Ribbed Bedforms in Palaeo-Ice Streams Reveal Shear Margin
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Early Break-Up of the Norwegian Channel Ice Stream During the Last Glacial Maximum
Quaternary Science Reviews 107 (2015) 231e242 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Early break-up of the Norwegian Channel Ice Stream during the Last Glacial Maximum * John Inge Svendsen a, , Jason P. Briner b, Jan Mangerud a, Nicolas E. Young c a Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Postbox 7803, N-5020 Bergen, Norway b Department of Geology, University at Buffalo, Buffalo, NY 14260, USA c Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA article info abstract Article history: We present 18 new cosmogenic 10Be exposure ages that constrain the breakup time of the Norwegian Received 11 June 2014 Channel Ice Stream (NCIS) and the initial retreat of the Scandinavian Ice Sheet from the Southwest coast Received in revised form of Norway following the Last Glacial Maximum (LGM). Seven samples from glacially transported erratics 31 October 2014 on the island Utsira, located in the path of the NCIS about 400 km up-flow from the LGM ice front Accepted 3 November 2014 position, yielded an average 10Be age of 22.0 ± 2.0 ka. The distribution of the ages is skewed with the 4 Available online youngest all within the range 20.2e20.8 ka. We place most confidence on this cluster of ages to constrain the timing of ice sheet retreat as we suspect the 3 oldest ages have some inheritance from a previous ice Keywords: Norwegian Channel Ice Stream free period. Three additional ages from the adjacent island Karmøy provided an average age of ± 10 Scandinavian Ice Sheet 20.9 0.7 ka, further supporting the new timing of retreat for the NCIS. -
A Review of Ice-Sheet Dynamics in the Pine Island Glacier Basin, West Antarctica: Hypotheses of Instability Vs
Pine Island Glacier Review 5 July 1999 N:\PIGars-13.wp6 A review of ice-sheet dynamics in the Pine Island Glacier basin, West Antarctica: hypotheses of instability vs. observations of change. David G. Vaughan, Hugh F. J. Corr, Andrew M. Smith, Adrian Jenkins British Antarctic Survey, Natural Environment Research Council Charles R. Bentley, Mark D. Stenoien University of Wisconsin Stanley S. Jacobs Lamont-Doherty Earth Observatory of Columbia University Thomas B. Kellogg University of Maine Eric Rignot Jet Propulsion Laboratories, National Aeronautical and Space Administration Baerbel K. Lucchitta U.S. Geological Survey 1 Pine Island Glacier Review 5 July 1999 N:\PIGars-13.wp6 Abstract The Pine Island Glacier ice-drainage basin has often been cited as the part of the West Antarctic ice sheet most prone to substantial retreat on human time-scales. Here we review the literature and present new analyses showing that this ice-drainage basin is glaciologically unusual, in particular; due to high precipitation rates near the coast Pine Island Glacier basin has the second highest balance flux of any extant ice stream or glacier; tributary ice streams flow at intermediate velocities through the interior of the basin and have no clear onset regions; the tributaries coalesce to form Pine Island Glacier which has characteristics of outlet glaciers (e.g. high driving stress) and of ice streams (e.g. shear margins bordering slow-moving ice); the glacier flows across a complex grounding zone into an ice shelf coming into contact with warm Circumpolar Deep Water which fuels the highest basal melt-rates yet measured beneath an ice shelf; the ice front position may have retreated within the past few millennia but during the last few decades it appears to have shifted around a mean position. -
May Be Xeroxed
CENTRE FOR NEWFOUNDLAND STUDIES TOTAL OF 10 PAGES ONLY MAY BE XEROXED (Without Author's Permiss•on) ,. (J Contemporary Frontal Moraine Formation in the Yoho Valley , Br~tish Columbia . b y Martin J. Batterson B.A. (Hens.) , University of Wales, l978 A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of ~aster of Science . Departmen~ of Geography ~emorial Unlversity or Newroundland 1980 Abstract The northern terminus or Emerald Glacier (510 3 l' N, 116 0 32 ' W) in the Yoho Valley , British Columbia was bordered by a small , actively forming frontal moraine during summer 1979 . Strati- graphic and morphological contrasts existed r ound the ice front , which primarily resulted from a contrast in the distribution of supraglacial debris . Sedimentological and geotechnical techniques were utilised to determine the origin of stratigraphic units within the moraine ridge . Moraine A, at the margin of heavily debris covered ice , exhibited a complex stratigraphy. At most sites a lens of subglacially derived till was evident , between units of supra- glacially derived material . It is proposed that the moraine forming process involved the initial development of an ice- front talus apron , which was subsequently pushed and over- ridden . A plastic subglacial till was squeezed from beneath the supra- morainal ice margin , and overlain by a sorted supraglacial unit during glacier retreat . The moraine was actively advancing during the field season due to the main- tenance of glacier- moraine contact resulting rrom the retardation of ice- melt afforded by the supraglacial debris co':er . Moraine B is located at the margin or debris-free ice . -
Ilulissat Icefjord
World Heritage Scanned Nomination File Name: 1149.pdf UNESCO Region: EUROPE AND NORTH AMERICA __________________________________________________________________________________________________ SITE NAME: Ilulissat Icefjord DATE OF INSCRIPTION: 7th July 2004 STATE PARTY: DENMARK CRITERIA: N (i) (iii) DECISION OF THE WORLD HERITAGE COMMITTEE: Excerpt from the Report of the 28th Session of the World Heritage Committee Criterion (i): The Ilulissat Icefjord is an outstanding example of a stage in the Earth’s history: the last ice age of the Quaternary Period. The ice-stream is one of the fastest (19m per day) and most active in the world. Its annual calving of over 35 cu. km of ice accounts for 10% of the production of all Greenland calf ice, more than any other glacier outside Antarctica. The glacier has been the object of scientific attention for 250 years and, along with its relative ease of accessibility, has significantly added to the understanding of ice-cap glaciology, climate change and related geomorphic processes. Criterion (iii): The combination of a huge ice sheet and a fast moving glacial ice-stream calving into a fjord covered by icebergs is a phenomenon only seen in Greenland and Antarctica. Ilulissat offers both scientists and visitors easy access for close view of the calving glacier front as it cascades down from the ice sheet and into the ice-choked fjord. The wild and highly scenic combination of rock, ice and sea, along with the dramatic sounds produced by the moving ice, combine to present a memorable natural spectacle. BRIEF DESCRIPTIONS Located on the west coast of Greenland, 250-km north of the Arctic Circle, Greenland’s Ilulissat Icefjord (40,240-ha) is the sea mouth of Sermeq Kujalleq, one of the few glaciers through which the Greenland ice cap reaches the sea. -
Glacial Processes and Landforms-Transport and Deposition
Glacial Processes and Landforms—Transport and Deposition☆ John Menziesa and Martin Rossb, aDepartment of Earth Sciences, Brock University, St. Catharines, ON, Canada; bDepartment of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON, Canada © 2020 Elsevier Inc. All rights reserved. 1 Introduction 2 2 Towards deposition—Sediment transport 4 3 Sediment deposition 5 3.1 Landforms/bedforms directly attributable to active/passive ice activity 6 3.1.1 Drumlins 6 3.1.2 Flutes moraines and mega scale glacial lineations (MSGLs) 8 3.1.3 Ribbed (Rogen) moraines 10 3.1.4 Marginal moraines 11 3.2 Landforms/bedforms indirectly attributable to active/passive ice activity 12 3.2.1 Esker systems and meltwater corridors 12 3.2.2 Kames and kame terraces 15 3.2.3 Outwash fans and deltas 15 3.2.4 Till deltas/tongues and grounding lines 15 Future perspectives 16 References 16 Glossary De Geer moraine Named after Swedish geologist G.J. De Geer (1858–1943), these moraines are low amplitude ridges that developed subaqueously by a combination of sediment deposition and squeezing and pushing of sediment along the grounding-line of a water-terminating ice margin. They typically occur as a series of closely-spaced ridges presumably recording annual retreat-push cycles under limited sediment supply. Equifinality A term used to convey the fact that many landforms or bedforms, although of different origins and with differing sediment contents, may end up looking remarkably similar in the final form. Equilibrium line It is the altitude on an ice mass that marks the point below which all previous year’s snow has melted. -
Ice Stream Formation
Ice stream formation Christian Schoof1, and Elisa Mantelli2 1Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada 2AOS Program, Princeton University, Princeton, USA November 6, 2020 Abstract Ice streams are bands of fast-flowing ice in ice sheets. We investigate their formation as an example of spontaneous pattern formation, based on positive feedbacks between dissipa- tion and basal sliding. Our focus is on temperature-dependent subtemperate sliding, where faster sliding leads to enhanced dissipation and hence warmer temperatures, weakening the bed further, although we also treat a hydromechanical feedback mechanism that operates on fully molten beds. We develop a novel thermomechanical model capturing ice-thickness scale physics in the lateral direction while assuming the the flow is shallow in the main downstream direction. Using that model, we show that formation of a steady-in-time pattern can occur by the amplification in the downstream direction of noisy basal conditions, and often leads to the establishment of a clearly-defined ice stream separated from slowly-flowing, cold-based ice ridges by narrow shear margins, with the ice stream widening in the downstream direction. We are able to show that downward advection of cold ice is the primary stabilizing mechanism, and give an approximate, analytical criterion for pattern formation. 1 Introduction Ice streams are narrow bands of fast flow within otherwise more slowly-flowing ice sheets, often forming near the margin or grounding line of the ice sheet as outlets that can carry the majority of the ice discharged [1]. Some ice streams are confined to topographic lows that channelize flow [2], but not all, and those that are not controlled by topography may occur in parallel arrays of roughly similar ice streams. -
A Water-Piracy Hypothesis for the Stagnation of Ice Stream C, Antarctica
Annals of Glaciology 20 1994 (: International Glaciological Society A water-piracy hypothesis for the stagnation of Ice Stream C, Antarctica R. B. ALLEY, S. AXANDAKRISHXAN, Ear/h .~)'stem Science Center and Department or Geosciences, The Pennsyfuania State Unil!ersi~y, Universi~)' Park, PA 16802, U.S.A. C. R. BENTLEY AND N. LORD Geopl~)!.\icaland Polar Research Center, UnilJersit] or vVisconsin-Aladison, /vfadison, IYJ 53706, U.S.A. ABSTRACT. \Vatcr piracy by Icc Stream B, West Antarctica, may bave caused neighboring Icc Stream C to stop. The modern hydrologic potentials near the ups'tream cnd of the main trunk o[ Ice Stream C are directing water [rom the C catchment into Ice Stream B. Interruption of water supply from the catchment would have reduced water lubrication on bedrock regions projecting through lubricating basal till and stopped the ice stream in a tCw years or decades, short enough to appear almost instantaneous. This hypothesis explains several new data sets from Ice Stream C and makes predictions that might be testable. INTRODUCTION large challenge to glaciological research. Tn seeki ng to understand it, we may learn much about the behavior of The stability of the West Antarctic ice sheet is related to ice streams. the behavior of the fast-moving ice streams that drain it. ~luch effort thus has been directed towards under- standing these ice streams. The United States program PREVIOUS HYPOTHESES has especially focused on those ice streams :A E) flowing across the Siple Coast into the Ross Ice Shelf Among the The behavior of Ice Stream C has provoked much most surprising discoveries on the Siple Coast icc streams speculation. -
Quaternary Geology of Manitoba: Digital Compilation of Point and Line Data, with Updating of the Dataset Using Remotely Sensed (SPOT) Imagery by M.S
GS-18 Quaternary geology of Manitoba: digital compilation of point and line data, with updating of the dataset using remotely sensed (SPOT) imagery by M.S. Trommelen, G.R. Keller and B.K. Lenton Trommelen, M.S., Keller, G.R. and Lenton, B.K. 2012: Quaternary geology of Manitoba: digital compilation of point and line data, with updating of the dataset using remotely sensed (SPOT) imagery; in Report of Activities 2012, Manitoba Innovation, Energy and Mines, Manitoba Geological Survey, p. 189–193. Summary in Manitoba at the most detailed The aim of this project is to provide an up-to-date scales available, along with a digital compilation of historic and new ice-flow and database index of metadata, has geomorphic data to better assist drift prospecting, land-use been completed (Figure GS-18-1). Tables GS-18-1 and and research projects in Manitoba. Current objectives of -2 provide a list of the included line and point features. the project are to compile data, complete quality control, Line features are digitized to scale, whereas points update with high-resolution remote-sensing imagery represent features occurring at a site but are not to scale. (SPOT1) and digitized aerial photographs, and augment Because this is a compilation, not all original data—such with newly acquired field data. as site numbers, striae characteristics (type, position, abundance) and fossil radiocarbon lab numbers—are Introduction preserved. Instead, the compiled database will serve as a Up-to-date, queryable surficial geological data are guide and the reader will be referred to the original maps essential for the successful interpretation of ice flow and publications for more information. -
Pleistocene Geology of the Embarrass Area, St. Louis County
UNNERSITY OF MINNESOTA This is to certify that I have examined this copy of a master's thesis by James Davis Lehr and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examining committee have been made. Charles L. Matsch Name of Faculty Advisor Signature of Faculty Advisor May 12, 2000 Date GRADUATE SCHOOL PLEISTOCENE GEOLOGY OF THE EMBARRASS ST. LOUIS COUNTY, MINNESOTA A THESIS SUBMITTED TO THE FA CUL TY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY JAMES DA VIS LEHR IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE May,2000 © James Davis Lehr 2000 TABLE OF CONTENTS Page TABLE OF CONTENTS ..................................................................................................... i LIST OF ILLUSTRATIONS .................................................................. ........................... iv ACKNOWLEDGMENTS ................................................................................................ vii INTRODUCTION ............................................................................................................... 1 STUDY AREALOCATION ................................................................................... l STUDY OBJECTIVES ............................................................................................ 3 METHODS OF INVESTIGATION ........................................................................ 3 FIELD METHODS .................................... ................................................. -
Ice Streams As the Arteries of an Ice Sheet: Their Mechanics, Stability and Significance
Earth-Science Reviews 61 (2003) 309–339 www.elsevier.com/locate/earscirev Ice streams as the arteries of an ice sheet: their mechanics, stability and significance Matthew R. Bennett School of Conservation Sciences, University of Bournemouth, Dorset House, Talbot Campus, Fern Barrow, Poole, Dorset, BH12 5BB, UK Received 26 April 2002; accepted 7 October 2002 Abstract Ice streams are corridors of fast ice flow (ca. 0.8 km/year) within an ice sheet and are responsible for discharging the majority of the ice and sediment within them. Consequently, like the arteries in our body, their behaviour and stability is essential to the well being of an ice sheet. Ice streams may either be constrained by topography (topographic ice streams) or by areas of slow moving ice (pure ice streams). The latter show spatial and temporal patterns of variability that may indicate a potential for instability and are therefore of particular interest. Today, pure ice streams are largely restricted to the Siple Coast of Antarctica and these ice streams have been extensively investigated over the last 20 years. This paper provides an introduction to this substantial body of research and describes the morphology, dynamics, and temporal behaviour of these contemporary ice streams, before exploring the basal conditions that exist beneath them and the mechanisms that drive the fast flow within them. The paper concludes by reviewing the potential of ice streams as unstable elements within ice sheets that may impact on the Earth’s dynamic system. D 2002 Elsevier Science B.V. All rights reserved. Keywords: ice streams; ice flow; Antarctica; subglacial deformation 1. -
I!Ij 1)11 U.S
u... I C) C) co 1 USGS 0.. science for a changing world co :::2: Prepared in cooperation with the Scott Polar Research Institute, University of Cambridge, United Kingdom Coastal-change and glaciological map of the (I) ::E Bakutis Coast area, Antarctica: 1972-2002 ;::+' ::::r ::J c:r OJ ::J By Charles Swithinbank, RichardS. Williams, Jr. , Jane G. Ferrigno, OJ"" ::J 0.. Kevin M. Foley, and Christine E. Rosanova a :;:,..... CD ~ (I) I ("') a Geologic Investigations Series Map I- 2600- F (2d ed.) OJ ~ OJ '!; :;:, OJ ::J <0 co OJ ::J a_ <0 OJ n c; · a <0 n OJ 3 OJ "'C S, ..... :;:, CD a:r OJ ""a. (I) ("') a OJ .....(I) OJ <n OJ n OJ co .....,...... ~ C) .....,0 ~ b 0 C) b C) C) T....., Landsat Multispectral Scanner (MSS) image of Ma rtin and Bea r Peninsulas and Dotson Ice Shelf, Bakutis Coast, CT> C) An tarctica. Path 6, Row 11 3, acquired 30 December 1972. ? "T1 'N 0.. co 0.. 2003 ISBN 0-607-94827-2 U.S. Department of the Interior 0 Printed on rec ycl ed paper U.S. Geological Survey 9 11~ !1~~~,11~1!1! I!IJ 1)11 U.S. DEPARTMENT OF THE INTERIOR TO ACCOMPANY MAP I-2600-F (2d ed.) U.S. GEOLOGICAL SURVEY COASTAL-CHANGE AND GLACIOLOGICAL MAP OF THE BAKUTIS COAST AREA, ANTARCTICA: 1972-2002 . By Charles Swithinbank, 1 RichardS. Williams, Jr.,2 Jane G. Ferrigno,3 Kevin M. Foley, 3 and Christine E. Rosanova4 INTRODUCTION areas Landsat 7 Enhanced Thematic Mapper Plus (ETM+)), RADARSAT images, and other data where available, to compare Background changes over a 20- to 25- or 30-year time interval (or longer Changes in the area and volume of polar ice sheets are intri where data were available, as in the Antarctic Peninsula). -
A Community-Based Geological Reconstruction of Antarctic Ice Sheet Deglaciation Since the Last Glacial Maximum Michael J
A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum Michael J. Bentley, Colm Ó Cofaigh, John B. Anderson, Howard Conway, Bethan Davies, Alastair G.C. Graham, Claus-Dieter Hillenbrand, Dominic A. Hodgson, Stewart S.R. Jamieson, Robert Larter, et al. To cite this version: Michael J. Bentley, Colm Ó Cofaigh, John B. Anderson, Howard Conway, Bethan Davies, et al.. A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum. Quaternary Science Reviews, Elsevier, 2014, 100, pp.1 - 9. 10.1016/j.quascirev.2014.06.025. hal-01496146 HAL Id: hal-01496146 https://hal.archives-ouvertes.fr/hal-01496146 Submitted on 27 May 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum Michael Bentley, Colm Cofaigh, John Anderson, Howard Conway, Bethan Davies, Alastair Graham, Claus-Dieter Hillenbrand, Dominic Hodgson, Stewart Jamieson, Robert Larter, et al. To cite this version: Michael Bentley, Colm Cofaigh, John Anderson, Howard Conway, Bethan Davies, et al.. A community- based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum.