DOCSLIB.ORG

Subglacial Basins: Their Origin and Importance in Glacial Systems and Landscapes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Subglacial Basins: Their Origin and Importance in Glacial Systems and Landscapes This is a repository copy of Subglacial basins: Their origin and importance in glacial systems and landscapes. White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/100951/ Version: Accepted Version Article: Cook, S.J. and Swift, D.A. orcid.org/0000-0001-5320-5104 (2012) Subglacial basins: Their origin and importance in glacial systems and landscapes. Earth-Science Reviews, 115 (4). pp. 332-372. ISSN 0012-8252 https://doi.org/10.1016/j.earscirev.2012.09.009 Article available under the terms of the CC-BY-NC-ND licence (https://creativecommons.org/licenses/by-nc-nd/4.0/) Reuse This article is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs (CC BY-NC-ND) licence. This licence only allows you to download this work and share it with others as long as you credit the authors, but you can’t change the article in any way or use it commercially. More information and the full terms of the licence here: https://creativecommons.org/licenses/ Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ This is an author-formatted version of manuscript http://dx.doi.org/10.1016/j.earscirev.2012.0 .00 . Please cite this work as Cook, S.J. and Swift, D.A. 2012. Subglacial basins: their origin and i portance in glacial syste s and landscapes. Earth Science Reviews, Volu e 115, Issue 4, Pages 332+3,2. Subglacial basins: their origin and importance in glacial systems and landscapes COOK, S.J.1,',( and S)IFT, ,.A.2,' 1 Centre for -laciology, Institute of -eography and Earth Sciences, Aberystwyth .niversity, Ceredigion, S/23 3D0, .1 2 Depart ent of -eography, .niversity of Sheffield, 2inter Street, Sheffield, S10 2TN, .1 ABSTRACT C.osed topographic basins are found beneath contemporar0 ice masses and 1ithin the footprint of former ice masses in a.. g.aciated regions. )e present the first integrated revie1 of subg.acia. basin occurrence and formation and the imp.ications of such basins for g.acio.ogica. processes and the evo.ution of .andscape. Our purpose is to motivate research in areas 1here understanding of basin origin and process significance is 1ea2. 3asins on the order of 10-102 m deep and 102-103 m .ong are produced b0 g.acia. erosion of subg.acia. roc2 and/or sediment and are 2no1n as 5overdeepenings6. Out.et and va..e0 g.aciers can 5overdeepen6 their beds far be.o1 sea .eve. or .oca. f.uviati.e base .eve.. 7arger basins, t0pica..0 in ice sheet contexts, ma0 have a pre-g.acia. 8usua..0 tectonic9 origin. Subg.acia. basins are important g.acio.ogica..0 because the0 re:uire ice, 1ater and sediment to ascend an adverse subg.acia. s.ope in order to exit the g.acia. s0stem, the efficienc0 of 1hich is dependent upon the gradient of the adverse s.ope and that of the ice surface. 3asins thus inf.uence subg.acia. drainage s0stem morpho.og0 and transmissivit0, the thic2ness and distribution of basa. ice and sediment .a0ers, and the mechanisms and d0namics of ice f.o1. Adverse gradients that exceed 11 times that of the ice surface ma0 even permit the formation of subg.acia. .a2es. )e specu.ate that, in comparison to ice masses 1ith fe1 or no subg.acia. basins, those 1ith numerous or ver0 .arge basins ma0 respond to c.imatic changes 1ith unexpected vigour. In addition, erosion rates and transport path1a0s of 1ater and sediment through the g.acia. s0stem, and the expression of these processes in the sediment and .andform record, ma0 be unexpected.0 comp.ex. Further, our revie1 sho1s that, in a 1arming c.imate, ice masses resting on adverse s.opes 1i.. be vu.nerab.e to rapid and potentia..0 catastrophic retreat; ne1 .a2es in subg.acia. basins exposed b0 mountain g.acier retreat 1i.. present ' The authors contributed e:ua..0 to this 1or2. Correspondence to ,. A. S1ift [email protected]; te.ephone +44 114 222 7 5 9 or S. J. Coo2 [email protected]; te.ephone +44 161 24712029. ( Present address: Schoo. of Science and the Environment, Aanchester Aetropo.itan Bniversit0, Chester Street, Aanchester, A1 5C,, BK. Page 1 of 76 an increasing haDard; and subg.acia. .a2es ma0 drain catastrophica..0. On even .onger time sca.es, 1e specu.ate that the g.acia. excavation and post-g.acia. fi..ing of basins in mountainous regions shou.d contribute important.0 to c.imate-re.ated changes in isostas0 and re.ief. A.though the contro.s on overdeepening and their inf.uence on other g.acia. and .andscape processes remain uncertain, 1e h0pothesise that overdeepened g.acia. s0stems ref.ect an e:ui.ibrium ice-bed geometr0 that maximises the efficienc0 of ice discharge. Improved understanding of overdeepening processes, especia..0 overdeepened-bed h0dro.og0, is therefore necessar0 to understand fu..0 the d0namic behaviour of va..e0 and out.et g.aciers, and thus the fate of Earth6s .argest ice masses. Keywords: g.acier d0namics; g.acier h0dro.og0; overdeepening; sediment transfer; g.acia. geomorpho.og0; .ands0stems; .andscape evo.ution; haDards; c.imate sensitivit0 1. I TRODUCTIO Subg.acia. basins 8i.e. c.osed topographic depressions in the beds of present and former ice masses9 are a ubi:uitous feature of g.aciated environments. In this paper, 1e demonstrate that man0 subg.acia. basins are produced b0 g.acia. erosion. This t0pe of basin is 2no1n common.0 as an 5overdeepening6. Eo1ever, man0 basins are .i2e.0 to be non-g.acia. in origin, and ma0 have undergone on.0 .imited modification b0 g.acia. processes. Our intention is to high.ight the process significance of subg.acia. basins in genera.; hence, 1e do not restrict our attention to those basins of exc.usive.0 g.acia. origin. Neverthe.ess, the appetite of ice masses to 5bite deep.0 into sound roc26 87inton, 1 639 means 1e focus primari.0 on the origin and process significance of g.acia. basins, and consider the process significance of presumed non-g.acia. basins on.0 1hen it is pertinent. This paper is primari.0 a revie1 that aims to motivate research 1here understanding of the origin and process significance of overdeepening is 1ea2. Neverthe.ess, 1herever possib.e, 1e have attempted to dra1 out and present ne1 ideas and h0potheses in order to i..ustrate the diverse and potentia..0 important imp.ications of overdeepening for g.acia. s0stems and geomorphic processes. The first three sections revie1 the context, occurrence, and origin of subg.acia. basins, focussing on the distribution and formation of g.acia. overdeepenings. )e then revie1 pub.ished 1or2 pertinent to the g.acio.ogica. importance of subg.acia. basins in t1o parts: first.0, the importance for g.acier h0dro.og0 and seasona. d0namics, ice f.o1 and the stabi.it0 of ice masses, and re.ated phenomena; and second.0, the importance for g.acia. geomorphic processes and .ong-term .andscape and ice sheet evo.ution. This revie1 and ana.0sis of pub.ished .iterature does not intend to be exhaustive; rather, 1e see2 to identif0 and support essentia. concepts. For brevit0, 1e do not inc.ude governing e:uations that can be found in cited .iterature. The sixth section is a discussion that dra1s on the evidence provided b0 pub.ished 1or2 to high.ight areas of uncertaint0 and future research :uestions. It is recommended that readers 1ho are fami.iar 1ith the concept of overdeepening and have an expert understanding of g.acier erosiona., h0dro.ogica. and ice d0namic processes s2ip to this section. The fina. section conc.udes the revie1 and discussion. 2. GLACIOLOGICAL CO TE(T A D DEFI ITIO S C.acia. erosion during the Guaternar0 period has contributed enormous.0 to the scu.pting of .arge regions of the g.obe, carving spectacu.ar a.pine .andscapes, scouring vast areas of continenta. crust, and generating prodigious :uantities of sediment for transport and deposition b0 g.acia., aeo.ian and f.uvia. processes. The evo.ution and g.acio.ogica. significance of man0 .arge-sca.e g.acia. erosiona. forms common to such regions, inc.uding B-shaped fjords and va..e0s, expanses of aeria. scouring, and cir:ues and arHtes, is no1 1e.. understood. In former.0 g.aciated regions, the distribution and morphometr0 of these .andforms has been exp.oited 1ide.0 for the purposes of pa.aeog.acio.ogica. Page 2 of 76 Figure 1. Schematic diagrams i..ustrating the t0pica. g.acia. and post-g.acia. context of over-deepened basins under temperate va..e0 g.aciation. and process reconstruction 8C.asser and 3ennett, 20049. Advances in remote sensing, numerica. mode..ing and geochrono.og0 continue to enab.e investigation of .andscape evo.ution at ever greater spatia. and tempora. sca.es, providing ne1 insight into the g.acio.ogica. significance of .andscapes and their component forms, even beneath contemporar0 ice sheets 83ingham et a.., 20109. C.acia. erosion is c.ose.0 .in2ed to spatia. patterns of ice f.o1 and sediment transport and deposition 8e.g. A..e0 et a.., 1 79, and, over mi..ion-0ear timesca.es, g.acia. .andscape evo.ution ref.ects and inf.uences the d0namics of tectonics and c.imate 8e.g.
Load more

Recommended publications
  • Baseline Water Quality Inventory for the Southwest Alaska Inventory and Monitoring Network, Kenai Fjords National Park
    Baseline Water Quality Inventory for the Southwest Alaska Inventory and Monitoring Network, Kenai Fjords National Park Laurel A. Bennett National Park Service Southwest Alaska Inventory and Monitoring Network 240 W. 5th Avenue Anchorage, AK 99501 April 2005 Report Number: NPS/AKRSWAN/NRTR-2005/02 Funding Source: Southwest Alaska Network Inventory and Monitoring Program, National Park Service File Name: BennettL_2005_KEFJ_WQInventory_Final.doc Recommended Citation: Bennett, L. 2005. Baseline Water Quality Inventory for the Southwest Alaska Inventory and Monitoring Network, Kenai Fjords National Park. USDI National Park Service, Anchorage, AK Topic: Inventory Subtopic: Water Theme Keywords: Reports, inventory, freshwater, water quality, core parameters Placename Keywords: Alaska, Kenai Fjords National Park, Southwest Alaska Network, Aialik Bay, McCarty Fjord, Harrison Bay, Two Arm Bay, Northwestern Fjord, Nuka River, Delight Lake Kenai Fjords Water Quality Inventory - SWAN Abstract A reconnaissance level water quality inventory was conducted at Kenai Fjords National Park during May through July of 2004. This project was initiated as part of the National Park Service Vital Signs Inventory and Monitoring Program in an effort to collect water quality data in an area where little work had previously been done. The objectives were to collect baseline information on the physical and chemical characteristics of the water resources, and, where possible, relate basic water quality parameters to fish occurrence. Water temperatures in Kenai Fjords waters generally met the Alaska Department of Environmental Conservation (DEC) regulatory standards for both drinking water and growth and propagation of fish, shellfish, other aquatic life and wildlife. Water temperature standard are less than or equal to 13° C for spawning and egg and fry incubation, or less than or equal to 15° C for rearing and migration (DEC 2003).
    [Show full text]
  • NORSK GEOLOGISK TIDSSKRIFT 45 by IVAR KLOVNING and ULF
    NORSK GEOLOGISK TIDSSKRIFT 45 AN EARLY POST-GLACIAL POLLEN PROFILE FROM FLÅMSDALEN, A TRIBUTARY VALLEY TO THE SOGNEFJORD, WESTERN NORWAY BY IVAR KLOVNING and ULF HAFSTEN (University Botanical Museum, Bergen) Abstract. Pollen analysis and radiocarbon measurements of nekron-mud from the base of a 5 m deep organic deposit in a pot-hole on Furuberget, a rocky promontory in the lower part of the Flåmsdalen valley, show that this part of the valley was free of ice befare 7000 B.C. Introduction Flåmsdalen, a 20 km long, much glaciated tributary valley to the Sognefjord, cutting southwards into the peripheral parts of the Har­ dangervidda plateau, contains a number of erosional features from the time the ice retreated from this valley (H. HoLTEDAHL 1960). Among these is a series of sharply incised, mostly very narrow canyons of different sizes and shapes, often fringed with pot-hoies. The canyons form a system, with a major canyon, present in parts of the main valley, forming the river channel of the present river and a series of tributary canyons which are mostly dry at the present time. These tributary canyons, which are supposed to be sub-glacial erosional phenomena, are very numerous on and around Furuberget, a broad and steep, rocky promontory (riegel), nearly 200m high, that almost doses the Flåmsdalen valley 5 km south of the head of the Aurland fjord (Fig. 1). The fact that the river here, at this typical valley step, has cut a deep canyon, indicates that the valley once was com­ pletely closed at this place. The most extensive canyon occurring on Furuberget runs in an are from southwest to east across the central part of the promontory and contains a series of pot-hales that are, especially in the flat, eastern part of the canyon, completely filled with organic matter (KLOVNING 1963).
    [Show full text]
  • Basal Control of Supraglacial Meltwater Catchments on the Greenland Ice Sheet
    The Cryosphere, 12, 3383–3407, 2018 https://doi.org/10.5194/tc-12-3383-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Basal control of supraglacial meltwater catchments on the Greenland Ice Sheet Josh Crozier1, Leif Karlstrom1, and Kang Yang2,3 1University of Oregon Department of Earth Sciences, Eugene, Oregon, USA 2School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China 3Joint Center for Global Change Studies, Beijing 100875, China Correspondence: Josh Crozier ([email protected]) Received: 5 April 2018 – Discussion started: 17 May 2018 Revised: 13 October 2018 – Accepted: 15 October 2018 – Published: 29 October 2018 Abstract. Ice surface topography controls the routing of sur- sliding regimes. Predicted changes to subglacial hydraulic face meltwater generated in the ablation zones of glaciers and flow pathways directly caused by changing ice surface to- ice sheets. Meltwater routing is a direct source of ice mass pography are subtle, but temporal changes in basal sliding or loss as well as a primary influence on subglacial hydrology ice thickness have potentially significant influences on IDC and basal sliding of the ice sheet. Although the processes spatial distribution. We suggest that changes to IDC size and that determine ice sheet topography at the largest scales are number density could affect subglacial hydrology primarily known, controls on the topographic features that influence by dispersing the englacial–subglacial input of surface melt- meltwater routing at supraglacial internally drained catch- water. ment (IDC) scales ( < 10s of km) are less well constrained. Here we examine the effects of two processes on ice sheet surface topography: transfer of bed topography to the surface of flowing ice and thermal–fluvial erosion by supraglacial 1 Introduction meltwater streams.
    [Show full text]
  • Calving Processes and the Dynamics of Calving Glaciers ⁎ Douglas I
    Earth-Science Reviews 82 (2007) 143–179 www.elsevier.com/locate/earscirev Calving processes and the dynamics of calving glaciers ⁎ Douglas I. Benn a,b, , Charles R. Warren a, Ruth H. Mottram a a School of Geography and Geosciences, University of St Andrews, KY16 9AL, UK b The University Centre in Svalbard, PO Box 156, N-9171 Longyearbyen, Norway Received 26 October 2006; accepted 13 February 2007 Available online 27 February 2007 Abstract Calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world. Calving rates can increase dramatically in response to increases in velocity and/or retreat of the glacier margin, with important implications for sea level change. Despite their importance, calving and related dynamic processes are poorly represented in the current generation of ice sheet models. This is largely because understanding the ‘calving problem’ involves several other long-standing problems in glaciology, combined with the difficulties and dangers of field data collection. In this paper, we systematically review different aspects of the calving problem, and outline a new framework for representing calving processes in ice sheet models. We define a hierarchy of calving processes, to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events. The first-order control on calving is the strain rate arising from spatial variations in velocity (particularly sliding speed), which determines the location and depth of surface crevasses. Superimposed on this first-order process are second-order processes that can further erode the ice margin.
    [Show full text]
  • Jökulhlaups in Skaftá: a Study of a Jökul- Hlaup from the Western Skaftá Cauldron in the Vatnajökull Ice Cap, Iceland
    Jökulhlaups in Skaftá: A study of a jökul- hlaup from the Western Skaftá cauldron in the Vatnajökull ice cap, Iceland Bergur Einarsson, Veðurstofu Íslands Skýrsla VÍ 2009-006 Jökulhlaups in Skaftá: A study of jökul- hlaup from the Western Skaftá cauldron in the Vatnajökull ice cap, Iceland Bergur Einarsson Skýrsla Veðurstofa Íslands +354 522 60 00 VÍ 2009-006 Bústaðavegur 9 +354 522 60 06 ISSN 1670-8261 150 Reykjavík [email protected] Abstract Fast-rising jökulhlaups from the geothermal subglacial lakes below the Skaftá caul- drons in Vatnajökull emerge in the Skaftá river approximately every year with 45 jökulhlaups recorded since 1955. The accumulated volume of flood water was used to estimate the average rate of water accumulation in the subglacial lakes during the last decade as 6 Gl (6·106 m3) per month for the lake below the western cauldron and 9 Gl per month for the eastern caul- dron. Data on water accumulation and lake water composition in the western cauldron were used to estimate the power of the underlying geothermal area as ∼550 MW. For a jökulhlaup from the Western Skaftá cauldron in September 2006, the low- ering of the ice cover overlying the subglacial lake, the discharge in Skaftá and the temperature of the flood water close to the glacier margin were measured. The dis- charge from the subglacial lake during the jökulhlaup was calculated using a hypso- metric curve for the subglacial lake, estimated from the form of the surface cauldron after jökulhlaups. The maximum outflow from the lake during the jökulhlaup is esti- mated as 123 m3 s−1 while the maximum discharge of jökulhlaup water at the glacier terminus is estimated as 97 m3 s−1.
    [Show full text]
  • Seismic Model Report.Pdf
    Scientific Report GEFSC Loan 925 The Character and Extent of subglacial Deformation and its Links to Glacier Dynamics in the Tarfala Basin, northern Sweden Jeffrey Evans, David Graham, and Joseph Pomeroy Polar and Alpine Research Group, Loughborough University ABSTRACT A pilot passive seismology experiment was conducted across the main overdeepening of Storglaciaren in the Tarfala Basin, northern Sweden, in July 2010, to see whether basal microseismic waveforms could be detected beneath a small polythermal arctic glacier and to investigate the spatial and temporal distribution of such waveforms in relation to known glacier flow dynamics. The high ablation rate made it difficult to keep geophones buried and well- coupled to the glacier during the experiment and reduced the number of days of good quality data collection. Event counts and the subsequent characterisation of typical and atypical waveforms showed that the dominant waveforms detected were from near-surface events such as crevassing. Although basal sliding is known to occur in the overdeepening, no convincing examples of basal waveforms were detected, which suggests basal microseismic signals are rare or difficult to detect beneath polythermal glaciers like Storglaciaren, a finding that is consistent with results from alpine glaciers in Switzerland. The data- set could prove useful to glaciologists interested in the dynamics of near-surface events such as crevassing, the opening and closing of englacial water conduits, or temporal and spatial changes in the glacier’s stress field. Background Smith (2006) found that pervasive soft-bed deformation characterised parts of the Rutland Ice Stream in West Antarctica and produced 6 times fewer basal microseismic signals than regions where basal sliding or stick slip movement dominated.
    [Show full text]
  • An Esker Group South of Dayton, Ohio 231 JACKSON—Notes on the Aphididae 243 New Books 250 Natural History Survey 250
    The Ohio Naturalist, PUBLISHED BY The Biological Club of the Ohio State University. Volume VIII. JANUARY. 1908. No. 3 TABLE OF CONTENTS. SCHEPFEL—An Esker Group South of Dayton, Ohio 231 JACKSON—Notes on the Aphididae 243 New Books 250 Natural History Survey 250 AN ESKER GROUP SOUTH OF DAYTON, OHIO.1 EARL R. SCHEFFEL Contents. Introduction. General Discussion of Eskers. Preliminary Description of Region. Bearing on Archaeology. Topographic Relations. Theories of Origin. Detailed Description of Eskers. Kame Area to the West of Eskers. Studies. Proximity of Eskers. Altitude of These Deposits. Height of Eskers. Composition of Eskers. Reticulation. Rock Weathering. Knolls. Crest-Lines. Economic Importance. Area to the East. Conclusion and Summary. Introduction. This paper has for its object the discussion of an esker group2 south of Dayton, Ohio;3 which group constitutes a part of the first or outer moraine of the Miami Lobe of the Late Wisconsin ice where it forms the east bluff of the Great Miami River south of Dayton.4 1. Given before the Ohio Academy of Science, Nov. 30, 1907, at Oxford, O., repre- senting work performed under the direction of Professor Frank Carney as partial requirement for the Master's Degree. 2. F: G. Clapp, Jour, of Geol., Vol. XII, (1904), pp. 203-210. 3. The writer's attention was first called to the group the past year under the name "Morainic Ridges," by Professor W. B. Werthner, of Steele High School, located in the city mentioned. Professor Werthner stated that Professor August P. Foerste of the same school and himself had spent some time together in the study of this region, but that the field was still clear for inves- tigation and publication.
    [Show full text]
  • Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA
    Brigham Young University BYU ScholarsArchive Theses and Dissertations 2019-07-01 Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/etd BYU ScholarsArchive Citation Barkdull, Natalie Shepherd, "Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA" (2019). Theses and Dissertations. 8590. https://scholarsarchive.byu.edu/etd/8590 This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull A thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Master of Science Gregory T. Carling, Chair Barry R. Bickmore Stephen T. Nelson Department of Geological Sciences Brigham Young University Copyright © 2019 Natalie Shepherd Barkdull All Rights Reserved ABSTRACT Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA Natalie Shepherd Barkdull Department of Geological Sciences, BYU Master of Science Shrinking alpine glaciers alter the geochemistry of sensitive mountain streams by exposing reactive freshly-weathered bedrock and releasing decades of atmospherically-deposited trace elements from glacier ice. Changes in the timing and quantity of glacial melt also affect discharge and temperature of alpine streams.
    [Show full text]
  • A Significant Acceleration of Ice Volume Discharge Preceded a Major Retreat of a West Antarctic Paleo–Ice Stream
    https://doi.org/10.1130/G46916.1 Manuscript received 26 August 2019 Revised manuscript received 23 November 2019 Manuscript accepted 26 November 2019 © 2019 Geological Society of America. For permission to copy, contact [email protected]. A signifcant acceleration of ice volume discharge preceded a major retreat of a West Antarctic paleo–ice stream Philip J. Bart1 and Slawek Tulaczyk2 1 Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA 2 Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, California 95064, USA ABSTRACT SEDIMENT AND ICE DISCHARGE For the period between 14.7 and 11.5 cal. (calibrated) kyr B.P, the sediment fux of Bind- FROM THE PALEO–BINDSCHADLER schadler Ice Stream (BIS; West Antarctica) averaged 1.7 × 108 m3 a−1. This implies that BIS ICE STREAM velocity averaged 500 ± 120 m a−1. At a fner resolution, the data suggest two stages of ice Radiocarbon ages from benthic foramin- stream fow. During the frst 2400 ± 400 years of a grounding-zone stillstand, ice stream fow ifera (Bart et al., 2018) (Table 1) indicate that averaged 200 ± 90 m a−1. Following ice-shelf breakup at 12.3 ± 0.2 cal. kyr B.P., fow acceler- the paleo-BIS grounding line had retreated ated to 1350 ± 580 m a−1. The estimated ice volume discharge after breakup exceeds the bal- 70 km from its maximum (LGM) position by ance velocity by a factor of two and implies ice mass imbalance of −40 Gt a−1 just before the 14.7 ± 0.4 cal.
    [Show full text]
  • Analysis of Groundwater Flow Beneath Ice Sheets
    SE0100146 Technical Report TR-01-06 Analysis of groundwater flow beneath ice sheets Boulton G S, Zatsepin S, Maillot B University of Edinburgh Department of Geology and Geophysics March 2001 Svensk Karnbranslehantering AB Swedish Nuclear Fuel and Waste Management Co Box 5864 SE-102 40 Stockholm Sweden Tel 08-459 84 00 +46 8 459 84 00 Fax 08-661 57 19 +46 8 661 57 19 32/ 23 PLEASE BE AWARE THAT ALL OF THE MISSING PAGES IN THIS DOCUMENT WERE ORIGINALLY BLANK Analysis of groundwater flow beneath ice sheets Boulton G S, Zatsepin S, Maillot B University of Edinburgh Department of Geology and Geophysics March 2001 This report concerns a study which was conducted for SKB. The conclusions and viewpoints presented in the report are those of the authors and do not necessarily coincide with those of the client. Summary The large-scale pattern of subglacial groundwater flow beneath European ice sheets was analysed in a previous report /Boulton and others, 1999/. It was based on a two- dimensional flowline model. In this report, the analysis is extended to three dimensions by exploring the interactions between groundwater and tunnel flow. A theory is develop- ed which suggests that the large-scale geometry of the hydraulic system beneath an ice sheet is a coupled, self-organising system. In this system the pressure distribution along tunnels is a function of discharge derived from basal meltwater delivered to tunnels by groundwater flow, and the pressure along tunnels itself sets the base pressure which determines the geometry of catchments and flow towards the tunnel.
    [Show full text]
  • COLD-BASED GLACIERS in the WESTERN DRY VALLEYS of ANTARCTICA: TERRESTRIAL LANDFORMS and MARTIAN ANALOGS: David R
    Lunar and Planetary Science XXXIV (2003) 1245.pdf COLD-BASED GLACIERS IN THE WESTERN DRY VALLEYS OF ANTARCTICA: TERRESTRIAL LANDFORMS AND MARTIAN ANALOGS: David R. Marchant1 and James W. Head2, 1Department of Earth Sciences, Boston University, Boston, MA 02215 [email protected], 2Department of Geological Sciences, Brown University, Providence, RI 02912 Introduction: Basal-ice and surface-ice temperatures are contacts and undisturbed underlying strata are hallmarks of cold- key parameters governing the style of glacial erosion and based glacier deposits [11]. deposition. Temperate glaciers contain basal ice at the pressure- Drop moraines: The term drop moraine is used here to melting point (wet-based) and commonly exhibit extensive areas describe debris ridges that form as supra- and englacial particles of surface melting. Such conditions foster basal plucking and are dropped passively at margins of cold-based glaciers (Fig. 1a abrasion, as well as deposition of thick matrix-supported drift and 1b). Commonly clast supported, the debris is angular and sheets, moraines, and glacio-fluvial outwash. Polar glaciers devoid of fine-grained sediment associated with glacial abrasion include those in which the basal ice remains below the pressure- [10, 12]. In the Dry Valleys, such moraines may be cored by melting point (cold-based) and, in extreme cases like those in glacier ice, owing to the insulating effect of the debris on the the western Dry Valleys region of Antarctica, lack surface underlying glacier. Where cored by ice, moraine crests can melting zones. These conditions inhibit significant glacial exceed the angle of repose. In plan view, drop moraines closely erosion and deposition.
    [Show full text]
  • Glacial Cirques As Palaeoenvironmental Indicators: Their Potential and Limitations
    Glacial cirques as palaeoenvironmental indicators: their potential and limitations Barr, I. D., & Spagnolo, M. (2015). Glacial cirques as palaeoenvironmental indicators: their potential and limitations. Earth-Science Reviews, 151, 48-78. https://doi.org/10.1016/j.earscirev.2015.10.004 Published in: Earth-Science Reviews Document Version: Peer reviewed version Queen's University Belfast - Research Portal: Link to publication record in Queen's University Belfast Research Portal Publisher rights ©2015 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc- nd/4.0/ which permits distribution and reproduction for non-commercial purposes, provided the author and source are cited. General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in the Research Portal that you believe breaches copyright or violates any law, please contact [email protected]. Download date:24. Sep. 2021 Glacial cirques as palaeoenvironmental indicators: their potential and limitations Iestyn D. Barr (Corresponding author) School of Geography, Archaeology and Palaeoecology, Queen’s University Belfast, BT7 1NN, Belfast, UK Email: [email protected] Tel: +44 (0)28 9097 5146 Matteo Spagnolo School of Geosciences, University of Aberdeen, Elphinstone Road, AB243UF, Aberdeen, UK Abstract Glacial cirques are armchair-shaped erosional hollows, typified by steep headwalls and, often, overdeepened floors.
    [Show full text]