii Introduction...... 1 Data sources and literature review ...... 2 Canada ...... 2 A la s k a ...... 3 Data tabulation...... 3 Station selection...... 3 Description of tabulated d ata...... 3 Station location and ice measurement site descriptions...... 5 Review of previous studies on maximum ice in North A m erica...... 6 Maximum ice thickness m aps...... 6 Date of maximum ice ...... 7 Plotting of the ice decay curves...... 7 General procedures...... 7 Categories of water bodies...... 7 Ice decay at sea ice locations...... 8 Envelope curves ...... 8 Average curves...... 8 Snow-ice form ation...... 8 Ice decay at lake ice locations...... 10 Average curves...... 10 Regional variations and sim ilarities...... 11 Ice decay at river ice locations...... 11 Variations in ice thickness...... 11 Rapid ice clearance...... 12 Comparison between Alaskan and Canadian river ice decay curves .... 13 Incremental extraction of ice decay data for analysis purposes...... 13 Selection of ice decay intervals...... 13 Preliminary evaluation of the methodology...... 14 Further considerations of the methodology...... 14 Relationships between ice decay and thawing air temperatures...... 16 Average daily vs maximum daily air temperature...... 17 10-day increments vs accumulated values...... 19 Total years vs year-to-year analysis...... 20 Evaluation of use of 0°C as a base...... 22 Final format of the relationship between ice decay and A T D D ...... 23 Evaluation of the final form at...... 25 Possible causes for variations in slope values...... 27

iii Page Decreasing sea ice thickness and thawing air temperatures...... 28 Factors affecting sea ice d e c a y ...... 28 Relationship between ATDD and sea ice decay ...... 29 Influence of solar radiation and wind on sea ice decay ...... 31 Literature c ite d ...... 34 Selected biblio grap hy...... 35 Appendix A. Ice thickness measurements and other related (or associated) observations for stations in Canada and Alaska ...... 37 Appendix B. Maps of least and greatest ice thickness observed at the time of maximum growth, and average date of occurrence ...... 117 Appendix C. Annual ice decay curves for stations in Canada and Alaska . . 121

ILLUSTRATIONS

Figure 1. Location of Canadian statio n s...... 5 2. Location of Alaskan statio n s...... 5 3. Ice decay envelope curves for three sea ice lo ca tio n s...... 9 4. Average ice decay curves for seven sea ice lo catio n s...... 9 5. Average ice decay curves for seven lake ice locations...... 10 6. Average ice decay curves for seven river ice lo catio n s...... 12 7. Relationship between increasing amounts of ice decay and accumulated thawing degree days at Baker Lake, N.W.T., Canada. 16 8. Semilog plot of 10-day increments of ice decay vs concurrent average daily air temperatures at Baker la k e ...... 17 9. Semilog plot of 10-day increments of ice decay vs concurrent average maximum daily air temperatures at Baker L a k e ...... 18 10. Computer plot of linear relationship between accumulated amounts of ice decay and concurrent accumulated thawing degree days at Baker L a k e ...... 20 11. Computer plot of linear relationship between accumulated amounts of ice decay and concurrent accumulated thawing degree days, Bethel, A la s k a ...... 20 12. Line of best fit of the annual relationship between decreasing amounts of ice thickness vs ATDD for Mankomen Lake, Alaska. . . 25 13. Relationship between rate of lake ice decay and surface area of the la k e ...... 27 14. Sea ice temperature curves, 1950-51, for Eureka, N.W.T., Canada. . 29 15. Relationship between annual decreasing amounts of sea ice thickness and accumulated thawing air temperatures, Resolute, N .W .T., C a n ad a...... 30

IV Figure Page 16. Relationship between average decreasing amounts of sea ice thickness and accumulated thawing air temperatures for seven sea ice lo ca tio n s...... 31 17. Relationship between annual decreasing amounts of sea ice thickness and accumulated incoming solar radiation, Resolute, N .W .T., C a n ad a...... 33

TABLES

Table 1. List of Canadian statio n s...... 4 2. List of Alaskan statio n s...... 4 3. Tabulation of ice thickness values and concurrent air temperatures during the period of ice decay at Baker L a k e ...... 15 4. Regression data for log 10-day ice decay increments vs average and maximum concurrent daily air temperature...... 18 5. Linear regression data for accumulated ice decay vs accumulated thawing degree days using various bases...... 19 6. Am ount of ice decay per thawing degree d a y ...... 21 7. Number of years with 10% ice erosion before thawing air tem perature o ccu rre d ...... 22 8. Example of extracted tabulated ice decay and air temperature data sets for M ankom en Lake, A la s k a ...... 23 9. Statistics on the relationship between ice decay and ATD D ...... 26 10. Annual rate of decrease in fast sea ice thickness as related to A T D D ...... 32

v MAXIMUM THICKNESS AND SUBSEQUENT DECAY OF LAKE, RIVER AND FAST SEA ICE IN CANADA AND ALASKA

Michael A. Bilello

INTRODUCTION American network is presented and examined. Included in the report are 1) tabulations of the In a cooperative program between CRREL and weekly ice thickness measurements and obser­ a number of Canadian and U. S. government vations of ice conditions, 2) a series of curves agencies, a network of ice observing stations that show the rate of ice decay, 3) a listing of the was established throughout northern North dates when the bodies of water studied become America between 1956 and 1962. This network clear of ice and 4) an analysis of the rate of ice provided weekly measurements of ice thickness decay vs concurrent meteorological conditions. and reports of surface ice conditions on lakes, The investigation covers periods of record rang­ rivers, bays, fiords, and along other seacoast ing from 3 to 16 winters, and includes ob­ locations in Canada and Alaska. Detailed infor­ servations made at 40 stations in Canada and 26 mation on this program, including the names of stations in Alaska. the participating agencies, the ice measuring Most of the literature on the decay and break­ equipment and the names and locations of the up of ice on water bodies relates to studies of stations in the network is given in a previous rivers and lakes for navigational purposes report (Bilello 1974). (Zubov 1945, Burbidge and Lauder 1957). Some The regional distribution of ice observing sta­ studies on the rate at which sea ice or freshwater tions in this network provides a representative ice decreases in thickness have been conducted coverage of ice conditions on various water (e.g. Piotrovich 1961) but such investigations are bodies in the arctic and subarctic regions of not common. The freshwater ice studies are North America. Studies on the data collected based on observations of deteriorating ice condi­ from this network in which dates of ice forma­ tions including some measurements on the de­ tion and rates of ice accretion were related to crease in ice thickness. Theoretical equations concurrent meteorological conditions have been similar to those available for sea ice growth have previously conducted (Bilello 1961a, 1964a). not been applied extensively to studies of ice Although no emphasis was placed on the contin­ decay. The many variables which affect ice abla­ uation of ice thickness measurements during the tion and also the lack of observed data have decay (or ablation) period, sufficient informa­ hindered the development of methods to predict tion has been compiled to justify an analysis of the rate of ice decay. the data collected during that phase of the ice Some research relating to ice ablation, deteri­ season. oration, breakup or decay on lakes, rivers, and In this study, then, the portion of the data re­ sea ice has previously been done. In order to lating to maximum ice thickness and subsequent determine the objectives, scope, and extent of decay (i.e. the amount and rate of decrease in these earlier studies, a limited literature search ice thickness) collected from this North using the CRREL Bibliography on Cold Regions Science and Technology (U.S. Army 1951-1979) personnel at the Joint Arctic Weather Stations in was conducted. A list of the pertinent papers on the Canadian Archipelago. With proper precau­ ice decay and breakup obtained from this survey tions the hand auger from the kit can drill a hole is given in the Selected Bibliography of this through ice 200 to 250 cm thick in 15 to 20 min­ report. Unfortunately, none of these references utes. To measure the ice thickness, a graduated contained consistent ice thickness data during tape with a short rod attached to the end is the decay period for water bodies in northern lowered into the hole. When the rod is below the North America that might have been used here. ice sheet it swings to a horizontal position. The In this study, the association between two im­ tape is then lifted until the tilt rod presses portant meteorological elements (air tempera­ against the underside of the ice, and the ture and solar radiation) and the decay process thickness of the ice is read directly from the of ice is also investigated . Complete and tape. A separate wire attached to the end of the reliable air temperature data, in particular, rod draws the rod and tape back through the made it possible to analyze the relationship be­ hole. During 1958, correspondence with the Can­ tween accumulated thawing degree days and ice adian Department of Transport (DOT), Meteoro­ ablation. Since suitable solar radiation data logical Division! resulted in a southward expan­ were available for only a few stations in the net­ sion of the ice thickness network. By May 1960, work, the analysis between this parameter and 30 stations north of 53°N latitude in Canada the decrease in ice thickness received less em­ were incorporated into the program. phasis. Other factors affecting ice ablation and The weekly observations of ice thickness, ice breakup, such as snow-ice formation, snow conditions, and depth of snow cover on the ice cover depths, and wind, are also briefly dis­ in Canada for the first four winters (starting in cussed. 1958-59) were published in Parts I and II of a series of CRREL Special Reports (Bilello 1961b and 1964b). Subsequently, the Canadian Depart­ DATA SOURCES AND LITERATURE REVIEW ment of Transport began to compile and publish the ice thickness data in a series of ice Circulars. Ryder (1954) conducted a "review and sum­ The 1962-63 and 1963-64 ice data, for example, mary" of available ice thickness measurements are available in DOT Circular 3918, Ice 77 (DO T in the northern hemisphere in connection with Canada 1963), and Circular 4153, Ice 19 (DO T construction and maintenance of airdromes on Canada 1964), respectively. To avoid duplica­ ice. His report contained a comprehensive bibli­ tion, therefore, previously published ice thick­ ography on lake and river ice and a tabulation of ness observations for Canada were omitted in brief records on ice thickness for 41 stations in the CRREL series. However, considerable infor­ the contiguous United States, 38 stations in mation on ice conditions and some delayed ice Canada (only 6 of which were north of 54°N thickness reports from these sites later became latitude) and 6 stations in Alaska. Attention was available. This information (along with the directed to the limited and fragmentary nature observed ice thicknesses at the time of maxi­ of available ice data, and the need for a planned mum ice and during the ice ablation period) was program for ice thickness observations was included in the CRREL series. stressed. A program which systematically col­ The Canadian Meteorological Service has also lected and recorded ice cover information was published the third in a series of publications established throughout northern North America, relating to the dates of freezeup and breakup of starting with the winter of 1958-59. A discussion rivers and lakes in Canada (Allen and Cudbird of the two networks (Canadian and Alaskan) in 1971). This publication contains computer-tabu­ this program follows. lated data on dates of maximum ice thickness, ice breakup, and ice clearance for 274 sites Canada throughout Canada up to and including the In the spring of 1956, the author introduced 1969-70 ice season. Although no ice thickness the SIPRE* ice thickness measurement kit to the data during the ablation period are given, the

* U.S. Army Snow, Ice and Permafrost Research Establish­ Now called the Department of the Environment, ment, became a part of CRREL on 1 February 1961. : Canada, Atmospheric Environment Service.

2 report is useful because it provides other related clearance dates on the water bodies are information collected since the stations first presented. This information is given in Appendix started taking observations, which in some cases A and discussed in the following section. was prior to 1900.

Alaska DATA TABULATION Attempts to expand the Canadian ice thick­ ness network to Alaska were unsuccessful prior Station selection to 1961 because observers were not available. Over the 16 years of consecutive ice observa­ Because of these staffing problems at remote tions, stations in the networks have been added, locations, it became apparent that a cooperative deleted or temporarily moved to new locations. program (in which ice observers could be To qualify for inclusion in this study, a station recruited from an existing weather observation must have been in operation for at least three network) had to be established. Through the co­ winters* and provided some useful information operation of the Alaska Regional Office of the on maximum ice and/or ice deterioration. Some National Weather Service, National Oceanic stations (such as Hall Beach, NWT, and Cree and Atmospheric Administration*, an ice thick­ Lake, Saskatchewan) were included in the ness observing program was started in Alaska by tabulation because three or more years of CRREL during the fall of 1961. The locations record were available, but detailed analysis on selected for these observations depended upon the rate of ice decay was later excluded because the existence of established weather stations the measurements during ice ablation were and the availability of local personnel who either insufficient or incomplete. could be trained to make the measurements. By the end of the 1965-66 winter season, Alaskan Description of tabulated data Eskimos, homesteaders, lodgekeepers, teachers The survey for the final tabulation included and clergy at 23 stations throughout the state all pertinent ice observations from the time of were providing information on ice cover observed maximum ice thickness through the thickness and conditions. date of ice clearance for each year of record for The data received from Alaska were initially 40 stations north of 50°N latitude in Canada (Ap­ published in CRREL Special Report 43, Part II pendix A, Table A1) and 26 stations in Alaska (Bilello 1964b), and later continued in Parts III (Appendix A, Table A2). Canadian stations south through VII in the series of CRREL Special Re­ of 50°N latitude were not included in this in­ ports (Bilello and Bates 1966, 1969, 1971, 1972 vestigation because seasonal ice sheets at these and 1975). The entire series, therefore, contains lower latitudes are often susceptible to mid­ ice records for Alaska for 11 winters extending winter thaws and/or alternate intervals of melt­ from 1961-62 through 1971-72 inclusive. Perti­ ing and refreezing. Such "unstable" ice sheets nent maximum ice and decay data for the two exhibit deterioration patterns, particularly with subsequent winters (1972-73 and 1973-74) for respect to continuity, that are not within the both Alaska and Canada (although not yet scope of this study. published) were also available for inclusion in The presentation of all available ice thickness this study on ice decay. values during the period of ice decay as well as Useful information on the observed dates of the visual observations of ice deterioration in specific events associated with the breakup of Appendix A accomplishes two main objectives. ice at approximately 80 to 120 locations in First, the compilation of these specific data from Alaska is published annually in the July issue of a number of sources makes it possible to as­ Climatological Data, Alaska (U.S. Department of semble essential information on ice decay in one Commerce, 1961-1971). Although no ice thick­ publication. Secondly, the tabulation includes ness values are given in this publication, infor­ mation on 1) the termination of travel on foot or by vehicle on the ice during breakup, 2) the * For the purposes of this investigation, a winter (i.e. an ice dates of shipping or aircraft activities, and 3) ice year) is defined according to the calendar year that com­ pletes the winter season. For example, in a winter season known as 1958-59; ice decay and ice clearance occurred dur­ ing 1959; therefore, this ice year is designated as 1959 on all * Formerly Weather Bureau, U.S. Department of Commerce. tables, graphs and appendices.

3 Table 1. List of Canadian stations Table 2. List of Alaskan stations

Years of Fresh or salt Years of Fresh or salt Canadian stations Body of water record water Alaskan stations Body of water record water

Alert Dumbell Lake 1959-1974 F Allakaket Koyukuk River 1962-1974 F Alert Parr Inlet 1959-1974 S Barrow Imikpuk Lake 1962-1973* F Arctic Bay Arctic Bay 1960-1969 S Barter Island Local lakes 1962-1974* S Baker Lake Baker Lake 1959-1974 F Bethel Kuskokwim River 1962-1974 F Brochet Reindeer Lake 1959-1974* F Betties Koyukuk River 1968-1974 F Cambridge Bay Cambridge Bay 1959-1974 S Chalkyitsik Black River 1968-1974 F Cape Dorset Cape Dorset Harbour 1971-1974 S Chandalar Lake Chandalar 1964-1974* F Cape Parry Amundsen Gulf 1960-1974 S Fairbanks Smith Lake 1966-1974 F Cartwright Cartwright Harbour 1960-1974* s Fort Greely Bolin Lake 1967-1973 F Chesterfield Inlet Hudson Bay 1960-1974 s Fort Yukon Yukon River 1962-1974* F Churchill Churchill River 1960-1973* Ft Galena Yukon River 1966-1972* F Clyde River Patricia Bay 1960-1974 S Gambell Troutman Lake 1962-1969 F Coppermine Coppermine River 1959-1974 F Holy Cross Walker's Slough 1962-1974* F Coral Harbour Munn Bay 1959-1974 S King Salmon Naknek River 1962-1974 F Cree Lake Cable Bay in Cree Lake 1971-1974 F Kobuk Kobuk River 1965-1974 F Ennadai Lake Ennadai Lake 1959-1974 F Kotzebue Kotzebue Sound 1962-1974 S Eureka Slidre Fiord 1959-1974 St Mankomen Lake Mankomen Lake 1966-1974 F Ft. Chipewyan Lake Athabasca 1962-1974 F McGrath Kuskokwim River 1962-1974 F Frobisher Bay Koojesse Inlet 1959-1974 S Nunivak Mekoryuk Bay 1962-1974 S Goose Bay Terrington Basin 1959-1974 Ft Point Hope Chukchi Sea 1962-1973* S Hall Beach Foxe Basin 1959-1974 S Port Alsworth Lake Clark 1962-1974 F Holman Island Kings Bay 1960-1968 S Snowshoe Lake Snowshoe Lake 1964-1974 F Hopedale Hopedale Harbour 1961-1974* S Tanacross Tanana River 1962-1974* F Inoucdjouac Innuksuak River 1959-1974* Ft Trapper's Creek Susitna River 1962-1974 F Inuvik Mackenzie River 1961-1974 F Unalakleet Kouwegok River Slough 1962-1974 F Isachsen Deer and Louise Bays 1959-1974* S Wild Lake Wild Lake 1964-1968^ F Island Lake Island Lake 1971-1974 F *Some years of the period of record shown are missing. Moosonee Moose River 1960-1974 Ft tThese bodies of water may be brackish. Mould Bay Mould Bay 1959-1974 S Nitchequon Lake Nichicun 1959-1974 F Norman Wells Mackenzie River 1959-1974* F Norway House Nelson River 1957-1974* F Pond Inlet Eclipse Sound 1965-1970* S Resolute Resolute Bay 1959-1974 S Sachs Harbour Amundsen Gulf 1959-1974 S Schefferville Knob Lake 1961-1974 F Schefferville Maryjo Lake 1961-1968 F Spence Bay Spence Bay Harbour 1960-1968* S Trout Lake Big Trout Lake 1961-1974 F Yellowknife Back Bay 1959-1974 F

*Some years for the period of record shown are missing. tThese bodies of water may be brackish. 70 80 80 70 60

Figure 1. Location of Canadian stations.

all the years of record for all stations in northern occasionally prompted the observer to record North America that provided useful and continu­ maximum and minimum snow depths. This infor­ ous observations. This enables all interested mation and notations of other surface condi­ readers to use this original information to con­ tions such as the number and extent of cracks in duct other interpretations and/or further analysis the ice, slush layers, pools of water, open leads, of the data if desired. floating brash ice and unusual weather events The ice and snow observations were made are given in the tabulations. Further information once each week unless prevented by adverse on all phases of the deterioration, breakup, and weather. The original measurements were most ice clearance with the date of occurrence and often read to the nearest inch, and occasionally data on the termination of vehicular traffic to the nearest half-inch. The English units were across the ice are also included in Tables A1 and converted so that the data in the tables are given A2. in centimeters. A description of the field obser­ vational procedures and methods, including a Station location and sample data sheet, is given in Part II of the ice measurement site descriptions CRREL series of ice thickness reports (Bilello Information contained in the list of 40 Cana­ 1964b). dian stations (Table 1) and 26 Alaskan stations Drifts of snow or instances of uneven surfaces (Table 2) include 1) the name of the body of

5 170 160 150 140 130

Figure 2. Location of Alaskan stations. water at each location, 2) the years in which ice REVIEW OF PREVIOUS STUDIES ON decay records were available for each site, and MAXIMUM ICE IN NORTH AMERICA 3) whether the bodies of water are fresh, salt, or possibly brackish. About half of the stations in Maximum ice thickness maps Canada and about 80% of those in Alaska are in­ Sufficient information on maximum annual land freshwater sites. The salt water bodies are ice in the North American Arctic and Subarctic ocean, bay or harbor locations where the ice made it possible to draw isoline maps showing thickness measurements are made on fast (but the least and greatest ice thickness observed at floating) sea ice sheets. The possible brackish the time of maximum growth. These two maps water bodies are at river mouths or deltas that are shown in Appendix B (Fig. B1 and B2, respec­ empty into tidal sea water, or in fiords that are tively), and were developed from data based on fed by glacial water. All the sites included in the 3 to over 10 years of records from 54 stations in study are shown on a Canadian station map (Fig. Canada and Alaska (Bilello and Bates 1966, Part 1), and Alaskan map (Fig. 2). A more precise des­ III). The diagrams show that in Canada the least cription of the location of each ice measuring ice thickness observed at the time of maximum site on the water body is given with each station ice ranged from less than 20 cm in the vicinity of in Tables A1 and À2. The site generally was Nova Scotia to near 200 cm in the northern located as close as possible to the town, village, regions of the nation. In Alaska, excluding the and/or meteorological station. Aleutian Chain and the southeast panhandle

6 regions, this least "end-of-the-season" ice PLOTTING OF THE ICE DECAY CURVES thickness value ranged from near 60 cm in the southern part of the state to 170 cm on the west General procedures coast. The observed ice thickness values given in The map of greatest ice thickness revealed a Tables A1 and A2 for all the years of data at range of 30 cm of ice near Nova Scotia to over each station were plotted and are shown in Ap­ 260 cm in parts of the Canadian Arctic, and from pendix C (Fig. C1-C40 for Canada, and C41-C66 100 cm in the southern regions of Alaska to 180 for Alaska). The zero mark on the ordinate (i.e. cm in the North Slope area. Additional informa­ ice thickness) scale in these figures denotes the tion on maximum ice thicknesses in Canada is time when the body of water is free of ice. Since given by the Department of Transport, Canada maximum ice thicknesses and the time required (1959) and by Williams (1963). Using average ice for ice clearance range considerably (see Tables growth rates, Williams presents relationships be­ A1 and A2), the lengths of the ordinate and tween the number of days from freezeup and abscissa scales in Figures C1-C66 are quite maximum ice thickness, and he suggests that the variable, In order to make direct comparisons limits provided by this method may be satisfac­ between stations possible, spacing of both the tory for many design problems for sites in ordinate (ice thickness) and abscissa (time) Canada where maximum ice data are not scales on all the figures was kept uniform. available. Note that the decay curve for each year was obtained by connecting each observation point Date of maximum ice by a straight line. The time interval between Results of an analysis on the average date points in most cases is one week and only occa­ when maximum ice thickness occurs, in which 67 sionally two weeks. In some instances, as during stations in Canada and Alaska were used, is 1959 in Figure C35, part or all of the ice decay given in Part VII of Bilello and Bates (1975). An curve was dashed. This was done when the inter­ isoline map showing the distribution of the aver­ val between ice observations was greater than age observed date, in which intervals of 15 days two weeks or when the reported values ap­ are presented, is also included in Part VII and is peared incorrect or unrepresentative. shown in Appendix B of in this report as Figure Safety requirements and cautionary proce­ B3. dures often prevented observers from making A uniform progression of the average date ice thickness measurements during the final two with latitude was noted in the eastern half of or three weeks of decay. The lines in these cases Canada, ranging from 1 March near the Great were not dashed if the rate of decay to the point Lakes region to 1 June in the Canadian Archi­ of ice clearance was reasonable and similar to pelago Islands. An exception in the progression other years when the record was more complete. occurs in the Lancaster-Baffin Bay region where However, if the date of ice clearance is missing the average date is earlier than in surrounding or if the time interval between measurements is areas. too long, then only the portion of curve for The results in the western provinces of Canada which data were available is shown. are less definite because of insufficient data. Unusual ice conditions during ice decay and However, the isolines in this region indicate a clearance, as during August 1964 at Cape Parry, slight change in alignment in that they tilt NWT (Fig. C8), required additional explanations slightly to the southeast-northwest instead of on the diagrams. Note that single data points, being parallel to the lines of latitude. such as the ice thickness value of 173 cm on 5 A similar progression in the date of observed June 1965 at Cape Parry and the ice clearance maximum ice with latitude is evident in Alaska, dates during 1957 and 1959 through 1962 at Nor­ although in this area the arrangement of the way House, Manitoba (Fig. C32), were also in­ isolines is more irregular. The latest date of cluded in the diagrams. observed maximum ice each year in Alaska (be­ tween 1 and 15 May) appears to be centered in Categories of water bodies the northwest interior part of the state rather The 6,6 stations presented in this study can be than along the north coast. separated into three different categories,

7 namely 1) sea ice, 2) lake ice, and 3) river ice. ablate slightly in early June, the melting pro­ Each of these types of water bodies yields differ­ ceeds rapidly in late June and early July, and, on ent ice decay "signatures." These differences are the average, the bodies of water become mostly due to contrasts in environmental conditions at­ clear of ice between mid-July and early August. tributable to various thermal, physical, and me­ A marked difference in maximum ice and the chanical factors. For example, deterioration of a rate of ice decay is noted (Fig. 4) between two lake ice sheet like Baker Lake (Fig. C4) is gener­ sea ice locations at similar latitudes, Kotzebue ally quite stable, and the progression of ice abla­ (67°N) and Coral Harbour (64°N). Kotzebue's tion is principally due to thermal processes, records show warmer air temperatures during whereas disruptive factors, such as tidal and the winter months (November through March) wave action at coastal stations (e.g. Cartwright, than those of Coral Harbour, but neither loca­ Fig. C9), and currents and flooding at river loca­ tion experiences average monthly thawing air tions (e.g. Trapper's Creek, Fig. C64) sometimes temperatures until June (Hogue 1956). Kotzebue affect breakup and ice clearance more radically. therefore would develop thinner ice sheets, but These three categories, therefore, are presented ice decay would be retarded and proceed at a separately in the following discussion on maxi­ slower rate. mum ice and the ice decay curves. Snow-ice formation Cartwright (Fig. 4) exhibits an unusual ice ICE DECAY AT SEA ICE LOCATIONS decay pattern; particularly in regard to the slight increases in ice thickness during the expected Envelope curves deterioration period. This anomaly in ice decay The effect of latitude on the annual growth of "signature" warrants some explanation regard­ fast sea ice thickness and the date when the ing its possible cause. The ice measurements at body of water becomes clear of ice can be Cartwright are made in Cartwright Harbour of shown by comparing observations made at three Sandwich Bay, which is a salt water body influ­ stations in Canada: Eureka (80°N), Coral Harbour enced by tidal action. A local phenomenon re­ (64°N), and Cartwright (54°N). Instead of annual sulting from this action is the formation of layers curves of the decrease in ice thickness, this com­ of "snow -ice" over the main sheet of fast sea parison is shown by drawing the upper and lower ice. Water, either by seeping from below or over­ boundaries of the observed sea ice thickness (i.e. running, saturates part or all of the snow cover envelope curves) for these locations (Fig. 3). and changes it to slush. Freezing temperatures This diagram shows that sea-ice accretion at solidify the slush, thereby adding to the overall Eureka is greater than twice that at Cartwright, ice thickness. This sudden accretion of surface and maximum ice thickness occurs four to six snow-ice occurred in late April-early May at weeks later at Eureka. Ice deterioration and Cartwright for the years 1971, 1973, and 1974 ablation are observed during June and July at (Fig. C9). When snow-ice formation is not a con­ Eureka, as compared to April, May and early tributing factor, maximum sea ice thicknesses of June at Cartwright. The envelope curve for Coral about 60 to 100 cm can be expected in Cart­ Harbour (Fig. 3) reflects an ice decay "signature" wright Harbour during April of each year. Major that lies between those of the other two sites. deterioration and decay of the ice sheet at this location is principally observed in May, and ice Average curves clearance can be expected most frequently be­ Further comparisons of maximum ice and the tween 15 May and 15 June. pattern of subsequent decrease in thickness Andrews (1962) also discusses snow-ice and were made by plotting the average curve for the its occurrence in the central Labrador area. In a years of record at seven sea-ice stations (Fig. 4). previous investigation (Bilello 1964b) it was Although each station displays an individual found that snow-ice was observed occasionally decay pattern, the decay curves for four of the at 21 lake, river or sea ice sites in Canada and five stations in the Northwest Territories (NWT) Alaska. The average increase in ice as a result of of Canada (Eureka, Mould Bay, Sachs Harbour the snow to snow-ice transition was about 12 cm and Coral Harbour) are similar. The ice reaches and the corresponding average decrease in snow maximum thickness at these stations in late depth was 15 cm. However, because of other un­ May, the ice sheet begins to deteriorate and known factors, such as new snowfalls during the

8 Average Ice Thickness (cm) a, F Scs abu, Rslt, H—Crl abu; Kteu, C—Cart­ K —Kotzebue, Harbour; CH wright). — RCoral —Resolute, Harbour, SFI(E —Sachs—locations Bay, MB —Mould ice seaEureka,seven for curves decay ice Average 4.Figure Figure 3. Ice decay envelope curves for three sea ice locations. seaice three for curves envelope decay Ice 3. 9

Figure 5. Average ice decay curves for seven lake ice locations.

transition phase and the inability to exactly Lake, and Knob Lake at Schefferville) are com­ define the time period, a meaningful correlation pared. Twice as much ice accumulates and max­ in the relationship could not be obtained. imum ice is observed about one month later at Baker Lake (64°18'N) as compared with Knob Lake (54°48'N). Although the ice decay curves ICE DECAY AT LAKE ICE LOCATIONS for the three Canadian stations are separated by about 1 5 to 20 days in time, their general config­ Average curves urations are similar. A comparison of observed maximum lake ice Three of the four Alaskan lake ice stations thicknesses and lake ice decay curves between (Barter Island, Mankomen Lake, and Snowshoe Canadian and Alaskan stations and between Lake) also revealed increasing maximum ice Canadian stations at different latitudes was con­ thicknesses with increasing latitude (Fig. 5). The ducted. Average ice decay curves for seven rep­ association differs slightly at Wild Lake, Alaska resentative lake ice locations in these areas were (67°32/N), where the average maximum ice thick­ compiled and plotted in Figure 5. The latitudinal ness is less than 100 cm as compared to Manko­ influence on the time of occurrence and the men Lake (62°59'N) where the average maximum thickness of maximum ice is evident when the is about 125 cm. three Canadian stations (Baker Lake, Ennadai

10 Regional variations and similarities meandering characteristics, as well as the fre­ Note the maritime-continental contrast in ice quent formation of snow-ice due to water over­ accumulation between the Canadian and Alas­ running, can result in unnatural accumulations kan stations evident in Figure 5. Stations in of ice at random points along and across rivers. Canada observe lake ice sheets that are on the Visual observations and thickness measure­ average 40 to 60 cm thicker at the end of the ments made on the Naknek River at King Salmon growth season than stations that are 6° or 7° (Table A2 and Fig. C54) indicate the annual varia­ higher in latitude in Alaska. However, the aver­ tions in ice thickness that can be expected at age rate of ice decay at the lake locations in some Alaskan river sites. The measurements at Alaska (except for Barter Island) does not appear King Salmon are taken about 50 to 1 50 m off the to be as rapid as that indicated at the Canadian village landing docks which are located near the stations. Although the dissimilarities are quite entrance to Kvichak Bay. This bay is an exten­ small, the following explanation may partially sion of Bristol Bay and the Bering Sea, and is account for the difference. The ice sheets on therefore subject to tidal action. Consequently, Baker Lake, Ennadai Lake and the lakes near the ice that forms near the mouth of Naknek Barter Island (Fig. 5) begin to decay much later in River can be partially or entirely disrupted, the season, extending into the time of maximum resulting in major ice jamming in March and elevation of the sun. The rate of ice decay at April (e.g. 1964 and 1970). these stations, therefore, would naturally pro­ The ice decay curves at King SalmonfFig. C54) ceed more rapidly at peak incoming solar radia­ also show the large irregularities in the rate of tion during )une and July. ice ablation and the date when the river be­ Incidentally, the lake ice thickness records comes clear of ice. It is obvious in such cases during the decay period at Barrow, Alaska, are that relationships between thermal parameters unsatisfactory (Fig. C42). Incomplete data can and rate of ice decay would not provide good (to some degree) be improved by comparison correlation coefficients. with information from another nearby site where the body of water and climatic conditions are Variations in ice thickness similar. The analogous site for Barrow would be Certain river sites in Canada are susceptible to Barter Island, Alaska, where the North Slope abnormally thick accumulations of ice, the lake ice conditions and climatic regime are simi­ causes of which are varied and often only parti­ lar. A reasonable extrapolation of the ice decay ally understood. A case in point occurs at Inouc- curves for Barrow, therefore, can be obtained .by djouac (formerly Port Harrison) Canada (Fig. comparing Figure C42 with Figure C43. Note that C24), where excessive ice thicknesses (as com­ the limited information shown for Barrow at the pared with surrounding stations) are often start of the decay season compares well with the observed. Initial explanations on the possible Barter Island data, and, in addition, there is causes for this anomaly included such factors as some indication that the rate of ice decay at Bar- a light snow cover and ice rafting or snow-ice row follows the pattern observed at Barter accumulation due to wind and wave action from Island. Hudson Bay (Bilello 1961b). A subsequent report confirmed the fact that this particular area is subject to unrepresentative maximum ice thick­ ICE DECAY AT RIVER ICE LOCATIONS nesses, and the reason given for the phen­ omenon is that "at the mouth of the Innuksuak Ice decay curves at some river ice locations River, fresh water comes in contact with colder exhibit marked differences in shape and uni­ sea water from Hudson Bay. The salt water pro­ formity from year to year. These differences are vides an additional heat sink, which precipitates largely due to disruptive factors such as ice jam­ faster ice growth..." (Leahey 1967). ming, ice rafting, and undercutting. Rapid cur­ Detailed studies on the ice conditions at spe­ rents, frequent shifts in channel location, and cific sites, for example at Churchill, Manitoba major fluctuations in water level contribute sig­ (Keith 1959), and also at Peters Lake, Alaska nificantly to the time and manner in which river (Muguruma and Kikuchi 1963), are available in ice sheets break up and move out. Variations in the literature for a few locations in northern the depth of the river bed, its gradient and Canada and in Alaska. Additional references on

11 Figure 6. Average ice decay curves for seven river ice locations.

such studies at other sites are given in the Alaska (Fig. C41, C45, and C55 respectively). In Selected Bibliography. some instances, ice sheets of 70 to 100 cm in Of the 40 Canadian stations included in this thickness were removed within a two- or three- study, only seven are river locations. In the fol­ day period, e.g. at Allakaket in 1964 and at Bet­ lowing discussion the pattern of ice decay at one ties in 1968. of these river sites, Coppermine, NWT (Fig. 03), Another interesting association between these is briefly reviewed. two stations is the timing of ice clearance during Although maximum ice thickness at Copper- 1969, 1970, and 1971. Ice observations at these mine lasts for a relatively long time, deteriora­ sites are made on the Koyukuk River, with Bet­ tion of the ice sheet is quite rapid and ice ties located about 70 km upstream from Alla­ removal occurs within a short period of time. kaket. The river became free of ice on 7 May at The breakup develops mostly during the first Betties and on 10 May at Allakaket in 1969, a dif­ half of June, and complete ice clearance on the ference of three days. In 1970 it was free of ice river was observed between 12 June and 1 July on 14 May at Betties and on 17 May at Allaka­ during 12 years of record (1959-1970 inclusive). ket, again a three-day difference. In 1974, ice at This rapid ice clearance is common on rivers, Betties was observed to move out on 17 May and and often depends on ice conditions down­ at Allakaket the river became free of ice on 18 stream, such as an abrupt release of an ice jam May, or about one day later. or other similar ice blockages. These associations suggest that there may be a chronological order of sudden ice removal in Rapid ice clearance particular stretches of certain rivers. Additional Instances of rapid ice clearance on rivers are surface observations and/or analysis of properly clearly evident at Allakaket, Betties, and Kobuk, timed satellite photography of vulnerable

12 stretches of important rivers may provide similar were found to be too brief because the time lag associations which can be used to predict im­ between the cause and effect processes pre­ pending ice clearances. cluded the use of small increment analysis of the data. Also, since almost no ice measurements Comparison between Alaskan and were made less than seven days apart, extraction Canadian river ice decay curves of ice decay amounts for five-day increments A comparison of maximum ice on rivers and from the graphs would not be advisable. the subsequent rate of ice decay between four Increments in which the weekly observations Canadian and three Alaskan locations is shown might be used were considered but also dropped in Figure 6. for two main reasons. First, since the measure­ The marked increase in maximum ice thick­ ments at each station are often made on differ­ nesses with increasing latitude noted earlier for ent days of the week and sometimes delayed a lake locations in Canada is not evident when the day or two because of inclement weather, the four river sites in Canada are compared (Fig. 6). data extraction became chaotic and inconsis­ For example, Inuvik and Coppermine are at tent. Secondly, attempts to extract the concur­ about the same latitude, but on the average, the rent weather data during these widely variant in­ ice sheet on the river at the latter station is tervals of ice decay became cumbersome and in­ about 40 cm thicker each year. efficient. The three river sites in Alaska shown in Figure Further, it seemed that, although monthly in­ 6 show smaller maximum ice thickness (values) tervals of ice decay were believed to be too as compared to the Canadian sites at similar large, it would be desirable to at least develop latitudes. All three sites are located between 61° some scheme in which month-to-month seg­ and 67°N and record average thicknesses of less ments of analysis could be maintained. If the ac­ than 125 cm, whereas the three Canadian sta­ tual weekly observations were used, then this tions located between 59° and 68°N record aver­ monthly separation of the data would not be age maximum thicknesses of 135 to 220 cm. possible. Maximum ice and ice clearance also occurs It was decided, therefore, to divide each much earlier at the Alaskan sites. month into three parts (i.e. mostly 10-day inter­ In general, it appears that when maximum ice vals) and to extract the rate of ice decay from occurs at an earlier date, the rate of ice decay the graphs in Appendix C over this time period. (up to the time of ice clearance) at these stations The following is a list of some of the advantages is slower than at stations where ice decay occurs that were gained by sectioning the ice decay later in the season. As previously noted, the curves by months, and dividing each month into added influence of rapidly increasing air temper­ three parts; 1) the 10-day increments were con­ atures and stronger solar radiation taking place venient to work with when extracting the ice at the later dates undoubtedly contributes to the thickness values from from the decay curves, 2) faster rate of ice decay. the concurrent air temperature from climatic records was easier to compile (especially with INCREMENTAL EXTRACTION OF ICE DECAY regard to the published Canadian records where DATA FOR ANALYSIS PURPOSES the data are separated into the same 10-day in­ tervals used here), 3) the capability of comparing Selection of ice decay intervals stations on a month-to-month basis was main­ Once the weekly ice thickness measurements tained, 4) the credibility of the extracted ice were tabulated and plotted, decisions had to be decay data was increased in that the intervals made as to how much information needed to be selected for study exceeded the seven-day obser­ extracted from the graphs (App. C) for analysis vation times, 5) the tri-separation of each month purposes. The main purpose was to statistically made it possible to label the sections as early, determine how well thawing air temperatures middle, and late parts of the month, thereby pro­ coincide with the rate and amount of ice decay viding a discussion of results in general terms on lakes, rivers, and sea ice sheets. The choice of when necessary, and 6) the effects of a time lag the time interval to be used in determining the between the variables were compensated for by decrease in ice thickness from the ice decay averaging the data over the 10-day intervals. curves was considered to be of prime impor­ Therefore, the ice thickness values shown on the tance. Intervals of five days or less of ice decay 10th, 20th, and the last days of each month were

13 extracted from the curves for the analysis. This temperature (°C) averaged over each interval, 6) means that, except for February and the months a summation of degree days (above 0°C)* for with 31 days, all intervals would be 10 days in each interval, and 7) a summation of degree days length. The interval for the third period for these (above 0°C) over the entire period of ice decay. exceptions would be 11 days, or for February The procedure proved feasible, and a prelim­ eight or nine days depending on leap year. inary analysis of the data showed that the rate of The fact that all ice thickness curves do not ice decay at this location was strongly depen­ necessarily begin or end on the 10th, 20th or ex­ dent on thawing air temperatures (Bilello 1977). actly at the end of a month would also result in The investigation showed that on the average ice decay intervals of less than 10 days. Flow- about 125 accumulated degree-days (above 0°C) eve r, when possible (e.g. when a choice could be are required to melt the first 100 cm of ice on made in the selection of the starting date on a Baker Lake, about 210 degree-days for up to 150 curve) these situations were kept to a minimum. cm of ice, and about 325 degree-days for 200 cm For example, if one observes that maximum ice of the lake ice sheet (Fig. 7). thickness at a station occurs on 5 April, that the ice sheet begins to decay on about 11 April, and Further considerations of the methodology that the body of water becomes clear of ice on Although the preceding analysis indicated 28 June, the dates for which ice decay values that the use of above-freezing air temperatures would be extracted are: provided a reasonable estimate of the rate of ice decay, there were numerous questions in the 11-20 April 10 days 21 -31 May 11 days relationship that needed to be answered, for ex­ 21-30 April 10 days 1-10 June 10 days ample: 1-10 May 10 days 11-20 June 10 days

11-20 May 10 days 21-28 June 8 days 1. Would maximum daily air temperatures, instead of mean average values, statistically provide better The above example is quite typical of the results ? f number and length of periods obtained from 2. Is the selection of 0°C as a base in the computa­ tions appropriate? In some instances the ice decay decay curves in this study, i.e. 8 periods per year curves showed that ice sheets often began to of which six are 10 days in length. Note that the decrease in thickness sometime before thawing air beginning and ending dates of each period are temperatures were observed. In such cases should included in the total number of days. The ice the base be lowered to -5 or -10°C ? thickness value extracted at the end of a preced­ 3. Further, since sea ice sheets form at water tempera­ tures of about -1 ,8°C, what (statistically) is the best ing period is the same as the value for the start temperature base to use to predict sea ice abla of the next period, and consequently there is no tion ? break between periods. Further, for those in­ 4. Should the association of the variables shown in stances when the period is greater or less than 10 Figure 7 be evaluated on a year-to-year basis or days in length, a mathematical weighted system combined as a group? Would it be considered worthwhile to statistically evaluate the difference is used (when necessary) to compensate for the when linear, semi-log and log-log transformations difference in subsequent computations. Unless are used to estimate the relationship between the otherwise indicated, these ice decay periods will variables ? be referred to as "10-day intervals" throughout 5. Should the association between ice decay and the paper. thawing temperatures be investigated using separate 10-day increments, or should ac­ cumulated amounts of ice decay be used with con­ Preliminary evaluation of the methodology current thawing air temperature ?. In a preliminary evaluation of the above pro­ cedure, data for 10-day intervals of ice decay and concurrent observations of the air tempera­ * Accumulated degree-days (above 0°C) are obtained by ture were extracted for Baker Lake for six years summing the difference between positive daily average air of record (1960 through 1965). The tabulation temperatures and 0°C. -j- Maximum daily temperatures were considered for two (Table 3) includes: 1) the starting and ending main reasons: first, their use would, in some instances, result dates of each interval, 2) the ice thickness value in the inclusion of a greater part of the ice decay curve at the for these dates (taken from Fig. C4), 3) the start of the season, and second, it was thought that the daily maximum temperature may possibly better represent the ice number of days, 4) the change in ice thickness decay conditions occurring at the time of peak solar radia­ during each interval, 5) the concurrent air tion in mid- to late afternoon.

14 Table 3. Tabulation of ice thickness values and concurrent air temperatures during the period of ice decay at Baker Lake.

Year Ice thickness N o. Avg. air temp. Acc. thawing a n d (cm ) D iti. o f during interval degree days d a te S ta rt E n d ( ± c m ) d a ys (o°c) (above 0°C)

I960 3-10 June 191 185 - 6 8 4.2 34 11-20 June 185 125 -60 10 10.2 136 21-30 June 125 60 -65 10 9.7 233 1-10 July 60 10 -50 10 13.4 367 11-12 July 10 0 -10 2 11.8 391

1961 2-10 June 236 225 -11 9 0.3 3 11-20 June 225 191 -34 10 5.1 54 21-30 June 191 112 -79 10 8.8 142 1-10 July 112 45 -67 10 10.4 246 11-17 July 45 0 -45 7 9.9 315

1962 1-10 June 239 230 - 9 10 - 1.7 11-20 June 230 184 -46 10 2.9 29 21-30 June 184 141 -43 10 5.4 83 1-10 July 141 93 -48 10 9.5 178 11-20 July 93 48 -45 10 12.3 301 21-30 July 48 0 -48 10 12.1 422

1963 17-20 May 231 229 - 2 4 -10.1 21-31 May 229 221 - 8 11 - 7.6 1-10 June 221 207 -14 10 - 1.4 11-20 June 207 183 -24 10 4.2 42 21-30 June 183 151' -32 10 6.3 105 1-10 July 151 105 -46 10 9.8 203 11-20 July 105 54 -51 10 11.1 314 21-31 July 54 0 -54 11 11.2 435

1964 29-31 May 236 234 - 2 3 - 2.2 1-10 June 234 227 - 7 10 - 0.2 11-20 June 227 193 -34 10 2.0 20 21-30 June 193 165 -28 10 5.6 76 1-10 July 165 90 -75 10 12.2 198 11-21 July 90 0 -90 11 10.8 317

1965 28-31 May 227 226 - 1 4 - 1.9 1-10 June 226 214 -12 10 0.5 5 11-20 June 214 185 -29 10 2.2 27 21-30 June 185 128 -57 10 5.6 83 1-10 July 128 78 -50 10 8.3 166 11-20 July 78 32 -46 10 11.9 285 21-27 July 32 0 -32 7 11.8 368

15 Accumulated Degree Days (Above 0 °C )

Figure 7. Relationship between increasing amounts of ice decay and ac­ cumulated thawing degree days (base 0°C) at Baker Lake, N.W.T., Canada.

In addition, since it is obvious that other mete­ observed air temperatures throughout this area orological factors contribute to ice decay, it was revealed average departures of from 3.5 to 5 considered useful to conduct similar statistical Celsius degrees (~ 6 to 9 F°) below normal during analyses on other critical parameters. In the February, March, April and May 1964 (U.S. following sections, results of investigations of Department of Commerce 1964). This unusually the above questions are explained and cold weather resulted in thicker ice sheets plus a evaluated. major delay in spring thaw. Ice decay and removal generally occur from mid-April through May in this region, but were instead observed RELATIONSHIPS BETWEEN ICE DECAY AND about 10 to 35 days later than usual in 1964. This THAWING AIR TEMPERATURES documented observation clearly indicates the need to investigate, in detail, the role that thaw­ The main emphasis in most of the remaining ing air temperature plays in the ice decay pro­ portion of this study is on an evaluation of the cess. association between ice decay and thawing air Seasonal 10-day intervals of ice decay and temperatures. The following events that took concurrent air temperature data similar to that place during late winter and the spring of 1964 in shown in Table 3 were compiled for all the years west-central Alaska clearly show the strong in­ of record at seven test stations. These seven sites fluence that air temperatures have on the timing were chosen to represent the three categories of of ice decay, breakup and removal. water bodies under study as follows: sea ice Examination of the ice decay curves for five (Kotzebue, Alaska, and Eureka, Canada), river stations in this area — Allakaket (Fig. C41), Bethel ice (Bethel, Alaska, and Coppermine, Canada), (C44), Holy Cross (C53), McGrath (C58) and and lake ice (Mankomen Lake, Alaska, and Unalakleet (C65) —show unusually late ice Baker and Nitchequon Lakes, Canada). By con­ clearance dates, the delay being about two to ducting detailed statistical investigations on the three weeks later than average. Review of the data from these seven stations, the most suitable

16 Figure 8. Semilog plot of 10-day increments of ice decay vs concurrent average daily air temperatures at Baker Lake.

representation of the relationship should developed to determine the correlation between become apparent and hopefully applicable to the variables. Based on test runs using logarith­ other comparable locations. mic transformations, it was found that the best straight line relationship occurred when air tem­ perature values were plotted against the log of AVERAGE DAILY VS MAXIMUM the amount of ice decay (i.e. a semilog relation­ DAILY AIR TEMPERATURE ship). Examples of this semilog plot using the 10-day In the first test, the relationship between increments of ice decay vs the daily average and 10-day intervals of ice decay was compared with daily maximum air temperatures are shown for 1) the concurrent average daily air temperature, Baker Lake (Fig. 8 and 9 respectively). The cor­ and 2) the concurrent daily maximum air temper­ relation coefficient and other statistical results ature. These air temperatures were taken at obtained from the calculations of the "best fit" weather stations adjacent to the bodies of water line shown in the figures are listed in Table 4. under study and are published by the Depart­ The tabulation also includes the statistics ob­ ment of the Environment, Canada (1959-1974), tained from the same computations using data and the U.S. Department of Commerce from the other six test stations. Inspection of the (1962-1974). In this test, 9- and 11-day ice decay correlation coefficients in Table 4 (which ranged intervals were included in the 10-day increments from 0.62 at Eureka to 0.88 at Baker Lake) indi­ and shorter intervals omitted. cates that a good association exists between the A linear regression computer program* was variables. In every case the F test also indicated acceptance of the linear hypothesis at the < 0.001 level. All of the statistics for both the average daily and maximum air temperature * The Dartmouth College Time-Share Kiewit Computer Center was used in this and all following statistical computa­ data are quite similar so that neither emerged as tions. the better correlating independent variable.

17 Average Maximum Air Temperature (°C) (10 day increments)

Figure 9. Semi log plot of 10-day increments of ice decay vs concurrent average maximum daily air temperatures at Baker Lake.

Table 4. Regression data for log 10-day ice decay increments (cm) vs average and maximum concurrent daily air temperature (°C).

Avg Correlation Standard F test or Slope of equation* coefficient error of acceptance Station max log y = a + bx R estimate level

Mankomen Avg 0.050 0.71 0.35 <0.001 Max 0.045 0.68 0.36 <0.001 Kotzebue Avg 0.091 0.73 0.34 <0.001 Max 0.089 0.68 0.36 <0.001 Bethel Avg 0.091 0.67 0.38 <0.001 Max 0.091 0.71 0.36 <0.001 Baker Lake Avg 0.064 0.88 0.20 <0.001 Max 0.056 0.88 0.20 <0.001 Nitchequon Avg 0.083 0.73 0.30 <0.001 Max 0.077 0.74 0.29 <0.001 Coppermine Avg 0.070 0.78 0.39 <0.001 Max 0.071 0.78 0.39 <0.001 Eureka Avg 0.105 0.65 0.34 <0.001 Max 0.093 0.62 0.35 <0.001

* where y = decrease in ice thickness a = Intercept = logy (at x = 0)^ b = slope X = average (or maximum) air temperature t Intercept values were purposely omitted from Table 4 because further improvement in the relationship followed.

18 Table 5. Linear regression data for accumulated ice decay (cm) vs accumulated thawing degree days using various bases.

Avg temp base = 0 ° C Max temp base = 0 ° C Avg temp base = - 1 0 °C

Correlation Standard error Correlation Standard error Correlation Standard error Station S lo p e coefficient of estimate S lo p e coefficient of estimate S lo p e coefficient of estimate

M an ko m en 0.38 0.96 10.5 0.19 0.94 12.7 0.14 0.92 15.8 K o tzeb u e 0.58 0.85 20.0 0.44 0.91 15.8 0.26 0.96 11.8 Bethel 1.20 0.85 20.3 0.63 0.86 19.8 0.28 0.88 19.6 B aker 0.55 0.94 23.4 0.37 0.96 20.0 0.26 0.96 21.0 N itcheq uo n 0.56 0.93 11.4 0.27 0.93 11.4 0.16 0.89 13.8 C o p p erm in e 1.14 0.66 37.1 0.61 0.65 37.7 0.36 0.74 44.0 Eu reka 0.92 0.90 30.2 0.59 0.93 26.1 0.30 0.92 28.3

10-DAY INCREMENTS VS In this analysis a straight line (as opposed to ACCUMULATED VALUES logarithmic) relationship provided the best fit for the data. Table 5 contains a summary of the Expanding on the preceding analysis, further statistical results obtained from computer calcu­ interpretations of the data were explored in lations for the seven test stations. Note that, ex­ which accumulated amounts of ice decay were cept for Coppermine, the correlation coeffici­ associated with the concurrent accumulated ents in all base temperature categories have im­ thawing degree days (ATDD).* This approach proved considerably when compared with those probably provides a more realistic association shown in Table 4. At Coppermine (a river site), between the variables than does the use of indi­ correlation coefficients similar to those ob­ vidual 10-day intervals of ice decay because of tained earlier occurred when a base temperature the following reason. During the initial stages of of -10°C was used in the accumulated interval ice ablation, the ice sheet is at maximum thick­ format. (Further clarification on the improve­ ness. At this point, the influence of thawing air ment in the relationship found for river sites temperatures is not as strong, due to the insulat­ when a base temperature other than 0°C is used ing properties of the ice, as later when the ice will follow.) Therefore it becomes apparent that, sheet becomes progressively less thick. In the because the correlation coefficients for all 10-day interval analysis, this factor was disre­ categories (except Coppermine) ranged from garded, since all 10-day intervals were included 0.85 to 0.96 in Table 5, the resultant relationships in the association irrespective of the time of oc­ provide optimistic first approximations. currence. Since neither the average nor maximum Included in the analysis on the association be­ temperature emerges as a definite better choice tween accumulated ice decay and ATDD for the for the independent variable, it was decided to seven stations were statistical evaluations on the discontinue further consideration of maximum use of 1) a linear vs non-linear relationships, 2) air temperature. This decision is further substan­ average daily vs maximum daily temperatures, tiated by the fact that average air temperatures and 3) 0° and -10°C as the base for calculating are more commonly used and available in the thawing degree days.t literature, and because ATDD's are generally always calculated from daily average, rather than daily maximum, temperatures. At this point, note that the base 0°C provided * Although selection of the word “ thawing" is uncommon results that were on par (except for Coppermine) with respect to the melting of ice, it is used here to indicate summations of air temperatures above a particular base (e g. with those obtained using -10.0°C as a base. 0°, -1.8°, -5°C, -10°C). Again, for the purposes of familiarity and in par­ t The base -10°C was considered here in order to include the ticular ease of calculation, the use of a base of entire ice decay curve in the analysis. Further comparisons in the use of 0°C instead of -1.8°, -5° or -10°C as a base are 0°C to calculate ATDD was continued. Ex­ given later. amples of the plot of accumulated amounts of

19 Figure 10. Computer plot of linear relation­ ship between accumulated amounts of ice decay and concurrent accumulated thawing degree days (base 0°C) at Baker Lake.

Figure 11. Computer plot of linear relation­ ship between accumulated amounts of ice decay and concurrent accumulated thawing degree days, Bethel, Alaska (base 0°C).

(Above 0° C)

ice decay vs ATDD using summations of 10-day cm/TDD at Bethel (a river site), to 0.38 cm/TDD intervals of average air temperature are shown at Mankomen Lake. Further investigation of in Figure 10 for Baker Lake (Canada) and Figure these differences is presented in a later section. 11 for Bethel (Alaska). The slope of the line of best fit shown in these figures (and in Table 5 for the other five stations) defines the estimated TOTAL YEARS VS YEAR-TO-YEAR ANALYSIS amount of ice that decays (cm) per each thawing degree day (TDD)*. Note that the slope varies In the preceding discussion, the data for all markedly from place to place, ranging from 1,2 the years of record at each station were com­ bined to derive the composite "computer-calcu­ lated" regression line (or slope). However, it was * The difference between the positive average air tempera­ ture and 0°C for a day. found that when the slope is calculated by the

20 Table 6. Amount of ice decay (cm) per thawing degree day (0°C).

Year Mankomen Kotzebue Bethel Baker Nitchequon Coppermine Eureka

1959 0.70 0.61 1960 0.51 0.39 0.89 1961 0.74 0.94 2.10 1962 1.12 1.41 0.51 0.68 2.31 0.71 1963 0.88 0.93 0.81 1.24 0.63 1964 1.53 1.08 0.68 0.64 4.24 1965 0.65 0.60 0.56 6.36 0.93 1966 0.26 0.43 0.54 1.37 1.15 1967 0.33 1.45 0.51 0.53 1.90 1.26 1968 0.40 1.10 0.97 0.55 0.48 1.20 0.85 1969 0.39 0.84 1.26 1.75 0.88 1.49 1.01 1970 0.41 0.69 0.92 0.58 0.32 0.69 1971 0.41 0.94 2.38 0.90 0.67 0.98 1972 0.67 1973 1.32 0.92 1974 1.32

Average 0.37 0.97 1.31* 0.70t 0.62 2.29* 0.94 Composite** slop e 0.38 0.58 1.20 0.55 0.56 1.14 0.92

*This value differs from those shown in Table 9 because a base of -5°C for calculating ATDD was later selected as the better relationship for the river sites. tThis value was based on 13 years of data, instead of 12 years, as given in Table 9 (the slope value for 1969 was later omitted). **These values were taken from Table 5.

least-squares method on a year-to-year basis, the Fig. C4) and should not have been included in average slope for all the years of record was not the final analysis. When this value is omitted, always in agreement with the composite slope. A the average slope for the 12 years of record be­ listing of the slopes obtained by the least comes 0.62 cm/TDD instead of 0.70. Later, when squares method on a year-to-year basis for the average slopes were calculated for 41 different seven test stations is given in Table 6. The table locations, each annually computed slope was ex­ also shows the arithmetic averages of these amined and obviously unrepresentative values slopes, and the computer-calculated composite were omitted, if justifiable. slope for each station. .Incidentally, examination of the slopes for While Eureka, Mankomen, and Nitchequon each year makes it possible to locate anomalous show good agreement with either method, Baker years at each station, as these slope values and Bethel show some discrepancy and Kotze­ would deviate somewhat from the average bue and Coppermine show poor agreement. value. The high rate of ice decay (0.92 cm/TDD) These differences prompted a closer examina­ at Baker Lake in 1973 (see Fig. C4), for example, tion of the results obtained from year to year, is associated with a period of warm rains with no and the investigation revealed that some obvi­ snow on the ice sheet between 21 May and 4 ously unrepresentative values existed in the June 1973 (Table A1), and by abnormally high air basic data. The best example would be that temperatures during the rest of June —see the shown for Baker Lake in Table 6 where (except Canadian Monthly Record for May and June for 1969) the computed rates of ice decay range 1973 (Department of the Environment Canada from 0.43 to 0.92 cm/TDD. It can be assumed, 1959-1974). Anomalies such as this would be a therefore, that the value of 1.75 cm/TDD ob­ useful tool for selecting those specific years tained in 1969 is certainly unrepresentative or when attempting to determine what other envir­ possibly erroneous. onmental factors contributed to either the rapid Examination of the original data revealed that erosion or the delaying processes of decay of an the ice decay curve for 1969 is incomplete (see ice sheet.

21 Table 7. Number of years with 10% ice erosion before thawing air temperature occurred.

Rivers Lakes Sea Ice Years of Total Years of Total Years of Total 10% years of 10% years of 10% years of Station erosion record Station erosion record Station______erosion______record

Churchill* 1 6 Baker 0 13 Arctic Bay 1 4 Coppermine 5 10 Brochet 4 12 Cambridge Bay 1 12 Inuvik 9 10 Ennadai 5 16 Cape Parry 2 11 Moosonee* 6 7 Fort Chipewyan 5 9 Cartwright 2 6 Norman Wells 3 5 Goose Bay* 5 14 Chesterfield 1 13 Inoucdjouac* 6 11 Nitchequon 4 14 Clyde River 0 13 Allakaket 2 7 Knob Lake 2 8 Coral Harbour 1 13 Bethel 10 12 Mary Jo Lake 2 7 Eureka* 1 9 Betties 3 6 Trout Lake 4 9 Frobisher Bay 1 10 Holy Cross 2 4 Yellowknife 0 10 Holman Island 2 7 King Salmon* 5 5 Barter Island 4 8 Hopedale 4 7 Kobuk 2 9 Fairbanks 0 6 Mould Bay 1 4 McGrath 10 12 Cambell 2 3 Pond Inlet 1 2 Tanacross 6 8 Mankomen 1 6 Resolute 0 11 Trapper's Creek 7 8 Port Alsworth 4 7 Sachs Harbour 4 7 Unalakleet* 3 6 Snowshoe Lake 0 9 Spence Bay 1 3 Wild Lake 0 4 Kotzebue 3 11

Total 80 126 42 155 26 143

*Brackish

EVALUATION OF USE OF 0°C AS A BASE occurred in 42 instances out of a possible 155 years at the lake sites, 26 out of 143 years for sea Although lakes and sea ice locations showed ice, and 80 out of 126 for the river locations. fairly consistent year-to-year slope values when It was decided, therefore, that for river loca­ 0°C was used as a base to compute ATDD, river tions a base of less than 0°C should be used to locations showed considerable variation. These calculate ATDD. Since a further test on the river variations may be partly due to the significant data showed that the amount of ice decay amounts of ice decay that occur in rivers before occurring between -10° and -5°C was minimal, the initial 10-day average air temperature use of a base of -5°C would include most of the reaches 0°C. Therefore, the use of a base of 0°C beginning portion of the curve previously omit­ for the starting point on the river ice decay ted. curves would eliminate relevant data. Incidentally, conjecture for this anomaly be­ A survey was conducted to determine more ing associated with rivers rather than lake or sea precisely what portion of the ice decay curve ice sites might be related to the ice erosion was being ignored by using a base of 0°C and caused by the rapid flow of water beneath river which river sites were being affected. The inves­ ice. As the ice sheet approaches an isothermally tigation calculated the number of years of "ripe stage," the bottom ice becomes suscep­ record when greater than 10% of the total tible to removal by the washing action, even amount of ice decay occurred before the aver­ though the air temperatures are still slightly age air temperature reached 0°C. Fifty of the 66 below freezing. Similar conditions can exist at stations listed in Tables 1 and 2 were included in certain sea ice sites that are subjected to major the survey, the results of which are shown in tides or currents. Since the motion of the water Table 7. Early portions of ice decay curves were under lake ice sheets (except near river inlets or excluded less frequently at the lake and sea ice outlets) is generally minimal, this condition is locations than at the river sites. The exclusions not an influential factor at most lake locations.

22 FINAL FORMAT OF THE RELATIONSHIP concurrent thawing air temperatures provided BETWEEN ICE DECAY AND ATDD encouraging correlations with respect to lake, river and sea ice sheets. The main purpose of the previous sections 2. Linear relationships, especially when ac­ was to determine statistically if and how thaw­ cumulated values of ice decay and concurrent ing air temperatures can be associated with the ATDD values are used, provided the best results, rate of ice decay. Investigation of several although logarithmic transformations were aspects to the study, including linear and sometimes useful. nonlinear relationships, the implementation of 3. Daily average air temperatures, rather than various base temperatures, and the considera­ daily maximum air temperatures, were useful tion of a number of ways to present the data, has because of convenience and familiarity. thus far shown the following: 4. A base of 0°C provided the best results for 1. Use of 10-day increments of ice decay vs lake and sea ice locations, but -5°C improved

Table 8. Example of extracted tabulated ice decay and air tem­ perature data sets for Mankomen Lake, Alaska.

Total Ice A verage Sum of sum of thickness No. 10-da y 10-da y 10-day (cm) D ili of temp temp temp Start End (± cm) days (°F) (°C) (°C) (°C)

1966 19-20 March 129 128 -1 2 5.0 -15.0 -30 21-31 March 128 122 -6 11 22.0 -5.6 -62 1-10 April 122 119 -3 10 23.5 -4.7 -47 11-20 April 119 101 -18 10 26.5 -3.1 -31 21-30 April 101 81 -20 10 19.4 -7.0 -70 1-10 May 81 (72) -9 10 33.5 0.8 8 8 11-20 May (72) (48) (-24) 10 33.0 0.6 6 (14) 21-31 May (48) (44) (-4) 11 37.5 3.1 34 (48) 1-10 June (44) (39) (-5) 10 48.5 9.2 92 (140) 11-20 June (39) 10 -29 10 47.0 8.3 83 223 21-23 June 10 0 -10 3 48.3 9.1 27 250

1967 11-20 March 110 111 + 1 10 10.0 -12.2 -122 21-31 March 111 109 -2 11 4.0 -15.6' -172 1-10 April 109 109 0 10 23.0 -5.0 -50 11-20 April 109 109 0 10 14.0 -10.0 -100 21-30 April 109 107 -2 10 22.5 -5.3 -53 1-10 May 107 104 -3 10 31.0 -0.6 -6 11-20 May 104 99 -5 10 33.0 0.6 6 6 21-31 May 99 67 -32 11 41.0 5.0 55 61 1-10 June 67 46 -21 10 45.0 7.2 72 133 11-20 June 46 22 -24 10 52.5 11.4 114 247 21-24 June 22 0 -22 4 52.0 11.1 44 291

1968 31 March 104 1-10 April 104 102 -2 10 17.6 -8.0 -80 11-20 April 102 98 -4 10 18.5 -7.5 -75 21-30 April 98 95 -3 10 28.0 -2.2 -22 1-10 May 95 90 -5 10 32.5 0.3 3 3 11-20 May 90 80 -10 10 39.0 3.9 39 42 21-3T May 80 67 -13 11 41.5 5.3 58 100 1-10 June 67 30 -37 10 43.0 6.1 61 161 11-16 June 30 0 -30 6 52.5 11.4 68 229

23 Table 8 (cont'd). Example of extracted tabulated ice decay and air temperature data sets for Mankomen Lake, Alaska.

Total Ice Average Sum of sum of thickness No. 10-day 10-day 10-day (cm) Diff of temp temp temp Start End ( ± cm) days (°F) (°C) (°C) (°C)

1969 5-10 A p ril 145 146 + 1 6 28.3 -2.1 -1 3 11-20 April 146 146 0 10 25.9 -3 .4 -3 4 21-30 April 146 142 -4 10 31.5 -0 .3 -3 1-10 M a y 142 135 -7 10 31.2 -0 .4 -4 11-20 M a y 135 127 -8 10 38.9 3.8 38 38 21-31 M a y 127 97 -3 0 11 43.8 6.6 73 111 1-10 ju n e 97 50 -4 7 10 46.0 7.8 78 189 11-21 ju n e 50 0 -5 0 11 55.5 13.1 144 333

1970 14-20 March 91 93 + 2 7 21-31 March 93 93 0 11 27.6 -2 .4 -2 6 1 -1 0 A p r i l 93 91 -2 10 20.1 -6 .6 -6 6 11-20 April 91 91 0 10 27.6 -2 .4 -2 4 21-30 April 91 90 -1 10 27.5 -2 .5 -2 5 1-10 M a y 90 88 -2 10 34.2 1.2 12 12 11-20 M ay 88 75 -1 3 10 39.4 4.1 41 53 21-31 M a y 75 44 -31 11 41.5 5.3 58 111 1-10 ju n e 44 22 -2 2 10 43.7 6.5 65 176 11-17 ju n e 22 0 -2 2 7 43.1 6.2 43 219

1971 6-10 M arch 137 137 0 5 -6 .7 11-20 March 137 142 + 5 10 13.2 -1 0 .4 21-31 March 142 130 -1 2 11 11.2 -1 1 .6 1-10 A p ril 130 130 0 10 17.6 -8 .0 11-20 April 130 135 + 5 10 22.2 -5 .4 -5 4 21-30 April 135 132 -3 10 26.3 -3 .2 -3 2 1-10 M ay 132 130 -2 10 30.8 -0 .7 -7 11-20 M ay 130 125 -5 10 33.7 0.9 9 9 21-31 M a y 125 120 -5 11 37.2 2.9 32 41 1-10 ju n e 120 98 -2 2 10 44.6 7.0 70 111 11-20 ju n e 98 47 -51 10 48.6 9.4 94 205 21-30 ju n e 47 0 -4 7 10 52.4 11.3 113 318

the association for river ice because these ice ice sheet can be obtained from forecasts of sheets apparently begin to erode prior to the subsequent daily air temperatures. onset of thawing air temperatures. The final selected format, therefore, consisted In addition, some thought was given as to the of computing the "best fit" least-squares line best way to graphically present the selected rela­ between accumulated amounts of decrease in tionships. Based on discussions with other ice thickness (the dependent variable) and the CRREL colleagues (W. Hibler and D. Nevel), it corresponding ATDD (the independent variable). was decided that, instead of using accumulated A sample compilation of these data sets is amounts of ice decay as the dependent variable, shown for six years of record at Mankomen Lake it would be more meaningful to associate ATDD in Table 8. with the corresponding decreasing observed ice A computer program was developed to calcu­ thickness values. In so doing, the absolute value late the least-squares slope and intercept using of the slope (rate of decay) would be unaffected, similar data sets for each year of record as and estimates of the thickness of the decaying discussed earlier. An example of this procedure

24 Figure 12. Line of best fit of the annual relationships between decreasing amounts of ice thickness vs ATDD for Mankomen Lake, Alaska.

and the results obtained for Mankomen Lake is Canada (12 sea ice, 10 lake, and 6 river sites), and shown graphically in Figure 12. Six slopes are 13 locations in Alaska (1 sea ice, 5 lake and 7 shown, one for each year, with the rates of ice river sites). In order to be included in this survey, decay corresponding to the values listed in at least five or more years of record were re­ Table 6. It is now possible to obtain either a quired. The ice decay curves for these stations "composite slope" (i.e. a best fit line for all the also had to be reasonably complete, with points shown in Fig. 12) or an "average of the reliable air temperature records available from yearly slopes." These are shown as 0.38 and 0.37 nearby weather stations. respectively in Table 6. Statistical results on the relationship between Following some discussion and thought on these variables for the 41 stations surveyed are this option, it was decided that the "average of shown in Table 9. The stations in the table were the yearly slopes" would be more valid because separated according to lake, river and sea ice it maintains the sequential relationship of the location and whether the site is in Alaska or data points on a year-to-year basis. The com­ Canada. The tabulation includes: 1) the years of puter program developed to calculate the least record used for each station, 2) the slope of the squares slope and the intercept for each year line obtained from the average of the yearly was then expanded to provide the average of the slopes, and 3) the computed standard deviation yearly slopes. The intercept value gives the of the average slope value, expressed as a average thickness of the ice sheet at the start of percentage. At Mankomen Lake, for example, ice decay. Of course, this latter value is only an analysis of the six years (1966 through 1971) of approximation; actual values will vary from year usable record provided the average slope of 0.37 to year. If the ice thickness at the start of thaw­ shown in Table 9. The standard deviation around ing temperatures is known at any site, then that this value was calculated to be ± 0.06 or ± value should be used rather than the intercept of 16%. Similar calculations were conducted for the line obtained from the average of yearly the other 40 stations studied and are listed in slopes. Table 9. Another value that could be extracted from the preceding analysis is an average intercept EVALUATION OF THE FINAL FORMAT from the lines of "best fit" at each station. This average intercept (on the ordinate scale in Fig. Sufficient annual ice decay curves and con­ 12) for Mankomen Lake was calculated to be 104 current ATDD data to conduct a survey on the cm. This value refers to the average thickness of final format were available from 28 locations in the ice sheet at the start of ice decay. It should,

25 Table 9. Statistics on the relationship between ice decay and ATDD*.

Base 0°C______Base 0°c Base -5°C Lake Yr of Avg Stan Sea-ice Yr of Avg Stan River Yr of Avg Stan locations record slope dev (% ) locations record slope dev {% ) locations record slope dev (% )

C an ad a C an ad a C an ad a Baker Lake 12 .62 26 Cambridge Bay 8 .96 26 Churchill 5 .65 28 Brochet 12 .56 13 Cape Parry 9 1.04 14 Coppermine 10 .98 28 Ennadai Lake 16 .54 22 Cartwright 5 1.01 25 Inoucdjouac 9 .95 16 Fort Chipewyan 7 .56 29 Chesterfield Inlet 12 .82 26 Inuvik 8 .55 20 Goose Bay 12 .59 23 Clyde River 11 .98 39 Moosonee 5 .49 24 Nichequon 14 .62 27 Coral Harbour 13 .92 28 Norman Wells 6 .53 28 Schefferville (Knob) 7 .89 16 Eureka 9 .94 21 Schefferville (M Jo) 6 .90 21 Frobisher Bay 11 .74 19 A lask a Trout Lake 9 .49 20 Holman Island 7 .91 27 A llakaket 7 .60 22 Yellowknife 9 .74 8 Hopedale 5 1.11 27 Bethel 10 .57 21 Resolute 9 .94 25 Betties 5 .53 11 A laska Sachs Harbour 7 1.00 19 Kobuk 7 .66 29 Barter Island 5 1.29 23 M cGrath 7 .41 15 Fairbanks 5 .43 16 A lask a Tanacross 7 .41 33 Mankomen Lake 6 .37 16 Kotzebue 8 .97 29 Unalakleet 8 .77 26 Port Alsworth 10 .80 23 Snowshoe Lake 9 .80 15

* Average slope refers to the computed rate of decrease in ice thickness as related to accumulated thawing degree days (cm of ice/ATDD; base of 0°C or -5°C as shown).

in fact, approximate the average annual max­ S = average slope value (cm/°C) imum thickness of the ice sheet at each location. ATDD = accumulated thawing degree days A survey on about 24 stations in Canada in­ (in °C with base 0°C for lake and dicated that the intercept values are about 8% sea ice locations, and -5°C for lower than the reported average maximum ice river locations). thickness. Since the ice thickness at the end of Inserting the values of 145 cm for /„., and 0.74 each growth season could vary, use of an observ­ cm/°C for S for Yellowknife it would require ed thickness of the ice sheet at the start of ice about 196 ATDD to reduce the ice sheet to zero, decay each season is advised, as previously i.e. noted. If the actual thickness is unknown, then / = l„ - S (ATDD) average maximum values as given in Allen and / = 145 - 0.74 (196) Cudbird (1971) for Canadian locations or the in­ / = 145 _145 form ation shown in Figures B1 and B2 could be / = 0 utilized. The following is an example of computations A survey of nine years of ice decay vs thawing using the maximum ice thickness value and the air temperature records at Yellowknife slope obtained from the average curve (which is (1959-1962 and 1964-1968 inclusive) yielded an an indication of the rate of ice decay). The average ATDD value of 192. The observed ice average maximum ice thickness on Back Bay thickness values at the start of ice decay were (Great Slave Lake), Yellowknife, Canada, is 145 then compared to the total ice decay predicted cm (Allen and Cudbird 1971), and the average by eq 1 and the results obtained were found to rate of ice decay as related to TDD is 0 74 ± 8% be quite reasonable. For six of the nine years the (Table 9). The relationship can be expressed as slope of 0.74 predicted total ice decay amounts that were within 10% (or better) of the observed / = /,„-S(ATDD) (1) amounts, and deviations were from 10 to 20% for the other 3 years. Comparisons such as this where / = thickness of the decaying ice would be useful in further investigation of other sheet (cm) possible factors contributing to ice decay /,„ = maximum ice thickness at the because it clearly separates the anomalous start of ice decay (cm) years.

26 POSSIBLE CAUSES FOR VARIATIONS IN SLOPE VALUES

Inspection of the slopes computed for all the lake locations (Table 9) revealed some variation. The rate of ice decay ranges from 0.49 to 0.90 cm/TDD (°C) at the Canadian stations, and from 0.43 to 1.29 at the Alaskan stations. To deter­ mine whether these differences were associated with latitudinal location, the slope values for each lake site were plotted on a map. The investigation disclosed nothing positive in the relationship in either Canada or Alaska. The possibility that the size and depth of a lake may affect the rate of ice decay was also considered. Data on the surface area for six of the stations in Canada (Baker Lake, Brochet, Ennadai Lake, Nitchequon, Trout Lake and Yellowknife) were obtained for the test.* A plot of the sets of corresponding variables on semilog paper (Lig. 13) shows a slight association be­ tween higher slope values and greater surface area. However, the relationship is rather weak Slope Value for Lake Ice Decay and perhaps may require the inclusion of the (See Table 9) depth (i.e. total volume) of the lake water. Lur- Figure 13. Relationship between rate of lake ice ther evaluation of this factor was terminated decay and surface area of the lake. due to lack of depth data for each lake. Note that except for Lrobisher Bay and was found. The effects of the current, unusually Chesterfield Inlet the slopes (Table 9) for the 13 high water, and/or flooding as well as dissimi­ sea ice locations are quite uniform, ranging from larities in size, shape and configuration of the 0.91 at Holman Island to 1.11 at Hopedale. Lur- river channel are undoubtedly important. ther discussion on these results, as well .as However, lack of information on the above fac­ reasons why 0°C rather than -1.8°C was used as tors at each of the river sites precludes further the base to compute ATDD at sea ice sites is analysis on these influences. given in the next section. Estimates on the total ATDD (base -5°C) re­ The slopes for the river locations (Table 9) quired to clear a river of ice at individual sites naturally cannot be compared with the ones ob­ can be obtained from the information given in tained for the lakes and sea ice sites because Table 9. Lor example, average maximum ice -5°C was used instead of 0°C for computing thickness on the Kuskokwim River at Bethel, ATDD. Although the base of -5°C provided the Alaska, is about 125 cm (see Ligs. B1 and B2), best results, the average slopes for the river sites and the average rate of ice decay as related to still revealed considerable variation, ranging TDD (base -5°C) is 0.57 ± 21 % (Table 9). Inser­ from 0.41 to 0.98 cm/TDD (°C). There are ting these values in eq 1 shows that about 220 numerous reasons that could account for these ATDD (base -5°C) are required between times of variations at the river sites. Lirst, a test for maximum ice and ice clearance, on the river. latitudinal influence on slope values, similar to A survey of the observed ATDD at Bethel that done for lake locations, was conducted and (base -5°C) for 10 years of record (1962-1964, no direct association between the parameters 1967-1971 and 1973-1974 inclusive) yielded an average ATDD value of 229. On a year-to-year basis, in which observed ice thickness and ATDD values are used, for 4 of the 11 years the slope of *This information was received by request in a letter dated 6 0.57 predicted total ice removal amounts within December 1961 from the Office of the Senior Standardiza­ 5 to 15% of the observed amounts, from 15% to tion Representative. U.S. Army Standardization Group, Canadian Army Headquarters, Ottawa, Canada. 25% of the observed amount during four other

27 years, and from 25 to 28% during the remaining During the ice growth stage, the heat flux is three years. principally unidirectional (vertical), which These year-to-year variations in the accuracy allows for the development of a model similar to of the predictions for each station are given by that presented by Untersteiner (1964) for the the standard deviations on the average slope Central Arctic. Since the thermal gradient within values (Table 9). This information is useful a decaying ice sheet approaches equilibrium, because it points out those stations where the development of similar heat balance equations rate of ice decay is apparently controlled by or models to predict ice erosion becomes more environmental influences other than air temper­ difficult. Work on this aspect of the problem, ature. however, has been attempted (e.g. Langleben 1972) and references to some other such studies are given in the Selected Bibliography . DECREASING SEA ICE THICKNESS AND As a first step in the development of sea ice THAWING AIR TEMPERATURES* decay models, it would be worthwhile to in­ vestigate the contributing effects of a key Factors affecting sea ice decay parameter — thawing air temperatures. In a It has been stressed that many environmental previous paper (Bilello 1961a), the observed factors besides air temperature should be in­ decreases in sea ice thickness and concurrent cluded in the ice deterioration and melt process. ATDD were investigated for four fast ice loca­ In addition to those mentioned earlier for lake tions in the Canadian Archipelago. A least- and river ice sheets, other parameters such as squares computation on 29 sets of observations tides, brine content in the sea ice and sea water, yielded a correlation coefficient of 0.93 in the and similar oceanographic phenomena undoubt­ equation edly contribute to the decay of fast sea ice sheets. However, some major problems encoun­ H = 0.551^ (2) tered in any attempt to develop complete models designed to simulate sea ice decay, where H is the decrease in ice thickness (cm) and breakup and removal are 1) insufficient or X the accumulated degree days above -1.8°C. unavailable data necessary for analysis pur­ These results, when compared with a similar poses, 2) the dynamic behavior of nonthermal Soviet study by D.B. Karelin, as quoted by Arm­ factors such as, for example, ice breakup due to strong (1955), indicated that the Canadian Arctic wind, and 3) the inclusion of disruptive features requires more accumulated degree-days than such as the formation of snow-ice layers in ther­ the Russian Arctic to produce the same amount mal modeling. of ice decay. In this current study, the relation­ It is also important to determine whether the ship is investigated in greater detail and includes principal erosion is taking place at either the top more stations and a wider geographic region of or bottom of the ice sheet. Sea ice temperature the North American Arctic. profiles made on Slidre Fiord, Eureka (Fig. 14) Discussions with CRREL colleagues* provided show that when the ice begins to deteriorate (in the following two principal reasons why 0°C in­ late May-early June) the temperatures within stead of -1 8°C was used as a starting point for the 200 cm of ice are close to isothermal (Bilello sea ice erosion. First, the salt (or brine) content 1965). Although the temperature at the bottom of the sea ice is reduced drastically during the of the sea ice sheet remains at or near the freez­ deterioration and melt period and second, fresh ing point, occasional influxes of warm ocean water undoubtedly exists at the top of the ice currents washing against the ice sheet in late and perhaps occasionally beneath a melting fast spring may cause some bottom erosion. At the sea ice sheet. Of course, this latter phenomenon same time, puddling and other forms of erosion could be counterproductive in that any fresh occur on the surface of snow-free sea ice sheets water that reaches the bottom of the sea ice (Tables A1 and A2). sheet comes in contact with sea water that is just below freezing in temperature and would there­ fore probably accrete new ice. *A portion of the results presented in this section are includ­ ed in the Proceedings of a Symposium on Sea Ice Processes *W.F. Weeks and G.D. Ashton, CRREL, personal and Models (University of Washington Press in press). communication 1977.

28 TEMPERATURE,

Figure 14. Sea ice temperature curves, 7950-57, for Eureka, N.W.T., Canada.

While the erosion at the bottom of a sea ice the beginning of ice deterioration in May sheet is principally due to water movement, the (Department of the Environment, Canada decay on the surface is largely due to thermal 1959-74). The difference in total ice growth, and processes. For this reason, the relationship be­ the subsequent extreme variation in the rate of tween thawing air temperatures and sea ice ice ablation in these two years can be largely at­ decay, as described in the preceding section, tributed to the different amounts of snow on the was investigated in detail. ice. This observation shows that the depth of For example, the results of this analysis for snow on the ice should be considered in any ex­ Resolute (Fig. 15) show that the association ap­ panded model of sea ice decay. pears reasonable except for 2 of the 10 years of record analyzed (1967 and 1971). For most years, Relationship between ATDD and sea ice decay the relationship between rate of ice decay and From the results shown in Figure 15 an TDD can be defined by 1) a general slope of ap­ average curve for the 10 years of record was proximately 1.0 cm per TDD, or 2) for greater drawn for Resolute (Fig. 16). Similar curves were detail, two lines of different slope (i.e. an initial then compiled for six other sea ice locations for slope of about 0.9 from the start of ice decay comparison purposes and are also shown in until about 100 cm of ice has melted, and Figure 16. Although there are some minor ir­ another slope of about 1.1 cm/TDD thereafter). regularities, the decrease in fast sea ice Note that the ablation rates at Resolute differ thickness as related to ATDD shows a near markedly during 1967 and 1971 (Fig. 15). In­ straight-line relationship for most of the stations. vestigation of the weather conditions during the Consequently, using the methods described in ice growth and decay periods in these two years the previous section, average slopes were com­ shows that air temperatures did not depart ap­ puted for 13 sea ice locations (Table 9). Although preciably from the normal. However, during these average slope values permit quick com­ 1970-71 the snow cover was two to four times as parison between stations, the rate of ice deep as it was in 1966-67 at the beginning of decrease per TDD can be more closely evalu­ winter, and almost twice as deep (48 vs 28 cm) at ated by examining the slopes obtained in the

29 Table 10. In 96 of the total 114 years studied, the the studied, years 114 total the of 96 In 10. Table mTD (°C). cm/TDD in shown are values year-to-year These locations. er fdt ue i te nlss noprt in­ incorporate analysis the in used data of years 13 all at year each for analysis squares least sidered when evaluating these deviations in the the in deviations these evaluating when 1.20 sidered to 0.60 from ranged ablation ice of rate .2 mTD °) t rbse By ad con­ and Bay, Frobisher at (°C) cm/TDD 0.92 in N 80° to 54° from water sea ranging of types locations at different sites 13 from 114 the formation that emphasized is it First, relationship. hwsoe rtso ea, uh sfo .1 to 0.51 from as such decay, of rates slower show to susceptible particularly are average), the from (Table A1). Third, some locations consistently consistently locations some Third, A1). (Table ations in slope, such as Clyde River (± 39% 39% (± River Clyde as such slope, in ations snow-ice formation, unusual tides and rafting rafting and tides unusual formation, snow-ice devi­ longitude. excessive in showing W 162° locations to some 57° Second, from and latitude Ice Thickness (cm) eea sgiiat ons hud e con­ be should points significant Several 30 vestigation of these regional differences would would differences regional these of vestigation °) s .3 mTD °) Fo e 1, eq From (°C). cm/TDD 0.93 is 0°C) sistently faster decay, such as 0.81 to 1.23 1.23 to 0.81 in­ as Further 10). (Table such Parry Cape at decay, (°C) cm/TDD faster sistently decrease in fast sea ice as related to TDD (base of (base TDD rate to related average as ice the sea fast in considered, decrease are 10 Table siaig h dces i sa c tikes s a as thickness ice sea in decrease the estimating oceano- process. or decay the in meteorological parameters other logical of relative the determine influence to order in worthwhile be ucin f hwn ar eprtrs ol be for would temperatures air approximation thawing of first function good a Therefore, h following: the hn l 1 optd lp ausson in shown values slope computed 114 all When = S - L = I / = = / lm -0.93 (ATDD). (ATDD). -0.93 (ATDD). nul eraig mut of amounts decreasing annual e ie hcns ad accumu­ and thickness ice sea F ae taig i temperatures, air thawing lated eoue NWT, Canada. N.W.T., Resolute, gr 1. eainhp between Relationship 15.igure (3)

Accumulated Degree Days (Above 0° C)

Figure 16. Relationship between average decreasing amounts of sea ice thickness and

accumulated thawing air temperatures for seven sea ice locations (E — Eureka, MB — Mould Bay, SH —Sachs Harbour, R —Resolute, CH —Coral Harbour, K —Kotzebue, C —Cart­ wright).

Influence of solar radiation and wind on sea ice that are rotting rapidly and subject to movement decay and breakup. It has been stressed throughout this report An effort was made to determine whether that meteorological elements other than thaw­ solar radiation rather than thawing air tempera­ ing air temperatures undoubtedly contribute to ture should be used as an index to predict ice ice deterioration and melt. However, attempts decay. Sufficient incoming daily solar radiation to evaluate the relative importance of these fac­ (ISR)* data were available for 10 years of record tors or to derive mathematical relationships at Resolute and were related to the concurrent become difficult. For example, the role that decreases in sea ice thickness-. Since measure­ solar radiation plays in the decay process would ments of ISR are not directly affected by the sur­ necessitate continuous measurement of 1) long­ face on which it falls, the values recorded at the wave incoming radiation, 2) shortwave (back and weather station would be about the same as reflected) radiation, 3) the penetrating effects of those occurring over the sea ice. radiation through a snow cover, snow-ice, and Computational procedures similar to those sea ice, and 4) the resultant effects of surface used to obtain the curves in Figure 15 were used erosion including the changes in albedo due to ponds of meltwater on the ice sheet. Very little *The unit of radiation is the langley (one langley equals 1 information of this kind exists for sea ice sheets gram calorie per square centimeter).

31 Table 10. Annual rate of decrease in fast sea ice thickness as related to ATDD (cm of ice/ATDD; base 0°C).

Station Cambridge Cape Cart­ Chesterfield Clyde Coral Frobisher Holman Hope- Sachs Year Bay Parry wright Inlet River Harbour Eureka Bay Island dale Resolute Harbour Kotzebue

. :o9 1.04 0.98 0.51 1960 0.83 0.84 0.47 0.93 0.89 0.92 0.58 1961 0.89 1.09 1.40 0.74 0.84 1.11 1.20 1.14 1962 0.65 0.81 1.17 0.71 0.95 0.91 0.81 1.12 1963 1.12 0.89 0.66 0.61 0.63 0.82 0.41 0.96 1.12 0.88 1964 0.61 1.23 0.61 1.14 1.53 1965 1.46 1.20 1.27 1.57 0.93 0.92 0.82 0.89 0.65 1966 0.63 1012 0.88 0.83 0.67 0.72 1.15 0.61 1.30 1.16 0.76 1967 1.23 0077 1.09 0.75 0.72 1.27 0.92 1.03 0.59 1968 085 1.06 0.70 1.57 0.85 0.70 1.11 1.23 1.10 1969 0.08 1.10 1.16 1.01 0.80 1.13 1.18 1.19 0.84 1970 0.81 1.03 1.01 0.99 0.78 0.77 0.98 0.69 1971 1.03 0.83 1.67 0.73 0.84 0.61 0.94 1972 0.91 0.87 0.69 0.90 1973 0.91 0.69 0.61 1.32 1974 0.63 1.08 0.64 Average slope 0.96 1.04 1.01 0.82 0.98 0.92 0.94 0.74 0.91 1.11 0.94 1.00 0.97 Stan dev (± % ) 26 14 25 26 39 28 21 19 27 27 25 19 29 Figure 17. Relationship between annual decreasing amounts of sea ice thickness and accumulated incoming solar radiation, Resolute, N.W.T., Canada.

in this analysis, i.e. concurrent values of ISR for data from Resolute, NWT, and for accumulated ISR and ice decay over 10-day in­ limited concurrent data at Goose Bay, Labrador. tervals. This was done in order to compare the The results showed that use of the ATDD is, resultant curves with those in which ATDD was statistically at least, the better independent used as the independent variable. The relation­ variable. The correlation coefficients obtained ship between accumulated ISR and ice decay in the test using ATDD were 0.93 and 0.90 for (see Fig. 17) is similar to that shown in Figure 15. Resolute and Goose Bay, respectively, and the However, a greater change in the slopes is shown coefficients were 0.89 and 0.87, respectively in Figure 17 and the inflection point occurs after when accumulated ISR data were used. about 70 cm of ice (instead of 100 cm in Fig. 15) According to these comparisons, therefore, has melted. Notice that the same two years (1967 attempts to use ISR data instead of ATDD do not and 1971) mentioned in the discussion of Figure appear advisable. Of course, in specific in­ 15 also appear as anomalies in Figure 17. stances when extended periods of abnormally A regression analysis was made on the rela­ clear or cloudy conditions exist, incoming solar tionship between ice decay and accumulated radiation cannot be ignored in the ice decay

33 process. Further, if reliable ISR values are far- Andrews, J.T. (1962) Variability of lake ice growth and quality in the Schefferville region, central easier to predict than air temperatures, then use Labrador-Ungava. journal of Glaciology, vol. 4, p. of the relationship shown in Figure 17 should be 337-347. considered for extended ice decay forecasts. Armstrong, T. (1955) Soviet work on sea-ice forecasting. It is also possible that a combination of both Polar Record, vol. 7, no. 49, p. 302-311. air temperatures and ISR would provide better Bilello, M.A. (1961a) Formation, growth and decay of sea ice in the Canadian Arctic Archipelago. Arctic, vol. 14, no. results than would be obtained when these two 1, p. 2-24. factors are considered separately. Consequently, Bilello, M.A. (1961b) Ice thickness observations, a multivariable regression analysis, in which North American Arctic and Subarctic, 1958-59, ATDD and accumulated ISR values were inte­ 1959-60. CRREL Special Report 43, pt. I. grated into the relationship, was conducted. Due Bilello, M.A. (1964a) Method for predicting river and lake ice formation, journal of Applied Meteorology, vol. 3, no. to lack of continuous and/or reliable solar radia­ I , p. 38-44. tion data at the sea ice sites, the test was con­ Bilello, M.A. (1964b) Ice thickness observations, fined to Resolute and Goose Bay. The statistical North American Arctic and Subarctic, 1960-61, results indicated a slight improvement in the 1961-62, CRREL Special Report 43, pt. II. association when the two independent variables Bilello, M.A. (1965) Sea-ice temperature curves for Slidre Fiord, Canada. CRREL Internal Report 332 were combined for Goose Bay (correlation coef­ (unpublished). ficient increased to 0.92) but showed no change Bilello, M.A. (1974) Surface measurements of snow and ice in the final outcome for Resolute. Unfortu­ for correlation with data collected by remote systems. nately, it is difficult to draw useful conclusions Advanced Concepts and Techniques in the Study of from the limited available data. Snow and Ice Resources, ISBN-0-309-02235-5, National Academy of Sciences, Washington, D C. Finally, it should be recognized that wind Bilello, M.A. (1977) Ice decay patterns on a lake, a river and a action at any particular location can be a critical coastal bay in Canada. Proceedings 1977 Annual component in the breakup and ice clearance Meeting of the Canadian Association of Geographers. process. For example, in Sachs Harbour the fast Bilello, M.A. and R E. Bates (1966, 1969, 1971, 1972, 1975) Ice sea ice sheet appears to be occasionally thickness observations, North American Arctic and Subarctic, 1962-63 through 1971-72. CRREL Special affected by winds. Note that in Figure C35 a Report 43, pts. III-VII. dashed line was used to define the decrease in Burbidge, F.G., and J.R. Lauder (1957) A preliminary investiga­ ice thickness in 1959. This extrapolation was tion into break-up and freeze-up conditions in Canada. necessary because on 14 July the observer noted Meteorological Division, Department of Transport, that strong north and northeast winds had Canada, Circular 2939. Department of the Environment, Canada (1959-1974) cleared the harbor of all ice except for a small Monthly record, Meteorological observations in patch near the shore. Canada. Atmospheric Environment Service, Toronto, Obviously, fast sea ice sheets throughout the Canada. coastal regions of the Arctic and Subarctic are Department of Transport, Canada (1959) Maximum winter vulnerable to sudden and fast removal. This ice thicknesses in rivers and lakes in Canada. Meteorological Branch, CIR-3195, ICE-4. rapid breakup can be expected when the proper Department of Transport, Canada (1963) Ice thickness data conditions of wind speed, wind direction, stage for Canadian selected stations, freeze-up 1962 to of deterioration and areas of thin ice or open break-up 1963. Meteorological Branch, CIR-3918, Ice water present themselves. In such cases, II . prediction of the rate of ice decay by thermal Department of Transport, Canada (1964) Ice thickness data for Canadian selected stations, freeze-up 1963 to relationships is nullified, but the methods break-up 1964, Meteorological Branch, CIR 4153, Ice presented in this study may still provide useful 19. information as to when an ice sheet has become Flogue, D.W. (1956) Temperatures of northern North America. substantially weakened and prone to breakup Headquarters Quartermaster Research and Develop­ and movement by tides and/or winds. ment Command, U S. 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35 Kniskern, F.E. and G.J. Potocsky (1965) Frost degree day, soveshchanii po gidrotekhnike, vol. 42, p. 317-324. related ice thickness curves, and harbor freezeup and Poliakova, K.N. (1966) Characteristics of the melting of the breakup dates for selected arctic stations, TR-60, U S. ice cover and the opening of the Middle Lena River. Naval Oceanographic Office, Washington, D C. Soviet Hydrology, Selected papers no. 3, p. 276-292. Kurdykina, A.P. (1970) Peculiar features of ice breakup at the Rogers, J.C. (1978) Meteorological factors affecting inter- estuary and in the lower course of the Yenisey River (in annual variability of summertime ice extenT in the Russian). Leningrad. Arkticheskii i Antarkticheskii Beaufort Sea. Monthly Weather Review, vol. 106, nauchno- issledovatel'skii institut. Trudy, vol. 290, p. American Meteorological Society. 34-55. Roots, E.F. (1971) Shore fast sea ice. National Research Langleben, M.P. (1966) On the factors affecting the rate of Council, Canada, Technical Memorandum No. 101, p.

ablation of sea ice. Canadian journal of Earth Sciences, 8- 20. vol. 3, no. 431. Savchenkova, E.l. (1972) Using an index of atmospheric Lindsay, DC. (1975) Sea ice atlas of arctic Canada, circulation for long range forecasting of river breakup. 1961-1968. Department of Energy, Mines, and CRREL Draft Translation 311, AD 737805. Resources, Publication HO83076. Ottawa, Canada. Shaw, J.B. (1965) Growth and decay of lake ice in the vicinity Liser, I. IA. (1978) Computer calculation of river ice of Schefferville (Knob Lake), Quebec. Arctic, vol. 18, weakening in spring (the layer-by-layer technique). no. 2, p. 123-132. Zapadno-sibirskii regional'nyi nauchno- Short, A.D. and W.J. Wisemore, Jr. (1975) Coastal breakup issledovatel'skii gidrometeorologicheskii institut, in the Alaskan Arctic. Geological Society of America Trudy, vol. 37, p. 37-47. Bulletin, vol. 86(2), p. 199-202. Luk'ianchenko, V.D., I N. Gartsman and D.V. Makarova Shuliakovskii, L.G. (1972) Modelling the river opening (1962) Forecasting spring ice conditions in the Amur process. Leningrad. Gidrometeorologicheskii nauchno- River Basin (in Russian). Vladivostok. issledovatel'skii sentr SSSR, Trudy, vol. 49, p. 3-10. Dal'nevostochnyi nauchno-issledovatel'skii institut po Timchenko, V.M. (1970) Heat flow toward melting ice of the stroitel'stvu. Sbornik nauchnykh rabot, vol. 3, p. Ussuri River, Vladivostok, Dal'nevostochnyi nauchno- 135-145. issledovatel'skii gidrometeorologicheskii institut. MacKay, D.K. (1962) Trends and factors affecting breakup Trudy, vol. 31, p. 158-166. and freeze-up dates in the Nelson River drainage Timchenko, V.M. (1974) Forecasting ice breakup dates for the system, Geographical paper No. 35, Geographical Ussuri River allowing for mechanical and thermal fac­ Branch Department of Mines and Technical Surveys, tors of ice cover deterioration (in Russian). Leningrad. Ottawa, Canada. Gidrometeorologicheskii nauchno-issledovatel'skii Mackay, J.R. (1967) Freeze-up and breakup predictions of tsentr SSSR, Trudy, vol. 117, p, 55-63. the Mackenzie River N.W.T., Canada, Northwestern Untersteiner, N. and G.A. M aykut (1969) Arctic sea ice. University, Department of Geography, Studies in Naval Research Reviews, May 1969, p. 12-23. geography, no. 14, p. 25-66, AD 664686. U S. Naval Oceanographic Office (1965) Report of the Arctic Maakevich, T.N., N.A. Aniskina and Z.A. Efimova (1964) ice observing and forecasting program— 1962, Special Forecasting river ice breakup for the western U S S R. Publication SP-70(62), Forecasting Branch, (Belorussia and Baltic regions). Gosudarstvennyi Oceanographic Prediction Division, Washington, D C. Gidrologicheskii Institut. Trudy, vol. 110, p. 83-144. Veinberg, B.P., V I. Al'tberg, V.E. Arnol'd-Aliab'ev and M.P. Maykut, G.A. (1978) On the heat and mass balance of the Arc­ Golovkov (1958) Ice: Properties, origin and disap­ tic ice pack. Naval Research Reviews, vol. 31(7), p. pearance of ice. T-R-101. Translated for Geophysics 17-35. Research Directorate, US. Air Force Cambridge McFadden, T. and M. Stallion (1975) 1974 Ice breakup on the Research Center, Bedford, Mass., by the American Chena River, CRREL Special Report 241, AD A018352. Meteorological Society. McGinnis, D.F., Jr. and S.R. Schneider (1978) Monitoring river Wake, A. and R.R. Rumer(1979) Effect of surface meltwater ice break-up from space. Photogrammetric Engineering accumulation on the dissipation of lake ice. Water and Remote Sensing, vol. 44, no. 1, p. 57-68. Resources Research, vol. 15, no. 2, p. 430-434. Mellor, M. (1963) Promoting the decay of sea-ice. Arctic, W alker, E.R. (1977) Aspects of oceanography in the vol. 16, no. 2, p. 142. archipelago. Institute of Ocean Sciences, IOS Note-3, Michel, B. (1966) Statement on state of research problems on Patricia Bay, Victoria, B.C. ice formation and break-up in rivers. National Wendler, G., R. Carlson and D. Kane (1974) Break-up Research Council, Canada. Associate Committee on characteristics of the Chena River Watershed, Central Geotechnical Research, Technical memorandum, no. Alaska. Advanced Concepts and Techniques in the 92, p. 194-196. Study of Snow and Ice Resources, ISBN 0-309-02235-5 Murakami, M. (1973) Method of forecasting date of breakup National Academy of Sciences, Washington, DC. of river ice. The Role of Snow and Ice in Hydrology: Williams, G.P. (1971) Predicting the date of lake ice breakup. Proceedings of the Banff Symposia, vol. 2, p. Water Resources Research, vol. 7, no. 2. 1231-1237. Yu, P.M. (1977) Ice dissiapation in Eastern Lake Erie. State Nuttall, j.B. (1970) Observations on break-up of river ice in University of New York at Buffalo, M S. Thesis (un­ North Central Alberta. Canadian Geotechnical Journal, published). vol 7, no. 4, p. 457-463. Pekhovich, A.I. and I.N. Shatalina (1968) Regularities governing the rate of ice melting under the conditions of free convection. Trudy koordinatsionnykh

36 APPENDIX A. ICE THICKNESS MEASUREMENTS AND OTHER RELATED (OR ASSOCIATED) OBSERVATIONS FOR STATIONS IN CANADA AND ALASKA

Table A1. Ice thickness measurements and observations of surface conditions on lakes, rivers and fast sea ice locations in Canada.

ALERT (DUMBELL LAKE), NORTHWEST TERRITORIES Ice thickness Snow depth Date______(cm) (cm) Measurements made on upper Dumbell Lake at distances of 50 to 150 m south of the pumphouse, or approximately 40 m east of the pump­ 1966 house. Jun 3 217 18 3 Approx. 5 cm of water on entire lake surface, pools to Ice thickness Snow depth 18 cm deep. Date (cm) (cm) 10 217 18 10 1 cm of water over entire lake surface, approx. 8 cm of 1959 water along shore. Jun 13 183 Unknown 17 217 13 15 178 Variable 24 Water along shore around entire-lake. Water areas up to 15 Snow cover deteriorating, now soft and wet over much 4.5 m wide in places and from 8 to 30 cm deep. of lake. Top 8 cm of ice cover becoming soft. 25 No further information available. Jul 6 Snow cover on lake has all melted. 1967 13 Numerous small streams fed by melting snow on May 12 211 adjacent hills have formed on the lake. Ice near sur­ 21 203 face very rotten, and wide shore leads observed. 26 196 14 No further information available. 27 No further information available. 1960 1968 May 18 173 28 May 31 203 26 168 53 61 Jun 7 Ice starting to deteriorate. 31 165 61 8 No further information available. Jun 8 153 51 15 Ice conditions unsafe, considerable water on 1969 16 No further information available. Jun 6 206 66 m 6 Surface wet, few cracks, ice conditions becoming unsafe for light vehicles. May 27 183 38 13 203 61 Jun 2 183 25 20 198 9 187 30 20 Ice starting to deteriorate. 19 175 27 Surface water covered, numerous cracks. Ice measure­ 26 Further observations considered unsafe. Lake has 30 cm of water on surface of ice and approx. 46 cm of snow. ment discontinued due to snow melt runoff on ice. Aug 8 Lake clear of ice. 1962 1970 May 26 211 28 Jun 8 Last date ice used by light aircraft. Jun 2 208 20 18 Ice starting to deteriorate. 9 Observation discontinued, ice starting to disintegrate. 20 213 24 Ice deteriorating rapidly. 36 Aug 23 Aug 5 Lake clear of ice. Lake still not clear of ice, 5/10 open water. 1971 1963 May 21 213 36 Jun 7 226 Unknown 28 216 14 Puddles 30 cm deep on ice surface. 46 Jun 4 218 43 22 Ice observations discontinued due to water and slush on 5 ice. No further information available. 1972 1964 May 12 235 Jun 5 231 18 30 19 229 30 7 Ice starting to deteriorate, conditions unsafe for use by 26 231 vehicles. 30 Jun 16 232 12 206 38 23 234 12 8 cm of water over ice. 25 23 19 191 Surface 10 to 15% covered with meltwater. 30 231 19 Top 23 cm of ice is candled. 10 30 Surface 20 to 25% covered with meltwater. 26 Lake surrounded by water, ice estimated to be between Jul 1 No further information available. 122 and 152 cm thick with 30 cm of candled ice. 27 No further information available. 1973 May 18 1965 175 71 25 174 Jun 4 208 20 61 Jun 1 178 43 11 201 15 8 175 53 18 196 10 15 160 36 18 Surface covered with 8 cm water, ice starting to deterio­ 15 6 cm slush beneath snow cover. rate. 29 60 to 120 cm of water on the surface. 25 188 10 Jul 1 Ice along shore line melting. 1974 2 155 3 May 31 201 46 6 Ice along shore line melted out for approx. 4 m around Jun 7 203 61 the lake. 14 206 41 9 Ice along shore line melted out to a distance greater than 21 207 36 6 m in many places. 28 146 3 10 No further information available. 28 Shore leads starting to open, puddles up to 20 m deep in some areas. 37 ALERT (PARR INLET OF DUMBELL BAY), Ice thickness Snow depth NORTHWEST TERRITORIES Date (cm) (cm) 1963 Measurements made on Parr Inlet at distances of approximately 50 to Jun 7 229 Unknown 200 m off the western shore; or near the middle of the adjacent 21 Ice conditions unsafe for use by vehicles. Dumbell Bay. 22 No ice thickness data obtained due to water and slush on ice. Ice thickness Snow depth Jul 20 Ice starting to deteriorate. Date (cm)___ (cm) Aug 29 Parr Inlet still not completely clear of ice, 9/10 open 1959 water. May 15 188 Unknown 1964 30 173 Unknown May 30 224 30 Jun 1 173 25 Jun 5 218 23 8 183 Unknown 7 Ice starting to deteriorate, conditions unsafe for use by 15 183 Variable vehicles. 15 Snow cover deteriorating. Very soft and wet snow over 12 206 large areas of the surface. Runoff from surrounding 12 8 cm of water over ice. hills is melting the surface ice over some areas and 19 198 forming puddles along the shore line. 19 Top 23 cm of ice is candled. 22 170 4 26 Bay surrounded by water. Ice estimated to be 122 to 152 22 Ice surface deteriorating rapidly. Heavy runoff from cm thick with approx. 30 cm of candle ice at surface. adjacent hills. River on east side of Parr Inlet now Jul 12 Less than 1/10 of Parr Inlet open water. open. Pools along tide crack and at mouth of river. 1965 29 165 Trace May 14 213 20 29 Very soft ice in large areas on Parr Inlet. Puddles range 28 213 15 in depth from several meters to a few centimeters. Jun 4 213 15 Jul 2 163 4 Extensive surface flooding, ice starting to deteriorate. 6 Wide shore leads have developed with a polynya off the 11 208 13 mouth of the river on the east side of Parr Inlet. 18 201 10 There is now open water with a few growlers in the 18 8 to 20 cm water along shore. Numerous pools of water narrows between the bay and inlet. on ice surface. 13 117 Jul 2 Crack opened due to south wind. 13 Shore leads and polynya on the inlet have increased 3 slowly in size over the past week. 9 191 15 107 9 Shore lead most of way around bay. 20 Slight increase in the size of shore leads and the polynya 13 Shore lead widened by strong southerly winds. in Parr Inlet. 16 Ice considered unsafe. Aug 10 A strong SW wind results in large areas of open water and 1966 causes the breakup of medium ice floes. May 27 224 10 24 Parr Inlet almost ice free. 27 Runoff water on ice surface. 27 Ice rind covers most of the inlet with frazil ice and ice Jun 3 230 8 sludge rapidly forming in the remainder of open water. 3 Approx. 1 cm water on surface with pools 8 cm deep in 31 A strong westerly wind has caused the breakup of ice in places. Parr Inlet, and by the 31st the inlet is almost ice free. 10 227 5 10 Approx. 1 cm water along edge of bay. 1960 17 229 5 May 18 224 25 17 No water observed on surface or along edge of bay. 26 218 46 24 201 0 31 216 28 24 Numerous puddles on surface 8 to 20 cm deep. Water Jun 8 213 20 around entire edge of bay up to 1.5 m wide in places, 15 213 3 10 to 30 cm deep. 15 Slush and water on surface, cracks in ice surface. 25 No further information available. 24 Ice observations discontinued, surface covered with water, large cracks. 1967 May 12 213 1961 21 213 Jun 2 170 58 26 203 9 165 46 Jun 22 Ice starting to deteriorate, estimated thickness 190 cm. 19 171 36 26 Ice considered unsafe for further measurement. Jul 21 Parr Inlet clear of ice. 1968 1962 May 31 20130 May 26 160 30 Jun 7 Ice starting to deteriorate. Jun 2 152 46 9 Winds and warm temp caused an early and rapid thaw. 1969 Presently 30 to 60 cm of water and slush on the bay. Apr 30 Inlet opening and closing with tidal action, 5 km north 21 Ice starting to deteriorate, estimated thickness 145 cm. of measurement site. Jul 19 Parr Inlet clear of ice. May 30 Ice thickness at center of inlet 213 cm. Ice thickness at inlet narrows 160 cm.

38 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1969 (cont’d) 1962 Jun 6 224 41 May 4 175 23 13 224 15 11 178 25 20 Measurements discontinued due to snow melt runoff on 25 178 23 ice, estimated thickness 210 cm. Jun 1 173 13 Jul 27 Parr Inlet clear of ice, but some new ice; occasionally 8 165 18 observed. 15 152 1970 15 Few cracks in ice. Jun 12 225 23 22 114 18 Ice starting to deteriorate. 22 Numerous cracks in ice. Aug 17 Parr Inlet still 9/10 covered with ice. Jul 6 84 6 Ice breaking up. 1971 13 Ice clearing from bay. May 21 198 28 28 201 38 1963 Jun 4 203 33 May 24 142 20 5 No further information available. 25 No further information available. 1972 1964 Jun 16 239 15 Apr 24 140 30 23 239 8 May 15 135 20 23 Surface 10% covered with melt water. Jul 22 Arctic Bay starting to break up. 30 239 3 1965 30 Surface 30% covered with melt water. Apr 30 159 41 Jul 1 No further information available. May 14 152 15 1973 21 152 15 Jun 1 221 38 28 150 10 8 217 51 Jun 4 142 5 15 10 cm water beneath snow cover at 90 m offshore. 11 140 5 22 221 13 18 135 0 29 209 3 19 Ice conditions unsafe for use by vehicles. 29 Surface of inlet 4/10 covered with puddles. 25 Shore leads have formed. Jul 6 Ice cover starting to deteriorate. 1974 9 Shore leads observed. May 24 202 41 28 Bay clear of ice. 31 203 30 31 Tidal cracks along shoreline. 1966 Jun 7 204 30 Apr 30 165 30 14 207 20 May 21 168 30 21 211 18 Jun 12 Ice conditions unsafe for use by vehicles. 28 146 3 Jul 1 Ice starting to deteriorate, estimated thickness 140 cm. 28 Tidal cracks have opened to form shore leads. Consider- 15 Bay clear of ice. able puddles, some 18 cm deep. 1967 29 No further information available. May 31 Maximum ice thickness estimated to be 147 cm, exact date of occurrence unknown. Jun 15 Ice conditions unsafe for use by vehicles. ARCTIC BAY, NORTHWEST TERRITORIES Jul 26 Bay clear of ice. 1968 Measurements made on Arctic |Bay approximately 800 m SW of sta­ tion. May 31 Maximum ice thickness estimated to be 157 cm, date of occurrence unknown. Jun 12 Ice conditions unsafe. Ice thickness Snow depth 15 Ice starting to deteriorate. Date______(cm)______(cm)______16 No further information available. 1959 I969 Missing May 20 Maximum ice thickness estimated to be 122 cm, date of 1960 occurrence unknown. May 13 135 28 26 Ice conditions unsafe. 21 137 28 30 Ice starting to deteriorate. 28 137 28 Jul 20 Bay temporarily clear of ice, new drift ice appearing. 29 No further information available. Aug 2 Bay clear of ice. 1961 May 19 109 18 26 112 13 Jun 2 112 13 23 84 0 30 69 0 30 Narrow cracks along shore. Jul 1 No further information available.

39 BAKER LAKE, NORTHWEST TERRITORIES Ice thickness Snow depth Date (cm) (cm) Measurements made on Baker Lake approximately 90-180 m south 1964 (cont’d) of the meteorological station. Jun 19 196 0 20 Ice cover deteriorating. Ice thickness Snow depth 26 183 0 Date ______(cm)______(cm) 30 Shore leads up to 30 m. Ice has lifted, no movement 1959 noticeable. Small streams and creeks flowing. May 29 206 13 Jul 1 Thelon River jammed with ice. Jun 5 203 5 3 152 0 12 198 0 3 Thelon River broken up. 19 180 0 7 Leads open to 3/4 km, ice movement with northerly 20 Ice cover unsafe for vehicular traffic. winds. 26 152 0 10 91 0 26 Thelon River breaking up. 17 Ice shifted to north shore, measurement area clear. Jul 3 76 0 21 Lake clear of ice. 10 Ice rotten, unsafe to walk on. 1965 17 West end of lake clear of ice. May 28 227 8 31 Lake clear of ice. Jun 4 224 8 1960 8 Ice cover unsafe for vehicular traffic. Jun 3 191 0 11 213 0 9 Last date ice cover used by light aircraft. 18 192 0 10 185 0 25 165 0 17 150 0 25 Ice cover deteriorating. 18 Thelon River broken up — main block moved to north Jul 2 114 0 shore. 9 Unsafe ice conditions at measurement site 24 89 0 21 Lake clear of ice. 25 North channel moved south, jamming central area and 1966 crushing main block of ice. May 20 229 0 30 Only few floes left. 27 225 0 Jul 12 Lake clear of ice. Jun 3 224 0 1961 10 208 0 Jun 2 236 0 14 Last date ice cover used by light aircraft. 9 229 0 17 187 0 10 Ice cover unsafe for use by aircraft. 24 155 0 16 201 0 24 Ice began to shift. 23 183 0 Jul 23 Lake clear of ice. 24 Ice cover deteriorating rapidly. 1967 30 112 0 May 12 236 Trace Jul 17 Lake clear of ice. 19 234 Trace 1962 26 234 Trace Jun 1 239 3 Jun 2 229 0 8 234 Trace 9 221 0 11 Ice cover unsafe for vehicular traffic. 16 221 0 15 221 0 23 191 0 22 168 0 29 Last day ice cover used by light aircraft. 29 145 0 30 155 0 29 Shore leads around northwest and west end of lake. 30 Narrow band of open water around shoreline, no ice 30 Ice moved to northwest shore of lake. movement. Jul 5 Breakup beginning. Jul 3 Water flowing over ice at mouth of Thelon River. 11 Northern half south bay open. 7 110 0 30 Approximate date lake clear of ice. Aug 1 Lake clear of ice. 1963 1968 May 17 231 Trace May 10 216 0 31 221 Trace 17 213 0 Jun 15 200 (estimated) 0 24 208 0 28 160 0 31 208 0 Jul 4 Ice cover deteriorating rapidly. Jun 7 206 0 5 130 0 7 Ice cover unsafe for vehicular traffic. 12 Measurement area clear of ice. 14 191 0 31 Lake clear of ice. 21 180 0 28 130 0 1964 Jul 2 Ice cover starting to break up. May 29 236 3 28 Lake clear of ice. 29 Water pools on ice. Jun 2 Ice cover unsafe for vehicular traffic. 1969 5 229 Trace May 17 Last day ice cover used by heavy vehicles. 3 12 226 0 23 248 30 244 Trace

40 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1969 (cont'd) 1974 (cont’d) Jun 6 239 Trace Jun 7 203 0 13 234 0 14 Measurements discontinued due to hazardous conditions. 20 226 0 20 Ice breaking away from edge of shore. 27 180 0 BROCHET, MANITOBA 27 Open lead along shoreline. Ice rotting and candling rapidly over entire area. Measurements made on Brochet Bay, which is part of Reindeer Lake, approximately 225 to 300 m from shore SE of the station. 1970 May 8 211 Trace Ice thickness Snow depth * 15 208 Tyace Date (cm) (cm) 22 210 Trace 29 197 0 1959 29 Surface ice melting rapidly. Some runoff of water onto Apr 17 99 43 ice along shore. 24 94 18 Jun 3 Last day ice cover used by heavy vehicles. May 1 94 23 n 191 0 8 84 13 12 170 0 15 84 3 19 137 0 22 79 0 22 Lake ice starting to break up. 29 76 0 Jul 13 Lake clear of ice. Jun 5 66 0 1971 8 Buchanans Lake clear of ice. May 7 227 0 11 Ice in Brochet Bay breaking up and moving. 14 224 0 12 Ice shifting in front of station. 21 227 3 13 Brochet Bay completely free of ice. 28 218 3 19 Some ice in center of Reindeer Lake but breaking up fast. Jun 4 208 3 1960 11 191 0 Apr 30 91 20 18 173 0 May 6 86 13 26 76 0 13 86 Trace Jul 3 38 0 15 Ice conditions unsafe for use by vehicles. 1972 22 74 0 May 26 236 8 22 Ice thoroughly candled. 26 Pools of shallow water on ice runway. 28 61 0 Jun 2 232 5 Jun 3 Ice cover deteriorating rapidly. 9 232 3 9 Brochet Bay clear of ice. 12 Ice sheet lifted overnight due to rising water. 1961 16 221 0 Apr 21 112 41 24 Shore lead open out to 9 m from shore. 28 Ice covered with slush. 29 Ice jam and some water overflow at mouth of Thelon May 5 104 25 River. 5 Ice covered with 23 cm of water, 30 127 0 12 91 10 30 Impossible to cross shore lead, ice thickness estimated. 19 91 0 1973 19 Surface ice candled. May 18 240 Trace 21 Ice conditions unsafe for use by vehicles. 22 Ice melting due to warm water and rain. 26 69 0 25 236 0 26 Ice beginning to move away from shore; 1 to 3 m water 25 Ice lifted due to rising water. around shore line. Ice thoroughly candled. 29 Water along shoreline due to runoff. Ice deteriorating. Jun 1 Linklater Bay clear of ice. Jun 1 204 0 2 Ice began to move. 7 Shore leads 6 to 12 m wide. Thelon River open. 4 Ice breaking up. 8 191 0 5 Brochet Bay clear of ice. 15 152 0 1962 15 Ice sheet becoming soft. May 11 97 15 17 Large open area at mouth of Thelon River. 18 86 5 22 114 0 24 Ice conditions unsafe for use by vehicles. 23 Wind moved ice from shore. 26 79 0 28 Wind moved ice toward shore. 26 Surface candled. Open water along edges of lake. 29 36 0 27 Small bays and narrows open. 1974 Jun 1 81 0 Apr 26 231 3 3 Open water along edges of lake extend outward to 15 m. May 10 230 10 5 Buchanans Lake open. 17 227 3 6 Linklater Bay open. 24 227 0 7 Narrows on Brochet Bay open. 31 217 0 9 Brochet Bay completely clear of ice.

41 Ice thickness Snow depth Ice thickness Snow depth Date (cm) i(cm) Date ______(cm)______(cm) 1963 1972 Apr 13 99 Unknown Apr 14 99 33 27 86 13 21 97 30 May 15 Last day ice cover used by light aircraft. 28 97 8 31 59 0 May 5 97 6 Jun 1 Leads approx. 5 m wide around shore. 12 89 0 2 Iinklater Bay (NE of station) clear of ice. 19 60 0 3 Ice began moving in the bay. 1973 7 Brochet Bay clear of ice. Apr 27 94 25 1964 May 4 86 15 Apr 25 114 25 11 82 0 May 9 Last day ice cover used by light aircraft. 18 47 0 16 74 23 18 Numerous cracks in the ice. 23 Observations discontinued due to unsafe ice conditions. 27 Ice breaking up. Jun 3 Brochet Bay clear of ice. 1974 1965 Apr 19 91 18 Mar 27 117 18 26 84 6 Apr 3 109 31 May 3 81 4 10 107 18 10 76 0 17 114 5 17 74 0 24 114 5 24 64 0 May 1 104 3 31 Measurements discontinued. 8 102 0 10 Last day ice cover used by light aircraft. 15 89 0 CAMBRIDGE BAY, NORTHWEST TERRITORIES 15 Surface candled. 22 86 0 Measurements made in Cambridge Bay approximately 90 m SSE of 27 81 0 townsite dock. Jun 6 Brochet Bay clear of ice . 1966 Ice thickness Snow depth May 7 86 5 Date______(cm) ______(cm) 14 74 8 1959 21 66 3 May 15 170 25 24 Last day ice cover used by light aircraft. 22 165 23 28 46 0 29 168 25 28 Ice conditions becoming unsafe. Jun 5 155 31 Jun 5 Brochet Bay clear of ice. 12 155 25 1967 12 Water beginning to form in pools. May 27 104 0 17 150 3 27 Surface dry and completely candled. 19 Stream and river water overflowing onto ice. Jun 3 81 0 26 145 Trace 3 Open water along shoreline and dark areas observed in ice. Jul 3 137 0 10 64 0 3 Ice lifted, pools of water remain on ice sheet. 18 Brochet Bay clear of ice. Main ice pack visible on Rein­ 10 20 0 deer Lake. 10 Thickness estimated, ice melting rapidly. 1968 17 Few ice floes. May 4 117 3 21 Bay clear of ice. 11 100 0 1960 18 86 0 May 27 236 10 24 Ice unsafe. 5/10 of bay is candled. 27 Snow on ice wet and melting quickly. Jun 4 Bay clear of ice. Jun 3 Considerable water on top of ice. 1969 10 196 3 Apr 18 90 3 10 Water sinking through rotten ice. 25 81 0 17 130 Trace May 2 76 5 17 Shore free of ice. 8 Last day ice cover used by light aircraft. 24 71 0 9 74 . 0 28 Ice moving away from shore. 16 74 0 Jul 9 Cambridge Bay clear of ice. 20 First leads, ice unsafe for traffic. 1961 26 Ice completely out of Brochet Bay. May 26 231 13 19 70 Jun 2 221 3 Omitted. Record incomplete. 9 221 3 9 Snow and ice saturated with water. 1971 16 218 Trace No record.

42 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm) Date (cm) (cm)

1961 (cont’d) 1969 (cont’d) Jun 23 208 Trace Jun 27 165 0 23 Ice starting to rot. Water on ice increasing rapidly. 27 Measurement taken 9 m SSE of pier, large body of open 29 Water along shore, ice conditions unsafe for use by water near original site. vehicles. Jul 17 Remaining ice cover starting to break up. Jul 7 64 0 22 Bay clear of ice. 7 Thickness estimated. Ice unsafe to walk on. Open water 1970 along shore. May 22 224 3 14 Bay almost clear of ice. 28 Last day ice cover being used to transport heavy equip- 20 Cambridge Bay clear of ice. ment. 1962 29 222 Trace Jun 7 193 8 Jul 13 Bay clear of ice. 14 163 Trace 1971 21 130 Trace Incomplete 21 Surface puddled to depth of 45 cm. Ice saturated. 1972 Jul 1 No measurement, ice starting to break up. Jun 2 226 10 1963 9 225 5 Jun 7 211 5 16 213 3 7 Some water visible. 30 183 0 14 201 0 Jul 7 170 0 14 Ice puddled to depths of 1546 cm in places. 8 No further information available. 15 Ice cover no longer being used by vehicles. 1973 21 Ice observations terminated due to unsafe conditions. May 11 246 3 Jul 13 Bay almost clear of ice. 18 245 5 18 Bay completely clear of ice. 25 241 0 1964 25 Snow melting due to warm temperatures. Puddles of Jun 19 213 Trace water near measurement site. 26 185 Trace Jun 1 236 0 Jul 16 Bay completely clear of ice. 8 229 0 1965 8 End of measurements, ice starting to break up. Jun 11 234 3 1974 18 224 0 May 31 213 5 18 Ice cover no longer being used by vehicles. Jun 7 211 5 25 216 0 14 203 0 Jul 17 Bay clear of ice. 14 End of measurements, shore lead too wide to cross. 1966 May 13 198 20 20 188 8 CAPE DORSET, NORTHWEST TERRITORIES Jun 3 188 0 10 157 Trace Measurements made on Cape Dorset Harbour approximately 450 to 750 17 142 0 north of the station. 24 No measurements ; shore lead too wide to cross. Jul 17 Bay clear of ice. Ice thickness Snow depth Date (cm) (cm) 1967 May 19 230 0 1971 26 227 3 May 14 119 36 Jun 2 227 Trace 24 114 30 9 229 Trace 28 114 28 16 227 3 31 109 28 16 Shore lead becoming too wide to cross. Jun 4 114 28 23 216 Trace 11 114 25 30 189 Trace 19 114 3 Jul 1 No further information available. 30 102 0 Jul 1 No further information available. 1968 Jun 7 211 3 1972 14 203 0 May 5 160 15 21 193 0 12 156 30 25 Ice conditions unsafe for use by light aircraft. 19 155 61 28 151 0 26 155 27 29 No further information available. 31 155 27 Jun 2 152 28 1969 9 152 33 Jun 6 226 3 16 152 34 13 216 5 30 147 3 17 Ice cover starting to deteriorate.

43 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1972 (cont’d) 1963 (cont’d) Jul 7 135 5 Jun 5 Ice sheet starting to deteriorate. 8 No further information available. Jul 13 Gulf clear of ice. 1973 1964 May 25 163 13 Jun 12 208 0 Jun 1 160 8 12 Numerous puddles on ice, average depth of pools 18 to 22 135 3 25 cm. 23 No further information available. 19 203 0 1974 28 203 0 May 10 170 38 28 Measurements ended because of wide shore leads, ice 17 168 36 sheet starting to deteriorate. 24 155 30 Aug 13 Date gulf became clear of ice unknown; gulf on this date 31 150 13 is 8/10 open water. Jun 7 137 5 1965 14 132 5 Jun 5 173 13 21 107 3 11 Ice breaking up, strong NE winds. 29 76 1 12 Bay 95% open water. 30 No further information available. 17 Gulf filled with pack ice. 18 No further information available. 1966 CAPE PARRY, NORTHWEST TERRITORIES May 13 201 13 18 Open water 3 km offshore due to strong SSE winds. Measurements made on Amundsen Gulf, 11/2 km west of station, 20 199 10 approximately 150 m offshore. 27 194 8 27 Ice re-formed near shore. Ice thickness Snow depth Jun 3 194 3 Date (cm) (cm) 6 Open water 6 1/2 km offshore. 1960 10 196 0 May 14 180 15 12 Ocean open approximately 3 km offshore. 20 178 15 13 Inlet ice covered. 27 178 13 17 183 0 1961 24 6-9 m open water between shore and ice. Apr 20 185 15 Jul 13 Gulf clear of ice. 27 180 15 1967 May 4 180 15 Measurement site changed, observations now being made 11 178 15 on Gillet Bay of Amundsen Gulf, 2 1/2 km south of 13 Open water observed (in the distance) in surrounding station, approximately 275 m off north shore. areas. Jun 9 204 10 18 178 13 16 199 10 25 175 13 23 185 10 25 Open lead 9 1/2 km north of station. 23 Strong NW winds, ice covers most of gulf. 31 Observations discontinued. Runoff water 25 cm deep at 29 Gulf open 5 km from shore. ocean edge. 30 163 5 Jun 12 Ice sheet deteriorating, estimated ice thickness 160 cm. Jul 14 138 5 Jul 14 Gulf clear of ice. 21 76 3 23 Ice on Amundsen Gulf moved towards shore, ice rotten. 1962 28 First movement of ice seaward. Gulf open 12.9 km from Apr 20 226 28 27 224 20 shore with some broken ice cakes. 28 Large body of open water northwest of station. 31 Ice in Gillet Bay rotten, no sign of ice movement. Aug 1 No information available during August 1967. May 4 203 25 11 198 30 1968 18 191 23 May 24 165 23 25 183 20 31 155 0 25 Extensive open water in Amundsen Gulf. Water on ice 31 Snow extremely wet due to warm temperatures, approxi­ over observation site and surrounding areas. mately 5 cm of water on most areas of ice cover. Jul 11 Gulf clear of ice. Jun 7 140 0 14 119 0 1963 Measurements made on Amundsen Gulf, 11/2 km NNE 21 94 0 of Federal Electric Company building approxi- 25 First breakup of ice on Amundsen Gulf. Ice in Gillet mately 200 to 300 m offshore. Site changed because Bay becoming slushy. whirlpools and fast water observed in summer at pre­ 28 Landfast ice extends 1 1/2-5 km offshore. vious site made area unsafe during periods of thin ice. Jul 5 33 0 May 17 188 13 13 Breakup of Amundsen Gulf. Few growlers left near 24 185 13 shore. 31 188 8 16 Gillet Bay 1/10 covered with slush and winter ice. 31 Lead 1 1/2 km offshore.

44 Ice thickness Snow depth CARTWRIGHT, NEWFOUNDLAND Date (cm) (cm) Measurements made in Cartwright Harbour of Sandwich Bay approxi­ 1969 mately 180-300 m south of the Canadian National Railway dock. May 30 213 5 30 Amundsen Gulf open except for shore ice. Ice thickness Snow depth Jun 6 207 5 Date ______(cm) (cm) 13 211 0 20 199 0 1960 27 170 0 May 6 74 10 Jul 25 Bay clear of ice. 13 71 10 1970 13 10 cm of slush and water on surface. Ice becoming soft. May 22 198 10 20 64 13 29 189 5 20 Snow watery, surface slushy, ice disintegrating rapidly. 29 Open water east to west 3 km from nearest point of north 27 38 0 ' shore. 27 Surface soft and black. Ice starting to move out. 31 Ice cracks in all directions during end of May. 28 Ice moved out of harbor. Jun 5 184 5 1961 12 184 5 Apr 21 94 3 19 171 5 28 86 0 26 140 3 May 5 81 0 Jul 3 107 3 12 66 0 10 84 0 19 Ice unsafe, surface soft. 19 Bay clear of ice. 20 Ice moved out of harbor. 1971 1962 Jun 4 196 15 May 11 107 8 11 173 5 18 97 5 18 152 5 25 81 0 25 112 0 26 No further information available. Jul 2 Unsafe ice conditions. 1963 1972 Missing Jun 2 173 18 1964 17 166 Trace Missing 17 Puddles of water forming on the surface. 23 Note: Ice measurements made on 9 and 23 June appear 1965 to be too thick to be representative and may have been May 7 114 13 made in an area of rafted ice. 14 84 5 30 113 Trace 21 Ice breaking up. 30 Large open cracks in vicinity of measurement site. 22 No further information available. Jul 7 100 0 1966 1973 Apr 2 62 0 May 18 173 43 8 56 0 18 Water penetrating into bottom 30 cm of ice. Open water 16 57 0 along shoreline of local fresh water lake. 22 51 0 26 161 30 29 38 0 26 Water penetrating into bottom 61 cm of ice. 10 cm of May 6 28 0 water on surface of fresh water lake ice. 6 8 cm of crust on top, water between ice and crust layers. Jun 1 150 0 13 Ice unsafe for measurement. 8 148 0 22 Harbor clear of ice. 8 Open leads in Amundsen Gulf, 90 to 275 m offshore. 1967 Western side of Police Point Bay mostly ice free. Apr 28 69 18 17 114 0 28 Open lead 1600 m long and 800 m wide west of station 17 Amundsen Gulf open to the horizon. due to strong tide. 23 110 0 May 5 56 13 23 Narrow shore lead, few melt holes near measurement site. 5 Ice covered with considerable water and slush 13 cm deep. 29 97 0 12 Ice conditions unsafe. Harbor half covered with rough 29 Numerous melt holes near measurement site. ice, open water west of station contains drifting ice Jul 6 Shore lead 23 m wide in Gillet Bay. pans. 9 Amundsen Gulf ice-free. 20 Harbor clear of ice. 1974 1968 May 17 201 5 Apr 5 79 43 31 196 3 13 77 0 Jun 7 191 3 20 67 0 14 171 0 26 67 0 21 141 0 26 23 cm of slush on top of ice. 28 Ice shifted, unable to cross large open crack near shore. May 4 23 0 4 Slush on ice with numerous small open holes.

45 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1968 (cont’d) 1974 (cont’d) May 8 Cartwright Harbour 95% ice-free, drifting ice pans moving May 5 131 18 with the tide. 5 Top 64 cm of ice rotten, lower 67 cm of ice cover solid. 10 Landfast shore ice unsafe to walk on. 6 Channel west of the harbor opened. 13 Harbor clear of ice. 11 122 3 11 Top 61 cm of ice rotten, lower 61 cm of ice cover solid. 1969 17 74 5 Apr 4 83 8 24 61 3 11 77 8 31 61 10 18 79 8 31 Layer of rotten ice approximately 38 cm thick observed 25 74 8 between snow and ice layers on 17, 24 and 31 May. 25 Large open leads and channels in surrounding areas. Jun 7 61 8 May 2 79 3 8 2/10 of harbor ice gone. 9 69 8 11 Open water around dock and expanding toward the 17 36 0 measurement site. 17 25 cm of slush on surface and numerous shore line 14 One large pan of ice left. cracks. Harbor free of ice. 25 Ice in Cartwright Harbour broken up and moved out due 16 to strong south wind. Sandwich Bay is 80% ice free, some drifting ice floes. CHESTERFIELD INLET, NORTHWEST TERRITORIES 1970 Incomplete Measurements made beyond tidal flats on Spurrel Inlet of Hudson Bay, 1971 approximately 300 to 800 m east of the station. Apr 2 Ice cover between Cartwright and Earl Island began to open. Ice thickness Snow depth 3 69 84 Date (cm) (cm) 9 61 91 16 71 71 1960 May 20 155 10 23 122 5 20 Soft snow on surface. 23 Major increase in ice thickness apparently due to forma­ 8 tion of snow-ice because of sudden decrease in depth 29 152 Inland lakes starting to break up. of the snow cover. 29 Jun 3 147 3 30 89 33 3 Ice unsafe for runway or roadway use due to water 30 Open water between Earl Island and Cartwright. around shore line. May 7 61 53 127 0 14 64 20 10 17 112 0 21 58 0 Jul 6 Considerable amount of ice remains in Spurrel Inlet, 28 Ice conditions unsafe. approx. 4/10 open water observed. 1972 1961 Apr 22 97 13 May 19 188 25 28 Ice solid. Air temperatures rarely went above freezing 26 185 20 during month. 26 NW winds broke up the ice. Open water approx. 1 1/2 km May 5 91 5 offshore extends as far as visible. 14 91 20 Jun 2 175 10 14 New snowfall observed. 9 145 8 20 91 0 9 Water and slush on surface. 26 76 0 16 137 0 Jun 3 46 0 Water covered surface. Harbor ice broke up into pan ice and drifted out into 16 23 132 0 channel. 30 124 0 1973 30 Ice extends approx. 400 m offshore and becoming unsafe. May 152 5 Jul 4 Inlet temporarily clear of ice, new ice formed and drift ice Top 25 cm of ice cover not solid, apparently top layers later reappeared. consist of snow-ice which had formed during April. Ice thickness on 31 Mar was 122 cm and snow depth 1962 0 58 cm. Water observed underneath top 25 cm of ice. Jun 15 160 22 150 0 12 145 0 29 114 0 21 91 0 Jul 2 Ice conditions unsafe for traffic. 21 Ice free from shoreline and rises during high tide. Numer­ ous cracks and melt holes in ice, ice considered unsafe. 13 Considerable ice deterioration. 25 Inlet clear of ice. 1974 Apr 19 61 30 1963 Jun 7 211 Unknown 19 30 cm of slush between snow and ice layers. 14 Warm air temperature has puddled ice to depths of 3-8 cm. 26 71 36 175 0 26 56 cm of slush between snow and ice layers. 21

46 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1963 (cont’d) 1970 Jun 21 Few larger cracks have appeared at the edge of tidal flats. May 17 169 3 28 147 0 28 Ice conditions becoming unsafe for vehicular traffic. Jul 5 117 0 29 163 0 8 Ice broke up and temporarily went out of Spurrel Inlet. Jun 2 Ice cover starting to deteriorate. 10 Ice moving in and out of Spurrel Inlet with tidal action 5 160 0 and winds. 15 145 (estimated) 13 Inlet became clear of ice at approximately this time. Jul 2 Inlet clear of ice. 1964 1971 May 29 208 0 May 28 178 0 31 Numerous ice hummocks around shore during May. Jun 4 176 0 Jun 26 168 0 11 166 0 26 Landfast ice edge approx. 2.5 km from shore. Some 18 142 0 water on ice. 25 124 0 Jul 2 132 0 26 No further information available. 2 Ice broke up outside Spurrel Inlet. 1972 10 117 0 Jun 16 196 8 10 Numerous chunks of ice along shore,, numerous puddles 16 Ice deteriorating. of water on ice. 23 193 0 14 Ice broken away from shore and drifting in and out of 30 168 0 Spurrel Inlet. Jul 7 130 0 1965 8 No further information available. May 21 191 3 1973 28 188 0 May 11 206 3 Jun 4 183 0 11 First measurement since 8 Apr because of unserviceable 11 183 0 equipment. Ice thickness on 8 Apr was 178 to 193 cm. 18 150 0 Maximum ice may have occurred earlier than 11 May 25 130 0 and perhaps was slightly more than 206 cm. Jul 2 114 0 19 202 3 7 Ice broken up beyond tidal flats. Some brash ice and 25 197 0 floes on shore. Jun 1 194 0 8 Tidal flats clear of ice. 6 Large portions of ice cover breaking off, ice edge now 13 Spurrel Inlet clear of ice. about 1.2 km from measurement site. 1966 8 185 5 May 6 168 0 8 Melt holes all around measurement site. 13 165 0 15 Ice unsafe, numerous large cracks and melt holes. 20 152 0 1974 27 152 0 May 10 Three ice thickness observations were made, measurements Jun 4 142 0 varied from 198 to 211 cm. 10 137 0 17 206 8 17 102 0 24 206 3 24 79 0 31 201 3 30 Ice break-up, Inlet covered with 60 to 70% open pack ice. Jun 7 198 0 Jul 11 Inlet clear of ice. 7 Spurrel Inlet is 85% covered with ice. 1967 14 173 0 Jun 3 202 15 15 Large lead about 11 km south of inlet. 10 201 5 21 157 0 15 Ice conditions becoming unsafe for vehicular traffic. 29 Ice unsafe, wind moved main ice pan far from shore. 16 191 0 30 North wind moved main ice pan half-way out of the inlet. 22 Ice across mouth of Spurrel Inlet began to break up. About 20% open water and considerable pack ice visi­ 23 Wind and tide moved ice several miles offshore. Large ble. amounts of floe ice in bay. Ice piling on tidal flats. Jul 12 Inlet clear of ice. 1968 CHURCHILL, MANITOBA May 17 160 30 Jun 1 152 Unknown Measurements made near mouth of the Churchill River approximately 8 152 Unknown 125 to 175 m off the station wharf. 15 150 Unknown 22 147 Unknown Ice thickness Snow depth Jul 10 Ice cover deteriorating rapidly. Date______(cm)______(cm)______18 Inlet clear of ice. 1960 1969 Apr 11 152 May 31 179 8 25 150 Jun 14 Ice cover starting to deteriorate. May 26 Ice conditions unsafe for vehicular traffic. 15 Last day ice sheet used by light aircraft. Jun 10 River free of ice. Jul 13 Inlet clear of ice.

47 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1961 1971 Apr 17 170 41 May 14 180 May 24 Ice conditions unsafe for vehicular traffic. 21 175 Jun 12 Ice cover breaking up. 28 170 13 River free of ice. Jun 4 163 160 1962 11 Incomplete 12 Ice starting to move. 13 No further information available. 1963 May 17 Water observed on ice. 1972 196 27 Ice conditions unsafe for vehicular traffic. Apr 21 31 150 10 21 River ice free of snow during most of winter. Jun 6 Ice cover deteriorating rapidly. 28 191 13 River freë of ice. May 5 193 12 191 1964 13 No further information available. May 1 145 30 8 140 Unknown 1973 0 15 135 Unknown Apr 6 173 173 9 22 132 Unknown 13 9 29 122 5 27 173 Jun 5 122 28 No further information available. 12 Ice conditions unsafe for vehicular traffic. 14 Ice cover deteriorating rapidly. CLYDE RIVER, NORTHWEST TERRITORIES 20 River free of ice.

1965 Measurements made on Patricia Bay approximately 140 to 360 m west Apr 30 River ice flooded and refrozen. of the station buildings. May 10 180 0 14 178 0 Ice thickness Snow depth 21 178 23 Date (cm) (cm) 28 178 3 Jun 3 170 0 1960 17 River free of ice. Jun 3 137 56 38 1966 11 160 15 Apr 15 168 46 17 170 22 157 46 17 Ice between 3 and 17 June increased in thickness due to refreezing of melting snow and water runoff. May 2 160 36 8 2 Surface lightly rafted. 24 160 6 163 33 24 Numerous cracks near shore. 6 Surface moderately rafted. 25 No further information available. 13 160 25 1961 Jun 1 Ice conditions unsafe for vehicular traffic. May 12 147 38 3 124 0 19 140 41 10 Ice moving out into bay. 26 142 51 20 Approximate date river becomes free of ice. Jun 2 145 56 56 1967 9 137 Meltwater from surrounding land covers ice surface to a May 12 165 25 14 Jun 2 147 depth of 25 cm. 25 2 Ice conditions Unsafe for vehicular traffic. 16 137 9 Ice cover completely breaking up. 16 Snow cover slushy. 11 River free of ice. 20 Melt water all drained away. 23 140 3 1968 30 112 0 Missing Jul 7 71 0 1969 10 Small area in northeast corner of bay broken up. May 16 178 5 14 800 X 1600 m area including measuring site broken up. 23 175 21 1 /3 of bay at north end breaking up gradually. 30 5 to 8 cm of water observed on ice surface. 22 Entire bay broken up, some ice still in bay. 15 Jun 6 168 1962 5 13 163 May 4 163 41 17 145 11 157 48 Last date ice cover used for light traffic. 18 18 157 48 20 Ice broken up. 25 155 51 24 River free of ice. 25 Ice along shoreline rough due to tides and winds. 1970 Jun 1 155 53 Incomplete 8 157 56

48 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

962 (cont’d) 1966 (cont’d) Jun 15 160 41 Jul 16 107 0 22 163 15 16 Water on surface increases during high tide. Shore lead 22 Shore cracks due to tides. or polynya at north end of bay increasing in size. 29 155 15 Ice disintegrating along shore with some rafting due 29 Snow cover slushy, surface puddled. to strong winds. Jul 6 145 0 17 Some open water at NW end of bay caused by influx of 7 Ice conditions unsafe for traffic. creek water. 13 119 0 23 61 0 20 89 0 30 North part of bay open with ice floes. Ice remains along 22 Ice cover deteriorating rapidly. east shoreline. 31 Patricia Bay is clear of ice. Aug 14 Bay clear of ice. 963 1967 Jun 21 165 20 Jun 24 157 5 21 Local freshwater lakes unsafe for dog sled travel. Jul 2 140 3 29 155 8 8 142 0 29 Local lakes open. 15 97 0 Jul 5 150 3 22 69 0 12 132 3 Lead from shore to a polynya at head of bay formed. 12 Open water where river enters the bay. Aug Breakup occurred, but brash ice carried into bay by in­ 19 112 0 coming tidal action. 24 Breakup, 1/3 of bay clear of ice. Southern half of bay 1968 beginning to break up. Jun 28 170 13 31 Half the bay clear of ice, remaining half contains broken Jul 5 160 Unknown ice. 12 145 3 1964 20 Ice conditions unsafe for use by aircraft. Jun 12 152 51 26 105 0 15 Runoff water on ice, 5 to 15 cm deep, becoming slushy. 26 River water flowed into north end of Patricia Bay and 18 Creek began flowing. opened an area 400 to 800 m in width. 19 147 0 27 No further information available. 20 cm of snow and 13 cm of slush over ice. 19 1969 Freshwater lakes covered with water. Many tidal cracks 20 May 9 142 30 along shoreline. Last date ice cover used for light 16 135 51 traffic. 23 137 46 26 140 0 30 131 51 26 8 cm snow and 15 cm slush over the ice. 30 10 to 13 cm of water on top of ice underneath snow cover. Jul 10 Ice cover starting to deteriorate. 31 Last date ice cover used for traffic by heavy equipment. 25 Bay is free of ice. Jun 6 133 48 1965 20 133 43 Jun 11 157 28 27 140 28 18 152 15 27 Wide cracks have broken through the barrier ice on the 25 142 3 NW side of Patricia Bay. 30 Snow melting on bay surface since 13 Jun. Up to 15 cm 30 Ice thickness variable during June due to formation and of water over ice. decay of snow-ice layers. Jul 2 127 3 Aug Bay clear of ice. 10 102 0 1970 .10 Shore polynya 400 m square formed at head of bay. Jun 19 157 8 16 94 0 26 140 10 23 64 0 Jul 3 105 3 23 Surface puddled and candled. 4 No further information available. 30 2 1/2 km open area at head of bay contains ice cakes, brash ice and small ice floes. Shore lead formed. 1971 Aug 4 Ice moved out of bay. May 8 137 41 14 135 61 1966 21 133 64 Jun 4 142 53 28 130 64 11 137 38 Jun 11 127 53 11 Surface extremely soft and slushy. 20 123 8 19 133 30 25 97 0 26 126 23 26 No further information available. 26 Creek at station site open and water flowing into bay. Jul 2 118 13 1972 3 Many puddles forming on ice, considerable slush and May 19 130 79 water on ice surface. 26 127 58 109 5 Jun 2 122 74 Several melt holes, ice appears honeycombed in many 9 118 58 places. 18 118 66

49 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1972 (cont’d) 1962 Jun 23 123 64 May 18 203 20 23 Unusually deep snow cover and the differences in distri- 25 206 15 bution may account for variations in ice thickness 31 206 10 during May and June. 31 Overflow from up river covering river ice. 30 140 33 Jun 15 River clear of ice. 30 Increase in ice thickness may have been caused by 1963 formation of snow-ice. May 7 198 5 Jul 7 132 30 7 8 to 48 cm of water along shore. 14 124 5 17 152 21 110 17 Ice partly candled, remainder deteriorating near shore. 28 94 Water 61 cm deep on ice. Aug 4 83 Jun 10 Ice conditions unsafe for use by vehicles. 5 No further information available. 11 Ice deteriorating rapidly. 1973 18 River clear of ice. Jun 9 147 89 1964 15 155 64 Jun 5 158 Trace 22 185 43 12 147 Trace 22 It is possible that the increase in ice thickness was caused 18 Breakup, but some ice still observed in harbor. by the formation of snow-ice. 20 Coppermine River free of ice. 29 156 43 30 Some ice visible approx. 4 km from shore. Jul 7 143 0 13 122 0 1965 May 28 165 18 1974 Jun 15 Surface runoff since 1 Jun, water draining through candled Jun 8 146 53 ice. 14 137 41 16 Water moving along shore for first 15m into river. 23 152 0 22 River break up commenced. 23 It is possible that the increase in ice thickness was caused 23 Breakup in harbor between sandbar and river complete, by the formation of snow-ice. river free of ice. 29 123 0 Jul 7 Open water outward to 8 km. 29 Numerous leads have formed. Measurement site covered with 8 cm of water. 1966 Apr 8 194 20 29 193 18 COPPERMINE, NORTHWEST TERRITORIES May 6 191 15 13 191 5 Measurements made in Coppermine River approximately 90 m out from 13 Water from land runoff and from upstream where river is the Department of Transport dock. partially broken up overflowing on river and harbor ice and shorelines. Ice thickness Snow depth 20 180 5 Date (cm) (cm) 21 Wide opening between tidal crack and shore ice. 24 Ice badly candled at measuring site. 1959 27 152 0 Apr 17 152 46 Jun 3 127 Trace 24 152 38 3 Shore lead approx. 45 m wide. May 8 145 31 10 102 0 22 145 25 11 Lead widening to 0.8 km along shore, open pack ice. 29 145 20 23 River and harbor broke up and ice moved out to west and Jun 3 158 13 north. Open water out to 8 km. 3 Numerous deep cracks on ice. 1967 9 Ice conditions unsafe for use by vehicles. Measurement site relocated. Observations now made on 22 Ice deteriorating rapidly. Coronation Gulf near mouth of Coppermine River 30 River clear of ice. approximately 90 to 140 m north of the Ministry of 1960 Transport dock. May 20 168 20 May 20 203 3 Jun 1 Ice conditions unsafe for use by vehicles. 27 203 5 14 Ice deteriorating rapidly. Jun 2 193 5 16 River clear of ice. 9 183 5 1961 14 Ice starting to deteriorate. Apr 30 201 5 16 137 3 May 25 Ice conditions unsafe for use by vehicles. 16 Open area from water runoff extended 45 m from shore. Jun 2 191 3 20 Shore lead now 75 m wide and 1.6 km long. 9 178 23 51 9 Numerous deep cracks, last measurement. 23 Thickness estimated, unsafe ice due to shore lead. 12 Ice deteriorating rapidly. 24 Brash ice moving continually; sandbar occasionally clear 14 River clear of ice. of ice. Lead about 275 m wide, 800 m long.

50 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm) Date (cm)______(cm) 1967 (cont’d) 1959 (cont’d) Jun 30 River ice breaking up. Jun 19 173 5 Jul 1 Mouth of Coppermine River free of ice. 19 3 cm of water covering ice. 1968 26 147 0 May 24 218 8 26 Tidal cracks widening at the top, ice becoming unsafe 28 3 to 5 cm of slush or water on ice within 90 to 140 m for use by vehicles. from shore. Ice surface normal further out. Jul 3 142 O' 31 142 0 10 109 Jun 7 117 0 10 Cracks 96 cm wide, ice soft and full of holes. 8 Shore lead formed. Open water along shore and at the river mouth. 12 Candled ice, conditions unsafe. 21 Bay clear of ice. 16 Lead gradually widened to 65 m, ice floes started 1960 moving. May 13 168 23 26 Mouth of Coppermine River free of ice. 20 168 20 1969 27 173 15 Apr 4 178 20 27 Few narrow tidal cracks along shore line. 11 163 20 Jun 3 180 0 May 2 168 15 3 8 cm of slush and water on ice. 9 Surface soft and rough, numerous cracks. 10 152 0 16 165 13 10 Ice conditions unsafe for use by vehicles. 23 165 15 17 112 0 30 174 13 24 Ice cover deteriorating rapidly. 30 Surface hard and rough, numerous cracks. Jul 4 Bay clear of ice. Jun 11 Last day ice cover used by light aircraft. 1961 30 Mouth of Coppermine River free of ice. May 26 173 33 1970 26 Patches of open water approx. 24 to 32 km from shore. May 9 202 3 Jun 10 15 cm of slush on the ice. Inland rivers began to break 15 196 3 up, ice becoming unsafe for use by vehicles. 22 198 3 16 173 28 Last day ice cover used by light aircraft. 16 Surface slushy, few cracks. 29 Ice inaccessible due to water overflow. 23 142 Mouth of Coppermine River free of ice. 23 Two layers of ice, top 61 cm soft and easy to drill through, Jun 12 30 Ice thickness approx. 46 to 76 cm. Surface slushy, open 1971 water along shore, ice cover breaking up. Apr 11 211 25 Jul 10 Open water extends approx. 800 m from shore, and again 18 206 25 approx. 8 km out. 25 206 20 12 Bay clear of ice, escept for a few scattered pieces. May 1 203 13 8 206 15 1962 15 213 13 May 11 157 20 22 170 8 Jun 1 163 25 23 No further information available. 8 160 15 15 147 0 1972 15 Snow cover patchy, numerous cracks, 10 to 15 cm of May 21 208 25 water over the ice. 28 193 25 20 Ice conditions unsafe for use by vehicles. Jun 4 191 23 22 137 0 1973 Omitted - record incomplete 22 Numerous cracks. Ice 75% water-covered. 1974 30 Open water visible. May 10 160 48 Jul 5 Channels of open water across the bay and also along the 17 163 25) shoreline. 25 146 5 11 Bay clear of ice. 27 Water overflowed onto ice, measurements discontinued. 1963 Apr 27 178 38 May 4 Ice wet and soft beneath top 60 cm. CORAL HARBOUR, NORTHWEST TERRITORIES 25 149 43 25 Ice surface soft during May. Measurements made on Munn Bay (formerly South Bay) approximately Jun 21 Breakup of local creeks and rivers. Ice covered by 20 cm 800 to 1600 m south (occasionally SW) of Snafu Beacon (Snafu Point). of water and slush at measurement site. 22 142 Ice thickness Snow depth Jul 6 112 Date (cm)______(cm)______6 Ice soft and porous, conditions unsafe for vehicular traffic. 13 67 1959 20 62 Jun 12 188.0 5 20 Ice breakup around shoreline. 12 Snow cover slushy. 23 Lead 30 m wide has formed, remaining ice deteriorating rapidly.

51 Ice thickness Snow depth Ice thickness Snow depth Date______(cm) ______(cm) Date (cm) (cm)

1963 (cont’d) 1968 Jul 25 Breakup complete, bay clear of ice. May 15 First day of above-freezing air temperatures 1964 31 177 46 Apr 25 183 61 31 5 cm of water under the first 10 cm of ice. 25 Considerable snowfall during week. Jun 2 Ice conditions unsafe for use by vehicles. May 30 169 36 7 No measurement due to large amounts of meltwater 30 Snow crust fairly soft. on ice. Jun 13 8 to 10 cm of water and slush on ice from runoff. Creeks Jul 8 Ice cover deteriorating rapidly. and lakes broke up earlier in week. 12 Bay clear of ice. 20 Substantial runoff, cracks increasing in size at shore, 1969 surface porous. Jun 13 155 30 27 135 Trace 13 Due to water on the ice, no further observations. Water 27 Some holes present, no sign of open water on horizon. from rivers and creeks flowing onto the surface of ice. Jul 4 Runoff water practically negligible, holes increasing in Slush covers most of ice, last day ice cover being size, no open water, surface porous. used by light vehicles. 11 83 0 15 Unknown Trace 11 Many large holes around measuring site, no movement 25 Ice cover starting to deteriorate. of ice. Jul 17 Bay clear of ice. 18 Large, wide leads along shoreline. Floe edge 5-6 km away extends around shoreline of bay. Main body 1970 of ice appears to have some movement. May 30 Snow cover on the bay melting and very soft and wet. 21 Bay clear of ice. Jun 8 159 0 16 145 0 1965 17 Last day ice cover being used by light vehicles. May 8 145 36 20 144 0 16 140 46 Jul 8 Bay clear of ice. 29 140 41 Jun 5 142 5 1971 5 Surface layers consist of snow, snow and water, and ice Jun 4 166 18 with water. 11 160 8 12 137 3 18 165 5 12 Definite deterioration of ice started, cracks and deep 25 117 0 holes close to shoreline. Surface of ice becoming Jul 2 76 0 porous and spongy. 3 No further information available. 19 132 3 1972 19 Surface 25% water-covered, numerous cracks. May 19 193 25 20 Ice conditions unsafe for use by vehicles. 19 Measurement made at a slightly different location due 26 102 0 to a white-out. 26 Small holes and water pools on surface. Jun 2 191 20 Jul 3 Considerable breakup of ice near shore, conditions unsafe 9 178 15 for travel on foot. 16 178 10 5 Ice moving in and out with the tide, at low tide the ice 23 188 3 was approx. 900 m from shore. 23 About 1/10 of ice surface is covered with puddles of 6 Definite indications of impending breakup. water. 7 Bay clear of ice, except for a few scattered pieces. 30 183 0 1966 30 About 6/10 of ice surface is covered with puddles of Jun 4 141 15 water. 4 Ice becoming very soft, snow cover mixed with water Jul 7 142 0 due to thawing. 14 123 0 11 138 0 15 No further information available. 18 136 10 1973 20 Ice conditions unsafe for use by vehicles. May 25 192 30 26 80 5 Jun 1 193 18 26 Ice thickness diminishing very rapidly. Snow meltwater 8 Ice measurements ended, water covers most of ice on draining into cracks. bay. Jul 1 Lead approx. 400 m wide extends from open bay to 22 Water over ice approx. 30 cm deep. within 800 m offshore. 29 Water over ice decreased, but ice conditions unsafe. 3 62 0 1974 5 Measurements terminated, ice moving offshore with the May 31 175 8 (slush) tide. 31 Surface 50% covered with pools of water. Cracks 13 Bay clear of ice. 10-25 cm wide also filled with water. 1967 Jun 7 178 15 (slush) Jun 9 199 28 7 Surface 75% covered with pools of water. Open 17 196 15 water at river mouths. 24 159 14 157 0 Jul 15 Ice cover deteriorating rapidly. 21 107 0 28 Bay clear of ice. 28 Wide shore lead, 75% of remaining ice field water covered. Edges of ice cakes estimated to be 46 cm thick, ice conditions unsafe.

52 CREE LAKE, SASKATCHEWAN Ice thickness Snow depth Date (cm) (cm) Measurements made on Cable Bay of Cree Lake approximately 100 to 250 m from the station dock. 1959 (cont’d) Jun 12 Lake candled completely. Ice thickness Snow depth 17 Ice cover unsafe for vehicular traffic. Date (cm) (cm) 19 99 0 26 Ice measurement approximately 30 cm to 45 cm. Open 1971 water extends 30 m to 60 m from shoreline. Numer­ Apr 2 84 36 ous holes and ice bulging, ice conditions unsafe. 9 84 18 Jul 8 Lake free of ice. 16 84 10 1960 23 79 0 Apr 22 198 36 30 67 0 29 196 38 May 7 61 0 May 6 191 8 No further information available. 38 13 175 23 1972 13 25 cm of slush on surface. Apr 21 81 30 20 155 0 28 IS 8 27 145 0 28 3 to 18 cm of water on ice surface. Jun 3 25 cm of water to 12 m out from shore. May 5 64 7 Ice cover unsafe for vehicular traffic. 5 Some open water near shore, 3 m wide in places. Slush 10 104 0 observed on ice that is near shore. 10 Open water out to 12 m from shore. Ice thoroughly 12 Ice unsafe for measurement, no further information candled. available. 17 89 0 1973 24 58 0 Apr 6 79 23 24 Open water out to 30 m from shore. Boat used to get on 13 86 3 ice on 10, 17 and 24 Jun. 13 Some slush which had formed on ice is now frozen. 26 Ice deteriorating rapidly. 20 81 0 Jul 5 Lake free of ice. 20 Some melting observed along shoreline. 1961 27 77 3 Apr 28 168 41 May 4 74 0 May 5 165 33 11 Ice very rotten and honeycombed, conditions unsafe. 12 168 36 12 No further information available. 19 170 28 1974 26 160 18 Mar 29 81 30 26 Approx. 13 cm of water under the snow. Apr 5 76 36 30 Ice began candling. 12 76 23 Jun 1 A 61-cm-wide lead extends completely across the lake. 19 66 Trace Ponds and inlets free of ice. 19 8 to 13 cm of water and slush on surface of ice. 2 Pew open holes. Surface temp. 32.39P, bottom of lake 26 51 0 33.4°P. Depth of lake at measurement site estimated May 3 61 Trace 3 m. 10 41 0 9 124 0 11 Ice considered unsafe. 16 Surface candled. Water approx. 12 m in width around 20 Numerous leads have formed. lake. Ice unsafe for vehicular traffic. 28 Lake free of ice. 24 Ice starting to break up. Jul 1 Lake completely clear of ice. 1962 ENNADAI LAKE, NORTHWEST TERRITORIES May 27 130 30 Jun 1 122 30 Measurements made on Ennadai Lake, west of the station, approxi­ 8 119 0 mately 90 m offshore. 12 Ice cover unsafe for vehicular traffic. 15 91 0 Ice thickness Snow depth 22 61 0 Date (cm) (cm) 27 46 0 30 Ice cover deteriorating rapidly. 1959 Jul 8 Lake free of ice. May 8 183 20 1963 15 180 15 May 10 193 15 22 178 13 17 Ice covered with 20 to 31 cm of water. 29 173 8 31 171 1 31 Considerable snow melted off ice surface during month. Jun 3 Shore, ice free. Ice decaying on surface. 7 132 0 Jun 5 173 3 10 Ponds and inlets open, ice cover no longer being used to 5 Rain and warm temp, completely removed snow from transport heavy equipment. lake. Local rivers flowing. 14 89 0 12 135 0 16 Increasing winds, widened shore leads 9 m.

53 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date______(cm)______(cm)

1963 (cont’d) 1968 (cont’d) Jun 21 61 0 Jun 1 142 0 25 Main ice started to shift. 3 First sign of shore lead on south side of bay. Ice candled. 28 30 0 7 135 0 Jul 1 Northeast arm of lake clear of ice. 8 Large lead observed. 3 Lake completely clear of ice. Winds very strong and 14 124 variable last 6 days. 15 Ice conditions unsafe for vehicular traffic. 21 99 1964 22 Ice badly candled. May 1 169 13 30 Large cracks across lake, ice extremely rotten. Jun 5 137 0 Jul 9 Lake free of ice. 8 Lead along shore. 15 Ice cover unsafe for vehicular traffic. 1969 24 Crack extends from point to small islands across bay. May 10 Last day ice cover used to transport heavy equipment. 26 53 0 30 190 5 27 Two cracks to the islands. Ice in the bay completely 30 Snow on shore melting, water puddles on ice during free from shore, and floating. daytime. 30 Lead along shore from 3 to 45 m in width. Jun 5 Water on ice melted small holes, water seeping through ice. Jul 9 Lake free of ice. 6 177 3 15 178 3 1965 20 165 May 21 168 8 27 152 28 160 5 27 Surface candled to about 30 cm in depth. Jun 2 Lead around shore. Jul 21 Lake free of ice. 4 130 Trace 9 Ice cover unsafe for vehicular traffic. 1970 11 99 Trace May 1 145 25 11 Surface candled, few cracks. 8 145 20 18 38 0 22 122 15 18 Crack extends from shore to small islands across bay. 28 Last day ice cover used to transport heavy equipment. 19 Ice in bay completely free from shore and floating. Jun 16 Ice cover deteriorating rapidly. 28 Lake free of ice. 25 Lake free of ice. 1966 1971 May 10 140 30 Apr 23 193 20 135 8 30 189 27 135 5 May 7 184 27 Ice very soft, in places to a depth of at least 15 cm. 14 174 Water on the ice close to shore. 21 170 Jun 3 117 0 28 142 10 89 0 Jun 4 105 11 Ice cover unsafe for vehicular traffic. 11 91 13 First breaks occurred on lake. 1972 14 Ice movement on lake. Apr 21 196 13 15 Ice cakes massed together at end of lake due to wind. 28 191 5 All smaller bays and lakes ice free. May 5 191 10 28 Lake free of ice. 12 193 1967 19 174 May 19 216 20 26 160 19 A layer of water covers ice, varying from 3 to 8 cm. Jun 2 133 26 207 15 9 121 Jun 2 201 Trace 16 109 9 194 Trace 23 91 14 Last date ice cover used by light aircraft. Ice thicknesses during June were estimated. 16 171 0 1973 19 Shore lead developed near station. 23 141 0 May 4 165 8 26 First ice movement occurred. Ice rotten in places and 11 152 5 generally candled to a depth of 15 to 30 cm. 11 5 cm of crystalline ice on surface, ice cover soft. 29 Several large cracks in ice between station and island. 18 147 3 30 90 0 25 103 0 Jul 11 High winds cleared a portion of the bay of ice. 31 Open area 2 to 15 m wide all along shoreline. Small open 17 Some ice remained south of station until high winds and holes in some areas on lake. Ice sheet not broken but warmer temperatures resulted in complete melting. undulates with wave action. 1968 1974 May 17 151 48 May 2 180 15 24 142 0 10 176 3 28 Few holes in ice. 17 165 1

54 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm) Date (cm) (cm)

1974 (cont’d) 1963 (cont’d) May 24 142 0 Jul 26 119 0 31 102 0 26 Ice in rotten state, with numerous holes. 31 Open water 61 to 91 cm wide along shoreline, lead 1964 about 18m long formed north of station. Ice Jun 5 243 3 sheet starting to candle and rot. 5 Water on ice along shore. Jun 7 61 0 15 41 0 1965 21 25 0 Jun 4 215 46 (slush) 21 Measurements on 15 and 21 June estimated. 10 Ice conditions unsafe for vehicular traffic. 25 Strong SW winds breaking up remainder of ice. 11 216 10 (frozen slush) 26 Breakup complete, lake free of ice. 18 212 3 25 208 3 25 Shore lead approx. 30 m wide. Water on surface of ice. EUREKA, NORTHWEST TERRITORIES Jul 2 Water holes forming on surface. 9 124 0 Measurements made on Slidre Fiord, south of the station, approxi- 16 97 0 mately 45 to 275 m offshore. 23 74 0 23 Surface broken up, numerous cracks. 1959 26 Breakup. Some ice still moving around Fiord. May 1 201 20 1966 17 198 33 Jun 10 258 0 31 201 31 18 259 0 Jun 10 Ice conditions unsafe for vehicular traffic. 24 227 0 16 Unable to continue ice measurements because runoff Jul 1 183 0 water covered ice measurement area. 8 155 0 1960 15 122 0 May 8 190 28 15 Fiord 2/10 open water 15 183 33 22 94 0 Jun 1 193 28 22 Numerous leads since 18 June. 7 Extensive puddling and deep channels cut in shore ice 26 Ice breakup. by runoff make it dangerous in measurement area. 1967 15 Numerous-cracks 1 to 3 m wide running length of bay. May 20 267 5 20 Cracks in fiord. 20 Water running off land onto fiord ice. Depth of water on Jul 2 Ice moved. ice varies from 10 to 38 cm. 13 Fiord entirely free of ice. 21 Ice cover becoming unsafe for vehicular traffic. 1961 26 256 15 Jun 2 229 30 Jun 2 251 3 9 224 20 2 Numerous puddles forming on fiord from snow melt and 16 213 5 water runoff from land. 16 Snow mixed with water. Water and cracks make further 10 239 3 measurements unsafe. 16 203 0 Jul 6 Ice cover starting to deteriorate. 24 191 0 30 165 0 1962 30 Holes observed on ice, polynya forming at mouth of river May 25 226 13 and creek and into fiord. Jun 1 226 25 Jul 8 140 4 Station creek began running, puddles at confluence of 8 Advanced honeycombing and thaw holes; shore lead 185 m fiord. in width observed. 5 Measurement site flooded. 13 114 7 Puddling from snow cover began on fiord, large pools 13 Slidre Fiord breaking up. along north shore fed by numerous creeks. 15 Fiord 30% open water and extends to at least 9Vi square km 8 Ice along north shore rotting rapidly. in front of station. 10 Fiord ice rotten. 29 Fiord free of ice. 16 Shore lead 30 m wide along north shore of fiord. 27 Ice cover starting to move. 1968 Jul 24 Slidre Fiord 9/10 open water, some ice still visible. May 24 211 Unknown 26 Ice conditions becoming unsafe for vehicular traffic. 1963 Jun 7 211 May 31 241 23 14 202 Jun 10 Water from station creek, spreading over ice at mouth of 21 170 creek. Extensive water areas on ice surface over Slidre 28 132 Fiord, with ice along northern shore rotting. 28 Shore lead 30 m in length observed. 22 Ice along northern shore covered with water. Jul 5 104 Jul 5 208 3 9 Lead 152 m in width running directly across fiord from 5 Numerous puddles on ice. station. 12 178 0 12 94 20 140 0

55 Ice thickness Snow depth Ice thickness Snow depth Dette (cm) (cm) Date (cm) (cm)

1968 (cont’d) 1963 (cont’d) Jul 19 71 Apr 5 74 21 Complete breakup.. Slidre Fiord free of ice. 26 58 26 10 cm of slush on surface. 1969 27 Last day ice cover used by light aircraft. May 31 Last day ice cover used by light vehicles. May 3 Unable to take measurements because of water overflow Jun 13 234 5 and openings in ice near shore. 20 231 3 5 Ice went out of main channel in the afternoon. 20 Three or four 2-3 m wide leads near station. Ice covered 20 Approx, date lake became free of ice. with water from shore out to approx. 90 m. Water is from snow melt runoff. 1964 Aug 5 Fiord free of ice. Apr 3 8 cm of slush on the ice. 17 124 1970 17 Channel ice sunk 1.2 m below main channel banks. May 29 262 25 27 Ice conditions unsafe for vehicular traffic. Jun 5 264 25 264 25 May 1 94 12 1 Water and snow 30 cm deep over measurement site at edge 12 Last day ice cover used by light vehicles. of main channel. 15 Ice measurements discontinued, ice cover starting to 8 Water level rose, shore ice moved 90 m out from shore. deteriorate. 9 No further information available. Aug 8 Fiordfree of ice. 1965 1971 Feb 26 109 25 May 14 240 30 26 Surface drifted and compact. 21 231 38 Mar 5 109 18 28 237 25 12 89 30 Jun 4 237 25 12 Dip in ice indicates water level has dropped 75 cm in 236 11 channel. 18 183 19 91 30 1972 26 91 25 Jun 16 246 5 Apr 2 91 20 23 244 3 9 91 8 23 Shore lead has formed. 16 89 3 30 Unsafe ice conditions. 23 89 0 0 1973 30 71 May 25 240 30 30 Ice conditions unsafe for vehicular traffic. Jun 1 Unknown 15 May 3 Breakup of ice started. 1 Ice measurement not taken due to excessive water runoff 5 Channel clear of ice, except few chunks of ice flowing on surface of ice and open leads around shore of fiord. out to the lake. 17 Lake clear of ice. 1974 Jun 7 234 41 1966 14 230 53 Mar 4 55 33 30 21 234 25 11 55 33 21 Up to 15 cm slush on ice due to melt water runoff. 18 53 25 53 30 Apr 1 52 23 FORT CHIPEWYAN, ALBERTA 8 52 10 15 51 13 'Measurements made about 400 m south of the station on Lake Athabasca, 22 47 3 at distances of 100 to 300 m south of the landing dock near mouth of the 29 53 8 Rocher River. 29 75% of ice covered with snow to depth of 8 cm, remainder clear. Frozen puddles increasing in depth. Ice thickness Snow depth May 4 Bay at Fort Chipewyan considered unsafe for aircraft. 0 Date (cm) (cm) 6 38 6 Bay approx. 30% water, 30% ice and 40% ice and/or slush. 13 Bay completely clear of ice. 1962 Mar 9 114 55 1967 Unknown 16 114 48 Apr 7 91 23 109 61 15 91 ” Winter ice road on ice considered unsafe. 30 109 43 15 25 Apr 6 109 38 21 91 15 13 109 36 28 85 20 Unable to take ice measurements due to overflow of water May 1 Ice cover starting to deteriorate. on ice. 21 Lake clear of ice. 30 Overflow water on ice in bay. Few channels of open water 1968 appearing VA km south of bay. Remainder of lake Mar 1 Large pressure ridge formed approx. 60 m north of site. solid ice. 29 93 8 May 1 No further information available. 1963 Mar 28 Snowcover variable due to drifting from 8 Feb to 28 Mar.

56 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1968 (cont’d) 1974 (cont’d) Apr 4 Ice used for ski-plane landings considered unsafe. Apr 7 104 15 5 93 5 10 Lead formed at mouth of channel. 10 Ice conditions unsafe for vehicular traffic. 12 7-9 28 12 93 5 12 New leads formed and becoming wider. 19 86 3 19 76 23 26 85 3 19 Ice thickness estimated, excessive overflow, 23 cm of 30 84 water beneath snow cover near the shore. 30 Few leads in shallow bay below townsite. 23 Pilot reports several large leads on west end of lake. May 20 Lake clear of ice. 26 61 5 26 Open area 300 x 600 m at mouth of channel. 18 cm of 1969 water and slush over ice, thickness estimated. Mar 7 145 28 14 137 28 29 Ice breaking up, ice moving due to river currents. 21 128 23 25 Last day ice cover used to transport heavy equipment. FROBISHER BAY, NORTHWEST TERRITORIES Apr 11 127 3 18 127 25 102 Measurements made on Koojesse Inlet of Frobisher Bay at approximately 25 Extensive leads on both sides of channel. Part of the 200 to 500 m from the Ministry of Transport causeway. lake adjacent to Fort Chipewyan is clear of ice except for the channel area where ice measurements Ice thickness Snow depth are taken. Main part of lake remains covered with ice. Date (cm) (cm) May 19 Lake clear of ice. 1970 1959 158 20 Mar 13 193 10 May 22 13 cm of water on ice from melting of snow. 20 193 15 22 160 3 27 168 8 29 0 30 Last day ice cover used to transport heavy equipment. Jun 5 150 132 0 Apr 3 150 20 12 0 11 150 20 19 117 Ice broke up on the Sylvia Grinnell River. Ice on inlet 21 Ice cover starting to deteriorate. 19 unsafe for vehicular traffic. Jun 9 Lake clear of ice. 26 99 0 1971 Jul 3 Numerous cracks formed on ice between 26 June and Feb 20 119 8 3 July. 20 Heavy ridge formed on edge of main channel. 28 Inlet clear of ice. 26 117 20 Mar 5 113 20 1960 13 13 112 30 May 12 155 Few cracks running parallel 66 to 98 m from shore. 19 109 30 12 Unsafe ice conditions around shore. 26 117 30 20 Apr 3 116 30 1961 11 104 30 Mar 31 Tidal ridging 60 m from shore. 12 No further information available. Apr 28 145 18 Tidal ridging continues to build. 1972 28 142 18 Apr 7 112 46 May 5 18 14 109 38 12 142 20 145 20 2.1 107 36 152 23 28 86 26 No further information available. 28 Large amounts of water on ice, ice thickness estimated. 31 May 5 51 1962 5 Wide shore leads have developed and ice in channel is May 15 163 18 candled. 21 160 20 10 Ice breakup occurred. 28 165 18 Jun 5 170 5 1973 No observations due to water on ice. Apr 7 83 13 11 Sylvia Grinnell River open above falls. 13 81 5 15 No further observations due to water on ice. 20 84 3 18 24 Few leads observed. 1963 27 81 0 May 17 135 33 28 No further information available. 31 122 20 Tidal ridging 3 m high extending 60 m from shore. 1974 31 129 27 Mar 29 112 28 Jun 7 122 8 29 Pilot reports several large pressure ridges on lake. Some 21 open water and overflow due to ice ridging also noted 21 Open leads in Sylvia Grinnell River, below falls since 20 at several locations. 22 Upper portion of the river and falls open.

57 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1963 (cont’d) 1969 (cont’d) Jul 16 Fast ice broke up. Jun 6 132 10 18 Koojesse Inlet completely ice-free. 6 5 cm of water on ice at measurement site 23 Frobisher Bay ice-free west of longitude 68° W. 13 122 4 1964 21 102 3 Apr 29 4-m tidal ridging 60 m from shore. 27 86 May 6 160 5 27 A few cracks in Inner Koojesse Inlet. 2/10 to 3/10 7 Ice auger lost through ice, no more measurements this puddling, maximum depth of puddles 20 cm. month. Jul 6 Last day ice cover used by pedestrians. 31 Ice cover unsafe for vehicular traffic. 10 Inlet clear of ice. Jun 11 137 1970 18 Ice observations discontinued, area considered unsafe. May 15 155 10 20 Upper portion of Sylvia Grinnell River open above falls. 21 Ice observation 120 m from causeway, thickness 132 cm. Jul 15 Inlet clear of ice. and halfway between Mair Island and Cairn Island, 1965 thickness 140 cm. May 21 140 25 22 149 21 8 cm of water on ice. 29 150 28 130 13 Jun 5 152 5 Jun 4 127 8 12 147 11 119 8 15 Ice cover starting to deteriorate. 18 91 8 19 124 18 Surface covered with 8 cm of slush. 27 119 25 Measurement site alternately open water or covered with Jul 8 91 pan ice, depending on wind conditions. 10 Ice considered unsafe to walk on. Jul 4 Approx, date inlet becomes clear of ice. 23 Inlet clear of ice. 1966 1971 May 13 170 8 Apr 10 Extensive tidal ridging along shoreline. 20 168 5 30 165 8 27 Tidal ridging 50 m from shore 6 m high. May 7 165 3 Jun 3 170 3 14 152 8 3 Ice breaking up along shore. 21 152 8 10 152 3 28 160 5 17 137 3 Jun 4 155 3 17 Approx. 50% of ice surface covered with water. 11 150 24 127 3 18 123 24 Approx. 40% of ice covered with water. Ice soft except 25 99 for several inches of hard ice at bottom. Jul 3 65 30 102 3 10 Inlet clear of ice. Jul 8 Ice cover unsafe to walk on. 1972 13 Approx, date inlet becomes clear of ice. Jan 1 Heavy ridging and numerous hummocks along shoreline. 1967 from tidal action. May 19 175 20 Apr 7 Ice probably rafted this year. 26 173 5 May 5 198 8 31 Tidal ridge 6 m high runs parallel and approx. 75 m from 5 Slush ice at 90 cm from top of ice from 14 April to 5 May. shore. 12 198 8 Jun 3 Open leads forming and gradually widening. 19 198 8 9 160 3 26 197 5 16 135 3 26 Slush ice observed from approx. 15 to 90 cm below the 23 97 3 ice surface. 30 Ice considered unsafe to walk on. Jun 2 196 5 Jul 14 Inlet clear of ice. 9 196 5 15 199 3 1968 23 192 3 May 31 165 13 30 199 3 31 Ice beginning to deteriorate, very soft from top to bottom. Jul 8 185 3 Jun 7 165 10 14 156 3 14 160 8 21 142 5 1973 26 137 5 May 4 Slight puddling due to melting of surface snow cover. Slush Jul 3 109 5 ice near top of ice. 5 102 5 17 185 25 5 Ice considered unsafe, no further measurements. 25 197 5 26 Approx, date inlet becomes clear of ice. 25 Puddling increasing, many holes forming on ice, snow melting and refreezing. 1969 Jun 1 185 3 May 31 147 10 8 180 3

58 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1973 (cont’d) 1960 (cont’d) Jun 15 157 3 May 20 48 10 22 141 3 25 Terrington Basin ice-free. 29 117 3 1961 29 Shore lead near causeway opened to 30 cm in width. Mar 31 81 23 30 Ice conditions deteriorated during June, numerous holes, 31 Slush under snow along shoreline due to tidal action. puddles, leads, and stretches of partially open water. Apr 7 84 8 Jul 6 102 0 7 Ice covered with snow and slush. 6 Shore lead 2 m wide along causeway extends halfway to 14 81 Long Island. Open area 2.5 m wide along shore, ice 14 Ice covered with frozen slush. thickness on 6 July estimated. Considerable areas of 21 81 open water. 28 Ice considered unsafe for traffic, open cracks and pools of 11 Ice in Koojesse Inlet broke up due to high tide. Some water along shoreline and near wharf. ice observed 3 to 5 km out in bay. May 10 Terrington Basin clear of ice. 1974 1962 May 10 185 8 Mar 30 94 8 17 Puddles forming in many areas. Apr 6 91 24 183 3 13 91 30 31 170 3 20 97 25 31 Numerous large cracks near causeway and along shore. 27 97 20 Ice surface wet, numerous puddles and small holes. May 4 97 Jun 8 173 Trace 4 Average snow depth 5 to 13 cm. 14 145 Trace 11 79 21 104 Trace 11 Average snow depth 3 to 5 cm and slushy. 21 Lead near causeway running southeastward and in­ 15 Ice conditions unsafe for vehicular traffic. creasing in size. 18 53 28 84 0 18 Small bays open at both ends of dock. Ice rotten and 28 Many leads throughout inlet, some are impassable. candled. 28 Ice has deteriorated rapidly during June, ice breaking up 25 No measurement due to water along shoreline and wharf. along shoreline. Open water in inlet extends out to 28 Ice breakup complete, basin clear of ice. causeway. Ice cover south of causeway and into Fro- isher Bay has numerous holes and leads. Ice expected 1963 Mar 22 94 64 to break up within next few days. 22 Snow cover drifted. Apr 8 Approx. 10 cm slush-ice. 15 91 5 GOOSE BAY, NEWFOUNDLAND 15 20 cm of slush beneath 5 cm of snow. Measurements made on Terrington Basin approximately 10 to 100 m May 10 64 10 Ice thickness estimated, cracks and open water along off the landing dock. shoreline. Ice conditions unsafe for vehicular traffic. 17 70% ice coverage on Terrington Basin. Ice thickness Snow depth 20 No ice visible on Terrington Basin or Goose Bay. Date ______(cm)______(cm)______1964 Apr 10 91 13 1959 17 86 5 Apr 3 112 13 24 Terrington Basin covered by 30 cm of slush. 10 107 8 May 1 66 17 107 8 1 Ice layer beginning to break away from the bank of Goose 24 76 0 River. This portion of river is narrow and currents are 24 Surface ice decaying. strong. 80% of ice layer on river appears to be rotten. May 1 69 0 Hamilton River intact although streams leading into the 1 10 cm of slush on surface. river are open. 7 Ice conditions unsafe for vehicular traffic. Ice unsafe, no measurements. 8 41 0 8 Ice breaking up. 8 Wide lead along shoreline, difficult to get on ice. 15 Terrington Basin clear of ice. 17 Terrington Basin becomes ice-free due to westerly winds. 26 1965 1960 Mar 26 Flooding along shore. Apr 8 82 61 13 cm of slush on ice. 8 3 cm of water on surface. Apr 10 91 5 15 82 33 17 8 cm of water of ice. 15 10 cm of slush on surface. 17 24 86 5 22 79 18 24 13 cm of water of ice. 29 86 10 86 0 29 Snow wet. 15 cm of slush on surface. May 1 15 cm of slush on ice. May 6 79 10 1 8 76 15 8 Crack 15 m from shore. 14 64 0 13 56 13

59 Ice thickness Snow depths Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1965 1969 (cont’d) M ay 15 Ice cover starting to deteriorate, conditions becoming J u n 2 Terrington Basin clear of ice. unsafe for vehicular traffic. 1970 2 2 51 0 A p r 10 91 18 J u n 4 Terrington Basin clear of ice. 17 81 3 1966 23 81 3 M ar 11 83 20 M ay 4 Ice cover starting to deteriorate. 18 7 5 2 0 22 Terrington Basin clear of ice. 25 8 0 10 1971 25 Ice covered with 10 cm of slush. A p r 2 10 to 28 cm of slush on ice, 53 cm of snow on top of slush. A p r 1 7 6 3 16 77 15 8 61 0 16 15 cm of snow over 5-cm ice layer which is over 33 cm of 8 Ice covered with 20 cm of slush. Open w a te r n e a r slush. sh o re lin e . 3 0 53 5 15 66 0 3 0 Top 5 cm of snow on 18 cm of slush. 15 Patches of open water near shoreline. M ay 7 55 5 23 61 0 7 13 to 33 cm of slush on ice. 23 Cracks 90 cm wide along shoreline. 13 Numerous cracks and open pools of water. Ice thickness 29 53 0 estimated to be between 38 and 51 cm thick. M ay 6 Terrington Basin clear of ice. 1972 1967 M ar 2 4 104 8 3 0 100 5 M ar 10 Snow over the ice contains 20 to 30 cm o f slush. A p r 9 100 20 31 8 4 20 14 9 5 13 A p r 7 77 15 21 9 4 13 14 77 15 2 8 89 25 21 81 5 M ay 5 88 18 28 7 6 5 18 89 5 M ay 5 55 3 18 8 cm of slush on ice. 12 4 8 2 0 2 5 79 3 12 Cracks and leads along shoreline, some s»mail open holes 25 10 cm of slush on ice. in ice. J u n 3 62 3 19 Ice considered unsafe. 2 8 Basin completely clear of ice. 1973 1968 M ar 3 0 84 63 3 0 Some water on ice surface all m onth due to pressure on ice. M ar 3 0 86 A p r 6 7 2 56 3 0 Ice covered with 10 to 15 cm of slush. 6 About 5 cm of water between snow cover and top of ice. A p r 12 86 41 13 71 4 6 12 Ice covered with 10 to 15 cm of slush beneath snow. 19 69 3 0 21 76 27 6 6 8 2 6 7 6 2 7 About 18 cm of water on ice, shore leads and numerous M ay 3 6 4 cracks have formed. 3 5 to 10 cm of slush on ice surface. M ay 4 48 (estimated) 3 (slu sh ) 17 Terrington Basin 5/10 open. 12 37 (estimated) 3 (slu sh ) 21 Terrington Basin 9/10 open. 12 Basin 9/10 covered with ice. Open shore leads. 2 2 Terrington Basin clear of ice. 18 15 (estimated) 0 1969 18 Basin 5/10 covered with ice. M ar 15 Last day ice cover used by light aircraft. 2 0 Basin 3/10 covered with ice. 21 9 4 10 2 2 Basin 1/10 covered with ice. 2 8 93 10 23 Basin free of ice. A p r 4 91 8 1974 11 8 8 18 M ay 3 74 4 6 18 91 13 10 6 6 8 18 5 cm of frozen slush on surface. 17 4 8 3 25 91 15 21 Basin 9/10 covered with ice from 2 to 6 May. 2 5 Ice becoming soft and granular. 2 4 3 4 0 M ay 2 89 5 2 6 Basin 6/10 covered with ice. 9 71 10 31 15 0 16 4 3 31 Basin 3/10 covered with ice. 16 Surface slushy, numerous cracks 23 Ice cover unsafe to walk on. 2 6 Terrington Basin 15% open. 2 7 Terrington Basin 25% open. 2 8 Terrington Basin 50% open. 30 Terrington Basin 90% open.

60 HALL BEACH, NORTHWEST TERRITORIES íce,thickness Snow depth Date (cm) (cm) Measurements made in harbor opening into Foxe Basin about 100 to 300 m from end of landing dock. 1962 (cont’d) Jul 13 Ice cover deteriorating rapidly. 14 No further information available. Ice thickness Snow depth 1963 Date (cm) (cm) May 31 269 46 31 Sea free of ice beyond sea wall, except for occasional 1959 brash ice since 8 May. Jun 10 Ice conditions becoming unsafe for heavy traffic. Jun 7 274 36 12 216 13 15 Ice cover starting to deteriorate. 19 216 8 21 241 19 Surface pools, numerous cracks. Ice extends 800 m to 21 Snow cover includes 15 cm of slush beneath 5 cm of pressure ridge. Bay clear to horizon except for oc­ snow. casional floe. 28 Snow cover includes 23 cm of slush beneath 3 cm of 26 211 Trace snow. Ice conditions unsafe. Occasional block of ice Jul 7 Ice broke completely free from shore. Bay clear to beyond sea wall during June. approx. 450 m offshore with the rest full of pack ice. Jul 21 Foxe Basin clear of ice. 10 Ice extends approx. 800 m but broken away from shore in many places. Bay almost full of pack ice except 1964 for occasional areas of clear water. May 1 216 25 22 Bay temporarily clears of ice, but new ice re-forms and Ice cover becoming unsafe for heavy traffic. some drift ice reappears. Open lead approx. 1.6 km offshore. 25 cm slush beneath 31 Bay clear to horizon, no ice visible. snow layer. Aug 14 Bay clear with some patches, large amount of pack ice 15 Open lead 200 m offshore 9-13 May, closed with wind along horizon. shift 14 May, and opened again 15 May. 22 Bay again completely free of ice. 30 Lead 400 m offshore, 200 m wide. Aircraft report 48 km of open water from shore ice towards sea and north 1960 and south as far as visible. Apr 29 Pressure ridge and open lead approx. 1V2 km offshore. Large amount of drift ice being moved around by 1965 wind and tides. Jun 25 198 5 25 Ice soft and rotten, and covered with slush and water. May 6 198 15 13 201 13 Jul 12 Ice cover starting to break up. Leads from 0 to 800 m wide depending upon offshore wind. 20 201 18 27 10 31 Drift ice visible daily since breakup. 27 Some open water from 10-13 May. 1966 Jun 3 8 Jun 20 Ice cover becoming unsafe for vehicular traffic. 10 5 24 179 0 10 Surface wet, many large cracks. Water on ice, 10 cm 24 Lead approx. 1 km from shore gradually widening, deep in places. Ice conditions becoming unsafe for allowing previously rafted ice to break loose. Fast traffic. ice extends less than 800 m out with open water 17 Pressure ridge 1.6 km offshore with open water extending beyond. to horizon. Jul 1 161 0 24 Pressure ridge at edge of shore ice. Large floes and drift 8 130 0 ice in open water beyond ridge. Cracks widening but 9 No further information available. no sign of movement of shore ice yet. 1967 Jul 4 Ice cover deteriorating rapidly. May 31 Lead about 1 km offshore varies in width and length with 12 Bay became temporarily clear of ice, but new ice re-formed wind direction, and closes during onshore winds from and some drift ice reappeared. Feb. through May. 1961 Jun 23 201 15 Jun 16 211 23 Water observed on ice. 16 Ice thickness estimated. Open water 1.2 km from shore. 25 Ice cover no longer being used for traffic. Small drifting ice floes. Ice rotten and covered with 30 175 slush and water. 30 Pools of water and slush on ice, numerous cracks. 23 20 to 25 cm water and slush on ice. Ice soft and rotten, 1968 numerous open cracks. Small drifting ice floes. Ice May 4 Lead approx. IVi km from shore, varies from 200 to 400 m conditions unsafe. in width depending on wind direction and speed. 1962 25 Outer edge of lead not discernible due to strong NW winds. Apr 27 Ice thickness not measured, snow depth 58 cm. Open Jun 28 208 8 lead 1.6 km from shore, 275 m wide. 28 Edge of fast ice is about 300 m offshore. Puddles of water May 25 Ice thickness not measured, depth of snow 51 cm with forming on top of ice surface. drifts. Fast ice extends 0.8 to 1.2 km from shore, 30 Ice cover unsafe for vehicular traffic. then open water beyond to horizon. 1969 Jun 239 May 30 Large lead extending in north-south line, varies in size Jun Rotten ice and open leads make ice unsafe for further depending upon wind and current. Large amounts of observations. pressure ice about 300 m from measuring site, and some open water visible.

61 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1969 (cont’d) 1974 (cont’d) Jun 13 152 41 May 31 Open water extending 1 to 3 km offshore observed during 20 150 5 May. 27 145 13 Jun 8 Open lead at about 1 km offshore extends to horizon. 27 Open water in front of station extending out for 80 km. 14 201 0 Growlers, bergs, pan ice and bergy bits observed. 21 180 0 Large amount of pressure ice visible along coast. 21 Open water 800 m offshore with few ice cakes. Jul 4 Ice cover considered unsafe to walk on. 28 Open water 800 m offshore, extends to horizon. Open 25 Foxe Basin clear of ice. cracks forming on shore fast ice. 1970 29 No further information available. Feb 27 Open water visible all month. Lead width constantly changing and producing considerable fog. HOLMAN ISLAND, NORTHWEST TERRITORIES Apr 30 Large lead approx. 1.6 km offshore. Lead extends as far as the eye can see along coast in both directions. Measurements made on Kings Bay due west of station building about May 15 188 10 29 156 28 40 m beyond shoreline tidal crack. 29 Open water as far as visible except for a strip of ice approx. l 1/^ km wide along the shoreline. Ice thickness Snow depth Jun 157 15 Date ______(cm)______(cm)______103 8 Ice cover starting to break up, ice no longer safe to walk on. 1960 Jul 15 Basin clear of ice except for a few scattered pieces. May 2 208 Unknown 208 1971 9 Jun 18 208 15 16 208 25 218 3 23 206 30 206 Ice cover starting to deteriorate. Jul 2 221 0 Jun 4 3 No further information available. 20 Ice on bay breaking up. 29 Bay clear of ice, except for some scattered pieces. 1972 Apr 30 Large lead between the land fast ice and main ice sheet 1961 observed during most of April. Winds caused main ice May 12 216 8 sheet to move a few miles out into Foxe Basin. Ice 19 218 5 started to move back by end of month. 26 221 218 May 26 Open lead in area during May. Ice in Foxe Basin extends Jun 2 800 m out from shore. Few bergy bits visible further 9 185 out in basin. 16 157 Ice cover deteriorating, conditions becoming unsafe for Jun 2 227 15 20 9 234 18 traffic. 23 218 15 23 89 Ice free from shore. Wide crack across entrance of harbor. 30 Fast ice extends 800 m out from shore. 25 Jul 7 208 5 30 25 14 Ice conditions unsafe. Jul 7 Bay clear of ice. 31 No ice visible in Amundsen Gulf. 1973 Apr 30 Major leads observed 1 and 5 km offshore. 1962 193 8 May 25 213 33 May 11 18 194 Jun 1 216 20 8 203 15 18 Snow depth 5 to 8 cm. 25 194 8 Fast ice extends to only 400 m offshore. 194 15 203 3 Jun 1 15 Fast ice extends to only 200 m offshore. 8 145 22 185 3 8 Shore cracks. 29 153 0 15 107 Ice conditions unsafe for vehicular traffic. Jul 6 132 0 15 6 Shore ice extends to only 200 m off landing dock. 22 79 8 Shore ice broke free. Jul 1 Bay clear of ice. 1974 1963 May 17 206 Apr 26 Fast ice extends to about IV2 km offshore, then open water for about Vh to 3 km, with ice beyond that Jun 14 150 point. Some brash ice in lead, and frequent forma­ 15 Approx, date ice cover became unsafe for vehicular traffic. tion of arctic smoke (or ice fog) over open water. 21 122 May 3 Open lead observed about 120 m off landing 23 Ice cover deteriorating. 10 208 13 Jul 6 Ice in bay starting to move. 17 201 10 29 Bay clear of ice. 24 198 10 31 194 13

62 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1964 1968 (cont’d) May 22 213 3 Jun 20 Ice cover unsafe to walk on. Jun 18 Slight ice movement in Amundsen Gulf. 6-m lead off 25 Ice cover deteriorating rapidly. point from Kings Bay to Holman Island, opens with Jul 5 Bay 1/3 open water, date of complete ice clearance un­ east wind, closes with west wind. known. 20 Ice cover unsafe for vehicular traffic. 26 152 Jul 10 61 HOPEDALE, LABRADOR 10 Open holes in ice, numerous cracks in Amundsen Gulf. Ice partially broken. 15 Small lakes free of ice. Measurements made on Hopedale Harbour approximately midway between 17 Floating ice in bay approx. 30 cm thick. the US. Air Force landing dock and Ellen Island. 19 Ice on Amundsen Gulf broken but piling up against shore. 20 Large lakes still 80% ice covered. Breakup was late due Ice thickness Snow depth to extremely cold weather in June and July. Date______(cm)______(cm)______22 Bay clear of ice except for a few scattered pieces. 1965 1961 Jun 4 204 3 Mar 24 122 25 11 201 0 31 122 30 18 196 0 Apr 7 117 3 25 180 0 14 112 25 Small lead opening up between mouth of Queen’s Bay 21 107 and Holman Island. Ice cover unsafe for vehicular 28 102 traffic. May 5 102 30 Water began to form around edges of small lakes and 12 94 ponds during last few days of June. 12 Narrow cracks on north shore of harbor. Jul 2 112 0 19 Ice not considered safe for measurements, very rotten-with 2 Lead widening between Queen’s Bay and Holman Island. numerous cracks. 9 46 0 26 Ice very rotten, approx. 8/10 of harbor still covered with 9 15 m of open water between shore and ice in King’s Bay. ice. 10 Small lakes and ponds cleared of ice. 27 No further information available. 13 Ice solid in King’s Bay but commencing to move. 1962 22 Bay clear of ice. Missing 1966 1963 Apr 29 206 5 Incomplete 29 Ice movement and open patches of water in Amundsen Gulf. 1964 May 6 206 3 Missing 13 211 3 1965 20 0 Missing 20 Open water in Amundsen Gulf within 1 Vi km of King’s 1966 Bay. Ice melting rapidly. Mar 15 Cracks developing in ice, generally along shoreline. Jun 7 Ice cover unsafe to walk on. 31 83 5 10 Ice in bay breaking up. 31 Slush forming on ice due to above-freezing temperatures. 12 Bay clear of ice except for a few floating pieces. Apr 10 84 0 1967 20 79 0 Jun 9 213 8 30 74 0 16 210 30 Two layers of ice separated by approx. 5 cm of water. Top 23 193 layer approx. 13 cm thick; bottom layer very soft. 30 177 May 9 66 5 30 Small lead from 23 to 30 June between Holman and 16 66 8 Holman Island. Lead opens and closes with wind and 20 Ice cover starting to deteriorate. tides, avg. width 10 to 15 m. Small ice movement, 27 Ice cover unsafe for vehicular traffic. weather cold and no signs of breakup. Small lakes Jun 7 Harbor clear of ice. still completely frozen except along shorelines. 1967 Jul 2 Ice cover unsafe to walk on. Mar 31 105 10 10 Ice in bay starting to deteriorate. 31 Ice surface covered with frozen snow. 11 No further information available. Apr 7 104 8 1968 15 102 10 Mar 29 Open water in Amundsen Gulf approx. 8 km from 21 99 8 Holman Island. Open water and large leads observed 28 94 8 in moving ice, extending across Amundsen Gulf to May 5 86 mainland. 12 81 5 Jun 1 Maximum ice thickness 206 cm, date of occurrence un­ 12 Approx. 5 cm of slush on ice. known. 19 83 3

63 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1967 (cont’d) 1971 May 26 71 5 Mar 20 91 30 27 Open lead in extreme West end of harbor around U.S. 26 85 28 Air Force docks, widening rapidly. Apr 2 91 36 31 Ice thawed along shoreline, boat used to gain access to 17 84 30 ice for measurement. Open lead 23 m wide around 17 5 cm of slush of ice. shoreline along north side of harbor. 25 91 5 Jun 1 Large open lead between Anniowaktook and Ellen Islands. 25 10 cm of slush on ice. 2 38 26 No further information available. 3 Last aircraft landing on ice. 1972 4 Ice began to break up. Apr 28 128 30 5 Few loose ice cakes left in harbor, May 5 121 25 7 Harbor completely clear of ice. 13 122 20 1968 21 119 10 Apr 19 99 5 26 122 5 19 Increase of ice thickness from 12 to 19 April due to snow 27 No further information available. cover on ice melting and then refreezing. 1973 22 Ice beginning to thaw along shoreline on village side of Apr 13 124 15 harbor. 21 130 15 26 98 3 27 117 8 30 Ice still deteriorating along shoreline of village. May 4 107 8 May 8 84 3 11 89 3 8 Last date ice cover used by light aircraft. 18 Few cracks along shoreline and small holes forming on 10 74 25 52 0 19 61 3 29 Harbor completely open except for a few pans of ice. 24 30 24 Lead at west end of harbor extending from U.S. Air Force 1974 dock across mouth of harbor, also open water along Apr 12 102 15 shoreline. 20 102 25 31 10 26 102 18 31 Numerous leads in harbor. Ice measurements taken on May 3 99 13 24 and 31 May Were estimated due to unsafe ice con­ 10 97 8 ditions. Most of harbor free of ice but easterly winds 17 100 4 (slush) drifting ice into harbor. 24 85 3 Jun 5 Harbor clear of ice. 24 Holes starting to form around the dock. 31 67 0 1969 31 Open area 90 x 180 m around the dock. May 9 91 5 Jun 1 No further information available. 16 76 8 23 60 24 Last date ice cover used by light aircraft. INOUCDJOUAC (formerly Port Harrison), QUEBEC 30 38 30 Lead running between Ellen Island and Anniowaktook Measurements made approximately in the center of Innuksuak River ) Island and another running perpendicular to the har­ approximately 400 to 700 m upstream from its mouth. bor at a distance of 5 km from shore. Ice deteriorating rapidly due to mild weather. Ice considered unsafe Ice thickness Snow depth for vehicles or man after this date. Date (cm)______(cm)______Jun 9 Harbor clear of ice. 1970 1959 Apr 17 112 5 May 8 239 24 102 5 15 226 May 1 102 3 22 216 8 103 3 29 211 8 Observed 8 cm of slush over ice. Also approx. 30 cm of Jun 5 196 3 soft surface ice with approx. 5 cm of water between 5 Small creeks clear of ice, large openings in lakes. layers. 6 Water flowing over top of ice due to ice jam upriver. 15 93 3 7 Water covered 2/3 of ice. 15 Small open pool of water near U.S. Air Force dock. 12 Unsafe ice conditions. Ice melted along both shores and Approx. 10 cm of slush and water between ice layers, large holes in ice. Slush 60-90 cm deep on top of ice. ice soft. 15 Two cracks across river and widen during day. 22 74 17 Ice starts to move from river. Jun 2 Last date ice cover used by light aircraft. 18 River clear of main ice sheet. 5 25 19 River clear of ice except for a few scattered pieces. 12 Ice cover breaking up. 19 Ice starts to move from bay at mouth of river. 28 Harbor clear of ice. 26 Bay clear of ice.

64 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1960 1966 Apr 29 226 25 May 5 Last date ice cover used by light aircraft. May 4 Ice cover becoming unsafe for vehicular traffic. 6 206 3 6 236 0 13 211 o 13 231 0 20 .196 5 20 No report due to flooding of ice. 20 5 cm of slush on surface. Jun 10 River clear of ice. 27 160 8 1961 May 27 8 cm of slush on surface. Ice melting along shoreline, Apr 14 229 8 forming many patches of open water. 21 226 8 Jun 3 132 0 28 216 3 3 38 cm of slush ice near surface included in total ice thick­ May 12 213 3 ness values. Lead approx. 3 to 6 m wide extends across 19 213 3 river 55 m below ice site. 26 193 3 8 Open water 3 to 6 m wide along edges of river. A polynya Jun 5 Ice cover starting to deteriorate. approx. 15 to 30 m in size midstream 90 m down river 9 165 from measurement site. Breakup commencing. 15 Ice cover unsafe for vehicular traffic. 9 River clear of ice, except for some scattered pieces. 16 132 1967 16 Some variation in ice thickness on river in June may be May 15 Last date ice cover used by light aircraft. due to undercutting by the current. 20 259 25 21 Ice begins to break up. 20 Snow very wet, ice covered with pools of water from 24 Main channel clear. Fast ice in shallows still solid. runoff of a small stream. 28 River clear of ice. 27 246 3 1962 Jun 3 239 May 4 239 3 3 Ice beginning to move out from shore, many soft spots 11 244 5 around drifting site. 18 213 13 10 Shore leads 60 to 180 cm in width on both sides of river, 18 Snow cover slushy. center still solid but some open areas forming. Ice 25 198 15 estimated to be 203 to 216 cm thick. 27 Ice surface flooded by water upstream. Water later freezes, 17 Shore leads have widened considerably. Ice still solid at forming a crust. site. Jun 1 183 15 21 Ice moves out in early morning, piling up approx. 400 m 8 170 15 south of dock. 8 Ice cover unsafe for vehicular traffic. 22 River clear of ice. 15 102 30 1968 15 Ice cover deteriorating rapidly. Mar 26 Rapids above station open slightly allowing water to flood 25 River clear of ice. ice past measurement area. Site under slush and water 1963 for a few days. May 17 251 Unknown May 3 Last date ice cover used by light aircraft. Jun 5 Open water noted along shoreline. Candling progressively 10 257 5 increases, reaching depths of 60 cm. 17 249 6 Ice cover unsafe for vehicular traffic. 21 High water from river causes a lead to form along shore. 8 Ice in the shallows begins to recede from shorelines. 24 231 14 178 3 27 Ice along shores of river becoming rotten. 15 Open water upstream and along both shores of river. 31 218 21 142 Jun 3 Ice cover starting to deteriorate rapidly. 21 Ice movement to seaward. 18 Approx, date river clear of ice. 22 Lead opens across river. 1969 26 River clear of ice. Mar 14 Ice observation point shifted 60 m east due to a slush 1964 puddle at former location. Incomplete 28 Ice crack oriented north-south 60 to 120 m in length 1965 and approx. 20 to 46 cm in width. May 27 Meltwater on the surface of the ice. May 6 Last date ice cover used by light aircraft. Jun 6 175 16 Shore ice cracks appear due to tidal action. 8 10 Ice cover becoming unsafe for vehicular 21 266 1 traffic. 13 135 28 273 1 10 20 107 28 60 cm of semifrozen slush at bottom of ice cover. 10 27 61 Jun 4 276 0 10 27 4 Surface ice candled. Shore lead observed on 20 and 27 June, Large areas of open water visible. 10 Water flowing along shore, ice deteriorating. Jul 3 River clear of ice. 11 232 0 15 Several open holes form, and ice fragments observed flowing 70 under the main ice sheet. River clear of ice in places. Apr 17 217 5 17 River clear of ice. 24 203 3

65 Ice thickness Snow depth ¡ce thickness Snow depth Date______(cm)______(cm[______Date______(cm)______(cm)

1970 (cont’d) 1961 (cont’d) May 1 204 3 May 6 119 46 8 210 3 13 119 46 15 208 3 20 124 3 22 207 3 20 Variable ice thicknesses possibly due to formation of 3 29 203 snow-ice. Jun 1 Last date ice cover used by light aircraft. 27 Ice conditions unsafe. 5 183 3 1962 12 173 3 May 4 142 25 19 145 5 11 132 25 19 Ice cover starting to break up. 18 140 15 28 River clear of ice. 18 8 cm of water on ice. 1971 20 58 cm of water on ice. Apr 16 232 23 91 cm of water on ice. 18 First flowing water appeared on river. 26 124 0 23 218 27 River level up 4 m and the ice moved about 15 m. 23 River completely covered with water. 29 Ice moved about 120 m. 27 Water level subsided and top layer of rivei: ice remained Jun 2 Channel clear of ice. candled. 1963 May 7 213 Apr 26 104 36 14 213 May 3 99 30 21 185 3 Ice covered with approx. 20 cm of water along banks and 28 168 8 cm near midstream. Jun 4 Some variation in ice thickness noted, due possibly to 10 91 25 rafting. 10 Approx. 1 m of water along banks 11 124 17 Measurements terminated because of water on ice. 1972 18 Ice moved approx. 15 m. May 5 276 10 19 Last date ice used by light aircraft. 12 284* 10 31 River clear of ice. 283 10 19 1964 26 277 10 May 1 IT 2 30 Jun 3 259 3 1 First runoff water appeared on river edge. 16 256 15 107 20 23 234 15 Approx. 38 cm of runoff water at river edge and 5 cm on 23 Considerable open water extending out a few feet along ice at midstream. Measurements terminated due to shore. water on ice surface. 30 Unsafe ice conditions. 27 Water level 1.3 m above winter ice level. 1973 28 Ice shifted slightly. Last date ice used by light aircraft. Apr 20 212 30 30 Ice broken up. 27 207 41 Jun 12 River clear of ice. 202 38 May 4 1965 0 11 183 Apr 16 163 8 175 0 18 23 160 8 21 Ice starting to break up. 30 142 25 23 Ice conditions unsafe. 30 Less ice thickness probably due to deeper snow cover. 1974 May■ 7 152 10 May 3 180 8 7 20 cm of water on ice at river edge. 17 185 0 14 Water level 76 cm above winter ice level. 24 157 0 24 Water level 2 m above winter ice level. Ice cover unsafe 24 Open water in shallow areas along shoreline. to walk on. 31 Measurement site inaccessible due to open water along 27 Ice moved during afternoon. the shoreline. Jun 9 River clear of ice. 1966 Apr 29 165 15 INUVIK, NORTHWEST TERRITORIES Ma>r 6 170 10 11 Water on ice 3 to 4 m from river bank. 18 Ice at dock level. Measurements made on east branch (channel) of the MacKenzie River 21 Ice 2.5 m above winter level. about 70 m off the landing dock. 23 Last aircraft off ice. 25 Ice moved at 1300 local time. Ice thickness Snow depth 30 Water level up 3 m over winter level. Large open areas on Date______(cm)______(cm)______small lakes in vicinity. Jun 6 River clear of ice. 1961 Apr 23 124 25 30 117 46 * Ice thickness data appear high, ice possibly rafted.

66 Ice thickness Snow depth ISACHSEN, NORTHWEST TERRITORIES Date (cm) (cm) Measurements from 1959 through 1970 were made SSW of station in Deer Bay at distances of 100 m to 1 km offshore. Measurements 1967 from 1971 through 1974 were made SSE of station in Louise Bay Apr 7 137 18 approximately 45 to 90 m offshore. 14 132 30 21 122 36 Ice thickness Snow depth 28 113 8 Date (cm) (cm) Apr 28 Water on top of ice near shore, snow very wet. May 5 3 to 4 m of open water between main ice sheet and shore­ line. Water covers approx. 25% of ice. 1959 31 Open water on both sides of river. Distance from shore­ Jun 15 246 line to ice sheet varies between 15 and 30 m. 15 Snow and slush mixed. Jun 5 River clear of ice. Jul 1 203 1 Ice soft, water puddles 10 cm to 20 cm deep. 1968 15 180 Apr 19 Water flowing up through augered hole. 15 Ice 50% covered by water and candled to depths of 30.5 May 3 99 25 to 61 cm. Wide leads near shore. 10 95 20 Aug 4 Bay ice broken into large floes of rotten ice about 61 cm 10 Snow cover wet. thick. 15 Ice cover starting to deteriorate. 17 Open water along river bank out to 4 to 6 m. 1960 26 Last date ice cover used by light aircraft. May 15 213 23 28 Open water out to 15 m from river bank, small pieces of 22 208 floating ice. 22 16 cm of hard-packed snow with 4 cm of soft snow on top. Jun 6 River clear of ice. 29 211 18 Jun 1 Ice cover becoming unsafe for vehicular traffic. 1969 12 198 Apr 11 127 20 12 Ice mostly covered with water. Numerous cracks 8 to 18 122 20 13 cm wide. Ice conditions unsafe. 25 97 23 30 Surface puddled, about 3 m of water along the shore. May 1 Some water observed on the surface. Jul 5 Numerous pools and considerable water on ice. Jun 1 Last date ice cover used by light aircraft. 16 Ice started to drift during moderate north wind. 5 River clear of ice. 31 East end of bay open, ice cover remaining beyond open 1970 area. Apr 17 112 25 1961 24 112 28 May 13 248 18 May 10 Ice cover starting to deteriorate. 13 11 cm of hard-packed and 7 cm of soft new snow. 18 Last date ice cover used to walk on. 23 239 18 Jun 5 River clear of ice. Jun 10 244 15 6 First ship of the season using the river. 10 9 cm of hard-packed snow, 6 cm of new soft snow. 1971 15 Ice cover becoming unsafe for vehicular traffic. Apr 2 141 20 20 244 9 135 30 20 4 cm of slush covered ice surface. 23 135 20 27 Numerous large puddles on surface. 30 124 15 Jul 7 Surface soft, large puddles and large bands of water on May 7 124 15 shore line, ice considered unsafe. 14 Ice conditions unsafe. 14 170 1972 14 Open water with some raft ice approx. 5 km from shore. 21 135 Apr 28 170 23 21 20% pooled water to 8 cm deep. May 5 127 23 28 109 14 Several meters of water overflow along shore and cover the 28 Surface soft, open water along shore line. 30- to 41 -cm- ice surface. wide crack 45 m north side of bay. 30 Water level on ice continued to rise between 15 and 30 May. Aug 15 Deer Bay not completely clear of ice, date of maximum Jun 5 Ice breakup observed. open water unknown. 1973 1962 Apr 27 113 33 Jun 1 226 23 May 4 114 15 10 Ice cover starting to deteriorate, conditions unsafe for ve­ 11 Water rising and flowing along edge of river. hicular traffic. 18 9 m of open water along shoreline. 16 Water on ice estimated to be 60 cm deep. Ice conditions 25 14 m of open water along shoreline. unsafe for pedestrians. 30 River clear of ice. Jul 31 Deer Bay temporarily clear of ice. New ice and/or drift ice reappears later. 1974 Apr 19 155 8 1963 26 156 3 Jun 2 229 28 May 3 152 3 14 2/10 to 3/10 puddling across entire surface. 10 Water level at dock up 137 cm above winter low point. 26 Shore leads, 4 to 6 m wide. 3 to 5 m of open water along shore. 30 Ice cover unsafe for vehicular traffic. 17 Water level 2.7 m above winter low and rising about 46 cm a day. 31 Water level up to 4.6 m, some slight movement of ice ob- served.

67 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1963 (cont’d) 1970 Aug 24 Deer Bay not completely clear of ice; 6/10 open water Jun 5 193 76 on this date. 12 196 46 1964 12 Last date ice cover used by light vehicles. May 29 224 30 19 193 30 23 Jun 19 4 cm slush on ice, ice cover starting to deteriorate. Water on ice surface, unsafe for measurement. Aug 1 26 213 10 Deer Bay only 2/10 open water on this date. Jul 15 Deer Bay only 1/10 open water on this date. 1971 Jun 4 1965 255 43 9 First open lead observed. Jun 15 Maximum ice thickness approx. 224 cm on this date. 10 Many large patches of open water observed on far side 20 Ice cover unsafe for vehicular traffic. of bay. 22 4 to 6 m lead around north side of bay. 11 Lead 45 m wide extends around 30% of shoreline. Ice 25 20% of ice surface covered with puddles. measurements can no longer be made. Ice in bay 28 40% of ice surface covered with puddles. flooded with runoff water. Jul 15 Deer Bay only 1/10 open water. 18 Bay completely covered with ice, except for a shore lead 1966 approx. 27 m wide. Jun 3 255 28 1972 255 13 Jun 2 226 26 254 0 33 9 235 13 26 Snow meltwater on top of ice forming numerous puddles 16 224 and slush. Open water, along shore edge 1 to 4 m wide. 28 23 Polynya forming at mouth of river. 224 20 Jul 7 218 3 Jul 1 239 0 8 15 239 0 No further information available. 15 Ice thicknesses estimated during July and August. 1973 22 229 0 Jun 1 267 25 29 203 0 9 279 25 Aug 5 183 0 9 Ice covered with numerous large puddles, largest one 5 Bay 75% puddles with rapid deterioration of rotten ice, located at mouth of Delta River. open water up to 15 m wide from shoreline. 12 Shore lead 2 to 5 m wide formed, some ice visible under 12 165 0 surface water. Two other large leads visible 12 and 12 Bay 70% puddles and shorelead up to 18 m wide. 15 m from shore. 21 102 0 13 No further information available. 21 Bay 60% puddles, shorelead 90 m wide, polynyas at river 1974 mouth. May 17 179 58 26 89 0 24 176 46 26 Ice rind approx. 1 cm thick forming on 60% of shore lead. 31 179 48 All ice thickness measurements made visually from the Jun 7 175 56 station. During month shore lead ranged from 15 to 90 m 14 176 61 wide. 21 170 61 1967 28 Some small cracks observed, 30% of ice surface covered May 253 51 with puddles. 237 29 No further information available. Jun 229 Last date ice cover used by light vehicles. 229 44 ISLAND LAKE, MANITOBA Slush around shore 45 cm deep, extending out along shore onto the ice for 15 to 30 m. 23 Shore puddles 45 to 90 m in width. Measurements made on Island Lake at distances of from 0.7 to 1.8 km 24 Open area of water 800 m across bay. from the station buildings. 25 Puddles cover 20% of bay area. 27 Puddles cover 60% of bay area. Ice thickness Snow depth 28 Puddles cover 80% of bay area. Date (cm) (cm) Jul 1 Shore puddle 45 to 90 m wide extends completely around bay area. 1971 4 30% of bay covered with puddles. Snow and slush cover Apr 9 8 cm of slush on top of ice. other parts of bay. 16 76 3 1968 16 15 cm of slush on top of ice. Data doubtful, information not used. 23 72 0 23 20 cm of slush on top of ice has refrozen. 1969 30 56 0 May 30 227 66 30 8 cm of slush on top of ice. Lead 15 m long and 6 m wide Jun 6 Last date ice cover used by light vehicles. on western tip of Stevenson Island. Lead approx. 5 m 18 Ice cover starting to deteriorate. wide and 5 km long extends from Stevenson Island to 19 No further information available. the SSW. May 1 No further information available.

68 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1972 1961 Apr 14 86 13 Mar 17 89 30 14 Numerous patches of slush 13 cm thick. 17 20 cm of slush ice included in thickness measurement. 21 75 5 24 79 18 21 Water seeping though cracks in ice. Open water on east 31 81 18 side of Wass Island. 31 20 cm of slush ice included in thickness measurement. Apr 28 62 3 Light hummocks along tidal crack. 28 10 cm of slush on surface. Open water WNW of Stevenson Apr 7 71 Island. Many small open holes in ice. 7 20 cm of slush on surface. May 5 51 3 14 71 5 14 Numerous puddles and considerable tidal water on surface. Open water 700 m SSW of measurement site. 21 74 5 12 Ice conditions unsafe. 22 Last date ice cover used by light aircraft. 1973 28 Ice conditions unsafe. Apr 20 74 18 May 1 Moose River breaking up, first boat crossed. 20 Numerous patches of open slush and layer of water under 10 River clear of ice. snow cover. 1962 27 71 5 Mar 31 66 23 27 Patches of frozen slush 5 cm deep on surface. Apr 6 May 4 63 Trace 56 13 4 6 Surface lightly ridged, tidal cracks and leads Lead off northern tip of Stevenson Island 9 m long and 24 Last date ice cover used by light aircraft, ice thickness 14 m wide. Crack 1 cm wide and 30 m long off Wass estimated 50 cm. Island. May 4 11 53 Trace Breakup begins. 11 Most cracks have refrozen, no slush observed. 12 River clear of ice, except for a few scattered pieces. 18 Ice conditions considered unsafe. 1963 1974 Mar 22 71 41 Apr 12 81 15 22 Tidal cracks with some surface water during high tides. 19 84 4 29 Some light hummocking, occasional tidal water. Observa­ 26 Top 10 cm of ice consists of frozen slush, 3 to 8 cm un­ tion site inaccessible because of flood water. frozen slush beneath snow cover. Open lead 9 x 15 m Apr 9 Last date ice cover used by light vehicles. in size off Stevenson Island. 28 Ice cover deteriorating rapidly. May 69 3 May 3 River clear of ice. 57 Trace 1964 Open water along most of shoreline. Apr 10 Maximum ice thickness approx. 86 cm on this date. Ice considered unsafe. 23 Last date ice cover used by light vehicles. No further information available. 24 15 m wide lead on left bank of river. 28 Breakup of river. 30 River clear of ice. MOOSONEE, ONTARIO 1965 Mar 18 107 20 Measurements made on Moose River about 30 to 75 m offshore, SE of 25 103 20 the station buildings. Apr 1 77 5 8 71 3 Ice thickness Snow depth 15 69 0 Date ___ (cm) (cm) 15 Leads formed along shore and extend to tidal crack. 25 Ice cover starting to deteriorate rapidly. 1960 29 Last date ice cover used to travel on. Apr 1 79 33 May 10 River clear of ice. 1 Tidal crack frozen. 1966 8 79 28 Apr 8 86 5 15 79 15 8 36 cm of slush ice between snow layer and ice. 15 8 cm water between ice and snow cover. 15 76 Trace 22 66 Trace 15 25 cm of slush ice on ice. 22 3 cm surface water refrozen. 20 Last date ice cover used by light vehicles. 29 Conditions unsafe due to rising water. 22 74 5 30 Last date ice cover used by light vehicles 22 Layer contains 5 cm of slush over 10 cm of water, over 5 cm May 2 Ice cover deteriorating rapidly. of slush ice on surface. 3 No further information available. 29 Ice conditions unsafe. May 15 Approx, date river became clear of ice. 1967 Mar 17 83 28 25 77 25 Some slush ice observed along the tidal cracks. 30 Water on ice along shore. 31 76

69 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date ______(cm) (cm)

1967 (cont’d) 1973 (cont’d) Mar 31 Patches of water on river ice, many tidal cracks. Mar 30 70 0 Apr 7 71 5 30 Several thaws have melted the snow and formed large 7 Few tidal cracks. accumulations of water on the ice. 14 66 31 No further information available. 14 Last date ice cover used by light vehicles. jgyj 17 Water along shore over tidal crack. ^pr 3 cm of water under snow cover, ice 25 cm from the top 21 Open water along shore, unable to reach measurement site. is soft. 28 Ice cover starting to deteriorate rapidly. ^9 82 15 May 25 River clear of ice. 19 Many areas covered with water due to tidal flooding. 1968 20 Ice considered unsafe. Mar 31 Maximum ice thickness of 107 cm observed on about May 11 Start of breakup. this date. Apr 7 102 7 8 cm rotten ice on surface, numerous puddles along shore- MOULD BAY, NORTHWEST TERRITORIES line from runoff. 14 Lead along west bank 15 m in width. Observation site Measurements made in Mould Bay at distances ranging from 0.8 to 2.4 km inaccessible due to rotten ice. Large deep puddles on west of the station buildings and runway, ice from creek runoff. 16 Last date ice cover used by light aircraft. Ice thickness Snow depth 17 Ice starting to break up. Date______(cm) ______(cm)______26 River clear of ice. 1969 1959 Apr 6 79 10 May 15 221 18 6 Few shoreline tidal cracks. 15 Several large cracks in ice. 11 76 31 218 20 15 Last date ice cover used to carry heavy equipment. Jun 5 218 3 18 70 5 Snow loose and wet. 18 Water on 75% of ice, tidal cracks along shore. 15 Ice cover unsafe for vehicular traffic. May 2 River broken up. Ice measurements terminated due to Jul 2 Ice measurements discontinued. cracks and excessive water. 1960 13 River clear of ice. Jun 13 221 5 1970 13 Numerous snow-covered cracks. Measurements made Mar 13 76 25 2.5 km out on bay in line with west side of runway. 20 72 10 21 Reports terminated due to water runoff and shore cracks. 28 74 10 1961 Apr 21 Ice cover starting to deteriorate. Jun 2 213 18 22 Last date ice cover used by vehicles 2 Snow becoming very coarse. Ice from the drilled hole May 9 River clear of ice. mushy. 1971 9 Measurements discontinued. Considerable surface water Feb 21 Measurement site flooded by tidal action. (up to 5 cm deep) covering dangerous cracks out to 27 Measurement site clear of snow due to tidal flooding. measurement site, 1.6 km from camp. Apr 3 81 5 1962 9 80 5 May 4 198 33 10 No further information available. 4 Depth of water beneath ice sheet at measurement site is 1972 approx. 27 m. Mar 31 Surface 30% covered with water. Top 38 cm of ice 11 180 46 candled. 25 188 51 Apr 7 102 13 Jun 1 183 43 7 Some water observed between two layers of ice. 1 Few cracks. 14 84 5 5 Ice cover unsafe for vehicular traffic. 14 5-cm layer of water observed between ice layers 33 cm 7 No measurements taken, water on ice. and 46 cm from top. 20 Ice thickness estimated to be 175 cm. 21 71 5 Jul 23 Bay clear of ice. 21 15 cm of water on ice at observation site. Numerous tidal 1963 cracks observed from 7 to 21 April. Jun 14 193 36 28 27 14 Ice cover unsafe for vehicular traffic. 28 3 cm of ice over 3 cm of water over 22 cm of ice. It is Aug; 3 Ice cover deteriorating rapidly. candled with several cracks and a few open leads. Open 22 Bay not completely clear of ice, approx. 9/10 open water observed near measurement site along sides of water on this date. sand bar. Lead at site estimated to be 4 m wide and 12 m long. 1964 May 29 173 74 1973 Jun 1 Surface conditions becoming unsatisfactory for use by Mar 23 71 Trace vehicles.

70 Ice thickness Snow depth Ice thickness Snow depth Date______(cm) (cm) Date______(cm) (cm)

1964 (cont’d) 1969 (cont’d) Jun 5 8 cm of slush on surface. Jun 13 231 36 12 25 cm of slush on surface. 15 Last date ice cover used by light vehicles. 19 157 25 Ice cover starting to deteriorate. 19 30 cm of slush and 8 cm of water on surface. Several 26 No further information available. 10-cm-wide cracks running lengthwise to bay. 1970 26 175 Jun 12 194 64 26 33 cm of slush and water on surface Numerous cracks 19 188 64 up to 3 cm wide. 19 Last date ice cover used by light vehicles. Jul 127 25 Ice cover starting to deteriorate. Water 25 cm deep on ice. Numerous cracks up to 25 cm Jul 29 Less than 1/10 open water observed in the bay. wide. Measurements discontinued; ice considered unsafe. 1971 Aug Bay does not completely clear of ice this year. May 21 201 25 28 191 1965 25 Jun 4 198 20 Jun 224 28 5 No further information available. First sign of water overflow onto ice from river. 196 23 1972 Water almost reaching ice measuring area. Ice considered May 19 Riot reported an open lead 50 km wide and 100 km long unsafe for vehicles. oriented N-S, 125 km west of Mould Bay. Numerous 20 Water from river combined with water at base of Thunder leads also reported running E-W approx. 200 km west Mountain. Water on ice extends from shoreline to of Mould Bay. horizon. Jun 9 198 41 25 203 38 18 205 20 Jul 2 191 0 23 201 13 9 Measurements discontinued. 23 Numerous cracks. Extensive areas of open water appear­ Aug Bay does not completely clear of ice this year. ing along shore. 30 Ice 60% covered with meltwater. 1966 Jun 165 30 1973 161 30 May 25 Snow cover becoming soft and wet. Ice cover unsafe for vehicular traffic. Jun 1 197 43 157 30 8 189 25 Jul Ice cover deteriorating, ice thickness estimated to be 50% of bay covered with pools of water. Depth of mnoff 130 cm. up to 61 cm in places. Aug 23 Bay clear of ice. 15 Ice becoming coarse, measurement site inaccessible due to 1967 surface flooding. 90% of ice surface covered with melt and runoff water. Apr 28 Ridging of ice greatest near shore line. May 5 217 33 1974 12 216 51 May 24 206 36 19 216 51 31 193 25 19 Ice crack 15 cm in width runs perpendicular from shore­ Jun 14 201 36 line at Thunder Mt., across length of bay. 21 188 58 26 215 28 Open area of water has formed along shoreline. Considerable Jun 2 218 46 melting and water runoff from the land. Water on ice 2 Ice soft and snow cover slushy. surface several centimeters in depth. Ice considered unsafe. 9 213 48 9 Light ridging of ice near shore. 16 218 41 NITCHEQUON, QUEBEC 30 Snow melted off bay leaving ice snow free, ice surface soft and wet. Runoff water from creek covering shore­ Measurements made on Lake Nichicun approximately 50 to 100 m SSW line area. of the landing dock. Aug 15 No significant clearing of ice on the bay observed this year. 1968 Ice thickness Snow < Date (cm) (cm Apr 26 Open leads reported by pilots approx. 50 km south of station. May 13 Ice thickness on small fresh water pond 1.6 km east of 1959 station 216 cm. Apr 24 94 46 31 175 64 May 1 91 43 Jun 1 Ice cover unsafe for vehicular traffic. 8 89 10 3 Meltwater over land began flowing onto ice. 15 84 5 19 A 1.2-km ice crack extends across the bay. 22 81 5 Jul 15 Ice cover deteriorating, ice thickness estimated 150 cm. 22 30-m lead running east 800 m in small bay. Aug 23 Bay clear of ice. 25 Ice cover unsafe for vehicular traffic. 1969 29 71 0 Jun 5 Numerous holes and cracks along entire shoreline. Ice con­ Jun 6 229 36 sidered unsafe.

71 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1959 (cont’d) 1964 (cont’d) Jun 11 Lead 30 m wide runs 400 m along shore. Numerous patches of broken ice in open water along shore. Apr 24 84 23 12 Ice breaking up and moving. Southern portion of lake 24 Shore cracks. and surrounding small bays open. May 1 15 cm of slush on surface. 13 Breakup complete, lake clear of ice. 8 Ice porous, conditions unsafe for vehicular traffic. 22 58 1 1960 23 Numerous shore leads. Apr 22 84 43 24 NE portion of lake completely free of ice. 22 10 cm of slush 60 m from end of dock. 29 Ice unsafe for measurements. 29 81 25 Jun 7 Ice broken up. May 6 79 8 6 5 cm of slush on surface. 9 Lake clear of ice. 13 74 8 1965 13 10 cm of slush on surface. Open lead on small bay in NE May 7 112 43 corner of lake. 7 3 cm of slush at snow/ice interface. 20 38 14 110 28 20 13 cm of slush on surface. 14 Surface water on ice in small pools near shoreline. 23 Ice cover unsafe for vehicular traffic. 21 107 5 27 Not measured due to unsafe ice conditions. Numerous 28 89 Trace cracks and holes. Small bay in NE corner of lake com- 28 Open water to the northeast. Open water increased con­ pletely open. siderably during strong winds, conditions unsafe for Jun 2 Breakup complete. Lake clear of ice. vehicular traffic. Jun 4 79 Trace 1961 8 Area NE of station free of ice. Apr 7 94 25 11 Ice appears to be approx. 30 cm thick at water’s edge. 14 91 20 but breaks easily. Lead 8 m wide along shore extends 14 5 cm of slush on surface. 1 km from station in SW direction. Ice breaking up 21 89 18 rapidly, lake approx. 50% free of ice by nightfall. 28 89 15 19 Lake completely clear of ice. 28 8 cm of slush on surface. May 5 81 5 (slush) 1966 12 71 3 (slush) Apr 1 93 20 19 64 0 22 91 0 26 Ice conditions along shoreline unsafe. Thickness estimated 29 86 0 to be 46 to 51 cm. May 6 84 0 Jun 2 25 0 6 Few patches of snow on ice. 2 Large leads along shoreline. 13 88 0 6 Breakup complete. Lake clear of ice. 13 Surface ice darkening near shore. 20 72 0 1962 55 3 Apr 27 99 28 27 Ice porous with many cracks, conditions unsafe for vehicular 27 Slush in bay part of lake. 27 traffic. May 4 99 20 31 No leads on the main part of the lake, the mouth of Ft. 4 10 cm of slush on surface. George River, SE of station, is 90% free of ice. 11 97 20 Jun 13 Breakup complete. Lake clear of ice. 11 18 cm of slush on surface. 18 86 3 1967 25 76 May 12 104 10 25 Ice very porous, large portion of NE part of lake ice-free. 19 102 Jun 1 51 26 90 8 25 31 The narrows at head of Ft. George River open all month. 8 Shore lead about 30 m wide. All large streams entering or leaving lake have opened 11 NE part of lake completely open, leads along shoreline also. and large amounts of water visible. 30 Ice rotten, lake breaking up. Jun 2 71 7 Open water all along shore of lake. Many small lakes nearby 1963 Apr 19 Snow cover variable 33-41 cm. 8-15 cm water on surface. are free of ice. 26 Water and slush on surface. 9 Lake considered unsafe. May 3 13 cm of water and slush on surface. 17 Main lake completely clear of ice. 10 99 1968 17 91 Apr 12 94 44 31 Ice cover unsafe for vehicular traffic. 19 91 8 Jun 7 36 19 Mouth of Ft. George River opened. 9 Open water out from shore approx. 30 m. 26 86 14 11 Breakup complete, lake clear of ice. 26 15 to 25 cm of slush observed on top of ice during April. Scattered areas of slush and snow observed. 800 m open 1964 30 Apr 3 102 water visible at mouth of Ft. George River. 5 17 18 cm of slush on surface. May 3 86

72 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1968 (cont’d) 1973 May 15 Ice cover unsafe for vehicular traffic. Apr 15 Channels are clear of ice with rapidly moving water. 17 64 20 117 46 24 33 27 104 38 31 Breakup proceeding quite rapidly. All small lakes, ponds 27 8 cm of slush and 5 cm of water at snow/ice interface. and streams ice-free, main lake still approx. 75% May 4 107 15 ice-covered. 11 89 0 Jun 1 Lake 50% ice-covered. 15 Open lead formed around shoreline. 2 Lake 5% ice-covered. 18 Ice thickness estimated to be between 46 and 61 cm. Ice 3 Breakup complete, lake clear of ice. conditions unsafe, numerous cracks and holes observed. 25 Ice appears black and candled, thickness estimated to be 1969 20 cm. Apr 19 Last date ice cover used to hold heavy equipment. 2 leads have formed further out on the lake. May 2 91 20 27 12 Area of open water approx. 800 m east of station. Ice 1974 melted in many places on lake where water is moving. Apr 19 116 36 Lead nearest station is approx. 1 km in length and 26 109 30 30 to 400 m in width. May 10 109 10 16 79 3 11 No further information available. 23 76 30 58 5 30 Ice very rotten. Many pools of water on ice surface. Thaw NORMAN WELLS, NORTHWEST TERRITORIES holes and crystalline ice make ice conditions unsafe. Jun 6 43 Measurements made on the MacKenzie River at distances of 100 to 300 fn 6 Many leads formed around the edges of the lake, but ice offshore, south of the station buildings. in the center remains quite strong. 10 Ice very rotten and crystallized. Ice thickness Snow depth 13 Heavy rain followed by strong winds, breaks up ice. Date (cm) (cm) 14 Lake approx. 60% ice-free. 15 Approx. 95% of ice melted or washed downstream. Lake 1959 nearly clear of ice. Apr 10 180 1970 24 Surface conditions becoming unsatisfactory for vehicular Apr 24 112 23 traffic. 29 Last date ice cover used by light aircraft. May 1 175 May 1 91 8 175 3 8 79 8 Large cracks in ice, unable to make further measurements. 15 53 20 Ice starting to break up. 22 46 21 No further information available. 29 36 1960 Jun 5 36 Apr 26 Surface conditions becoming unsafe for vehicular traffic. 14 Lake starting to break up. 29 175 0 17 Lake clear of ice. May 20 Ice starting to break up. 1971 21 River clear of ice, except for a few scattered pieces. Apr 16 91 43 1961 23 79 13 Apr 157 8 May 7 66 28 157 14 53 May 5 Ice cover considered unsafe for vehicular traffic. 21 33 5 23 Ice starting to break up, ice estimated to be 80 cm thick 28 15 Jun 1 River clear of ice. 72 1962 Apr 14 109 20 Apr 150 53 28 100 33 20 147 51 May 5 104 25 27 147 38 12 99 23 27 Numerous cracks in ice. 13 Outlet of Lake Nichicun is open. May 4 Considerable water on ice, conditions unsafe for vehicular 19 91 3 traffic. 26 90 3 23 Ice cover breaking up, ice estimated to be 60 cm thick. Jun 2 69 . 5 28 River clear of ice. 9 43 16 18 1963 16 Shore lead is 15 m in width. Ice thickness was estimated. Apr 19 152 25 18 Lead 300 m out from shore is 60 m in width. 26 Vehicular traffic terminated because of excessive water on 21 Lake completely free of ice. ice. May 10 Ice starting to break up. 31 River clear of ice.

73 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1964 1971 (cont’d) Apr 3 183 Apr 30 Pools of water on surface of river from melting snow. 28 Surface conditions becoming unsatisfactory for vehicular 5 cm of new ice formed on water lying on surface of traffic. river ice. 30 River ice appears to have lifted during past week, a few May 1 No further information available. areas of slush on edge of river. 1972 May 1 180 25 Mar 31 163 41 8 No further ice thickness measurements possible, ice unsafe. 31 Bottom 30 cm of ice appears to be candled and rotten. 27 Ice cover breaking up. Apr 7 157 36 31 River clear of ice, except for a few scattered pieces. 21 160 36 1965 28 155 36 Mar 20 183 0 28 Bottom 30 to 38 cm of ice candled and rotten. Thickness Apr 10 178 0 of candled ice varied slightly from day to day. 17 175 0 May 5 145 36 24 Shallow pools of water forming on top of ice along shore. 12 Shore lead 45 m wide along shore made it impossible to 26 173 0 measure ice thickness. May 24 Ice breakup starting. 1973 30 River clear of ice, except for a few scattered pieces. Mar 23 161 18 1966 30 160 10 Apr 8 131 5 31 No further information available. 22 122 5 1974 29 128 5 Mar 29 183 20 May 6 119 0 Apr 5 180 18 6 Ice rotten, candle ice covering surface, several thaw holes. 12 181 18 9 Ice cover unsafe for vehicular traffic. 19 173 10 10 Open water along shoreline. 26 169 8 15 First movement of ice. 27 No further information available. 16 Open areas of water. Heavy flow of ice with continuous breaking and jamming. 28 River clear of ice. NORWAY HOUSE, MANITOBA 1967 Apr 28 150 20 Measurements made on Nelson River near the landing dock on the east May 1 Ice cover considered unsafe for vehicular traffic. side of Forestry Island. 5 123 5 Ice candled to a depth of 46 cm, water on ice along shore- Ice thickness Snow depth line. Date (cm) (cm) 19 Ice starting to break up. 28 River clear of ice. 1957 1968 Mar 1 Maximum ice thickness approx. 122 cm. Apr 29 Surface conditions becoming unsafe for vehicular traffic. Apr 15 Ice cover unsafe for vehicular traffic. May 5 150 15 27 Ice starting to break up. 12 147 0 May 4 River clear of ice. 19 137 0 1958 26 119 0 Information missing. Jun 10 River clear of ice. 1959 1969 Apr 19 Ice cover unsafe for vehicular traffic. Ice thickness observations omitted. Measurements made May 6 Ice starting to break up. at different sites are inconsistent. 11 River clear of ice. Apr 12 Last date ice cover used by heavy vehicles. 18 Measurements made 180 m from shore. Depth of water 1960 under ice only about 15 cm. Apr 15 Ice cover unsafe for vehicular traffic. May 25 River clear of ice. 21 Ice cover deteriorating rapidly. May 3 River clear of ice. 1970 Mar 20 166 10 1961 27 157 10 Apr 20 Ice cover unsafe for vehicular traffic. Apr 3 145 10 28 Ice starting to break up. 6 Last date ice cover used by heavy vehicles. May 3 River clear of ice. 10 145 10 1962 12 Ice cover starting to deteriorate. Mar 1 Maximum ice thickness approx. 61 cm on this date. 17 138 Apr 5 Ice cover unsafe for vehicular traffic. May 26 River clear of ice. 10 Ice cover starting to deteriorate. 1971 May 1 River clear of ice. Apr 9 182 23 16 180 41 23 177 18 30 165

74 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

No data available for 1963 - 1970. 1965 (cont’d) 15 1971 May 15 145 Feb 26 114 20 22 142 15 28 Very cold weather first part of month has increased thick- 29 141 15 ness of ice. Warmer weather during balance of month Jun 5 142 15 15 has caused decrease in height of snow drifts. 12 145 Mar 5 112 20 12 Leads forming near shoreline. 13 114 23 19 142 15 Apr 3 91 23 26 132 15 from point 900 m 9 91 5 26 Lead 3 m wide, 3 km long running NNE 16 91 3 east of Hudson Bay Company store. 24 76 Jul 3 104 15 30 71 3 Ice broken along shore to 9 m offshore. May 1 No further information available. 10 89 0 10 Ice broken along shore to 90 m offshore.. Some holes in ice. 1972 11 Lead formed from north end beach SW for 1.2 km, 4 m Feb 25 104 25 wide. 25 Surface mostly covered with hard and drifted snow. No 17 74 0 cracks in ice visible. 17 4/10 coverage along shore to 800 m offshore, then 10/10 Mar 3 81 25 ice coverage. 10 81 25 24 2/10 coverage along shore to 3 km offshore, then 10/10 ice 17 79 20 coverage. 24 79 13 31 8/10 coverage along shore to 800 m offshore, then 10/10 31 79 13 ice coverage. 31 Snow cover settled due to warm daytime air temperatures. Apr 7 79 13 1966 14 79 13 May 14 163 23 20 21 76 21 164 21 Patches of snow observed on ice. 28 165 18 26 Small open water patches in areas where river current is Jun 4 165 13 strong. 5 No further information available. 27 High water lifted ice cover in river. 1967 28 71 Missing. 28 Some cracks in ice along shoreline. 1968 29 No further information available. May 31 141 25 1973 31 Pressure ridges near shoreline breaking up, water present Feb 28 71 25 during high tide. Snow cover very soft and wet, melt- Mar 2 61 25 ing fast. 12 53 0 Jun 7 127 20 27 53 0 14 119 17 Apr 4 56 13 21 117 10 13 53 0 28 114 13 Holes have formed in river ice. 28 Ice unsafe for aircraft landing. Pot holes., cracks and water 19 Open water near United Church Point approx. 400 m away. on surface. 2-4 m of open water along shoreline. Lead 20 No further information available. in river 8 km SW of settlement gradually opening. 1974 Jul 5 95 Mar 21 61 30 12 86 21 8 cm of slush and water observed beneath snow cover 17 Lead 1.6 km NE of settlement, approx. 8 km in length, during March. 1-2 m in width. Open water extends from settlement Apr 5 66 48 to Salmon River, distance from shore to ice is approx. 12 66 41 \Vx km. 19 66 25 (slush) 19 76 26 Major crack formed on ice. 19 Ice broken up and drifted out to 5 km from shore with tide. 30 38 0 26 61 May 1 No further information available. Aug 30 During first 2 weeks in August considerable ice in the sound, consisting of large pans and pack ice which on occasion close off the inlet but move with wind or tidal changes. POND INLET, NORTHWEST TERRITORIES Inlet clear of ice on 14, August but floating pans of ice were still observed on 30 August. Measurements made on Eclipse Sound off Baffin Bay about 1 km 1969 north of the settlement. Incomplete. 1970 Ice thickness Snow depth May 1 117 25 Date______(cm)______(cm)______8 117 20 15 114 25 1965 22 117 25 May 8 147 15 29 117 25 30 No further information available.

75 RESOLUTE, NORTHWEST TERRITORIES Ice thickness Snow depth Date (cm) (cm) Measurements made in Resolute Bay at distances ranging from 100 to 800 m offshore toward the center of the bay. Apr 27 178 43 Ice thickness Snow depth May 4 165 58 Date (cm) (cm) 12 168 51 19 165 51 1959 25 165 46 Apr 27 213 23 Jun 2 163 48 May 5 211 20 2 Surface slushy. 12 Snow hard-packed on top. Bottom 31 to 46 cm of ice 8 175 38 seemed soft and possibly contained some water. 8 Tidal cracks observed near shore. 21 206 23 15 175 27 203 15 Surface covered with 20 cm water, many cracks. 27 23 cm of melting snow on surface. 22 155 Jun 13 208 28 22 Ice rotten and puddled. 13 Snow cover slushy. 29 132 21 Snow cover slushy. Bottom 61 cm ice soft. 29 Cracks over the entire bay. Holes and open water visible 28 8 cm of water and slush on surface. to seaward. Jul 7 155 Jul 7 114 13 147 7 Bay mostly open water. 13 Many shallow pools of water on surface. 13 89 20 137 (Estimated) 13 Wide shore leads and open water at mouth of bay. 20 Large water pools on surface. Measurement impossible 18 Ice broken. Bay clearing rapidly. due to open water along shore 2 to 6 m wide. 19 Bay clear of ice except for a few scattered pieces. 24 6/10 of bay ice-covered. SW bay area completely free. 1963 Outside of entrance to the bay is clear of ice. Jun 21 211 13 1960 21 Freshwater pools 15 cm deep on ice, small shore leads. May 24 178 41 28 Ice conditions becoming unsafe for vehicular traffic. Jun 1 175 41 29 201 6 173 41 29 Surface 75% water-covered. Few cracks across bay. No 12 173 41 open water observed. 20 163 41 Jul 6 191 20 Surface 50% water, few tidal cracks appearing around edge. 6 Numerous cracks and holes observed, average width 30 cm. 27 160 12 165 27 Surface 60% water. 12 Heavy puddling, shore cracks widening. Jul 4 132 19 130 12 102 19 Surface puddled, no leads observed. 12 Surface dry with icy crust on remaining melt puddles. 26 122 18 15 ice measurements taken 91m offshore toward center Aug 21 Bay clear of ice except for a few scattered pieces. of bay. Maximum thickness 91 cm, minimum 53 cm. 1964 Surface 51% puddled, eastern portion of bay (adjacent Jun 12 193 Unknown to stream inlet) is 1/10 open water. 19 Narrow cracks in ice, due to tidal action. Snow cover 25 1/7 of bay on NE side free of ice. Entire bay beyond 120 m saturated with water. from shore is open water. Open water between bay 24 Puddles of water at ice/snow cover interface. mouth and Griffith Island. Open water visible 19 to 26 188 33 24 km S and SE from bay mouth. 27 No further information available. 1961 1965 Jun 16 213 37 Jun 11 211 43 16 Surface puddled. Surface snow mostly packed and wet. 18 208 36 23 206 18 Auger lost through the ice. Ice becoming rotten. 23 Site covered with 18 cm water-slush. Bay 60% surface 25 Surface smooth and puddled, no cracks. Snow extremely covered with pools of water 8 to 13 cm deep. wet. 30 193 26 No further information available. Jul 7 Ice thickness variable 173 to 188 cm, snow cover is wet. 14 Ice thickness variable 137 to 170 cm, Barrow Strait com­ 1966 pletely open with rafted ice 5 km offshore of Corn- May 27 199 41 wallis-Somerset Islands. Jun 3 196 41 21 Ice thickness variable 117 to 135 cm. Ice visible offshore 10 199 43 of Somerset Island. 17 196 43 28 Ice thickness variable 89 to 109 cm. Only ice visible is 24 206 25 landfast ice in inner bay, open water along shore at 24 Surface soft and wet. creek entrance. Jul 1 183 13 Aug 7 Bay temporarily clear of ice, new ice and/or drift ice 1 Ice conditions becoming unsafe for vehicular traffic. reappeared later. 8 157 0 15 141 0 22 127 0 29 76 0

76 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm) Date (cm) (cm)

1966 (cont’d) 1971 (cont’d) Jul 29 Tidal shore lead 2 to 3 m wide. Large open area at mouth Jul 9 114 of river. Surface smooth, numerous cracks. 16 88 Aug 5 38 (estimated) 0 1972 5 Large open area observed. Jun 23 188 58 8 25 0 30 165 30 12 Complete breakup. Bay clear of ice except for a few Jul 7 155 scattered pieces. 8 No further information available. 25 Bay completely clear of ice on this date. 1973 1967 Jun 8 170 51 Jun 23 236 15 8 Few narrow cracks in ice. 30 231 15 180 15 (slush) 30 Tidal cracks, 8 cm of water on ice surface, conditions be­ 15 Water observed in cracks on ice, some water on surfa coming unsafe for vehicular traffic. 22 180 0 Jul 7 Large shoreline crack and considerable amounts of water 22 5 cm of water on surface. on ice. 29 138 0 15 198 29 Surface 3/10 covered with puddles. 22 178 1974 28 152 May 17 186 33 28 Bay approx. 60% covered with ice. Considerable cracking 24 173 33 of ice and puddling on surface. Jun 7 160 53 Aug 14 Bay clear of ice. 14 163 66 1968 28 160 20 Jul 5 206 5 28 Few cracks visible. 12 172 28 No further information available. 12 Numerous leads near shore. 19 163 19 Fresh leads forming across bay. SACHS HARBOUR, NORTHWEST TERRITORIES 26 138 26 Surface crusty. Large lead across mouth of bay. Measurements made in Sachs Harbour, which extends into Amundsen Gulf, Aug 2 Ice measurement discontinued, unsafe ice conditions approximately 50 to 150 m offshore, south of the RCMP office. and wide shore leads. Aug 10 Approx, date bay becomes temporarily clear of ice. New Ice thickness Snow depth and/or drift ice reappeared later. Date ______(cm) ____ (cm) 1969 Jun 20 201 1959 27 193 May 15 Snow cover wet. 27 Last date ice cover used by light vehicles. 25 Large lead in the harbor 5 km from shore, widening rapidly. Jul 5 168 31 206 20 11 173 (estimated) 31 Ice thickness on a nearby lake 203 cm. 15 Ice cover starting to deteriorate rapidly. Jul 1 168 5 18 131 1 Snow wet, water patches 5 to 13 cm deep. Several cracks 25 122 in ice approximately 30 to 91 cm wide. Aug 14 Bay clear of ice. 14 Strong north and northeast winds cleared harbor of all ice 16 New and/or drift ice has reappeared in the bay. except small patch near shore. 1970 1960 Jun 19 175 64 May 31 196 19 Last date ice cover used by light vehicles. 31 Snow 2 to 25 cm deep. Open water approximately 8 km 26 155 43 offshore. 26 Water on surface of ice. Jun 15 173 Jul 10 Average of ice thickness measurements made on 3 and 10 15 Surface puddled, numerous cracks. Open water 3 to 5 km July is 146 cm. offshore. Scattered patches of wet snow. 17 124 26 Ice breaking up. 24 84 1961 31 75 May 19 229 Aug 10 Bay temporarily clear of ice, new and/or drift ice reappeared 19 Snow cover variable 5 to 8 cm. later. 26 226 1971 27 Sea water visible on horizon since 18 May. May 29 189 58 Jun 2 224 3 29 Surface smooth. 2 Numerous cracks. Jun 4 180 61 5 Ice conditions becoming unsafe for vehicular traffic. 11 175 61 9 185 18 168 30 9 Sea water visible from station. Jul 2 151 16 152

77 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1961 (cont’d) 1967 (cont’d) Jim 22 Ice breaking due to strong southeast winds. Jun 23 183 8 23 Ice moving in bay. 23 Lead now approx. 3 km wide. Jul 6 Harbor clear of ice. 30 Measurement not taken due to water on ice. Jul 4 Last date ice cover used by light aircraft. 1962 5 No further information available. May 25 183 30 25 Lead 8 km south of station, width variable depending on 1968 wind direction. May 24 155 23 Jun 1 185 76 30 Ice conditions becoming unsafe for vehicular traffic. 1 Snow drifts 23 cm in height. 31 152 13 8 170 3 Jun 7 135 8 Snow drifts 10 cm in height. 14 104 10 Ice conditions becoming unsafe for vehicular traffic. 21 58 12 Ice cover starting to deteriorate. 25 Large cracks opened up. Jul 12 Harbor clear of ice. 26 Cracks widened into leads. 27 Bay ice broke up and moved out. 1963 Jul 5 Harbor clear of ice. May 24 207 10 24 Snow cover drifted. 1969 31 Ice conditions becoming unsafe for vehicular traffic. Apr 25 171 10 Jun 7 199 May 2 169 10 14 152 9 168 10 14 Surface 50% puddled. 16 157 10 21 Ice unsafe to walk on, numerous deep puddles and cracks. 23 147 8 Jul 1 Breakup began. 30 140 8 12 Harbor clear of ice. Jun 6 138 8 10 Last date ice cover used by light aircraft. 1964 13 133 8 May 29 216 20 130 29 Ice conditions becoming unsafe for vehicular traffic. 27 97 Jun 19 203 Jul 4 Surface water covered. Shore lead approx. 75 m wide. 19 Water on ice. Ice unsafe, numerous deep cracks and puddles. 26 Open lead several km in width opened up outside of bay. Harbor 75% clear of ice. Ice unsafe, numerous deep cracks and puddles. 8 12 Harbor clear of ice. Aug 28 Bay clear of ice except for a few scattered pieces. Bay probably became temporarily clear of ice on earlier date. 1970 May 15 157 28 1965 23 155 23 May 28 188 8 30 155 3 Jun 18 175 0 30 Last date ice cover used by light aircraft. 25 163 0 Jun 6 151 25 Shore lead estimated 2 m wide and approx. 400 m in length. 13 146 Ice covered with thin film of water. Open water 5 to Harbor clear of ice. 8 km out depending on wind. Jul 10 27 Ice conditions unsafe for vehicular traffic. 1971 Jul 8 Ice cover deteriorating rapidly. May 7 183 18 18 Bay temporarily clear of ice. New ice or drift ice re­ 7 Maximum ice thickness observed. appeared later. 14 173 10 28 173 8 1966 Jun 5 178 8 May 13 196 8 12 174 8 20 191 0 19 155 5 25 Ice conditions becoming unsafe for vehicular traffic. 20 No further information available. 27 182 3 27 Few cracks. 1972 Jun 3 178 0 May 13 191 5 11 163 3 19 189 5 19 100 0 20 A large section of sea ice broke away from landfast sea 25 97 0 ice forming a lead approx. 8 km out from shore. 25 Numerous cracks from 10 to 25 June. 28 183 5 Jul 15 Bay temporarily clear of ice. New ice or drift ice re- 28 Slush forming on surface of sea ice and some small cracks appears later. becoming wider. Jun 2 175 5 1967 9 175 3 May 19 203 23 170 3 26 201 25 18 Ice unsafe for travel. Jun 2 201 25 28 No further information available. 9 201 28 29 16 198 23 16 Lead approx. 400 m wide and approx. 130 km long.

78 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1973 1961 (cont’d) May 4 165 23 Jun 1 Ice conditions unsafe for vehicular traffic. 11 155 18 2 46 18 152 20 2 Ice candled, considered unsafe for measurement. Ice cover 25 No thickness measurement made, runoff water flooded 80% concentrated at south end of lake. observation site. Open water reported 15 km from 9 25 (estimated) shore. 9 Ice cover 40%. Ice at south end of lake. Jun 1 147 0 11 Lake clear of ice. 8 No further observations, runoff from Sachs River has 1962 opened an area several meters wide along the shoreline. Apr 27 99 19 30 little ice in sight, few small floes observed. 27 Isolated slush patches cause local thawing followed by re­ 1974 freezing and hardening of ice. May 10 190 23 May 4 107 10 17 188 8 6 Considerable slush and standing water observed. 24 190 5 11 107 3 31 185 3 18 86 8 Jun 3 Large lead several kilometers wide developed, extending 18 Snow cover mostly slush. southward toward open water. 25 76 8 7 183 3 25 Snow cover mostly slush. 14 180 3 31 Ice becoming soft, and some open water and cracks observed. 17 Shoreline free of ice. Remaining ice cover in harbor is Jun 1 65 Trace about Wi km wide and 8 km long. 1 5% open water mainly in northwest bay. Ice deteriorating rapidly. 6 Pearce Lake free of ice. SCHEFFERVILLE (KNOB LAKE), QUEBEC 8 Knob Lake 80% ice-covered but ice too rotten to permit measurements, Measurements made in Knob Lake approximately 400 m off the north 13 Knob Lake clear of ice except for a little loose brash at shore. the south end. 1963 Ice thickness Snow depth May 3 113 36 Date (cm) (cm) 10 127 5 10 Ice thickness increased by final freezing of a slush layer 1959 present on the lake for nearly a month. Apr 20 Maximum ice thickness approx. 124 cm on this date. 15 Warm temperatures caused the ice to deteriorate rapidly May 4 Ice conditions unsafe for vehicular traffic. causing a marked decrease in ice thickness. 14 Ice cover deteriorating rapidly. 17 99 28 Lake clear of ice. 17 Pools of open water formed around the edges of the lake. 1960 24 86 5 Apr 20 Maximum ice thickness approx. 119 cm on this date. 31 79 May 15 Ice conditions unsafe for vehicular traffic, 31 Access onto lake becoming difficult because of shore leads. 20 Ice cover starting to deteriorate. Jun 7 51 Jun 4 Lake clear of ice. 7 Shore lead continuous around lake. Access onto lake gained by means of a wooden plank. 1961 18 Lake completely ice-free. Mar 24 122 29 31 122 21 1964 31 Crusted snow and areas of frozen slush. Apr 3 122 51 Apr 7 122 19 13 Snow cover on lake melting fast. 7 Snow depth variable 3 to 36 cm. Areas of slush 10 cm deep, 24 114 8 thin slush under soft snow. 24 Surface slushy. 14 117 14 May 22 Shore leads have formed. 14 Areas of frozen slush, thin crusted snow. 29 69 21 119 11 29 Ice thickness measurements during April and May made at 21 Snow depth variable 3 to 20 cm. Crystalline wet snow, west end of lake. numerous areas of slush with thin ice crust. Jun 12 Lake clear of ice. 28 112 6 1965 28 Snow depth variable 3 to 10 cm. Crystalline snow, 40% Apr 23 133 38 slush cover under thin ice crust, slush up to 20 cm 30 126 36 deep. May 7 128 38 May 5 99 Trace 14 133 3 5 Slush 15 to 20 cm deep and thin water layer beneath 21 114 3 12 94 Trace 28 103 3 12 100% frozen slush cover, ice thin along the lake shore. 31 Slush on ice during May. 19 86 Jun 17 Lake clear of ice. 19 Approx. 1 m open water along the shore. Ice very wet. 26 79 26 3 to 5 m open water along shore line. Ice very soft in places.

79 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1966 1971 Apr 22 105 0 Apr 24 91 20 29 97 Trace 24 Approx. 8 cm of water between the ice and the snow cover. May 6 93 3 May 7 85 15 13 98 5 14 79 5 20 83 3 21 74 27 61 5 31 58 27 Shore lead developed and cracks in ice began to open, con­ Jun 1 No further information available. ditions unsafe for vehicular traffic. 1972 Jun 3 50 3 May 5 147 23 3 Shore lead and some open cracks in ice. Extensive areas 12 121 16 of original lake ice noticed as the slush ice melted. Sur­ 19 110 3 face water pools up to 10 cm deep. 26 110 1 16 Lake clear of ice. 26 Surface was slushy and ice cover consists of mostly bubbly 1967 ice all month. Apr 28 137 20 Jun 1 No further information available. 28 Patches of bare ice beginning to show. 1973 May 5 136 5 Apr 27 135 33 12 123 May 4 104 13 12 Slush forming on surface. 4 Ice cover slushy. 15 118 11 97 5 26 102 12 No further information available. 26 Slush areas observed adjacent to shore. Jun 2 88 1974 2 Shore leads and a number of open cracks close to main Apr 5 127 30 inlet. First evidence of ice candling. 19 126 25 5 Considerable reduction in ice cover, lake 65% covered. 26 124 18 9 Ice conditions unsafe. May 3 124 20 10 Lake continued to clear under influence of strong NW winds. 14 107 3 12 Lake clear of ice. 24 100 0 25 No further information available. 1968 Apr 12 124 33 19 123 23 SCHEFFERVILLE (MARYJO LAKE), QUEBEC 26 Surface of lake flooded to a depth of 23cm. Depth of slush varied throughout month. May 3 118 10 Measurements made in Maryjo Lake approximately 200 m off the south 10 118 shore. 17 99 20 Small area of open water appeared in Post Office Bay. Ice thickness Snow depth 24 85 Date (cm) (cm) 24 Sh ore crack along the northwest and north side of lake developed. 1959 and 1960 31 Inshore ice still hard, ice further out very soft, and con­ Not available. sidered unsafe. Jun 6 Lake clear of ice. 1961 Mar 31 137 20 1969 31 Snow depth variable 5 to 36 cm. Crusted snow and areas Apr 25 104 41 of frozen slush. May 2 100 Apr 7 135 20 3 Last date ice cover used by light vehicles. 7 Slush area 20 cm deep near south end of lake. 15 A small polynya developed at the outlet of the lake. 14 135 13 16 94 3 14 Extensive area of frozen slush. Snow cover crusty. 23 97 3 21 130 4 30 A shore lead started developing. Top layer of white ice 21 50% snow coverage. Open water at south end of lake. turning into slush. Patches of slush. Jun 6 64 28 122 4 12 A cross channel lead developing. 28 Snow depth variable 0 to 8 cm. 50% frozen slush under 13 Shore lead widened, ice considered unsafe. ice crust. 18 Ice broken up. Lake clear of ice. May 5 109 0 1970 5 80% free water on top of ice. 30 cm slush and water in Mar 14 117 20 places. 21 114 30 12 97 Trace 28 112 53 12 Open water around most of shore. Surface honeycombed. May 8 Ice cover starting to deteriorate 19 91 0 Jun 13 Lake clear of ice. 19 Ice wet, 1 m of open water around shore.

80 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1961 (cont’d) 1967 (cont’d) May 26 Ice thickness estimated to be 76 cm. Ice considered un- May 5 108 safe. 10% open water around shore and at south 12 102 end of lake. 12 Extensive slush forming on surface of ice. Jun 2 Ice thickness estimated to be 41 cm. Ice cover 85%, no 19 98 snow on ice. South end of lake open. 22 Shore cracks noted along western shore. 9 Ice thickness estimated to be 30 cm. Ice cover 50%. Ice 26 91 separated into 3 large pans. 26 Lead developing westward from the southern inlet. 13 Breakup complete. Lake clear of ice. 31 Areas of slush adjacent to shore. 1962 Jun 2 70 Apr 20 114 36 2 Extensive shore leads and cracks extend from southern in­ 27 109 27 let, and along eastern shore. May 4 112 23 5 First candling and large reduction in ice cover between 2 11 109 23 and 5 June. Southern part of lake cleared first, due to strong southwest 18 109 5 8 25 97 5 winds and water inflow. 25 Stream flowing into the southern end of the lake opened 9 Slush ice on east shore of lake. on 4 and 25 May, but closed on 11 and 18 May. 10 Lake clear of ice. Jun 1 86 Trace 1968 8 Ice deteriorating rapidly. May 3 114 25 15 Maryjo Lake clear of ice. 10 99 5 1963 17 102 3 May 10 135 Trace 24 81 31 79 Trace 31 72 Jun 16 Lake clear of ice. 31 A meltwater stream started flowing onto the lake ice on 17 May in the SE corner. Flow opened up a small pool 1964 of water which broke the ice edge to about 18 m offshore Mar 20 Slush between the snow and the ice surface increased. by the end of the month. 5-18 cm of slush observed in places. Jun 6 I^ake clear of ice. Apr 17 130 23 17 Ice cover snow-free in spots. 1969 through 1974 24 119 15 Not available. 24 Surface slushy. 30 Considerable slush encountered by end of month. Ice SPENCE BAY, NORTHWEST TERRITORIES thickness slowly decreasing. May 1 Ice conditions unsafe for vehicular traffic. Measurements made in Spence Bay Harbour at distances of from 120 to 29 Ice thickness on nearby lake 69 cm. Jun 11 Lake clear of ice. 300 m south of the north shore. 1965 Ice thickness Snow depth Apr 23 131 38 Date ______(cm)______(cm)______23 Maximum ice thickness observed on east side of lake. May 7 126 20 7 Ice conditions unsafe for vehicular traffic. 1959 May 15 Maximum ice thickness approx. 183 cm on this date. 14 117 5 21 104 3 Jul 3 Ice cover starting to deteriorate. 10 Ice conditions unsafe to travel on. 28 91 0 28 Slush on surface during May. Aug 11 Spence Bay harbor clear of ice. Jun 16 Lake clear of ice. 1960 May 27 236 8 1966 Jun 4 236 7 Apr 22 104 0 10 224 0 29 98 Trace May 6 98 3 10 Leads opening up along shoreline. 13 99 5 24 132 0 20 86 5 24 Few cracks along shore. Jul 26 Spence Bay harbor clear of ice. 27 62 8 27 Shore lead has formed, conditions unsafe for vehicular 1961 traffic. May 5 234 20 Jun 3 50 5 12 236 25 3 Shore lead widened. 19 236 23 17 l^ake clear of ice. 26 236 20 Jul 7 127 1967 Apr 21 114 25 7 Few cracks observed. 14 61 21 Ice thickness measurements were taken on west side of lake. 14 Numerous cracks observed. All harbor ice floating free. 28 109 20 Harbor ice broken up. 28 Patches of bare ice observed. South inlet opening up, water 25 Harbor clear of ice. observed flowing into lake.

81 Ice thickness Snow depth TROUT LAKE, ONTARIO Date (cm) (cm)

1962 Measurements made in bays on eastern side of Big Trout Lake approxi­ May 15 Maximum ice thickness approx. 241 cm on this date. mately 50 to 150 m south of the station landing dock. Jul 20 Harbor ice breaking up. 27 Harbor clear of ice. Ice thickness Snow depth Date (cm) (cm) 1963 Incomplete 1961 1964 Apr 7 97 20 Apr 17 203 25 14 102 18 May 8 198 30 21 Wet snow on ice. Jun 26 183 3 28 99 Jul 13 Ice conditions unsafe for travel. May 5 86 Aug 30 Harbor clear of ice. 16 Ice conditions unsafe for vehicular traffic. 1965 19 81 May 7 239 25 21 Ice cover starting to deteriorate. 14 231 28 Jun 5 Lake clear of ice. 21 230 28 1962 28 229 30 Apr 13 97 25 Jul 8 Ice conditions unsafe for travel. 20 94 20 Aug 16 Spence Bay Harbour clear of ice. 27 94 18 1966 May 4 91 3 May 20 196 0 11 84 3 27 188 0 15 Ice conditions unsafe for vehicular traffic. 27 Few cracks in ice. 18 61 Jun 3 178 0 25 Ice breaking up. 3 Numerous cracks. 28 Front bay clear of ice. 10 165 0 Jun 5 Lake clear of ice. 17 157 0 1963 18 No further information available. Apr 5 124 8 1967 May 10 107 5 May 19 185 15 15 Ice conditions unsafe for vehicular traffic. 19 Ice becoming soft approx. 90 cm below surface. 17 84 27 184 17 Some open breaks along shore. Jun 2 184 15 24 74 9 183 15 Jun 17 Lake clear of ice. 178 23 1964 23 Unable to take ice thickness at regular site, water com­ Apr 24 109 pletely covering area. Thickness taken approx. 400 m May 5 Ice conditions unsafe for use by light aircraft. from north shore. 8 Open water around shoreline. 30 179 10 Ice gradually clearing from lake. Jul 11 Ice conditions becoming unsafe for travel. May 23 Lake clear of ice. Sept 15 Spence Bay Harbour does not completely become clear of ice this year. Maximum open water of 8/10 observed 1965 on this date. Apr 16 104 10 23 107 5 1968 30 102 3 May 31 231 25 May 7 86 0 31 Six pressure ridges along east shore. 12 Ice conditions unsafe for use by light aircraft. Jun 7 196 10 14 61 0 14 185 10 14 Surface candled, open cracks near shore. 173 21 27 Front bay clear of ice. 28 160 Jun 5 Lake clear of ice. 28 4 m-wide lead along shore extends eastward for 1 km. 60% of ice covered with water. 1966 Jul 5 151 Apr 8 89 30 12 117 15 86 20 12 Navigable lead extends 1.6 km along shoreline, west of 22 85 20 station. 60% of ice covered with water, mostly around 29 81 5 shore. May 13 81 0 13 No further information available. 20 79 0 21 Last date ice cover used by light aircraft. 1969 through 1974 22 Ice conditions unsafe. Not available. 23 Leads 3 to 6 m wide, ice cover deteriorating rapidly. 25 Back bay % open. 27 Front bay open. 28 Front bay clear of ice. Jun 5 Lake clear of ice.

82 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

'67 1971 (cont’d) Apr 21 Measurement site has 8 cm of water on top of ice. May 7 69 28 1 cm of ice on 8 cm of surface water. 14 Ice considered unsafe. May 12 127 5 1972 19 116 Apr 7 133 10 21 Ice cover starting to deteriorate. 7 At approx. 3 km west of station and about V2 km from shore, 26 104 water is 9 m deep. 26 Numerous cracks on ice. 14 133 5 31 Ice conditions unsafe for travel. 21 125 3 Jun 2 64 21 3 cm of snow on top of 1 cm of water and slush. 2 Open leads offshore and around entire bay. 28 110 8 Front bay clear of ice. May 5 107 18 Lake clear of ice. 12 93 '68 19 Narrow shore leads. Ice badly candled and considered un­ Apr 5 122 Trace safe. 12 112 3 1973 19 109 Apr 27 5 cm of snow-ice and 13 cm of slushy water on ice surface. 24 First small lead appeared in lake. May 4 112 3 26 91 Trace 4 Cover consists of 97 cm solid ice, 8 to 10 cm of slush and May 2 Last date ice cover used by light aircraft. 5 to 8 cm snow-ice on top. 3 89 11 90 0 10 76 Trace 18 79 0 10 Shore leads. 18 Ice cover very candled. 13 Lead extending out into lake. 24 Ice considered unsafe, extensive shore lead and large areas 17 30 of open water at creek mouth. 17 Large open lead approx. 60 m wide in south bay of lake. Ice unsafe, ice thickness estimated from broken edges. 1974 81 33 Strong winds have shifted ice resulting in many open Apr 12 19 77 20 leads. 27 90 0 22 Ice clear around Post Island. 27 Increase in ice thickness due to formation of snow-ice. Jun 4 Lake clear of ice. May 3 85 Trace 69 10 81 0 Apr 12 95 23 17 74 0 15 Ice cover rises slightly. Surface water has drained off and 24 Open leads around shoreline. Numerous wide leads in ice beginning to candle. North Bay. 16 Small lead in bay, north of island at narrows. 18 91 3 25 88 YELLOWKNIFE, NORTHWEST TERRITORIES May 2 79 :2 Last date ice cover used by light aircraft. Measurements made in Back Bay of Yellowknife Bay approximately 8 Shore leads. 140 to 160 m northwest of the Pacific Western Airlines float base. 9 65 15 Lead approx. 14 cm wide extends from shore to 1.6 km thickness Snow depth south. Date (cm ) (cm) 16 36 ------— 16 Surface candled, numerous cracks. 1959 20 Ice drifting with wind, back bay clear of ice, front bay 90% May 8 137 18 clear of ice. 15 130 20 Jun 5 Lake clear of ice. 22 127 114 70 29 Ice conditions unsafe for traffic. Apr 17 100 36 Jun 4 24 99 18 14 Back bay clear of ice. 28 Last date ice cover used by heavy vehicles. 1960 May 2 97 3 Mar 31 125 23 8 86 May 3 Measurements taken in a northeasterly direction were as 10 Ice cover starting to deteriorate. follows: 107, 122, 127, 107, 132 and 61 cm. Last 15 84 measurement was taken at about 8 m from dock where 22 Ice considered unsafe. Some open water in the north bay. 25 cm of water was on the ice surface. Ice breaking away from shore. 6 117 2 Jun 10 Lake clear of ice. 6 Some water on ice. Ice dry, some candling. 71 13 107 0 Apr 2 93 43 20 Slight candling, ice very soft, water along shore.1 9 95 30 20 Measurements discontinued, open water along shore and 16 97 25 27 23 95 ice cover deteriorating. 30 79 Jun 4 Back Bay clear of ice. 1961 May 12 137 15 19 130 19 Few patches of snow cover.

83 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1961 (cont’d) 1967 (cont’d) May 26 102 May 19 124 4 26 Surface candled, open water along shore. No further 19 Ice cover starting to deteriorate. measurements possible. 26 104 28 Ice conditions unsafe for traffic. 26 3 cm of water on surface, ice conditions unsafe for traffic. Jun 3 Back Bay clear of ice. Jun 2 61 1962 2 Ice unsafe, open water out to 8 m from shore. May 11 157 8 Back Bay clear of ice. 11 Patches of snow. 1968 18 145 May 10 135 18 Few thin patches of snow. 10 Surface slushy. 25 124 17 122 25 Surface candled. Last measurement due to open water 17 Surface ice candled. along shoreline. 24 99 30 Ice conditions unsafe for light aircraft. 24 Surface ice rotten, numerous cracks. Jun 10 Back Bay clear of ice. 28 Ice conditions unsafe for traffic. 1963 Jun 9 Back Bay clear of ice. Apr 19 127 15 1969 26 130 May 2 No ice thickness measurements made from December 1968 May 3 112 through April 1969. 10 Ice conditions unsafe for light aircraft. 9 93 26 Back Bay clear of ice. 17 91 1964 Jun 1 Back Bay clear of ice. May 1 152 1970 8 137 Apr 2 146 15 8 Snow cover patchy. 10 135 13 15 122 17 137 8 15 Surface candled. 24 137 20 Ice conditions unsafe for light aircraft. May 5 137 22 119 9 Ice cover starting to break up. 22 Open water along shoreline. Jun 2 Back Bay clear of ice. Jun 5 Back Bay clear of ice. 1971 1965 Mar 19 132 18 Apr 9 165 15 26 127 23 16 183 3 Apr 2 127 28 23 173 Trace 9 126 23 30 165 0 16 132 18 May 7 163 0 23 132 8 14 145 0 23 1-m open shore lead. Snow cover slushy. 14 Top 20 cm ice candled. 30 Ice not accessible due to water around shoreline. 21 127 0 1972 21 Top 30 cm ice candled. Last measurement due to water Apr 28 142 23 along shore. May 12 131 0 24 Ice conditions unsafe for light aircraft. 19 94 Jun 7 Back Bay clear of ice. 19 Open water around the shore makes access to ice difficult. 1966 Ice quite rotten throughout. Apr 22 140 25 1973 29 140 25 Mar 30 95 33 May 6 137 10 Apr 6 91 32 13 122 0 13 102 23 13 Surface ice candled. 13 Increase in ice thickness may be due to formation of 20 102 0 snow-ice. 20 Surface candled and puddled, numerous cracks. Ice condi- 20 94 20 tions unsafe for light aircraft. 20 No further measurements made due to excess water on the 27 38 0 ice. 27 Shore lead 3 to 6 m wide around entire bay. Back Bay approx. 65% covered with a free-floating and wind- 1974 driven pack ice. Apr 8 112 20 29 Back Bay clear of ice. 15 114 20 23 112 8 1967 23 Some water observed on the surface. Apr 28 135 20 May 1 102 0 28 Surface ice candled. 8 97 0 May 5 133 15 16 89 0 12 130 10 16 Ice cover in some areas rose about 15-20 cm. Shore lead 12 Snow cover wet. 60 to 90 cm wide. Ice cover completely candled.

84 ALLAKAKET, ALASKA Ice thickness Snow depth Date (cm) (cm) Measurements made on the Koyukuk River in front of the St. Johns in the Wilderness Church. 1967 (cont’d) Apr 29 86 38 Ice thickness Snow depth 29 Ice cover has lifted some. 38 cm of snow and water Date______(cm)______(cm)______mixed over the ice. Maximum ice thickness observed from 25 Feb to 29 Apr. 1961 May 6 81 Missing 6 48 cm of water on ice. 1962 9 Water level has risen 60 cm along shore, ice has lifted in Apr 30 84 23 middle of channel. May 7 81 20 10 Open water approx. 180 m upstream. 14 81 3 13 Open water approx. 45 m long and 15 m wide. 14 Open water about 90 m up river, 90 cm wide and 180 14 Ice breaking up. long. 3 cm overflow on the ice. 15 Ice running in river. 20 Ice moved out at 2235 LST. 20 Ice still flowing in river, water level has lowered. 21 Ice jam upstream broke up. Ice flowing bank to bank. 1963 22 Water high and ice flowing. Apr 8 76 66 23 River clear of ice. 9 3 cm of water on ice. 15 74 64 1968 22 81 69 Apr 27 89 51 29 79 43 May' 4 89 36 29 15 cm of water on ice. 4 Maximum ice thickness observed 13 Apr to 4 May. May' 6 61 5 7 Water 60 cm deep over the ice. 6 30 cm of water on ice. Open water approx. 275 m up 9 Open water north of Allakaket at confluence of Koyukuk river from the site, 30 m long, 60 cm wide. and Alatna Rivers. 13 Ice unsafe. 60 cm of water on ice. 11 Water up 90 cm. 15 Ice broke up, river clear. 16 Open water area approx. 4 m wide and 35 m long. 17 Ice breaking up at mouth of Alatna River. 1964 19 Ice jamming upstream near bend of Koyukuk and Alatna May 4 107 Rivers. 4 10 cm water overflow on ice. 20 Surface ice moving, water rising fast. 11 107 21 Ice running bank to bank in river. 18 104 26 Small amounts of ice on Alatna River. 25 102 25 15 cm water overflow on ice. 1969 30 River free of ice. Apr 5 80 56 12 80 43 1965 19 81 36 May 1 86 26 80 25 8 86 30 About 30 cm water over ice along edge of river. 8 8 cm water overflow on ice. May 1 Open water at mouth of Alatna River. 15 86 2 Ice jam at mouth of Alatna River. 15 28 cm water over ice. Maximum ice thickness from 3 Water level 60 to 90 cm above normal. 9 Jan to 15 May. 4 Ice moved downstream about 180 m and jammed. 22 Water running on sides of river out to approx. 1.2 m. 6 Ice started running. 24 Ice broke up at approx. 1300 LST. 9 Some ice in river coming from the Alatna River. 25 Ice cakes flowing in river bank to bank. 10 Water dropping, no ice flowing. Some ice grounded on 1966 sides of river. Apr 9 99 25 10 River free of ice. 16' 97 23 1970 23 97 23 Apr 11 89 48 30 91 15 18 89 25 May 7 76 8 25 89 13 9 76 25 13 cm water overflow on ice. 9 Approx. 10 cm water on ice. May 2 89 14 Water along shore on each side of river. 2 Maximum ice thickness observed from 14 Mar to 2 May. 15 River water level up 30 cm, open water approx. 90 m 25 cm of water on the ice. up river from measurement site, 6 m wide and 30 m 9 Open water 365 m upstream. long. 10 Water level rose 43 cm. 18 River water level up 50 cm, ice breaking up above 11 Brief ice jam, water rose 8 cm, then ice moved out at measurement site. Water up 1.2 m by noon, ice about 1500 LST. breaking up and flowing in river. 17 River free of ice. 21 Small amounts of ice flowing in river. 1971 1967 Mar 27 102 97 Apr 15 86 53 Apr 3 104 94 15 36 cm of water overflow. 10 104 91 22 86 46

85 Table A2. Ice thickness measurements and observations of surface conditions on lakes, rivers and fast sea ice locations in Alaska.

Ice thickness Snow depth Ice thickness Snow depth Date ______(cm)______(cm) Date______(cm)______(cm)

1971 (cont’d) 1967 Apr 17 104 84 Apr 29 156 36 24 104 76 29 Numerous cracks. May 1 102 74 30 No further information available. 30 cm water overflow covering the ice. 8 1968 Water up 90 cm. 15 Incomplete 16 Ice moves 90 m downstream. 17 Ice running from bank to bank. 1969 21 River free of ice. Incomplete 1972 1970 Apr 15 91 46 Mar 21 Few cracks 1 to 2 cm wide visible in the occasional snow- 22 91 43 free areas. 38 29 91 28 191 15 91 43 May 6 28 Snow cover hard-packed, medium sized crystals in bottom 6 30 cm water overflow on ice. Maximum ice thickness layer. observed from 25 Mar to 6 May. 29 No further information available. 7 60 cm water overflow on ice. 8 No further information available. 1971 28 1973 May 22 185 Apr 7 81 61 23 185 28 14 81 58 23 Few visible cracks in bare areas. 21 81 56 29 175 20 28 81 51 29 1-cm slush ice on surface of lake. 28 10 cm water overflow on ice. 30 No further information available. May 5 81 25 1972 5 20 cm water overflow on ice. 188 13 15 River free of ice. Apr 8 15 184 17 1974 22 181 18 Apr 13 91 46 29 184 13 20 91 41 May 6 181 23 27 91 25 180 22 May 18 River free of ice. 13 20 188 14 20 Cracks covered with 13 cm hard-packed snow during May. BARROW, ALASKA 21 No further information available. 1973 Measurements made on Imikpuk Lake at approximately 100 to 150 m Apr 28 193 17 off the west shore toward the center of the lake. May 12 193 13 13 Ice thickness Snow depth 19 193 13 Date (cm) ______(cm)______26 198 26 Some above-freezing air temperatures, but no water ob- 1961 served on ice. Snow cover settling. Missing 26 Depth of water at measurement site 2.8 m, maximum 1962 depth of lake approx. 3 m. Apr 21 182 10 Jul 12 North Salt Lagoon free of ice. 28 178 10 21 Middle Salt Lagoon free of ice. May 5 170 10 26 Imikpuk Lake free of ice. 12 161 9 28 Sea ice along north shore in Chukchi Sea moved out, 19 150 9 allowing ships to pass eastward from Pt. Barrow. 26 140 9 Jun 2 127 8 1974 2 About 3 cm of water on the lake ice. No further Incomplete measurements made. 1963 Missing BARTER ISLAND, ALASKA 1964 Measurements made on fresh water lakes located near the station at Missing approximately 20 to 100 m offshore. 1965 Incomplete Ice thickness Snow depth 1966 Date ______( c m )______(cm) Apr 18 154 36 19 No further information available. 1961 Missing

86 Ice thickness Snow depth Ice thickness Snow depth Date (cm) ____(cm) Date (cm) (cm) 1962 1968 (cont’d) Note: Measurements during 1962 only were made on Mar 30 Numerous cracks in ice, some quite deep. No leads or sea ice on Beaufort Sea approx. 1 km offshore north openings. Several large patches of snow-free ice on of the station. lake, but some drifts are 61 cm high. Ice thickness Apr 28 149 23 at water hole site is 124 cm, but that area is kept 28 Few leads and some open sea water reported by aircraft open artificially. 3 to 8 km from shore NW to NE of station. There Apr 6 178 8 is approx. 30 to 45 cm of water below the ice in the 13 178 15 freshwater lake. 20 175 8 May 5 145 18 20 Top layer of snow rather brittle. 12 141 18 27 175 8 19 135 5 May 5 170 8 26 126 Trace 11 165 6 26 Large area of open sea water reported approx. 8 km 19 157 4 offshore to the NW through NE of the station. Be­ 26 145 5 yond this point there are intermittent leads and open 30 124 4 water for a considerable distance out. There is approx. Jun 8 107 10 60 cm of water under the ice in the freshwater lake. 15 85 Trace 27 No further information available. 15 Lead extends across lake, 180 m long and 10 cm wide. 1963 22 55 Incomplete 29 33 29 1964 Part of lake covered only with pancake ice. Ice cover in Missing some areas soft. Ice measurements terminated due to rapid melting. Ice near shore still fast in numerous 1965 spots. Incomplete Jul 30 Beaufort Sea and Camden Bay free of ice. 1966 1969 Apr 30 213 3 Apr 5 198 13 May 7 213 5 12 196 14 7 Maximum ice thickness observed 16 Apr to 7 May. 19 194 19 16 211 3 26 191 13 21 211 10 26 Large crack extends NE to SW and numerous small 28 201 5 cracks branch outward. Jun 4 185 3 May 3 185 9 11 160 3 10 182 8 18 124 17 174 5 25 99 24 170 4 30 74 31 165 3 1967 31 Crack extends NE to SW, length undetermined due to Mar 25 154 22 snow cover. Ice appears to be decaying. Apr 3 156 8 Jun 7 132 8 152 8 7 Pools of water starting to appear. 15 140 6 14 98 22 132 5 21 56 29 127 4 21 Large leads developed near shore. May 5 124 5 28 13 12 122 1 28 Entire ice pack merely floating on lake with about 18 m 19 114 1 of open water between shore and ice. Ice observations 26 107 terminated. Jun 2 102 Trace 1970 9 95 Trace Apr 11 198 16 86 Trace 11 1/3 of ice surface clear of snow. 18 Open area 50x65 m in size in center of lake. Rapid 18 196 thawing observed. 18 1/2 of ice surface clear of snow. 23 61 25 198 1 23 Ice surface soft, numerous puddles of water. May 2 192 3 30 37 9 196 30 Breakup, ice considered unsafe for further measure­ 16 194 ments. Open leads and floating ice chunks. 16 40-knot winds removing'snow from ice cover, except for Aug 15 Camden Bay ice-free. an occasional drift. 18 Beaufort Sea ice-free. 23 Ice soft and spongy at 46 cm and water encountered at 19 Simpson Cove ice-free. 51 cm depth. 1968 30 Surface candled, numerous cracks. Ice spongy from top Mar 30 178 8 to bottom. Melt ponds along edge of ice.

87 Ice thickness Snow depth Ice thickness Snow depth Date (cm)______(cm) Date (cm) (cm)

1970 (cont’d) 1973 (cont’d) Jun 6 185 Jun 2 168 0 6 10 cm of candled ice on surface. 2 Large puddles of melt water on ice and 5 cm of candled 13 175 ice on top. 13 Bottom half of ice cover very soft. Area of open water 9 150 0 observed around the edge of ice. 9 Numerous melt ponds, some 15 to 20 cm deep. Top 10 20 165 cm of ice is candled. 20 2 to 8 m of open water surrounds floating lake ice. 16 142 0 27 147 16 Large areas of open water around shore of lake. Ice 27 10 to 25 m of open water surrounds floating lake ice. rotten down to 90 cm. Top 20 cm of ice is candled. 36 cm of candled ice on top and bottom ice slushy. 23 119 3 Numerous melt ponds. Jul 16 Lake free of ice. 1971 1974 Apr 3 204 10 Mar 30 190 0 3 Ice solid, no soft areas. Apr 6 189 0 10 206 10 13 185 0 10 Approx. 28 cm of water under ice at this part of the 20 184 1 lake. 27 185 0 17 208 10 Aug 1 Lake free of ice. 24 203 10 24 Bottom of ice cover becoming soft. May 1 Ice thickness measurement, made in an area which has BETHEL, ALASKA remained mostly clear of snow, 216 cm. 8 198 8 Measurements made on the Kuskokwim River at distances ranging from 8 Ice becoming soft 122 cm from the top and slushy 183 25 to 200 m off the north shore. cm from the top. 15 Ice thickness of 185 cm on this date does not appear Ice thickness Snow depth representative because some ice on top was candled Date (cm)______(cm) and the lower 122 cm was waterlogged. 1962 22 198 Mar 26 144 5 29 193 Apr 2 138 10 29 Surface candled. 9 132 0 Jun 5 180 9 Top 38 cm of ice extensively honeycombed. 5 Top 46 cm candled ice, remainder of ice rotten. 16 138 0 12 173 Trace 16 Cold weather has solidified surface, though top 38 cm 12 3 to 6 m of open water around edge of lake. still porous. 19 150 23 137 0 19 15 to 30 m of open water around edge of lake. Melt 30 128 0 ponds on ice with sections becoming quite rotten. 30 Ice extensively honeycombed. 26 Ice observations terminated, open water surrounding ice May 7 102 0 sheet. Surface ice candled with many cracks during 7 Top 30 to 46 cm extensively honeycombed and composed June. of alternate ice and water layers. 1972 15 93 0 Apr 22 203 15 Top 25 cm porous. Observer waded to hip boot height 22 Bottom of lake ice becoming porous. to get on ice. Last ice measurement. 28 211 25 Surface slushy, shore ice. 28 Ice cover solid on this date. 26 Surface jammed ice, numerous cracks. May 5 210 29 River channel free of ice. Only ice on bank and shore 5 Bottom layer of ice becoming soft again. remain. 12 208 31 River free of ice. 12 Lowest 90 cm of ice sheet soft. Surface ice candling. 1963 19 208 8 Apr 21 107 11 19 Top 60 cm ice is hard, mid 60 cm soft and lowest portion 27 102 10 of ice wet. 27 Snow cover slushy except for drifted areas. 26 210 10 May 5 100 Jun 16 160 5 River ice soft and slushy. River has risen approx. 60 cm. 16 30 cm of candled ice over softer ice. Rapid deterioration 6 South side of river ice under water for approx. 45 m from of ice with numerous melt ponds on surface. shore, due to a strong south wind. 24 137 12 91 142 30 12 Water overflow covering both banks and about 30% of 1973 river. Apr 24 188 10 13 River ice is honeycombing and crystallizing. River level May 5 189 15 up approx. 1.2 m. 12 189 10 16 River ice has moved approx. 45 m from shore. Main ice 19 191 10 is still solid. 26 188 8

88 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1963 (cont’d) 1966 (cont’d) May 18 Entire river ice is moving. Ice appears very honey­ Apr 26 Slush on top of ice over approx. 1/3 of river. combed and crystallized. 27 Approx, all of ice appears to have slush and snow crystals 21 Main river ice has broken up. at surface. 22 River is clear of ice, water level higher than normal. May 1 97 26 River free of ice. 1 Top 30 cm ice rotten, rest firm. Slush (up to 61 cm) 1964 covers most of river. Apr 19 132 23 4 Water over ice on south side of river. 19 Snow over the ice consists of 5 cm slush-ice, 18 cm ice 5 Approx. 1/5 of river on south side covered by water. crystals. Between 0-5 cm of water and slush at 8 74 bottom. Ice soft and watery. 13 Overflow ice breaking up. May 3 141 8 17 River rising, overflow ice moving. 3 Ice consists of 118 cm solid ice, 10 cm slush-ice and 13 18 Ice appears rotten and pitted at top. cm shell ice. 22 South side of river open. 10 135 3 23 Ice moving down channel. 10 Slush and shell ice frozen solid. 24 Ice running in river entire day. 17 140 3 25 Few floating ice cakes observed in river. 17 Top 46 cm ice soft and contained water. 26 River free of ice. 24 132 1967 25 Water beginning to collect over the river ice on the south Apr 16 117 side. 16 Cover consists of 8 cm crust ice over 15 cm water and 31 112 slush, then 10 cm of very soft ice all over the main 31 Considerable overflow, 15m area of open water on the ice layer. south side of the river. River ice honeycombed and 23 114 crystallized, no firm ice at test site. 23 3 to 20 cm loose ice crystals on surface. Jun 8 River free of ice. 30 91 1965 30 Few small open holes observed in ice. Overflow observed Mar 14 105 24 on south side of river during high tides. 21 103 May 3 Water over ice on south side of river is increasing in depth. 21 Snow cover has turned into slush and water 15 cm deep. 7 Shore ice is breaking up. 27 98 8 Shore and river ice has started to move. 27 All slush and water refrozen. 30 cm of soft and rotten 9 Most of ice now small chunks and needle-like in appear­ ice beneath 4 cm of loose ice crystals. ance. River still solid with ice. 31 Water starts to flow on ice near the south bank of river. 11 River about 1/3 full of ice and running on south side. Apr 4 97 12 River passed its crest. Few stray ice chunks in river. 4 Cover consists of 3 cm loose ice crystals at top, then 14 All ice gone. 20 cm of firm ice followed by 30 cm soft ice and 1968 water, and the rest of ice firm. Apr 7 108 Trace 11 94 8 14 1073 11 Top 30 cm of ice solid but crystallized, the rest soft. 14 Some water overflow on south side of river. 17 85 21 103 17 Ice soft and starting to rot. 21 8 cm slush and 23 cm soft ice on top. 24 71 28 Ice crystals 10 cm in depth observed on top of ice cover. 24 Top 20 cm ice crystallized and soft, the rest rotten and Bottom 66 cm of ice cover soft. crystallized. May 5 86 28 South side of river covered with water, and on the north 6 Tide action has piled ice on south side of river near a side overflow getting deeper. sand bar. May 8 33 11 Water covering 1 /3 of ice on south side; north side has 8 River ice has only 5 cm of firm ice near the top, rest is considerable overflow. rotten. 12 Shore ice breaking up and large holes observed. 17 Ice opened up at the bend on the west end of village. 14 Ice moved a little and then jammed. 19 Ice has started moving, river level rising a few meters, 16 Ice moved rapidly down channels on both sides of river. shore ice still holding. 17 Loose ice running near center of river. 20 River clear of ice except for a few stray cakes due to a 19 Small amount of ice left near banks of river. jam up in river. North wind has broken the shore ice 20 Ice entirely gone. loose. 1969 23 Ice flowing heavy most of the day. Mar 30 110 17 24 A few cakes of ice flowing in the river in morning, by Apr 6 109 17 afternoon all the ice is gone. 13 109 8 1966 13 Top 46 cm soft ice. Slush and water 0 to 20 cm deep on Apr 10 119 13 river. 17 122 16 Water overflow observed on ice. 17 Some overflow along shore. Snow cover across river 20 104 4 varies from 3 to 30 cm. 26 River water level rising. 24 121 27 90 3

89 Ice thickness Snow depth Ice thickness Snow depth Date______(cm) (cm) Date______(cm) (cm) 1969 (cont’d) 1972 (cont’d) Apr 27 5 cm honeycombed ice at top. Apr 23 133 30 29 Water covers large area of ice on south side of river. 30 140 25 30 Ice at test site becoming soft. May 5 Some ice flows in overflow on south side. May 1 No further information available, records for 1972 con­ 7 North half of river ice broke and moved leaving a large sidered to be incomplete. open area in front of town. 1973 9 Ice moved slightly, water level low. Apr 1 121 14 10 Water rising, ice moves and jams. 8 126 2 12 Heavy ice flow all day. 11 Some water observed on river ice. 13 River about 1/4 full with ice all day. 15 119 0 14 River free of ice. 15 Top 15 cm consists of slush and ice crystals. 1970 22 117 0 Feb 15 Water overflow on river ice making access difficult. 22 Ice cover soft. 22 119 29 108 0 22 Overflow of water on ice at various points along shore. 29 Top 46 cm ice has hardened. Mar 1 117 May 6 91 0 1 Top 15 cm ice was soft. 9 Open water on both sides of the river. 8 108 13 Ice moves slightly. 8 About 3/4 of river clear of snow, some drifts are 15 cm 17 Ice moves all day. deep. 18 Heavy ice flow, but no large pieces. 15 108 19 River about 50% full with ice. 22 105 20 Only few pieces of ice flowing in the river. 22 Top 15 cm ice soft, another 30 soft ice noted while 1974 drilling. Mar 10 127 15 29 102 17 122 19 29 Ice soft throughout and the top 15 to 20 cm starting to 24 124 0 crystallize. 24 3 to 5 cm of water on the ice, top 15 cm of ice soft. Apr 5 100 1 31 122 0 12 103 1 31 Ice cover contains some soft layers. Top of ice is honey­ 13 River ice covered with water and slush due to warm combed and contains some shell ice. weather. Apr 7 119 0 19 90 14 109 0 19 Top 30 cm of ice made up of ice crystals, the rest is soft. 14 Bottom 33 cm of ice soft. 20 Considerable water over ice on south side of river. 21 99 0 26 84 3 28 89 0 May 3 76 28 Ice cover entirely soft, top 10 cm consists of ice crystals. 10 Shore ice breaking up. 29 Ice unsafe for vehicular traffic. 12 First ice movement. Large open area formed and ice is May 12 River free of ice. very rotten. 15 Ice flow heavy. 17 Ice flow light. BETTLES, ALASKA 18 Ice completely out. 1971 Measurements made approximately 30 m offshore on the Koyukuk River Apr 11 152 1 about 1.5 km NE of Betties Airfield which is located about 8 m east of 12 Water overflow started to cover some parts of the river ice. village. 18 152 1 18 4 cm of water overflow on ice at measurement site. Ice thickness Snow depth 25 152 Date (cm) (cm) 25 Water was 13 cm deep over ice in areas on the river. May 2 145 1968 2 Ice cover soft and full of holes. Apr 20 81 52 4 Water overflow is extensive. 27 81 52 5 Shore ice breaking up. 27 Cold weather has prevented any melting or ablation of ice. 9 140 1 May 4 81 28 9 Top 8 cm of ice firm, rest getting soft. 11 79 3 16 136 1 18 71 16 Top ice very crystallized and rotten. 18 Small cracks in ice caused by rising water. 25 Ice moved a little. 21 River free of ice. 27 Ice jammed. 1969 29 Ice jam broke. Small amounts of ice observed. Feb 22 99 30 30 Last ice observed, river ice-free. 22 Small cracks about 30 m away, no water overflow. 1972 Mar 1 102 Unknown Apr 16 141 30 8 102 Unknown 16 Ice becoming soft. 15 102 Unknown

90 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1969 (cont’d) 1972 (cont’d) Mar 22 104 Unknown Mar 4 86 36 29 107 Unknown 11 81 36 Apr 5 109 25 18 84 36 12 109 15 18 Ice thicknesses between 4-18 Mar vary due to differences 19 107 6 in growth of snow-ice. 20 River ice unsafe for vehicles. 25 86 38 26 107 Apr 1 86 43 26 Some water on edge of ice, also on both banks of river. 8 89 41 30 River ice unsafe to walk on. 15 84 46 May 4 Ice conditions safe for travel by boat. 22 81 41 7 River free of ice. 29 84 36 Surface uneven 15 to 29 Apr due to strong winds and 1970 29 drifted snow. Feb 21 74 15 21 Surface uneven. 30 No further information available. 28 76 28 1973 28 Snow drifted by strong wind. Some water overflow on Feb 10 66 56 edge of river. At the middle of river, ice has arisen 10 5 cm slush and 10 cm water beneath the snow cover. approx. 60 cm. 24 74 36 Mar 2 Numerous areas of open water in river seen on flight to 24 Water beneath snow has frozen. Anuktuvik. Mar 3 75 38 7 79 25 31 76 28 14 79 25 31 Overflow in some areas results in thicker ice, wind has 26 79 36 blown some snow off surface. 28 81 33 Apr 7 84 25 28 Few cracks observed in ice due to ice pressure in the 14 86 20 middle of the river. 21 89 20 Apr 4 84 41 28 86 20 11 84 46 28 Approx. 8 cm of water beneath the snow cover. 18 86 10 May 5 79 0 18 10 cm water on ice beneath snow cover. 10 Ice conditions unsafe, ice moved at 2000 LST. 25 86 10 17 Water level peaked, but stage is low this year. 25 5 to 10 cm of water on ice beneath snow. 18 No further information available. 28 River ice unsafe for vehicles. 1974 May 10 River ice unsafe to walk on. Mar 30 97 30 14 River free of ice. Apr 6 99 28 1971 13 99 25 Feb 20 91 65 20 100 23 27 102 28 27 102 20 27 Surface uneven. Snow depth varies between 23 and 33 May 17 River free of ice. cm. The water overflow on ice is 20 cm deep with 3-cm ice on top. Wind had removed lots of snow from surface. The 102 cm of ice includes 20 cm of CHALKYITSIK, ALASKA surface slush which froze. Mar 10 97 27 Measurements made approximately 30 m offshore on the Black River, 17 99 19 about 100 m north of the village. 24 97 13 24 The ice thickness increased from 79 to 97 cm due to Ice thickness Snow depth freezing of slush on top of ice. 4 cm of water Date (cm) (cm) between ice layers. Apr 1 97 5 1968 74 46 8 94 Mar 16 36 8 Surface uneven, small crack 8 m out from shore. 23 79 May 10 Ice conditions unsafe for vehicular traffic, ice approxi­ 23 Ice thickness in nearby lake 72 cm and snow cover 36 cm. mately 75 cm thick. Snow on lake and river is very loose and powdery, but 15 Ice moved out at 1010 LST. Water has risen within starting to form a crust on top. 44 12 m of upper post. Water stays up for one hour and 30 71 43 then recedes. Apr 6 76 74 48 22 Last remnants of ice are gone. 13 20 76 47 1972 27 74 42 Feb 26 86 38 27 Ice thickness in nearby lake is 76 cm, snow cover 41 cm. 26 Water overflow observed between ice surface and snow 30 Weather warm and snow melting quite fast. Some water cover. Water flows up through drilled hole after each flooding beneath the snow on lake and river ice. measurement. May 6 76 8

91 Ice thickness Snow depth CHANDALAR LAKE, ALASKA Date (cm) (cm) Measurements made on Chandalar Lake near the main camp at distances 1968 (cont’d) of 15 to 60 m offshore. May 7 Water started to rise in river. 8 Water rising fast. Unable to get on river ice. Ice thickness Snow depth 10 Ice broke and started to run at 2000 LST. Date (cm) (cm) 11 Ice jammed below and above village, village partly flooded. 1964 13 Ice jam broke and water flowing freely in river. Apr 1 Numerous cracks occur in ice during 27 Mar earthquake but no large cracks and no actual displacement of ice 1969 is observed. Mar 1 94 28 114 43 8 93 32 20 27 114 43 15 93 32 4 114 41 22 91 32 May 11 114 41 29 89 30 18 114 37 29 During March strong winds have formed snowdrifts 25 approx. 1 to 2 ft in depth along the edge of the river. 25 114 25 Wet snow, 1 cm water on ice. 30 No further information available. 30 Ice has risen by water flow from creeks and river. Ice 1970 138 cm thick where snow has been packed during < Mar 7 89 Unknown craft landings throughout the winter. 14 89 Unknown Jun 2 Approx. 15 m of open water along shoreline. 21 84 Unknown 28 79 Unknown 1965 114 39 28 Strong winds have caused snow drifting during March. Mar 29 Apr 4 112 42 Apr 4 91 11 114 50 11 91 9 10 104 39 18 76 6 17 24 104 37 25 Water rising in river. 104 51 26 No further information available. May 1 8 105 44 1971 15 105 47 Incomplete 22 104 24 1972 29 Water around shore, unable to gain access to ice. Apr 1 109 Unknown 1966 8 109 Unknown Missing 15 109 71 22 84 32 1967 26 Some cracks in ice observed throughout winter. Con­ Missing siderable melting of snow, about 30 cm of snow on 1968 the ice now with slush and water observed between Missing the snow layer and ice surface. 1969 29 86 3 Apr 6 86 27 29 Water from melted snow covers the ground. Little snow 13 88 24 in village but lots of snow still outside of village. 19 89 22 30 No further information available. 26 89 17 1973 26 Ice thickness farther out on lake is 107 cm. Snow blown Mar 10 132 8 off ice by wind out in that area. 17 137 8 27 No further information available. 24 142 8 1970 31 142 0 Incomplete 31 Wind removed most snow from ice surface. May 12 River free of ice. 1971 Missing 1974 Mar 23 142 8 1972 Missing 30 152 5 Apr 6 157 8 1973 13 157 8 Mar 31 81 36 20 168 5 31 Occasional ridging observed in center of lake during March. 26 Snow cover starting to melt, puddles of water forming Major snow drifts due to strong winds have developed on river ice. during mid-March. 27 173 5 Apr 7 81 41 28 No further information available. 14 81 48 21 79 51 28 79 56 28 Cracks in ice extend north-south direction toward cen­ ter of the lake.

92 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1973 (cont’d) 1968 (cont’d) May 5 71 33 May 13 Water observed around edge of ice. 12 61 15 18 A few ice floes in center of lake. 12 Water from creeks running over lake ice , snow cover 20 Ice completely gone. decreasing and becoming slushy. 1969 19 30 (estimated) 0 Mar 28 67 44 19 Open cracks extend in all directions, open water along Apr 4 67 shoreline. 11 69 26 15 (estimated) 0 18 69 26 Ice cover moves with wind, open water areas dependent 25 69 on wind direction, 2/3 of lake still ice covered. May 2 Ice appears to be deteriorating. Ice detached from shore. 27 No further information available. open water along all shorelines of the lake. 1974 9 Ice honeycombed, ice area extends over about 2/3 of Mar 30 102 23 lake. 30 Few small cracks extend in north-south and east-west 14 Lake free of ice. direction. 1970 Apr 6 95 24 Mar 27 66 22 13 117 20 Apr 3 71 20 112 23 10 72 5 27 107 23 17 72 28 No further information available. 24 62 May 1 Ice starting to deteriorate, water appearing along shore and on ice. FAIRBANKS (COLLEGE), ALASKA 8 Open water between shore and ice. Approx. 2/3 of lake surface covered with ice. Measurements made on Smith Lake which is located at approximately 14 Ice entirely gone. 1200 m NNW of the College weather site. 1971 Ice thickness Snow depth Incomplete Date______(cm)______(cm)______1972 Apr 22 71 33 1965 22 No water overflows observed during Mar and Apr. Missing 29 71 29 1966 29 Snow cover is melting and wet throughout. Maximum Mar 27 86 36 ice observed from 8 to 29 Apr. 27 Maximum ice thickness from 20 Feb to 27 Mar. May 6 69 25 Apr 3 81 32 6 Snow cover is very slushy and ice is soft and wet. 9 81 28 7 No further information available. 16 76 29 1973 25 81 18 Mar 3 79 17 30 79 10 81 32 May 7 46 10 Considerable amount of new snow has fallen during 7 Surface honeycombed, water on surface. past week. 14 41 17 81 30 1967 24 81 30 Apr 6 70 18 31 81 20 6 18 cm water on ice. 31 Snow surface melting. 14 71 27 Apr 7 79 15 19 72 11 7 Snow cover deteriorating. 28 76 10 14 76 8 28 13 cm water on ice. 14 Water on surface of ice. May 10 No thawing yet along shoreline. May 5 Ice is approx. 20 cm thick, is candled and considered 20 Lake still frozen over, very little thawing along west unsafe. shore outlet of lake. 12 Many open areas, lake is 60% covered with ice. 22 Considerable thawing along west shore. 1974 28 Lake clear of ice. Mar 16 67 44 1968 23 69 42 Apr 1 75 20 30 69 41 8 74 20 31 No further information available. 15 74 22 22 72 17 27 Snow has been reduced to a hard crust up to 3 cm in depth. A few pools of water showing on ice. 29 69 May 6 Marshy area surrounding lake was flooded with runoff. Ice appears to be becoming honeycombed.

93 FORT GREELY, ALASKA Ice thickness Snow depth Date (cm) (cm) Measurements made on Bolin Lake approximately 30 to 45 m off­ 1962 (cont’d) shore and west of the ski lift on the Fort Greely Reservation. Feb 19 119 36 25 117 46 Ice thickness Snow depth 25 Strong winds now have built deep snow drifts on river. Date (cm)______(cm) Small open channel formed approx. 90 m downstream 1967 from measurement site. Swift currents beginning to Mar 24 81 25 undercut the ice cover in the immediate area. 24 Drifting snow on lake. Mar 3 117 46 31 76 15 11 109 46 Apr 7 76 18 102 30 7 Almost all snow on lake has melted. 8 cm of slush 25 99 20 present at measurement site. 31 Warm weather has softened snow. Many open leads have 13 76 10 formed in river. 13 At 45 m from shore 5 cm of frozen slush present be- Apr 2 99 20 tween snow and ice. Halfway across lake, 5 cm of 2 Snow cover crystallized. frozen slush ice under the snow and 5 cm of water 8 93 20 observed at 20-cm depth in the ice. 15 86 25 14 No further information available. 23 84 15 29 76 10 1968 29 Snow settling. Open lead in front of Fort Yukon, water Missing appearing on entire ice cover. 1969 May 6 46 8 Feb 27 104 13 10 23 Mar 27 102 13 Ice rotting fast, water over ice. Apr 28 71 20 Open water in all areas, ice moved in front of town. 29 No further information available. Water near flood state. During last 2 days some flow­ 1970 ing ice blocks were 2 to 3 m thick. Feb 26 123 31 Water level held high but not at flood stage. Apr 3 91 Jun 6 From 31 May through 2 June, Porcupine River, combined 28 69 with the Sucker, Black and Sheenjek Rivers raised 122 29 No further information available. cm over its banks flooding the Yukon, Porcupine and Black River valleys. 1971 Mar 2 81 Unknown 1963 30 91 Unknown Missing May 3 72 1964 4 No further information available. Apr 12 128 19 1972 19 132 15 Feb 28 84 25 26 Approx. 15 cm of water on ice. Mar 27 89 15 27 No further information available. Apr 24 99 1965 24 Trace of snow on ice. Incomplete 25 No further information available. 1966 1973 Incomplete Feb 1 84 8 1967 28 107 0 Incomplete Mar 30 109 0 1968 1974 Apr 13 84 38 Missing 20 84 36 27 84 30 May 4 No measurement taken due to approx, 20 cm of water FORT YUKON, ALASKA observed on top of ice. 9 River ice has “lifted” causing water on ice to drain Measurements from 1962 through 1969 were made on the Yukon River, through cracks. at Fort Yukon and at about 15 m offshore. Measurements from 1970 through 1972 were made on Hospital Lake located near the airport. 1969 Incomplete Ice thickness Snow depth 1970 Date (cm) (cm) Feb 28 No measurements made during Jan and Feb. Yukon River very low and open in many spots. 1962 Mar 29 91 28 Feb 4 124 15 29 Measurement made on Hospital Lake. 4 Strong winds have blown snow off the river near 94 18 measurement site. Cold temperatures and little snow 29 29 Measurement made on Launa Lake. to insulate the ice causing rapid thickening. May 25 Yukon River free of ice. 11 119 25

94 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date______(cm)______(cm)______

1971 1968 (cont’d) Feb 14 20 cm water overflow on ice under the snow cover. Apr 7 Surface snow fluffy. Ice rafted in places, in some spots Snowmobile became stuck in snow, ice and water at up to 2 m thick. edge of lake. 14 107 46 Mar 15 114 25 21 112 36 21 117 13 21 Snow over ice starting to melt. 28 119 5 28 122 61 Apr 4 127 5 May 5 61 11 127 5 5 Surface honeycombed, numerous cracks. 18 132 6 All snow melted and water observed on top of ice. 25 119 8 38 25 15 cm of water on lake ice. 8 More water overflow on ice and cracks along bank. May 27 Yukon River free of ice. 12 15 1972 12 Crack approx. 2 to 5 m long and 50 cm wide all along Mar 5 94 15 bank and out into channel. 12 99 10 15 10 12 Snow cover wind-blown. 17 Breakup of river occurred at approx. 0900 LST. 19 97 8 25 River safe for navigation. 26 99 8 28 River free of ice. 27 No further information available. 1969 1973 Missing May 16 Yukon River free of ice. 1970 1974 Missing May 25 Yukon River free of ice. 1971 Mar 27 80 71 27 Snow cover on ice settling gradually. GALENA, ALASKA Apr 3 80 69 10 76 74 Measurements made approximately 100 to 200 m offshore on the 17 74 61 Yukon River near the village. 22 71 53 22 Approx. 3 cm water on ice. Ice thickness Snow depth 24 71 51 Date (cm) (cm) 24 Approx. 10 cm water on ice. May 1 66 36 1966 1 Approx. 30 cm water on ice. Water observed along edge Feb 26 93 61 of river. light rain and warm weather during last two 26 River surface extremely rough due to ice rafting during days has caused the river to rise and water runoff to freeze-up. Dike repair has made it necessary to change increase. Last observation of season. observation site by approx. 8 m. Mar 5 94 65 1972 12 91 62 Mar 24 90 69 19 95 62 Apr 1 89 71 27 93 55 8 91 76 28 No further information available. 15 91 71 May 6 River ice unsafe for vehicular traffic. 22 89 64 10 River ice unsafe to walk on. 29 86 56 28 River free of ice. 29 Surface rough, no cracks in ice visible from 5 Feb to 29 Apr. 1967 30 No further information available. Mar 4 86 58 4 Snowdrifts of various depths in all areas of Yukon River. 1973 11 84 58 Incomplete 18 91 51 1974 25 114 56 Incomplete Apr 30 No observations taken in Apr. May 8 8 m of open water out from shore. 24 River free of ice. GAMBELL, ALASKA 1968 Feb 25 127 76 Measurements made on Troutman Lake, southeast of the village, approxi­ 25 Snowfall during Feb. resulted in 15 cm of crusted snow mately 150 m offshore. and 46 to 61 cm uncrusted snow over the ice. Mar 3 140 91 Ice thickness Snow depth 10 109 76 Date______(cm)______(cm)______17 122 91 24 112 76 1962 31 107 76 Apr 14 117 36

95 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date______(cm)______(cm)______1962 (cont’d) 1965 (cont’d) Apr 21 117 23 Jun 12 116 28 117 28 12 Open leads and cracks along shore enlarging in width. 28 All wide cracks filled with slush. Snow over ice is melt- 19 Unsafe for measurement. Open water along most of ting, ice-snow interface getting slushy. shoreline. May 5 117 34 1966 5 Maximum ice (117 cm) observed from 17 Feb to 5 May. Apr 2 146 22 12 116 18 9 145 24 16 114 17 16 144 30 26 114 13 23 142 29 26 Leads running along sides of ice cracks. Ice along the 30 144 33 coast has no snow cover. Approx. 10 cm of slush May 7 141 30 exists below deeper snow. Where the snow is thin, 14 137 water exists over the ice. 21 131 Jun 2 114 13 28 122 1963 Jun 4 116 Apr 13 102 20 11 108 13 Maximum ice (102 cm) observed from 30 Mar to 13 Apr. 18 Unsafe for measurements. Open leads around creeks 20 100 17 where they enter Troutman Lake. 20 1 cm water on ice. 25 Open leads along shore. 27 99 17 Jul 6 Ice observed in southern half of lake. 27 5 cm water on ice. Cracks barely visible due to slush and 13 Ice completely out. water over the ice. Ice surface appears to be deterio­ 1967 rating due to sunand rain. Apr 22 117 Unknown May 4 99 13 29 113 8 4 5 cm slush on ice. 29 Water on surface of ice below snow on most of lake. 11 99 30 No further information available. 11 Avg. snow depth along coast 18 cm. 3 cm slush on ice. 18 97 1968 18 Surface rough, numerous cracks. Avg. snow depth along Mar 30 109 38 coast 25 cm. Apr 6 110 25 25 Ice melting along coast. 13 110 30 Jun 1 Open water extends from shore approx. 45 m to ice 20 105 38 sheet. 27 109 38 23 Lake completely ice-free. 28 No further information available. 1964 1969 Mar 28 133 18 May 30 Lake ice unsafe for vehicular traffic. Apr 4 131 25 Jun 15 Lake ice unsafe to walk on. 11 127 15 20 Lake free of ice. 18 123 20 1970 25 119 14 Incomplete May 2 114 15 1971 2 Almost all cracks become closed from daytime ice ] Missing and freezing at night. 9 112 1972 16 108 Incomplete 16 Cracks filled with water. 23 107 23 Open water along shore. HOLY CROSS, ALASKA 30 Unsafe for measurements. Open water along shore, Jun 6 No ice on southern half of ice. Measurements made on Walker Slough off Yukon River, approx. 16 Lake ice free. 400 to 800 m NNE of the station. 1965 Ice thickness Snow depth Mar 27 150 25 Date (cm) (cm) Apr 3 147 32 10 149 20 1962 17 147 20 Mar 26 91 18 24 144 25 26 3 layers overflow and slush ice, snow very dry. Ic May 1 140 20 solid. 8 138 23 Apr 2 84 11 15 135 17 9 81 22 128 15 16 86 29 126 9 23 89 Jun 5 122 8 30 94 6 5 Lake opening up in a few places along shore. 30 46 cm overflow and runoff water on ice.

96 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm) Date (cm) (cm) 1962 (cont’d) 1966 May 7 91 Apr 15 88 15 7 Surface slushy, no cracks. 22 86 11 14 89 29 85 15 14 46 cm water on surface. 29 Small cracks run in a NE direction across slough. Snow 19 Water rising, ice beginning to float. practically all slush. 21 Further measurements impossible. All ice afloat but no 30 No further information available. running open water. Ice moving but water insuf­ 1967 ficient to carry ice away. Water rising 3 cm per hour. Incomplete 1963 1968 Mar 24 109 13 Incomplete 24 Snow cover slushy. 30 122 5 1969 Apr 7 124 Apr 6 117 24 7 Ice clear of dry snow. 13 121 24 14 127 20 122 17 21 122 20 Water starting to rise in the river. 28 119 27 122 28 Snow cover watery. 28 No further information available. May 6 112 10 1970 6 61 cm water on top of ice. Apr 26 74 1 13 91 10 26 Ice beginning to rot due to warmer weather. No measure- 13 Ice raised 20 cm, water along shore only, snow slushy. ments available prior to 26 Apr. 18 Ice moved in slough, water very high. Ice was still 91 cm May 25 River free of ice. thick when it moved out. 1971 19 All local ice gone on slough and Yukon River. Mar 14 109 25 26 Yukon River and Walker Slough free of ice. 21 109 23 1964 28 109 25 Mar 27 Ice has cracked and settled approx. 60 cm during the Apr 4 110 22 Alaska earthquake. May 30 River free of ice. 28 124 41 1972 31 Ice cracks have closed. Apr 16 128 25 Apr 4 130 25 23 129 39 11 135 11 30 131 20 15 Approx. 30 cm overflow water from settling ice and sur- 30 Ice growth slow during Apr due to warm weather. rounding drainage runoffs. May 1 No further information available. 18 135 8 31 Alaska Regional Office of the National Weather Service 25 130 reports Holy Cross region experienced flooding May 2 135 8 problems during May. 9 130 5 16 130 1973 23 127 Mar 25 114 36 24 Ice raised in slough. Ice in river still solid, no cracks. Apr 1 114 32 30 119 8 113 32 30 Ice starting to drift. 29 102 20 Jun 12 River free of ice. 30 April was very warm, ice reported melting at the bottom. May 6 99 0 1965 6 Ice becoming rotten. Mar . 6 97 48 24 Walker Slough and Yukon River free of ice. 13 102 43 20 102 38 1974 26 Layer contains 102 cm ice beneath 5 cm water and 38 May 23 Walker Slough and Yukon River free of ice. cm snow. 27 102 13 Apr 3 99 30 KING SALMON, ALASKA 3 28 cm water overflow on ice. 10 10 cm water overflow on ice. Measurements made on Naknek River at about 50 to 150 m off the 16 99 18 landing docks. 17 94 20 17 Ice lifted, no water overflow. Ice thickness Snow depth 24 86 Date (cm) (cm) 30 Several small areas of open water. 1962 May 7 86 Mar 3 98 8 7 Surface honeycombed, last measurement due to rise of 10 Open water in center of river approx. 3.2 km east of water level and movement of ice. measurement site. 27 River open to navigation. 17 84 15

97 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1962 (cont’d) 1965 (cont’d) Mar 24 79 13 Apr 24 Increasing amounts of ice flowing with tide. Ice heavily 31 37 ridged along shore, extending out 3 to 12 m. 31 Lead moved past measurement site and extends approx. May 4 Considerable amounts of floe ice drifting down river, 1.6 km west. Estimate only 8 km of shore to shore some may be from breakup of Naknek Lake. ice exists between King Salmon and Naknek. 8 River partially refrozen, small ice floes observed but river Apr 7 River open at King Salmon. Ice floes built up along remained open for navigation. shoreline and extend outward approx. 7.5 m. Numer­ 12 River completely free of ice and open for navigation. ous ice floes in river. 1966 14 Ice floes along shore and in river. Mar 19 76 5 21 River is completely free of ice. 26 76 5 1963 Apr 2 72 6 Feb 22 Water covered the ice 15-20 cm deep near the shore. 9 76 24 Ice broke up with a free flow of water in the channel. 16 61 Mar 1 River still open. Ice floes in river. Ice jammed on banks 16 Snow extremely wet. Some ice melted and a layer of to approx. 9 m from shore. slush formed approx. 10 cm deep in places. 11 Numerous small ice floes shore to shore. 20 Lead open. 13 River again frozen over but unsafe. 22 Ice breaking up. 22 River open in channel, numerous ice floes. 23 Large channel formed in ice and contains a few ice floes. 28 River again frozen over, and contains numerous ice floes. 30 Small amounts of shore ice observed. Many floes moving Apr 5 Heavy ice on both banks of river with channel clear. in and out with tide. Heavy accumulation of floating ice at high tide. May 10 River free of ice. 19 Ice extends 1.5 m from both shores with a moderate 1967 amount of floating ice at high tide. Feb 25 93 4 26 Both shores free from ice with little floating ice at all Mar 4 46 cm of water covering almost all of ice, some exposed stages of tide. ice near middle of river. May 3 River free from ice. Many creeks leading into river are 11 90 heavily jammed with ice. 11 Ice surface crusted and crystallized, two layers of ice in 10 River completely ice-free. some places. 1964 18 80 Feb 22 76 1 25 57 29 76 5 Apr 1 Ice breaking up, wide lead down center of river with ice Mar 7 69 5 jamming at the narrower points. Lead approx. 140 m 14 28 5 wide extends up river. 22 20 8 River clear of ice except for some ice along shore. 22 Water from melted snow on ice. Some holes in middle of 1968 river, ice unsafe 18 m out from shore. Feb 10 84 4 29 10 3 10 Water and slush on ice due to warm temperatures. 29 Open crack in middle of river. 17 85 31 Open channel in front of boat dock. River still frozen 24 83 1.5 km from site. 24 Warmer temperatures have melted all snow on ice and Apr 4 Open water in middle of channel contains ice floes. Ice pools of water beginning to form over entire surface jammed on banks to approx. 8 m from shore. area. Open water all along shore extends out 9 to 18 m. 11 Heavy accumulation of floating ice at high tide. Mar 2 Thin ice extends out from shore to approx. 30 m. 25 Moderate accumulation of ice at high tide. Ice has 9 Channel open, shelf of ice extends out approx. 18 m from jammed along 3 m of both shores. both shores, thickness varies from 81 cm near shore May 9 Many creeks leading into river still frozen over. to 23 cm near open water. 16 Numerous pieces of ice on shore at low tide. Some ice 16 Ice extends 12 m from each shore. River open, few ice flow at high tide. Naknek Lake remains frozen over. floes. 23 River open for navigation. 22 River open and navigable, very light shore ice. Jun 1 River free of ice. Apr 7 Few ice floes 38 to 76 cm thick drifting with tide and 1965 scattered along shoreline. Feb 27 90 5 14 Main channel of river free of ice. Mar 6 86 21 Few small ice floes scattered along shore, all ice rotten. 13 86 28 River open, shore ice nearly gone. 20 60 1969 24 A lead 30 m wide opened above measurement site and Feb 22 112 1 extends to approx. 400 m below site. 22 10 cm water overflow at site has refrozen. The area of 27 Fast ice extends 6 to 9 m from shore. overflow extended 1/3 the width of the river. Apr 3 Jammed ice floes extend 3 to 9 m from shore. Mar 1 112 5 10 Small amounts of ice along shore, estimated thickness 8 110 10 30 cm. 8 Some water overflow with ice on top. 17 Small amounts of ice on river and its tributaries. 15 112 5 21 River partially refrozen and ice jammed approx. 800 m 22 114 10 upstream from measurement site. 22 Large area of water overflow just up river.

98 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1969 (cont’d) 1971 (contd) Mar 29 114 8 Mar 20 Lead open from Naknek Lake to Rapids Camp. Snow 29 Some water overflow, mostly on the NW side of the crusty, ice very dry and hard to drill. river. 27 112 3 Apr 5 102 13 Apr 3 117 8 Ice went out at measurement site. 3 Water overflow near shore refrozen and very slick. Some 9 No further information available. areas slushy. 1970 10 114 3 Feb 7 56 18 10 Some patches of water on surface. 14 47 14 Patches of open water near Melokoshar Point. 14 Large amount of overflow water near the shore, approx. 18 Open channel from Naknek Lake to Grassy Point. 20 to 26 cm deep. Water over the measurement site 21 Open channel to Melokoshar Point. Ice moving with tides. is 1 cm deep. 22 No flowing ice in river observed. None of the smaller 16 River’s main channel open from Naknek Lake to Rapids lakes and ponds are open. Camp. 25 Channel open to just below Pauls Creek and up to just 21 44 beyond Red Salmon Cannery at Naknek. Tidal action 21 River open approx. 1.5 km between Lake Camp and the evident in Pauls Creek. King Salmon Creek melting, lake. but no tidal action observed. Warm weather lately but 28 20 few lakes open. Big Creek mostly open. Ice moving 28 Ice becoming mushy and rotten. Channel open from just out of the lake during the tides. above measurement site to beyond Grassy Point. 28 Large amounts of ice flowing with the tide. Ice jam be­ Date is early for first break-up. low Melokoshar Point. Channel open from Pauls Mar 1 Channel clear, some ice moving in and out with tidal Creek to around the river bend. Observed a huge action. Some solid ice attached to shore. section of ice separate and move out to the bay. Water 6 River open almost to Pauls Creek. River solid from from Eskimo Creek, King Salmon Creek and Pauls Pauls Creek to Naknek. Creek flowing over river ice. 7 River full of broken ice. 30 Naknek residents claim that the huge mass of ice observed 14 River open from Naknek Lake to Naknek. from the air is the largest solid mass to move out into 21 Lake ice running down river. the channel in 12 years. 28 Most of river free of ice. May 4 Ice solid from Horseshoe Bend almost to Telephone Point. Apr 2 Some fast shore ice observed, due to a bitter cold week. Postmistress at Naknek confirmed rumors that when 4 Ice running bank to bank. Shore ice breaks up with tidal the huge section of ice broke off it sheared off part of action. the dock and pilings at the cannery. 6 River ice solid across from Grassy Point to Melokoshar 8 Channel mostly open, but it is narrow where the ice has Point, caused by an ice jam which formed after a piled up on the sandbars. Still not many open ponds bitter cold week. or lakes. Naknek Lake, Brooks Lake, and other large 7 River solid with jammed ice. Some open areas with ice lakes are open only near their main drainage regions. forming on these areas. 10 River free of ice. 9 River clear of ice from boat dock beyond Melokoshar 1972 Point but solid with ice above boat dock around Mar 10 The following ice conditions were observed on a flight Grassy Point. over King Salmon-Naknek-Dillingham-Togiak: 14 Ice jam went out, considerable ice still running out of Kvichak Bay, some pack ice to about 800 m below lake. Nakeen, no open water in the Nushagak, fast running 18 Some ice left on shore but melting rapidly. Ice cakes streams were open between Dillingham and Togiak. flowing in the river. Togiak Bay appeared solid with ice. 19 No further information available. 18 96 1971 18 Ice pressure mounds on river appear higher. Feb 6 Warm air temperatures. Meltwater on ice estimated 25 24 Water overflow extends from Eskimo Creek to FAA dock. cm deep. 25 100 1 13 Reported ice thickness of 117 cm not representative. 25 Water overflow within 23 m of measurement site. Ice Measurement made in overflow pressure ridge near rough due to refreezing of water overflow. shore. Ice ridges collapse when stepped on. Layer 31 River at Naknek has huge blocks of ice 3 to 9 m thick contains 1 cm ice, 16 to 25 cm air or water and then piled up on the banks and sand bars. Open water ex­ ice crystals beneath. tends to Telephone Point (above the cannery). Ice 20 99 5 rough to Iniam Point. Pauls Creek has a pressure ridge 20 Three measurements taken across the river. Ice thickness down the center and shows evidence of tidal action ranged from 84 to 107 cm, snow depth from 3-8 cm. and water overflow. King Salmon Creek has some 27 100 18 patches of clear, smooth ice from water overflow or Mar 6 103 20 melt. 13 Lead open at Officers Camp. Record low air temperature Apr 1 Warm temperatures and rain melted most of old snow. of -42°F. Flight to Anchorage gave excellent view of 7 The following ice and snow conditions were observed on extreme pressure ridging on Lake Illiamna and Lake a cross-country flight over King Salmon-Levelock- Illiamna-Igiugig: Kvichak River is open from Lake Clark and a few open leads at the confluence of the Illiamna downstream to about 3 km. Open water with Illiamna Lake and River. 14 104 15 some ice in channel from Naknek Lake to near Rapids 20 107 13 Camp.

99 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm)______Date (cm) (cm)

1972 (cont’d) 1965 (cont’d) Apr 8 102 Apr 17 Layer consists of 23 cm of slush beneath 23 cm of snow. 8 Few pressure mounds and considerable water overflow. 24 99 50 15 Water overflow 13 cm deep on ice in places. Lakes 24 Layer consists of 27 cm snow, 8 cm snow-ice, 15 cm appear to be solid ice from the air. Pressure mounds slush on top of ice. almost all melted, it appears that these mounds form May 1 104 52 over large boulders or piles of rock. 8 100 54 22 Open water upriver from Naknek Lake to rapids. Few 8 Layer consists of 32 cm snow, 9 cm snow-ice, and 13 cm open areas of running water in the creeks. Few soft slush. spots in ice on the southern edge of Naknek Lake. 15 114 29 29 River at Naknek almost completely free of ice up above 22 105 Leader Creek out to bay. Tidal action evident in 22 Ice raised, water starting to flow along river banks, holes Pauls Creek; but none in King Salmon Creek. starting to appear in ice. Eskimo Creek water running high. 25 Ice moved. 30 No further information available. 29 Ice moved out. 1973 Jun 1 River free of ice. Mar 11 104 6 1966 11 Rapids and part of lower portion of lake now open. Apr 2 122 20 18 109 0 9 114 20 18 Considerable overflow observed. 16 114 20 24 117 0 23 122 15 24 River ice starting to decay. 23 Puddles of water observed on top of ice. 31 Partial break-up, drifting ice in river, shore ice 38 to May 14 122 3 51 cm thick. 14 Ice raised. Water running along shore. Apr 7 Ice drifting in river; large chunks of ice along shore. 21 114 14 Ice jammed at Pauls Creek, considerable ice still exists 21 First ice movement. on the lake. 29 61 21 No ice on the river, considerable ice jammed along 29 Ice broke up and moved out. shore and ice still observed in creeks. Water level Jun 1 River free of ice. very low. 1967 1974 Mar 25 84 41 Feb 23 No leads observed, rapids just below Naknek Lake Apr 1 84 41 covered with more ice. 8 84 43 Mar 2 99 10 15 84 56 9 99 8 15 Water flowing up through drill hole. 8 cm snow and 16 99 10 water on ice. 22 Crack 10 to 20 km long formed along shore of river. 22 81 36 Rapids and Big Creek open in many places. 22 33 cm of snow and water on ice. 23 91 0 29 81 10 23 Snow cover turned to slush. 29 28 cm of snow and water on ice. 30 91 0 May 6 79 5 30 Water about 1 m deep running over the ice along shore. 6 Large number of puddles of water on ice. Ice melting from the top. 13 64 Apr 1 Naknek River still ice covered, rapids and part of Naknek 13 Ice raised, open water at river edge, many bare spots on Lake open. Water 20 m wide and 1 m deep running ice, 23 cm of snow and water on ice. length of river along the north shore. 20 Many holes in ice, river open along both shores. Approx. May 1 River free of ice. 6 m open water between shore and main ice sheet. Ice moved about 30 m. 22 Ice went out. KOBUK, ALASKA 28 River almost free of ice, some ice cakes flowing down- stream. Measurements made on the Kobuk River directly in front of the village. 1968 Mar 30 95 51 Ice thickness Snow depth Apr 6 95 48 Date______(cm)______(cm)______13 95 46 94 43 1965 20 48 Mar 27 112 13 27 95 27 Air temperature reached +5.6°C this week, quite a few May 4 97 48 bare spots and melt water pools observed on ice sur­ 11 94 18 face. 11 Very wet snow. 61 25 Apr 3 107 18 18 3 Small amounts of water on ice. 18 Water and snow on ice. 30 10 107 48 25 56 10 Approx. 5 cm of water on top of ice. 25 Ice floating in channels. Open areas forming. 17 108 46 27 Ice broke up and moved out.

100 Ice thickness Snow depth KOTZEBUE, ALASKA Date (cm) (cm) 1969 Measurements made on Kotzebue Sound, about 15 to 45 m offshore from the village. Mar 8 Water overflow running on top of ice in front of creeks and rivers. Ice thickness Snow depth 29 150 Date (cm) (cm) Apr 5 150 4 12 147 1962 12 Snow on ice melted, puddles of water standing on ice. May 4 112 Unknown 19 145 11 110 Unknown 19 Open areas along shore. 18 108 Unknown 26 145 19 Kotzebue Sound unsafe for vehicular traffic. May 3 124 25 102 Unknown 3 Water running along both shores, ice quite soft. Jun 17 Kotzebue Sound free of ice. 7 River ice breaking up. 1963 11 River free of ice. May 4 124 Unknown 1970 11 124 Unknown Apr 4 112 30 18 122 Unknown 11 113 28 25 91 Unknown 18 113 13 26 Kotzebue Sound unsafe for vehicular traffic. 18 Melt water puddles on ice. 28 Ice on Kotzebue Sound unsafe to walk on. 25 112 31 River ice broke up and moved out during the past week. 25 13 cm of snow and water over ice. Jun 13 Kotzebue Sound free of ice. May 2 105 1964 9 102 May 16 135 9 Open water areas observed along shore. Unknown 23 122 Unknown 15 First movement of ice observed in front of village. 30 117 20 River free of ice. Unknown Jun 6 102 1971 6 Last ice thickness measurement due to breakup of ice Apr 10 130 20 sheet. 17 130 20 Jul 14 Ice conditions safe for shipping. 24 130 20 27 Kotzebue Sound free of ice. Last 2 observations may have May 1 127 19 occurred 12 Jun not Jul (author). 1 8 cm of water overflow on ice. 1965 8 124 15 May 15 138 8 10 cm of water overflow on ice. Unknown 22 137 15 122 Unknown 28 Kotzebue Sound unsafe for vehicular traffic. 15 Some snow drifts, but many puddles of water on ice. 29 136 21 Ice moved, then stopped. Unknown 29 Water on top of ice due to snow melt. 23 Ice moved out of river. Jun 2 25 River free of ice. Ice on Kotzebue Sound unsafe to walk on. 21 Kotzebue Sound free of ice. 1972 1966 Apr 8 144 28 May 21 123 15 146 38 28 123 22 146 30 Jun 4 99 29 146 25 5 No further information available. May 6 142 6 Water puddles on ice from rain. 1967 13 105 Apr 29 113 18 13 Water running and open leads along shore. May 6 108 20 86 13 102 20 Ice rotten. Thickness estimated and first ice movement 20 100 noted. 27 84 23 Large open areas on river. Jun 3 48 24 No further information available. 6 Ice on Kotzebue Sound unsafe to walk on. Jul 12 1973 Ice conditions safe for shipping. 15 Kotzebue Sound free of ice. Last 2 observations may have Apr 7 119 8 occurred 12 Jun not Jul (author). 14 119 0 1968 21 116 3 Apr 27 107 28 118 3 May 4 104 May 5 118 0 11 88 5 Puddles of water on ice, and open water along shore. 18 85 12 99 0 25 71 19 76 0 27 Kotzebue Sound unsafe for vehicular traffic. 19 Ice in river starting to move out. Jun 1 46 25 River free of ice. 1 Water overflowing on ice in front of town. 1974 2 Ice on Kotzebue Sound unsafe to walk on. May 4 Puddles of water on surface of ice. 3 Ice moving in channel. 18 Ice moving and too rotten to measure. 19 Kotzebue Sound free of ice. 22 River free of ice.

101 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm) 1969 1966 (cont’d) Apr 19 147 18 Apr 2 122 26 146 15 9 122 May 3 141 Unknown 16 107 5 10 131 Unknown 23 97 15 17 100 Unknown 30 81 19 Ice on Kotzebue Sound unsafe to walk on. 30 Surface slushy with some water puddles. Jun 7 Kotzebue Sound free of ice. May 7 79 3 1970 14 61 Apr 18 117 23 21 46 25 121 10 21 Ice varies from 46 to 97 cm in deep part of lake. May 2 121 9 28 46 9 118 8 Jun 4 Surface slushy with water, cracks and holes observed. 16 114 3 Water very high. 23 108 11 38 Ice moving in front of village, conditions unsafe. 11 Ice breaking up. 24 18 All ice broken free and floating. Ice thickness varies from Jun 18 Ice conditions safe for shipping. 0 to 30 cm. 22 Kotzebue Sound free of ice. 23 Lake completely ice free. 1971 48 1967 May 1 119 Mar 11 110 58 8 122 30 46 15 122 30 18 112 13 25 109 46 22 119 Apr 1 109 61 22 Ice surface wet. 8 109 61 24 Kotzebue Sound unsafe for vehicular traffic. 61 29 102 5 15 109 29 Ice surface wet, few cracks near river channel at approx. 22 109 56 20 to 45 m offshore. Lead runs NE-SW from station 29 107 51 May 6 107 41 to 3.2 km offshore. 13 102 15 Jun 5 70 20 99 25 5 Last report, ice moving out of Noatak River. 27 76 10 1972 27 Snow wet and mostly slush. Apr 29 137 46 Jun 3 61 (estimated) May 6 137 28 3 Open holes making conditions on lake dangerous. 13 135 15 10 46 (estimated) 20 132 10 23 15 (estimated) 27 91 24 Lake free of ice. No further information available. 28 1968 1973 Mar 31 104 30 Apr 28 119 28 31 Snow surface crusty. May 1 122 13 May 5 94 25 12 117 13 5 Surface slushy. 19 114 8 12 89 20 26 109 0 19 81 10 Jun 21 Kotzebue Sound free of ice. 26 76 1974 26 Ice rotten along shore. Surface slushy, holes in ice. Apr 13 155 13 Jun 2 64 20 152 13 2 Ice honeycombed all over lake. Many holes in ice. 27 152 14 9 Ice estimated to be 30 to 38 cm thick. Ice honeycombed : Jun 21 Kotzebue Sound free of ice. over lake. 16 Lake clear of ice. 1969 MANKOMEN LAKE, ALASKA Apr 5 145 20 12 147 15 Measurements made on Mankomen Lake offshore near the camp site. 19 147 13 26 145 10 Ice thickness Snow depth 26 Some water on ice from the melting snow and from water Date (cm) (cm) overflow onto ice from the creek. 1966 May 1 Creek beginning to open up. Mar 19 129 5 3 140 26 122 5 10 135 26 Water level rising again. Bottom 46 cm part of ice cover 17 130 is soft and wet. Water from some of the creeks flood- 24 122 31 97 ing lake. 31 Holes in ice.

102 Ice thickness Snow depth Ice thickness Snow depth Date (cm) ____(cm) Date (cm) (cm) 1969 (cont’d) 1972 (cont’d) Jun 7 66 Apr 28 114 8 7 Ice very rotten. May 4 114 15 14 30 (estimated) 11 117 8 14 Water on ice, and many holes. 18 109 8 21 Ice out. 25 102 3 1970 25 Some water overflow on ice during 11 to 25 May. 14 91 5 29 97 3 14 Snow melting slightly, some water running onto lake 29 Approx. 15 to 20 cm of water overflow on ice. from creek. 30 No further information available. 21 94 5 1973 28 94 Trace Mar 10 130 30 Apr 4 93 10 17 133 0 11 91 8 24 140 0 18 91 10 31 141 3 25 91 10 Apr 7 137 5 25 Ice appears to be deteriorating somewhat. 14 135 8 May 2 89 5 21 127 13 2 Surface wet, no cracks. 28 119 10 9 89 May 5 114 9 9 Water overflow on ice, surface slushy. 12 109 4 16 81 19 103 0 16 Creek flowing into lake is ice-free. 26 Ice conditions unsafe. 23 71 Jun 21 Lake free of ice. 30 46 30 Ice rotten and becoming unsafe to walk on. 1974 Jun 6 30 (estimated) Mar 23 150 13 6 Ice unsafe. 30 152 28 13 Ice thickness estimated to be 15-20 cm. Apr 6 153 28 17 Ice out, some land-fast ice remains around shores of lake. 13 155 20 20 155 15 1971 27 155 25 Mar 6 137 15 Jun 29 Lake free of ice. 6 Strong winds removed some snow cover. 13 137 10 13 Water level rising in lake. McGra th , Alaska 20 142 8 27 130 5 Measurements made on the Kuskokwim River off the southern shoreline Apr 3 130 and near the village. 3 Snow melting off lake. 10 130 10 Ice thickness Snow depth 10 Lake has crowned in center and some water overflow on Date (cm) (cm) north side. Snow cover slightly slushy. 17 137 5 1962 24 132 Mar 3 74 61 24 Cold winds refreeze some areas of water overflow on the 10 75 51 lake. 17 71 46 May 1 132 8 24 71 41 1 Snow very wet and creek is starting to open up. 31 71 30 8 132 13 Apr 7 74 48 8 Wet snow on surface and creek is open. 14 71 18 15 127 3 21 71 10 15 Snow slowly melting, some water on top' of ice. 28 71 5 22 124 May 5 70 8 29 122 5 Surface slushy, no cracks. Jun 5 117 12 Ice unsafe to walk on, 3 m open water along bank, water 12 91 rising 30 cm per day. 19 51 16 Ice has started moving, jamming, causing water to rise. 19 Open water holes on ice. Ice is rotten and candled along 17 Flooding occurs. edges. 18 Ice starts moving, and continues, water recedes. 30 Ice went out. Water level high due to considerable rain. 19 No further information available. 1972 1963 Mar 11 119 20 Apr 20 119 30 18 119 20 27 112 25 116 20 27 8-23 cm water overflow on surface. 29 112 13 May 4 114 10 Leads appeared on both sides of the river, river rose rapidly. 11 Overflow covered site, ice on river unsafe to walk on.

103 Ice thickness Snow depth Ice thickness Snow depth Date (cm)______(cm)______Date ______(cm)______(cm)___

1963 (cont’d) 1967 (cont’d) May 13 Ice moved in large sheets, followed by large and small Mar 4 89 41 floes, honeycombed and rotten with soft spots. Those 11 71 58 washed on shore were approx. 76 to 91 cm thick. 18 71 61 63 19 River free of ice. 25 74 25 30 cm of water overflow on ice. 1964 Apr 1 79 56 Mar 14 132 33 1 Top 8 cm of overflow frozen, 18 cm more of unfrozen 130 36 21 overflow over main ice. 28 131 36 8 69 30 28 Cracks separating shore ice from main ice on river. Shore 8 Snow cover melting. ice unusually thick due to slush ice freezing. 22 69 15 Apr 4 131 38 29 48 11 130 38 May 3 44 14 18 127 56 3 Surface covered with overflow water, numerous cracks, Top 46 cm of ice honeycombed. 18 41 cm of overflow in places. 20 Considerable water overflow. 4 Water overflow has drained off through holes in ice. 25 124 61 8 River free of ice. May 2 119 43 9 112 1968 16 Shore ice broke away from river ice leaving leads all along Mar 9 100 23 the river. 16 99 25 23 109 23 97 28 26 84 23 Slight erosion of ice indicated. 28 Ice moved. 30 94 36 31 Ice has gone out. Apr 6 91 23 Jun 2 Water high, numerous ice floes. 13 89 24 3 River free of ice. 20 76 17 20 Water overflow at measurement site. 1965 26 Water on ice flowing past measurement site, overflow Cracks along shore separating river ice from land-fast Feb 27 depth 30 cm. shore ice. Overflow of water from cracks to ice sur­ 27 71 face. 27 Ice measurement taken under the water overflow. Mar 13 99 0 May 4 67 4 20 97 11 64 23 Considerable overflow of water, large cracks along shore. 11 Ice becoming unsafe. Apr 1 River ice lifted and separated from shore ice. 15 Water rising slowly along and over shore ice to depths of 3 83 46 to 61 cm. 10 80 16 No further information available. 15 Water level rose, leads on bar side of river extending all along shore. 1969 17 74 Mar 8 84 Unknown 22 Water level dropped, new ice formed in some overflow 8 First water overflow on ice observed. Unknown areas. 15 86 24 53 22 84 Unknown 24 Surface of river ice appears deteriorated. 29 86 Unknown 27 Main river ice rotted and moved. 29 Deep cracks along shore line breaking off the main ice May 1 38 from the shore ice. 1 Ice melting fast and honeycombed. Apr 5 79 Unknown 8 30 5 Water overflow on ice 15 cm deep. 8 Ice beginning to move out. Large masses of sludge ice 12 69 Unknown across river moved downstream. 19 66 Unknown Unknown 9 River free of ice. 26 48 26 61 cm of overflow on top of the ice. Ice hummocks along 1966 shore, and main ice deteriorating fast. Mar 19 104 37 May 5 River free of ice. 21 3 cm water overflow under snow cover. 26 97 38 1970 20 Apr 2 94 41 Mar 14 74 Deep cracks all along shoreline, water overflow 8 cm deep. 9 81 43 16 18 16 79 28 21 69 Rain storm, snow melting and rain pools all over the ice. 21 74 8 21 28 71 Ice deteriorating very slowly. 18 28 Ice decaying rapidly, 76 cm water overflow on ice, 28 71 8 May 27 River free of ice. Apr 4 61 18 64 10 1967 25 Water along shore 1 m deep and rising. Feb 25 5 cm water overflow on ice. 28 Shore ice rose, water rising steadily. 31 Long crack between shore ice and main river ice.

104 Ice thickness Snow depth NUNIVAK ISLAND, ALASKA Date (cm) (cm) Measurements made on Mekoryuk Bay. 1970 (cont’d) May 2 61 Ice thickness Snow depth 2 Leads and cracks appear all along the shore line. Ice is Date (cm) (cm) rotten and deteriorating rapidly. 4 Ice first moved 90 m and then jammed. Water rising 1962 steadily. Mar 22 147 50 10 River free of ice. 29 127 48 1971 Apr 12 112 56 Mar 6 97 51 19 110 43 10 Water flowed out of holes causing overflow. 26 104 36 13 97 53 May 3 103 23 20 91 74 10 96 23 21 Water continues to flow out of holes in the ice. Warmer 17 88 22 temperatures started thawing the snow. 24 83 11 27 86 28 28 First lead observed on channel of bay. Apr 3 86 36 30 Ice moved out of Mekoryuk River. 10 89 38 31 Some ice floes from the sea have moved into Mekoryuk 17 89 25 Bay. 24 91 28 Jun 1 No further information available. 30 New long cracks observed 3 m out from the land-fast 1963 shore ice. 10 to 13 cm frozen overflow ice, and 3 m Apr 17 83 13 water overflow during April. 24 84 4 May 1 76 6 May 1 88 3 8 69 8 74 8 Leads and cracks along shoreline. Ice deteriorated fast 8 First lead in the middle of channel observed. last 2 weeks. 9 Channel has broken up, few ice floes in channel. 13 Ice first moved and jammed in front of town. Water rose 14 Channel open. 6 m above normal, about average for spring flood 22 Large ice floes. stage. 29 Some ice floes still in bay. 20 River free of ice. 30 Mekoryuk River free of ice. 1972 1964 Mar 25 A few large cracks observed along shoreline. Mar 10 79 47 Apr 1 94 33 17 79 47 8 94 38 24 72 46 15 91 51 31 66 56 22 89 61 Apr 7 65 56 29 86 33 14 64 52 30 No further information available. 23 Lead formed in channel. 1973 28 Thin ice cover broke up during day. Channel clear. Mar 10 109 Unknown May 5 5 cm of new ice in channel. 17 104 Unknown 12 Channel clear of thin ice. 24 107 Unknown 19 Channel clear except for few ice floes. 31 104 Unknown 26 Ice floes observed on part of bay. 31 Large cracks in ice along shoreline. 1965 Apr 7 104 Unknown Mar 13 95 42 14 104 Unknown 20 98 42 21 79 Unknown 27 99 20 21 Ice cover deteriorating fast. Apr 10 Warm, strong south winds have broken up ice. 28 51 Unknown 17 Channel clear of ice. 28 61 cm of overflow water on shore ice. 24 Cakes of ice move back and forth in channel. 1974 31 18 Mar 10 69 48 31 Many cracks in existing ice cover. 10 New snow cover of 13 cm became crusty. May 1 Large ice floes, channel clear. 8 Ice floes flowing in and out with tide. 17 69 46 Apr 13 61 25 15 Small ice floes. 22 Few ice floes, bay and ocean practically clear of ice. 20 Ice along shore unsafe. 29 Few ice floes still floating in river. 27 River shoreline completely free of ice. 1966 May 5 Ice breaking up and moving downstream, ice chunks Apr 16 100 56 approx. 45 cm thick. 23 103 29 8 First boats on river. 30 94 28 12 River free of ice.

105 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm) Date (cm) (cm)

1966 (cont’d) 1970 (cont’d) May 7 105 15 Apr 4 79 25 14 102 13 11 76 22 17 Channel ice unsafe to walk on. 18 71 25 19 First lead observed. 25 69 27 21 Ice in channel breaking up. May 2 62 38 28 Ice in bay breaking up. 9 64 28 Jun 4 Ice floes and slush on bay. 16 58 15 11 Small ice floes and small amounts of slush on bay. 23 38 6 18 Bay clear of ice. 28 Channel ice started to move. 1967 29 Ice breaking up farther out, up river. Mar 7 River channel has opened by strong winds. 30 Channel in front of the village started breaking up. 11 108 15 31 Ice breaking up in channel of bay and up river. Ice solid 18 Channel and part of bay opened, floating ice cakes further out at sea observed. 1971 25 Most of ice gone, ice cakes drifting back and forth with Apr 10 86 29 the tides. 17 64 39 Apr 8 Mekoryuk Bay mostly clear of ice. 24 62 36 29 Small ice cakes drifting in and out with the tide. May 8 43 28 30 Beach clear of ice. 15 41 15 May 6 Few ice cakes in river and bay. 22 39 10 20 Bay clear of ice. 29 33 5 1968 Jun 5 Ice cakes flowing in and out of channel with the tide. Mar 16 Depth of snow on ice varied from 0 to 10 cm from 1 Feb 19 Few ice cakes flowing downstream with the tide. to 16 Mar. 26 No ice observed. 23 76 15 1972 30 71 30 Apr 1 86 15 Apr 6 65 30 8 85 15 13 64 25 15 71 10 20 58 20 22 71 8 27 51 13 29 61 8 May 4 51 18 May 6 65 5 11 55 13 13 61 0 18 50 5 20 50 0 24 Entire channel has opened with the tide, ice in river has 27 Ice in river channel is rotten with many open holes. Ice moved out. unsafe for travel to lower river, Bay still solid, ice 25 Ice cakes start moving in and out with the tide. extends 400 m out into ocean. Jun 1 Ice floes still in bay. 28 No further information available. 8 Ice obstructs channel when the tide comes in. 1973 15 Few patches of ice in bay and flowing in river. Mar 3 81 20 1969 10 71 15 Jan 28 Ice sheet broken up by strong southerly winds of up to 17 69 20 30 mps. Most of bay has cleared of ice except on the 24 69 18 edges. 31 67 18 Feb 1 No solid ice, only ice cakes flowing in and out with the Apr 7 64 28 tide. 21 62 18 8 New ice cover has formed. 28 62 20 Mar 1 71 30 May 5 61 23 1 Measurement made on undisturbed last-fast shore ice. 12 60 25 8 65 20 19 53 15 8 Surface rough, many cracks. 26 47 10 15 53 18 26 Ice cover over channel up river and in bay has open areas 18 Portion of ice measurement site broken up. about 15 to 30 m long. 22 Ice cakes flowing in and out with the tide. 27 No further information available. 29 Upper part of observation site still solid ice. Ice floes in 1974 lower part of the bay. Mar 23 84 20 Apr 12 Ice on upper part of observation site is unsafe, lower 30 85 20 part is clear except for a few floes. Apr 6 63 23 19 Site clear except for flowing ice cakes. 13 64 20 26 Bay clear of ice, river has some packed and jammed ice. 20 66 15 May 18 Mekoryuk River clear of ice. 27 63 13 1970 28 No further information available. Mar 7 104 25 14 102 20 21 100 22 28 95 28

106 POINT HOPE, ALASKA Ice thickness Snow depth Date (cm) (cm) Measurements made on Chukchi Sea west and northwest of the village 1967 (cont’d) at about 20 to 150 m offshore. Jun 21 Ice drifted offshore from south beach. Anchor ice out Ice thickness Snow depth for approx. 45 m on north shore. Date (cm) (cm) 25 Some ice sighted approx. 8 km south of village. 1968 1962 Incomplete May 12 97 46 20 95 28 1969 27 102 0 Feb 15 Open water off south shore about 800 m out. 27 Snow has melted at measurement site. The additional 22 Open water froze over. Very cold weather -40 to -43°C. thickness possibly due to refreezing of melted snow. Mar 29 140 3 28 No further information available. 29 Open lead 1.6 km out off north shore. 30 No further information available. 1963 Mar 30 Strong southwesterly, cold winds during the past week 1970 have nearly swept the site clear of snow. Pressure Missing ridges have been observed near the measurement site. 1971 Apr 6 146 3 Mar 27 Open lead on south side of station approx. 5 km out. 13 147 3 Apr 3 142 8 20 149 13 10 146 3 27 150 8 17 147 3 27 Heavy snowfall and drifting snow from southeasterly 24 149 10 winds during the last two weeks of April. 24 No open leads. May 4 152 5 25 No further information available. 22 Ice broke up at south beach, leaving a small amount of 1972 pack ice at the point. Apr 15 234 10 25 Considerable amount of the pack ice melted. 22 241 8 26 No further information available. 29 244 5 1964 29 Open water on south side of South Beach, small water Apr 25 179 5 puddles on ice. 25 Lead northwest of observation point is approx. 800 m 30 No further information available. wide and 5 km long. 1973 May 2 180 5 Mar 31 Some open water on south side of the shoreline. Very 9 180 5 cold weather. 16 184 10 Apr 14 221 10 23 Ice broke up on South Beach. Leads 14.5 km to the 21 226 10 south. 28 231 8 31 160 May 5 234 3 31 Ice moved close enough to shore for measurement. Many 12 229 5 pools of water and considerable melting from spring 19 224 5 thaw at measurement site. Ice broke up on north 26 211 0 beach. 26 Open water on south side of shoreline. Ice cover becoming Jun 1 No further information available. unsafe, numerous deep holes in all areas. 1965 27 No further information available. Mar 27 156 8 1974 27 SE-NW oriented lead on the south beach approx. 3 km Incomplete. long. 28 No further information available. 1966 PORT ALSWORTH, ALASKA Mar 26 127 5 26 Open lead approx. 3 km west of the measurement site Measurements made on Hardenbourg Bay of Lake Clark in the vicinity of running SE to NW. Port Alsworth. 27 No further information available. 1967 Ice thickness Snow depth Apr 29 119 8 Date ______(cm)______(cm) 29 Surface smooth. 1962 May 6 117 5 Feb 24 130 13 114 5 24 Snow cover variable 15 to 30 cm in drifts. Surface rough 20 109 3 due to overflow, few cracks. 27 107 Mar 3 124 27 Open lead observed both north and south, approx. 90 m 10 119 offshore from measurement point. 10 Open hole in narrows. Jun 3 91 17 119 10 76 24 124 17 Water on ice.

107 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1962 (cont’d) 1966 M ar 31 124 M ar 2 6 118 5 31 Snow cover variable 30 to 46 cm, some overflow. A p r 2 122 Narrows open across from shore to shore. Ice very 9 112 soft on surface due to warm weather and overflow. 9 Water overflow 15 cm deep. A p r 7 107 16 10 4 14 99 16 5 cm water and shell ice. 21 9 4 23 9 9 2 8 76 23 Narrows open. 3 0 Open water in narrows and around edges. 3 0 9 4 M ay 5 71 3 0 Holes appearing. 12 43 M ay 7 4 6 3 19 Ice in middle of bay, conditions unsafe. 7 Snow cover crystallized, ice cover soft and becoming un- 2 6 Ice still in bay and main lake. safe, some holes appearing. 31 Ice on lower end of Lake Clark. Upper Lake Clark 14 25 partially open. Hardenbourg Bay clear of ice. 21 13 1963 2 4 Bay clear of ice. A p r 13 81 15 1967 2 0 79 8 M ar 25 103 8 2 7 69 A p r 1 99 10 2 7 Lead opened between island and mainland. Ice very soft 1 Water overflow, openings in narrows. and slushy. 8 9 7 13 M ay 4 56 8 Open water across narrows. 11 2 2 15 9 7 10 11 Surface crystallized. 15 Holes in ice near shore, along beaches. Snow cover wet, 18 10 surface rough, few cracks. 2 0 Ice cleared from bay. 2 2 91 15 1964 22 Huge holes along each shore. 29 79 M ar 2 8 Few cracks caused by earthquake of 27 Mar. Approx. 29 Ice unsafe and honeycombed at top. Water overflow 43 cm of ice on Lake Clark. increasing. A p r 4 103 25 M ay 14 Bay clear of ice. 11 9 9 10 18 103 1968 25 9 9 3 F eb 2 4 86 2 5 Several small holes near edge of bay. 2 4 Overflow along west shore. M ay 2 9 7 M ar 2 81 9 89 2 Ice started becoming honeycombed. 5 cm of water on 9 Surface crystallized, few cracks. su rface. 16 81 9 77 23 76 16 7 2 30 3 6 23 71 30 Cracks throughout ice. Open water out to approx. 6 m 3 0 6 7 from shore. Ice still remains in main lake. Water level A p r 6 6 7 in the lake is very low. 6 Water on ice crystallized. 31 No further information available. 13 61 1965 2 0 6 0 8 2 0 Open leads north side along shore to NE end of bay. F eb 27 102 3 27 4 3 2 7 Snow drifts hard and packed from wind. Ice clear of M ay 4 2 8 snow in places. 11 10 M ar 6 102 13 Hardenbourg Bay clear of ice. 6 3 to 15 cm water overflow. 13 89 1 1969 27 Narrows have opened up. No snow on shore. M ar 29 109 2 0 29 7 4 3 29 Snow wet and granular. Open water areas appearing in A pr 3 67 1 the channel. 10 6 2 A p r 5 109 15 10 Narrows open. 5 Open lead across narrows. 17 55 12 9 7 2 4 3 4 19 Top 15 cm snow and 30 cm of ice needled. 2 4 Ice all honeycombed and unsafe. 2 6 7 6 M ay 1 25 2 6 Ice needled all the way through. Ice becoming unsafe. 1 Open water around edges of lake. M ay 3 61 8 15 10 4 6 8 Bay 3/4 open. 10 Surface honeycombed. 15 5 13 Bay clear of ice. Water level lowest in station history. 2 2 Bay clear of ice. Lake Clark open.

108 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date ______(cm) (cm)

1970 1974 (cont’d) Feb 7 66 13 Mar 23 112 0 14 61 23 10 cm of water overflow on ice. 21 56 30 102 0 28 51 30 Open area across the narrows, a few holes in ice observed Mar 7 53 13 along the west shore. 14 53 Apr 6 94 0 21 47 13 94 0 28 42 20 84 0 28 Open lead in narrows and a few other open areas along 20 Open areas across the channel and around the shoreline. the shoreline. 22 Ice conditions becoming unsafe, ice cover needled. Apr 4 30 27 74 0 11 33 May 14 Lake clear of ice. 12 Open lead across narrows extending along western shore- line. 18 20 SNOWSHOE LAKE, ALASKA 18 2/3 bay open extending out from western shoreline. 25 13 Measurements made on Snowshoe Lake at approximately 180 m off the 25 1/2 bay open extending out from western shoreline. south shore from 1964 through 1967; at approximately 180 m off the May 2 13 east shore from 1968 through 1974. 2 Surface candled. 5 Bay ice free. Ice thickness Snow depth 1971 Date (cm) (cm) Apr 17 107 43 1964 17 Water on surface of ice. Apr 26 95 28 24 112 30 26 Ice thickness includes 4 cm of refrozen overflow. 24 Leads and cracks appearing NE of station and along north May 3 95 23 shore. Snow cover very wet and compacted with 13 10 90 18 cm slush on ice. 17 90 14 May 1 Top 10 cm of surface is wet and honeycombed. 17 Top 2 cm of ice very soft and wet. 8 104 29 Open water around edge of lake varying from 9 to 15 91 in width. Bay side of lake open. Estimated thickness 15 Surface wet and granular. Holes in ice observed along middle of lake 76 cm with numerous cracks and open NW shore. leads. Ice becoming very rotten. 22 76 30 No further information available. 22 Top 13 cm of ice honeycombed, jBay open in narrows and along shore edges NW, S, E and W of station. 1965 29 38 Apr 10 76 3 29 Surface honeycombed, numerous cracks. Bay 3/4 ice 10 Overflow now frozen, top 10 to 13 cm of ice not as hard covered, but open all around the shoreline. as rest of ice. 30 No further information available. 18 76 24 75 1 1972 24 Top few cm of ice soft and granular. Apr 22 119 20 May 1 74 29 119 10 1 The snow cover has melted , leaving crumbly shell ice over May 6 107 solid ice. 13 91 8 69 13 Bay open in narrows. 8 Bay at outlet breaking open and leads of water around 74 20 edge of lake. 20 Surface rough, and candled. 15 6.1 43 27 15 All of soft ice on top is gone, open water around most of 27 Bay open all around edges of shore, ice starting to move. lake shore. 1973 22 Ice no longer safe. Mar 31 114 5 31 Ice moved out under fairly steady southerly winds. Apr 7 117 0 31 Lake free of ice. 14 102 0 1966 21 97 0 Apr 10 67 20 21 Open area observed across the narrows. 16 67 15 28 91 0 23 67 11 28 Top 5 cm of ice is honeycombed. 30 65 4 May 5 51 0 May 7 56 12 38 0 7 Ice very mushy. Water covering ice in bay in SW corner 15 Open leads cover entire bay, shoreline also all open. of lake. 17 Bay clear of ice. 10 Bay in SW comer started opening. Open water along 1974 edges of ice. Mar 9 109 10 20 Ice quite rotten, generally detached from shore all 16 112 0 around lake.

109 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1966 (cont’d) 1969 (cont'd) May 26 Lake 1/3 to 1/2 open. May 10 Bay area of lake open. Ice honeycombed, band of water 28 Ice completely out. around shore edges. 15 Ice free from shores, moving freely with the wind. 1967 18 Large pieces breaking free of main sheet all moving with Feb 19 Water overflowed onto ice over large portion of lake. the wind. 10 cm of water over measurement site. 20 Strong SE winds, ice has disintegrated rapidly by late 25 Snow cover (50 cm) includes 14 cm water over ice. afternoon. Earliest and fastest ice deterioration Surface of ice rather mushy in upper 3 cm layer. conditions seen by observing personnel since residing Measurement site is moved approx. 100 ft south, at Snowshoe Lake. still in an extreme overflow area. Large portion of lake covered with water. 1970 Mar 5 Numerous holes in lake ice with water overflow. Snow Apr 19 67 9 cover includes approx. 20 cm of water over the lake 26 66 4 ice. 26 Top of ice soft and slushy. 11 Beneath the 24 cm of snow is thin layer of ice, then 20 May 3 61 cm water over regular ice. Surface of ice mushy. 10 53 18 Overflow freezing, a thin layer of water is observed be­ 16 28 tween regular ice and frozen overflow. 16 Some open water around edge of lake, ice rapidly be­ Apr 2 85 15 coming unsafe. Open water along shore, and holes 9 85 10 over lake surface. 16 84 10 20 Ice going very fast. Open area at south end and along 23 83 13 east shore, ice moving due to southerly winds. 23 Ice soft near surface. 21 Southerly winds most of day, only small isolated pans or 30 81 3 cakes of ice remain. 30 Top 25 cm of ice very soft. 21 Lake free of ice. May 7 79 1 1971 7 23 cm of ice and water mixed over regular ice. Apr 10 71 34 14 71 17 72 29 14 Bay at SW corner of lake at creek inlet and outlet free 24 72 28 of ice. 24 Increase in ice thickness during last two weeks probably 24 Ice free from shore and drifts between shorelines with due to surface melt water freezing on top of old ice. the wind. May 1 71 19 31 Lake approx. 1/4 to 1/3 ice-free. 8 71 10 Jun 3 Lake ice-free. 12 Pools of water appear at outlet in SW corner of lake with 1968 some open areas. Feb 25 Some water overflow observed over mos1: of lake. 15 69 Trace Mar 30 86 33 15 Ice very wet. Meltwater about 5-6 m wide along edges 30 Water and slush layers observed within the ice cover of lake on ice surface. throughout March. 17 Open water along edges and around entire lake. Apr 7 84 25 21 SW end of lake free of ice. 13 84 27 22 58 21 84 25 22 Ice very mushy, approx. 9 m open water along shoreline. 28 84 17 24 Ice free from shore. 28 Snow cover wet, especially near surface of ice. 31 Wind gradually eroding ice away and lake is approx. 1/3 May 5 83 10 ice free. 11 81 Jun 3 Lake free of ice. 11 Deep water over ice around edge of lake., Ice very mushy 1972 in top 25 cm, rest of ice granular and fairly soft and Apr 15 75 33 wet. 22 75 30 18 71 27 First signs of breakup, water on top of ice observed where 24 Ice rotten and starting to shift. Cache Creek enters the lake. 26 Entire mass of ice starting to break up. 29 75 25 31 Lake free of ice. May 6 71 1969 6 Cover consists of about 8 cm of wet snow and water Apr 13 76 13 (slush) over 20 cm of very soft ice. Bottom layer of 20 76 1 ice more solid. 20 Top 8 cm layer is frozen snow-ice, next 3 cm layer is soft 13 71 and wet slush-ice, with solid ice sheet beneath these 13 Some open water around edge of lake, runoff water layers. accumulating on ice. Cover consists of 5 cm ice over 27 74 10 cm water with rest of bottom ice soft. 27 Ice soft and slushy. 20 69 May 4 67 27 Ice broke free from shore and drifts as a solid sheet with 4 Many soft spots in ice while drilling. Open water at SW the wind. end of lake near inlet and outlet and also along edges. 28 Open holes and leads in ice, remaining ice appears very 10 58 rotten.

110 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1972 (cont’d) 1964 Jun 2 Ice went out of lake. Mar 24 88 15 1973 27 Earthquake opened ice below village. Mar 31 62 30 31 86 8 Apr 7 62 29 Apr 7 80 10 14 62 24- 14 71 5 21 62 19 21 62 18 21 Surface of ice is wet, ice cover becoming softer. 28 53 27 28 62 20 28 Heavy snow during last week. 28 Pools of water forming on ice surface. May 29 River free of ice. May 5 60 Trace 1965 7 Open water forming around shoreline. Missing 12 47 0 1966 12 Open water at creek inlet and outlet, also around entire Feb 26 Open lead on opposite shore near area where creek flows edge of lake. into river. 16 Ice cover unsafe, ice rotten, numerous holes and some 28 Considerable overflow from area at upper end of village. open leads. Remaining ice cover is free and drifting Open area next to gravel bar and at upper end of with the wind. village near the bank has frozen over. River below 19 Ice melting rapidly, lake almost 1/3 open. village open. 21 Lake free of ice by evening. Observer notes that this was Mar 12 76 58 an early breakup and an unusually fast melting of the 20 74 58 lake ice. 20 Lead on opposite shore slowly widening. Ice next to 1974 village and gravel bar safer than ice in center of river. Mar 16 Ice cover consists of 10 cm ice on top, 5 cm layer of 26 71 51 water underneath, and 60 cm of solid lake ice. 27 No further information available. 30 74 28 1967 30 Ice cover consists of 13 cm ice on top, 4 cm layer of Missing water underneath, and 57 cm of solid lake ice. Apr 6 72 28 1968 13 72 26 Apr 14 104 18 20 72 23 21 104 8 27 71 8 29 97 27 Ice cover consists of 17 cm ice on top, 1 cm water under­ 29 Ice porous. River has open areas. Surface slushy, numer- neath and 53 cm lake ice. Upper 20 to 25 cm of lake ous cracks. ice becoming soft. Wet areas on ice surface forming May 5 28 around edge of lake where runoff water occurs. 5 Ice is porous, numerous cracks. Conditions extremely May 28 Lake free of ice. hazardous. 12 Ice floes only observed from 12 to 15 May. 13 No further information available. TANACROSS, ALASKA 1969 Mar 15 Surface slushy, 3 cm water under snow on top of ice. Measurements made on Tanana River off the eastern bank directly in 22 91 18 front of the village. 22 Surface hard-packed. Snow has melted and refrozen. 29 89 20 Ice thickness Snow depth Apr 5 79 18 Date (cm) (cm) 5 Surface melting, many cracks. 12 66 10 1962 19 64 3 Apr 2 102 25 19 More melting, some open water. 9 99 25 26 51 16 102 15 May 15 River free of ice. 16 Ice becoming soft all the way through, numerous cracks. 23 99 1970 30 104 20 Feb 28 Ice was porous (slushy) due to unseasonably warm weather May 7 97 during the past week. 14 River open and no longer crossed safely. Mar 21 53 20 28 53 15 1963 Apr 4 48 10 Apr 6 83 8 11 43 15 13 69 5 18 56 18 One 60-cm crack in ice. River appears to open in approx, 25 Ice porous. the same place each year. May 15 River free of ice. 20 66 5 22 55 5 1971 30 33 3 Apr 3 104 10 30 Warming trend observed all month. 10 109 13 May 6 River free of ice. 17 104 10

i n Ice thickness Snow depth Ice thickness Snow depth Date ______(cm)______(cm) Date (cm) (cm)

1971 (cont’d) 1962 (cont’d) Apr 24 102 May 12 Some ice formed on either side of channel. 24 Surface porous, few cracks. 19 Susitna Channel ice free from bank to bank. May 1 91 26 Large ice blocks or floes floating down stream. 1 Surface very porous, numerous cracks. 29 Navigation started across river. 14 Bulk of ice has gone out. River level has risen approx. 1963 1.5 m. Mar 22 109 51 15 River free of ice. 22 Overflow on the ice during the week increased ice thick- 1972 ness. Apr 15 102 23 29 110 48 22 94 20 Apr 5 84 81 29 94 15 12 81 93 29 Ice becoming porous but not eroding as yet. 19 91 91 May 6 76 19 Snow on surface and overflow. 6 Surface slushy, numerous cracks. 26 123 29 9 Last day ice safe for traveling on foot. 26 Open water, numerous cracks. 10 First movement of ice. May 3 112 11 No further information available. 4 Ice thickness measurements made on 5, 12 and 26 Apr 1973 and 3 May appear unrepresentative due to the uneven snow depths, discontinuous formation of snow-ice, Mar 31 102 8 and/or possible ice rafting. Consequently, average 31 Ice thickness on opposite side of river was 97 cm. decreases in ice thicknesses from 29 Mar to 19 Apr Apr 7 99 0 and from 19 Apr to 15 May are shown on the ice 14 99 0 decay diagrams. 21 81 0 10 Water overflowed on the ice. 28 74 0 15 River ice free. May 5 Ice conditions becoming unsafe. 10 First movement of ice. 1964 11 Considerable ice movement. Mar 14 97 28 12 No further information available. 21 86 32 28 Ice has been cracked by the earthquake and appears 1974 unsafe. Mar 16 Ice thickness on opposite side of river was 104 cm. Apr 4 64 3 23 102 13 4 Overflow on ice. 30 13 97 11 61 15 Apr 6 102 13 25 Considerable overflow. Slush and thin ice layer over main 6 Second ice thickness measurement read 99 cm. ice sheet. 13 102 15 26 No further information available. 27 No measurements on 20 and 27 April due to water on 28 No further information available. 1965 Jan 30 Approx. 15 cm water overflow 300 m below measure­ ment site. TRAPPER’S CREEK, ALASKA Feb 20 94 41 27 81 51 Measurements made on Susitna River, over the main channel at the 27 8 cm water overflow above measuring point. village of Talkeetna or at distances of 400 m to 1 km west of Talkeetna. Mar 6 71 Unknown Station moved a short distance in 1968 and name was changed from 24 Numerous cracks along both shores, 30 cm water overflow. Talkeetna to Trapper’s Creek. 27 66 Unknown Apr 3 56 23 Ice thickness Snow depth 10 46 15 Date (cm) (cm) 15 30 cm water overflow on main channel. Leads or cracks extending across the main channel. 1962 16 First breakup of main channel. Feb 24 Heavy snowfall (about 122 cm deep) across the Susitna. 30 Main channel clear of ice. 145 114 Mar 3 1966 10 155 117 Mar 19 51 3 17 147 102 26 51 18 24 145 91 26 Water level dropped 30 cm. Cracks on both sides of main 31 130 76 channel. Apr 7 122 15 Apr 2 51 5 14 86 30 8 30 cm water overflow on main channel. Cracks along­ 21 58 46 side main channel. 28 28 36 9 48 28 Susitna Channel starting to open. Talkeetna Channel 16 46 open, water fast. Still crossing river by north route 23 46 but not very safe. May 3 First ice movement. May 5 Open channel 2 m wide. Water in Susitna Channel started 7 Main channel open water, approx. 1/3 way across the river. running.

112 Ice thickness Snow depth Ice thickness Snow depth Date______(cm)______(cm)______Date ______(cm)______(cm)______1966 (cont’d) 1969 (cont’d) May 14 Ice jams just below measurement site. Apr 20 Ice is moving in the main channel. Small ice jams in 21 Ice completely gone, only some ice coming down from narrow spots with very little rise in water. Chulitna River. 26 Talkeetna Channel is breaking up, ice running well. 1967 29 River free of ice. Mar 18 71 15 1970 25 71 15 Mar 14 81 20 Apr 1 71 13 21 81 8 70 43 21 Top 20 to 23 cm of ice is very porous. Ice is cracking 15 67 46 and dropping down to water level on many channels, 22 64 30 making depressions in the ice 60 to 90 cm deep. 29 55 10 28 69 29 Overflow on main channel. 28 Water overflow observed on nearly all channels. 30 First signs of breakup of main channel. Apr 4 66 May 1 No further information available. 4 Ice is honeycombed and becoming unsafe. 1968 11 64 Feb 17 15 cm of water overflow over measurement site. Ice 11 Cold nights causing ice to harden. beginning to rot. 18 Ice is breaking up. River is rising slightly and lifting ice 24 91 25 causing it to break into large chunks. Mar 2 River is unsafe, 30 to 45 cm of water overflow at measure­ 26 River is higher and channels starting to open, ice is moving ment site and over other channels. Cracks running a little. along edges of channels, formed when ice was forced 27 No further information available. downward to below water level. 1971 9 89 Mar 20 91 25 9 Water overflow frozen. 20 20 cm water overflow, ice becoming soft. 16 89 27 81 23 23 79 3 27 Ice wet and very soft. 15 cm water overflow. Icebreaking 30 76 3 away from shore and has dropped as much as 120 cm Apr 6 Cracks running parallel with channels are 3 to 30 cm in along shoreline. Ice heaving in main channel. width, some are 15 m or more in length. Ice soft with Apr 20 River unsafe for vehicle use, ice estimated to be 50 to 70 3 cm water overflow at drill site. cm thick. 13 74 May 4 Ice unsafe to walk upon. 20 51 20 River free of ice. 20 Ice very rotten, 20 cm water overflow at drill site. Many 1972 holes and cracks, open water in many places. Incomplete 27 Ice completely saturated with water and settling in places. Ice unsafe. 1973 May 4 Main channels of Susitna and Talkeetna River open. Ice Feb 24 76 36 estimated 30 to 46 cm thick. Surface wet, numerous 24 Some slight overflow near site, lower layers of snow cracks. soaked in spots. 8 Ice jamming near bridge site and water rising. Mar 10 69 36 11 All ice jams broken up, ice flowing in main channels. 17 71 30 25 River ice still flowing. River level is near normal. 24 71 25 26 No further information available. 24 10 cm of overflow under the snow cover. 31 71 25 1969 31 Considerable water on the ice. Edges of channels are Feb 22 85 20 collapsing leaving open water along banks. Ice is rotten 22 Channel is developing cracks 10 to 13 cm wide. Ice be­ and soft. coming porous and soft. May 17 Susitna River free of ice. Mar 1 Ice measurements moved to within 1/4 mile of Talkeetna. 8 61 46 1974 15 61 25 May 18 Susitna River free of ice. 22 64 30 22 Water overflow under snow cover 5 to 8 cm deep. 29 61 10 UNALAKLEET, ALASKA 29 Last measurement site caved in and is now under water. New site moved south 50 m. Ice is water-soaked. Measurements made on Kouwegok River Slough at distances ranging Apr 5 51 10 from 100 m of the village to 2 km upstream from the mouth of the 5 Ice is weak with wide cracks along edges of channel. 30 Unalakleet River. to 46 cm overflow in low spots up and down Talkeetna Channel. Ice thickness Snow depth 12 46 10 Date______(cm)______(cm)______12 Holes in main channel and water overflow still rising 30 1962 to 60 cm. Apr 14 164 23 19 41 8 14 Mild weather has caused snow on the surface of ice to 19 Ice is lifting and breaking into chunks. melt, then later it freezes.

113 Ice thickness Snow depth Ice thickness Snow depth Date (cm) (cm) Date (cm) (cm)

1962 (cont’d) 1966 (cont’d) Apr 21 163 15 May 4 127 25 28 170 11 117 May 5 173 Unknown 20 95 12 132 Unknown 25 89 12 Slush and snow over the ice. Some puddles of water 30 25 along the river ice and Kouwegok Slough. 31 River ice rotted out instead of breaking up, which is 19 Few cracks along slough and parts of the river. unusual. 26 No observations due to water on ice. Ice broke in main 31 River free of ice by evening. river. Ice still in Kouwegok River, but leads and 1967 cracks make it dangerous. Apr 22 145 36 30 River free of ice. 29 140 10 1963 29 Two large holes at center of the slough, each 6 m long. Mar 9 Ice is frozen to river bottom in places. Surface water covers the slough and the Unalakleet Apr 15 Ice measurements from 16 Mar to 14 Apr appear un­ River. 10 cm overflow at measurement site. representative, because observations were taken in May 6 132 shallow water and ice froze to the bottom. 6 Considerable thawing last week. Several large cracks on 27 170 23 ice. 27 Water coming through the tidal cracks freezes, increasing 14 104 the ice thickness. 20 86 May 4 165 25 27 Surface ice breaking up. 11 163 18 Jun 2 River free of ice. 11 Main river becoming unsafe. 1968 18 130 Apr 20 152 15 18 Crack in the middle of Kouwegok River. 27 155 10 20 Ice breakup of main river. May 4 155 25 No observations due to dangerous condition of shore ice. 4 10 cm water on ice, few cracks. Still some ice in Kouwegok River. 11 145 26 River free of ice. 18 99 1964 25 Some ice movement. Apr 25 170 84 Jun 1 86 May 2 166 67 3 74 9 160 61 4 33 16 157 56 1969 16 Approx. 7 cm of water on ice surface. Feb 1 Surface broken, many cracks. Extreme high tides and the 23 165 69 freezing of water overflow have made the ice much 23 Some open leads along main river. thicker. 30 Surface covered with water and slush. Melting snow re­ Apr 5 170 15 frozen on surface. Water deep along both shores of 12 170 5 main river. 19 157 Jun 6 56 25 Water all over the ice due to thawing. 6 Leads widening on east side of river slough. Main river 26 147 broken up. May 14 River free of ice. 12 River free of ice. 1970 1965 Apr 4 114 38 Apr 24 185 64 11 124 28 24 Depth of ice increasing fast due to slush and water turn- 11 Ice thickness increased due to freezing of the wet snow ing into snow ice. from previous week. May 1 216 22 18 124 8 203 8 18 36 cm of very wet snow and water over the ice. Water 8 15 cm of soft ice beneath snow. overflow in some places. 15 159 19 25 127 15 29 cm of soft ice beneath snow, followed by 25 cm of 25 10 cm of loose snow, and 32 cm of wet snow and water slush directly over the ice. First signs of water along directly over the ice. Water overflow observed 60 m river banks. from site. 22 Considerable amounts of open water along river banks. May 18 River free of ice. River ice breaking up in some places. 1971 25 Main river ice went out at 2215 LST. Apr 3 188 36 29 Some ice remains upstream. Open water along middle of 10 188 36 slough. 17 183 42 30 River free of ice. 17 5 cm of bottom slush ice has melted. 1966 24 181 48 Apr 16 136 22 May 1 183 43 26 121 39 8 188 30 30 116 48 8 Snow cover has become soft.

114 Ice thickness Snow depth WILD LAKE, ALASKA Date (cm) (cm) Measurements made on Wild Lake at about 30 m east of the camp site 1971 (contd) and approximately 10 m offshore. May 15 188 10 15 Snow cover soft and wet due to overflows. Ice thickness Snow depth 4 22 170 Date (cm) (cm) 29 Ice thickness not measured due to open water and broken ice. 1964 30 Ice went out overnight. River not quite clear of ice. Apr 24 90 53 31 No further information available. 24 Air pocket 74 cm from the top. 1972 May 1 86 51 Mar 4 Measurements during Mar and Apr made near mouth of 8 85 46 Kouwegok River slough, about 140 m south of 15 88 44 Peninsula Fisheries building. First snow in 4 weeks 22 85 33 has covered most cracks in ice. 22 4 cm water on surface. Air pocket 66 cm from the top. 18 Strong wind has blown away most of the snow cover. 28 Streams opened. 25 163 8 29 88 4 Apr 1 145 5 29 Air pocket 76 cm from the top. 8 150 8 31 Open water around edge of lake. 15 150 23 Jun 1 No further information available. 15 New wet snow cover. 1965 22 150 25 May 10 99 41 29 147 28 17 103 25 May 6 140 15 17 Approx. 6 cm water overflow at measurement site. Measurements during May made near mouth of Kouwegok 19 Streams open. Open water at stream’s mouth. River slough about 140 m south of cannery building. 20 Water on lake surface. 13 122 10 21 Considerable water on lake (15 cm in areas). Large volume 13 River water high due to melting snow. of water in streams. 20 104 23 Water on ice around edge of lake. Approx. 5 cm of snow 20 Cracks opening up to approx. 30 cm in width. River on lake except at the edges. rapidly clearing of ice, open water observed 1.6 km 24 95 3 upstream. 24 Ice beginning to lift from shore. 24 Measurement areas almost clear of ice; a small amount 29 Level of lake water rising, portions of lake free of snow, still observed in Koo-loo-ruk slough. 5 cm of slush and overflow in some areas. 1973 31 79 Mar 30 131 47 31 Small ice cakes breaking free from edges. Ice lifting to 30 Narrow cracks along shoreline. Melting snow refroze surface. Lead extends to shore. leaving a 5 cm crust on the surface. Jun 5 First movement of ice, pushing ice toward shore. Apr 20 Unknown 18 6 Lead 800 m wide has formed. 20 30 cm wide cracks over entire river. 7 57 27 Unknown 3 7 Ice sheet moving with wind. Few leads north and south. 27 Cracks in ice now 30 to 41 cm wide. Ice becoming 10 Water level rising steadily. candled. Overflow over some areas, mostly along 11 North wind has broken ice and pushed it approx. 1.5 km shoreline. south where it has jammed up. 28 No further information available. 15 Ice in lower half of lake. 16 Lake free of ice. 1974 Mar 16 Snow at measurement site removed by wind, on other 1966 areas of the river from mouth to 1.6 km upstream Apr 29 84 39 snow depth ranges from 13 to 53 cm. May 7 83 23 157 0 7 8 cm of snow and 5 cm of slush over main ice cover. 30 157 0 14 76 Apr 6 155 0 20 Ice crumbling along shoreline. 13 150 0 21 72 20 145 0 28 56 20 Surface ice starting to melt. Jun 2 Ice has broken into large floes at north end of lake. 27 137 0 3 41 27 Few cracks have formed due to tides. Considerable over­ Ice observed on south half of lake. flow, due to melting snow and tidal water observed. 10 Lake free of ice. 28 No further information available. 1967 Apr 25 89 36 25 Frozen overflow. 30 8 cm overflow under snow cover. Water has started flow­ ing onto lake from streams.

115 Ice thickness Snow depth Date (cm) (cm) 1967 ( con fd) May 2 91 25 2 Streams flowing freely. 9 84 18 16 84 15 23 79 30 51 30 Water overflow covering lake most of month. Open water around edges. Jun 5 Large leads have formed. 6 Ice has broken in small pieces. 8 Lake completely free of ice. 1968 May 15 79 20 Streams open. 22 76 26 Water around lake edge. 29 46 29 Frozen overflow approx. 20 cm thick has covered most of lake during past week. Jun 6 Ice out of north half of lake. 10 Lake completely free of ice. 1969 Incomplete.

116 APPENDIX B. MAPS OF LEAST AND GREATEST ICE THICKNESS OBSERVED AT THE TIME OF MAXIMUM GROWTH, AND AVERAGE DATE OF OCCURRENCE Figure Figure B1. Least observed "end of season" ice thickness. » 70 * 0 6

117 Figure B2. Maximum observed "end of season" ice thickness. Figure B3. Average date of observed maximum ice.

119

APPENDIX C. ANNUAL ICE DECAY CURVES FOR STATIONS IN CANADA AND ALASKA

Figures C1-C40. Annual ice decay curves for stations in Canada.

Figures C41-66. Annual ice decay curves for stations in Alaska.

Figure C7. Ice thickness (cm) et Pr Ilt, . .T. N.W Inlet), (Parr lert A FigureC2. \ \ ' 100 110 120 130 140 150 160 170 180 40 60 90 20 30 50 80 70 10 0 FigureC3. Ice thickness (cm) Ice thickness (cm) 123 F Figure C5. Figure igure C4. igure C7.

igure

F Ice thickness (cm) thickness Ice C6. Figure

0 40 10 70 90 80 60 50 30 20 40 190 180 160 130 120 210 170 150 140 110 100 2 230 220 200 250 u “

124 Ice thickness (cm) F igure C8. igure T

Ice thickness (cm) F igure C9. igure C11.

F c tikes (cm) thickness Ice igure C10. F

126 Figure C l2.

127 Ice thickness (cm) F igure C13. igure 128 Figure C 75.

129 Figure C76.

130 Figure C17.

131 Figure Cl 8.

132 Figure C 7 9 .

Figure C20.

133 Figure C21. Figure C22. Figure C23.

135 Figure C25. Figure (224. i— I— r T

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Figure C26.

137 Figure C28.

138 Figure C29.

Figure C30. 139 Figure C31.

Figure C32.

140 Figure C33.

141 Ice thickness (cm) F igure C34.igure 142 Ice thickness (cm) F igure C35.igure 143 Ice thickness (cm) Figure C37. Figure F igure C36. igure 144 240

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Figure C38. Ice thickness (cm) Fig Figure C40. Figure ure C39. ure 146 Figures C41-66. Annual ice decay curves for stations in Alaska.

Figure C41.

Figure C42.

147 Figure C43.

148 Figure C45.

149 Ice thickness (cm) Figure C47. Figure F igure C46. igure 150 Figure C48.

Figure C49.

151 Figure C57.

152 Figure C52.

Figure C^3.

153 Ice thickness (cm) Fig Figure C55.Figure ureC54. 154 Ice thickness (cm) F Figure C57. Figure igure 155 C56. Figure C58.

Figure C59.

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Figure C67.

157 Figure C62.

Figure C63.

158 Ice thickness (cm) F igure C64.igure 159 Ice thickness (cm) F Figure igure 160 C65. C66. A facsimile catalog card in Library of Congress MARC format is reproduced below.

Bilello, Michael A. Maximum thickness and subsequent decay of lake, river and fast sea ice in Canada and Alaska / by Michael A. Bilello. Hanover, N.H.: U.S. Cold Regions Research and Engineering Laboratory; Springfield, Va.: available from National Technical Information Service, 1980. vi, 165 p., illus.; 27 cm. ( CRREL Report 80-6. ) Bibliography: p. 34. 1. Air temperature. 2. Alaska. 3. Canada. 4. Ice decay. 5. Ice reporting. 6. Ice thickness. I. United States. Army. Corps of Engineers. II. Army Cold Regions Research and Engineering Laboratory, Hanover, N.H. III. Series: CRREL Report 80-6.

☆ U.S. G O V E R N M E N T PR IN TIN G O F F I C E : 1980 — 600-294/406