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Information to Users Variations In Ice Flow And Glaciers Over Time And Space Item Type Thesis Authors Elsberg, Daniel Harry Download date 24/09/2021 03:40:40 Link to Item http://hdl.handle.net/11122/8657 INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. ProQuest Information and Learning 300 North Zeeb Road, Ann Arbor, Ml 48106-1346 USA 800-521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VARIATIONS IN ICE FLOW AND GLACIERS OVER TIME AND SPACE A THESIS Presented to the Faculty of the University of Alaska Fairbanks in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Daniel Harry Elsberg, B.S. Fairbanks, Alaska May 2003 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3079039 ___ ® UMI UMI Microform 3079039 Copyright 2003 by ProQuest Information and Learning Company. Ail rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VARIATIONS IN ICE FLOW AND GLACIERS OVER TIME AND SPACE By Daniel Harry Elsberg RECOMMENDED: Chair, Department of Geology^md Geophysics APPROVED: Dean, College of Science, Engineering and Mathematics _______________ Dean the Graduate School '■ £ > * > _____________ Date Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract. Ice flows and glaciers change over many time and spatial scales. Glacier surfaces evolve over decades, and this change affects the glacier-climate interaction. When a mass balance is computed using an outdated map, that computation does not reveal actual mass change. We present a method by which a mass balance computed with an outdated map can be transformed into actual mass change. While the actual volume change of a glacier is relevant to hydrological studies, the change that would have occurred on a static surface is more relevant to certain glacier dynamics problems and most climate problems. We term this the reference-surface balance and propose that such a balance is better correlated to climatic variations than the conventional one. Ice responds to stresses over time scales from seconds to millennia. We observed this using two independent strain-gauge systems to measure the strain rates as functions of depth and time at Siple Dome, Antarctica. One system employed optical fibers to measure annual strain rates over 175 m depth intervals. The other used one-meter resistance wires to measure strain approximately hourly at discrete depths. The long­ term average strain rates from the two systems agreed to within 16%. The time- dependent strain rates measured beneath the divide by the resistance-wire gauges included intermittent strain events lasting up to 24 hours. We used the results from each system to compute an age-depth relationship assuming a time-independent ice flow geometry. Equilibrium line altitudes are related to climate, and they vary from year to year and among neighboring glaciers. We measured a regional pattern of equilibrium lines using remote sensing. Our goals were to evaluate the accuracy of such measurements, and to assess the spatial and temporal variability of the resulting data. Individual glacier equilibrium line altitudes varied by 100 m relative to a smoothed surface, and inter­ annual variations in equilibrium line altitudes at one glacier were 74 m. A map of the regional pattern of equilibrium line altitudes shows variations of 1000 meters from the south to the north side of the range, but no major trend from east to west. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table of Contents Signature Page............................................................................................................................. i Title Page....................................................................................................................................ii Abstract ......................................................................................................................................iii Table of Contents..................................................................................................................... iv List of Figures..........................................................................................................................vii List of Tables..........................................................................................................................viii List of Appendices...................................................................................................................ix Acknowledgments ..................................................................................................................... x General Introduction...................................................................................................................I Chapter 1. Quantifying the Effects of Climate and Surface Change on Glacier Mass Balance.......................................................................................................................................3 INTRODUCTION.................................................................................................................4 THE RELATIONSHIP BETWEEN CONVENTIONAL AND REFERENCE- SURFACE BALANCES......................................................................................................5 Mass balance notation.......................................................................................................5 Definition of the conventional and reference-surface glacier-wide balance rates 6 A relation between conventional and reference-surface glacier-wide balance rates...8 Transformation between conventional and reference-surface glacier-wide annual balances .............................................................................................................................10 Geodetic corrections........................................................................................................II Summary of the transformation method........................................................................12 APPLICATION TO SOUTH CASCADE GLACIER..................................................... 13 Data................................................................................................................................... 13 The exact transformation................................................................................................14 Approximations for the exact transformation...............................................................16 Cumulative effects of geometry changes on mass balance...........................................18 DISCUSSION...................................................................................................................... 18 What measurements are needed? ....................................................................................18 Choice of the reference surface...................................................................................... 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V Relevance of the reference-surface balance to glacier dynamics and climate studies 20 CONCLUSIONS................................................................................................................20 ACKNOWLEDGEMENTS.............................................................................................. 21 REFERENCES................................................................................................................... 33 APPENDIX 1.0: DETAILS OF MASS BALANCE CALCULATIONS.....................35 COMPUTING A GEODETIC CUMULATIVE BALANCE SERIES......................... 35 EXTRAPOLATION OF BALANCE-ELEVATION CURVES.....................................35 Chapter 2. Depth- and time-dependent strain rates and their variations at Siple Dome, Antarctica................................................................................................................................ 37 INTRODUCTION..............................................................................................................38 INSTRUMENTATION.....................................................................................................39
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