DOCSLIB.ORG

Radar-Detected Englacial Stratigraphy in the Pensacola Mountains, Antarctica: Implications for Recent Changes in Ice Flow and Accumulation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Radar-Detected Englacial Stratigraphy in the Pensacola Mountains, Antarctica: Implications for Recent Changes in Ice Flow and Accumulation Annals of Glaciology 54(63) 2013 doi: 10.3189/2013AoG63A371 91 Radar-detected englacial stratigraphy in the Pensacola Mountains, Antarctica: implications for recent changes in ice flow and accumulation Seth CAMPBELL,1,2 Greg BALCO,3 Claire TODD,4 Howard CONWAY,5 Kathleen HUYBERS,5 Christopher SIMMONS,6 Michael VERMEULEN4 1University of Maine, Orono, ME, USA E-mail: [email protected] 2US Army Cold Regions Research and Engineering Laboratory (CRREL), Hanover, NH, USA 3Berkeley Geochronology Center, Berkeley, CA, USA 4Pacific Lutheran University, Tacoma, WA, USA 5University of Washington, Seattle, WA, USA 6International Federation of Mountain Guide Associations (IFMGA)/American Mountain Guides Association (AMGA) Mountain Guide, Seattle, WA, USA ABSTRACT. We used measurements of radar-detected stratigraphy, surface ice-flow velocities and accumulation rates to investigate relationships between local valley-glacier and regional ice-sheet dynamics in and around the Schmidt Hills, Pensacola Mountains, Antarctica. Ground-penetrating radar profiles were collected perpendicular to the long axis of the Schmidt Hills and the margin of Foundation Ice Stream (FIS). Within the valley confines, the glacier consists of blue ice, and profiles show internal stratigraphy dipping steeply toward the nunataks and truncated at the present-day ablation surface. Below the valley confines, the blue ice is overlain by firn. Data show that upward-progressing overlap of actively accumulating firn onto valley-glacier ice is slightly less than ice flow out of the valleys over the past 1200 years. The apparent slightly negative mass balance (–0.25 cm a–1) suggests that ice-margin elevations in the Schmidt Hills may have lowered over this time period, even without a change in the surface elevation of FIS. Results suggest that (1) mass-balance gradients between local valley glaciers and regional ice sheets should be considered when using local information to estimate regional ice surface elevation changes; and (2) interpretation of shallow ice structures imaged with radar can provide information about local ice elevation changes and stability. INTRODUCTION combined with surface ice-flow velocities and accumulation Reconstructions of past changes in the thickness and extent rates, estimate ages of buried unconformities (e.g. Campbell of the Antarctic ice sheet are important for understanding and others, 2012) and infer differences in accumulation rates past and present sea-level change, and for validating numer- (e.g. Arcone and others, 2012). ical models, necessary to make realistic predictions of In recent years, cosmogenic-nuclide exposure dating changes under future possible environmental conditions. methods (Gosse and Phillips, 2001; Dunai, 2010; Balco, Direct observations of ice-sheet history from satellite data 2011) have been used to date glacial deposits in Antarctica extend back until the 1970s; obtaining longer records (e.g. Stone and others, 2003; Todd and others, 2010). Meas- requires the use of geologic and glaciological data. For urements of trace nuclides produced by cosmic-ray bom- example, radar-detected layers and dated ice cores have bardment of rock surfaces are used to determine the exposure been used to infer changes in ice thickness through the age of the surface. Although this technique has been used to Holocene (e.g. Conway and others, 1999; Waddington and reconstruct the overall pattern of LGM-to-present ice-sheet others, 2005; Price and others, 2007). Marine geologic data thinning in Antarctica, it has several limitations: (1) measure- have been used to infer ice-margin positions and the ment precision decreases at low nuclide concentrations, so presence or absence of ice shelves during the Last Glacial exposure ages from sites that have been exposed for less than Maximum (LGM) (e.g. Domack and others, 2005; Hillen- 1000 years can be subject to large uncertainty; (2) when ice brand and others, 2012; Stolldorf and others, 2012). surface-elevation changes are not monotonic, i.e. ice-sheet Terrestrial geologic data, including drift sheets and moraines thinning is interrupted or followed by thickening, exposure- deposited by outlet glaciers, have also provided important age records are ambiguous; (3) exposure ages of samples constraints on past ice thickness. Mapping of these deposits is collected from outcrops may reflect changes in local rather especially valuable when they can be dated by radiocarbon than regional flow, because the pattern of flow around or cosmogenic-nuclide exposure methods (e.g. Bockheim outcrops is typically complex. and others, 1989; Hall, 2009; Bentley and others, 2010; Here we evaluate the hypothesis that the internal stratig- Bromley and others, 2012; Whitehouse and others, 2012). raphy of ice adjacent to nunataks contains information about Radar has also been used to locate past ice-stream margin changes in ice surface elevation and flow dynamics over the positions (Catania and others, 2006), define boundaries past hundreds to thousands of years. Subsurface and between flow elements (e.g. King, 2009) and, when exposed nunataks affect ice flow and surface mass balance 92 Campbell and others: Englacial stratigraphy in the Pensacola Mountains Fig. 1. Locator maps of the Schmidt Hills and Foundation Ice Stream showing: (a) elevations from the RADARSAT-1 Antarctic Mapping Project (RAMP) digital elevation model (DEM), the current grounding-line interpretation from the Antarctic Digital Database (ADD) and the location of the Schmidt Hills in the Pensacola Mountains relative to FIS and Ronne–Filchner Ice Shelf; (b) QuickBird 0.6 m pixel resolution satellite image of the Schmidt Hills showing location of the Childs Glacier/FIS flow relative to GPR profiles 1–4 (white solid lines, L1–L4), GPR profiles collected but not imaged (white dashed lines), surface ice-flow velocities (black arrows, underlined lettering; m a–1), the meltwater pond near line 2 (MW), blue-ice areas (BIA), accumulation rates (circles; cm a–1) and the location of the photo shown as (c) (white arrow, P); and (c) photo with approximate radar profile locations (dotted lines; L1–L4), the shear margin and FIS with dotted arrow pointing towards the Ronne–Filchner Ice Shelf. Imagery #2012 DigitalGlobe, Inc. as the ice thickness changes. For example, ice will flow FOUNDATION ICE STREAM AND THE SCHMIDT around rather than over a topographic obstacle as it emerges HILLS through the ice sheet, and protruding nunataks influence patterns of snow transport by wind, resulting in localized Foundation Ice Stream (FIS) is the southernmost ice stream areas of accumulation and ablation. Such changes would be that flows into the Ronne–Filchner Ice Shelf in the Weddell 2 evident in the radar-detected stratigraphy. Following this Sea Embayment. The catchment of FIS ( 566 000 km ) reasoning, information from patterns of shallow stratigraphy consists of ice originating from both East and West near nunataks should help interpret exposure-age records of Antarctica (Joughin and Bamber, 2005; Rignot and others, ice surface-elevation change over the past millennia. Also, 2011). Thus, thickness and velocity changes in the lower FIS interpretation of local shallow stratigraphy may provide will contain a record of changes in both regions. The insight into similarities or differences in local vs regional Schmidt Hills are a group of nunataks situated near the accumulation and flow patterns, which is useful for regional eastern edge of FIS as it enters the Filchner Trough extrapolation of exposure-age data. embayment (Fig. 1) 40 km downstream of the currently We pursue this idea by conducting an ice-penetrating estimated grounding line (SCAR, 2012). The hills are radar study of the shallow (0–400 m) firn and ice surround- approximately 27 km long and 12 km wide, with nunatak ing the Schmidt Hills, Pensacola Mountains, Antarctica. We elevations reaching >700 m above the current ice surface. also measured surface ice-flow velocity and accumulation Childs Glacier drains from the southern boundary of the rate to help interpret the radar data. We show that the Schmidt Hills and turns north to merge into the eastern edge shallow-ice stratigraphy around these nunataks: (1) is of FIS. Other small valley glaciers originating within the complex; (2) reflects the interplay of through-flowing ice Schmidt Hills flow westward into Childs Glacier and FIS. associated with the adjacent Childs Glacier/Foundation Ice Graf and others (1999) collected firn cores along a Stream and locally sourced ice derived from alpine glaciers; traverse up FIS; these cores show a regional pattern of and (3) displays features that may reflect change in the increasing accumulation rate from the FIS grounding line to surface elevation of the ice stream. the north toward the ice-shelf edge. They estimated a Campbell and others: Englacial stratigraphy in the Pensacola Mountains 93 Fig. 2. Line 1 (L1) 100 MHz GPR profile. (a) Elevation-corrected full depth profile with labels for bedrock (BR), blue-ice areas (BIA), an ablation surface (AS), surface tensional ice fractures (Fx) and the approximate division between confined (valley) and unconfined (Open) ice flow. Depth is based on a dielectric permittivity (DI) of 3.0 and two-way travel time (TWTT). (b) Zoom from (a) showing detail of dipping stratigraphy in the BIA, AS and hyperbolas caused by the Fx. (c) Zoom from (a) showing detail of the firn overlap described as wind- deposited bedding sequences (BS), buried-firn–blue-ice unconformity (UC) and the ice beneath the UC which lacks internal stratigraphy. 10.1 Æ 3.0 cm w.e. a–1 average accumulation rate between lying the scoured and exposed blue ice within the Schmidt 1947 and 1994 at their core closest to the Schmidt Hills, Hills valleys, where winds are more confined (e.g. Bintanja, 20 km from the end of our ground-penetrating radar (GPR) 1999). In contrast, accumulation zones are situated near the profile 1 (L1 in Fig. 1b). Joughin and Bamber (2005) used mouth of each valley, where winds are not as confined. regionally derived elevation and velocity data to estimate regional mass balance through a flux-gate method.
Load more

Recommended publications
  • A New Bed Elevation Model for the Weddell Sea Sector of the West Antarctic Ice Sheet
    Earth Syst. Sci. Data, 10, 711–725, 2018 https://doi.org/10.5194/essd-10-711-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. A new bed elevation model for the Weddell Sea sector of the West Antarctic Ice Sheet Hafeez Jeofry1,2, Neil Ross3, Hugh F. J. Corr4, Jilu Li5, Mathieu Morlighem6, Prasad Gogineni7, and Martin J. Siegert1 1Grantham Institute and Department of Earth Science and Engineering, Imperial College London, South Kensington, London, UK 2School of Marine Science and Environment, Universiti Malaysia Terengganu, Kuala Terengganu, Terengganu, Malaysia 3School of Geography, Politics and Sociology, Newcastle University, Claremont Road, Newcastle Upon Tyne, UK 4British Antarctic Survey, Natural Environment Research Council, Cambridge, UK 5Center for the Remote Sensing of Ice Sheets, University of Kansas, Lawrence, Kansas, USA 6Department of Earth System Science, University of California, Irvine, Irvine, California, USA 7Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, USA Correspondence: Hafeez Jeofry ([email protected]) and Martin J. Siegert ([email protected]) Received: 11 August 2017 – Discussion started: 26 October 2017 Revised: 26 October 2017 – Accepted: 5 February 2018 – Published: 9 April 2018 Abstract. We present a new digital elevation model (DEM) of the bed, with a 1 km gridding, of the Weddell Sea (WS) sector of the West Antarctic Ice Sheet (WAIS). The DEM has a total area of ∼ 125 000 km2 covering the Institute, Möller and Foundation ice streams, as well as the Bungenstock ice rise. In comparison with the Bedmap2 product, our DEM includes new aerogeophysical datasets acquired by the Center for Remote Sensing of Ice Sheets (CReSIS) through the NASA Operation IceBridge (OIB) program in 2012, 2014 and 2016.
    [Show full text]
  • Ice-Flow Structure and Ice Dynamic Changes in the Weddell Sea Sector
    Bingham RG, Rippin DM, Karlsson NB, Corr HFJ, Ferraccioli F, Jordan TA, Le Brocq AM, Rose KC, Ross N, Siegert MJ. Ice-flow structure and ice-dynamic changes in the Weddell Sea sector of West Antarctica from radar-imaged internal layering. Journal of Geophysical Research: Earth Surface 2015, 120(4), 655-670. Copyright: ©2015 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. DOI link to article: http://dx.doi.org/10.1002/2014JF003291 Date deposited: 04/06/2015 This work is licensed under a Creative Commons Attribution 4.0 International License Newcastle University ePrints - eprint.ncl.ac.uk PUBLICATIONS Journal of Geophysical Research: Earth Surface RESEARCH ARTICLE Ice-flow structure and ice dynamic changes 10.1002/2014JF003291 in the Weddell Sea sector of West Antarctica Key Points: from radar-imaged internal layering • RES-sounded internal layers in Institute/Möller Ice Streams show Robert G. Bingham1, David M. Rippin2, Nanna B. Karlsson3, Hugh F. J. Corr4, Fausto Ferraccioli4, fl ow changes 4 5 6 7 8 • Ice-flow reconfiguration evinced in Tom A. Jordan , Anne M. Le Brocq , Kathryn C. Rose , Neil Ross , and Martin J. Siegert Bungenstock Ice Rise to higher 1 2 tributaries School of GeoSciences, University of Edinburgh, Edinburgh, UK, Environment Department, University of York, York, UK, • Holocene dynamic reconfiguration 3Centre for Ice and Climate, Niels Bohr Institute, University
    [Show full text]
  • The Million-Year Evolution of the Glacial Trimline in the Southernmost Ellsworth Mountains, Antarctica
    Edinburgh Research Explorer The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica Citation for published version: Sugden, D, Hein, A, Woodward, J, Marrero, S, Rodes, A, Dunning, S, Freeman, S, Winter, K & Westoby, M 2017, 'The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica', Earth and Planetary Science Letters, vol. 469, pp. 42-52. https://doi.org/10.1016/j.epsl.2017.04.006 Digital Object Identifier (DOI): 10.1016/j.epsl.2017.04.006 Link: Link to publication record in Edinburgh Research Explorer Document Version: Publisher's PDF, also known as Version of record Published In: Earth and Planetary Science Letters Publisher Rights Statement: © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license General rights Copyright for the publications made accessible via the Edinburgh Research Explorer 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 University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 11. Oct. 2021 Earth and Planetary Science Letters 469 (2017) 42–52 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl The million-year evolution of the glacial trimline in the southernmost Ellsworth Mountains, Antarctica ∗ David E.
    [Show full text]
  • 1 Compiled by Mike Wing New Zealand Antarctic Society (Inc
    ANTARCTIC 1 Compiled by Mike Wing US bulldozer, 1: 202, 340, 12: 54, New Zealand Antarctic Society (Inc) ACECRC, see Antarctic Climate & Ecosystems Cooperation Research Centre Volume 1-26: June 2009 Acevedo, Capitan. A.O. 4: 36, Ackerman, Piers, 21: 16, Vessel names are shown viz: “Aconcagua” Ackroyd, Lieut. F: 1: 307, All book reviews are shown under ‘Book Reviews’ Ackroyd-Kelly, J. W., 10: 279, All Universities are shown under ‘Universities’ “Aconcagua”, 1: 261 Aircraft types appear under Aircraft. Acta Palaeontolegica Polonica, 25: 64, Obituaries & Tributes are shown under 'Obituaries', ACZP, see Antarctic Convergence Zone Project see also individual names. Adam, Dieter, 13: 6, 287, Adam, Dr James, 1: 227, 241, 280, Vol 20 page numbers 27-36 are shared by both Adams, Chris, 11: 198, 274, 12: 331, 396, double issues 1&2 and 3&4. Those in double issue Adams, Dieter, 12: 294, 3&4 are marked accordingly. Adams, Ian, 1: 71, 99, 167, 229, 263, 330, 2: 23, Adams, J.B., 26: 22, Adams, Lt. R.D., 2: 127, 159, 208, Adams, Sir Jameson Obituary, 3: 76, A Adams Cape, 1: 248, Adams Glacier, 2: 425, Adams Island, 4: 201, 302, “101 In Sung”, f/v, 21: 36, Adamson, R.G. 3: 474-45, 4: 6, 62, 116, 166, 224, ‘A’ Hut restorations, 12: 175, 220, 25: 16, 277, Aaron, Edwin, 11: 55, Adare, Cape - see Hallett Station Abbiss, Jane, 20: 8, Addison, Vicki, 24: 33, Aboa Station, (Finland) 12: 227, 13: 114, Adelaide Island (Base T), see Bases F.I.D.S. Abbott, Dr N.D.
    [Show full text]
  • Here Westerlies in Patagonia and South Georgia Island; Kreutz K (PI), Campbell S (Co-PI) $11,952
    Seth William Campbell University of Maine Juneau Icefield Research Program Climate Change Institute The Foundation for Glacier School of Earth & Climate Sciences & Environmental Research 202 Sawyer Hall 4616 25th Avenue NE, Suite 302 Orono, Maine 04469-5790 Seattle, Washington 98105 [email protected] [email protected] 207-581-3927 www.alpinesciences.net Education 2014 Ph.D. Earth & Climate Sciences University of Maine, Orono 2010 M.S. Earth Sciences University of Maine, Orono 2008 B.S. Earth Sciences University of Maine, Orono 2005 M. Business Administration University of Maine, Orono 2001 B.A. Environmental Science, Minor: Geology University of Maine, Farmington Current Employment 2018 – Present University of Maine, Assistant Professor of Glaciology; Climate Change Institute and School of Earth & Climate Sciences 2018 – Present Juneau Icefield Research Program, Director of Academics & Research 2016 – Present ERDC-CRREL, Research Geophysicist (Intermittent Status) Prior Employment 2015 – 2018 University of Maine, Research Assistant Professor 2016 – 2018 University of Washington, Post-Doctoral Research Associate 2014 – 2016 ERDC-CRREL, Research Geophysicist 2014 – 2017 University of California, Davis, Research Associate 2011 – 2014 University of Maine, Graduate Research Assistant 2009 – 2014 ERDC-CRREL, Research Physical Scientist 2010 – 2012 University of Washington, Professional Research Staff 2008 – 2009 University of Maine, Graduate Teaching Assistant 2000 E/Pro Engineering & Environmental Consulting, Survey Technician 1999
    [Show full text]
  • Coastal-Change and Glaciological Map of the Ronne Ice Shelf Area, Antarctica: 1974–2002
    U.S. DEPARTMENT OF THE INTERIOR TO ACCOMPANY MAP I–2600–D U.S. GEOLOGICAL SURVEY COASTAL-CHANGE AND GLACIOLOGICAL MAP OF THE RONNE ICE SHELF AREA, ANTARCTICA: 1974–2002 By Jane G. Ferrigno,1 Kevin M. Foley,1 Charles Swithinbank,2 Richard S. Williams, Jr.,3 and Lina M. Dailide1 2005 INTRODUCTION fronts of Antarctica (Swithinbank, 1988; Williams and Ferrigno, 1988). The project was later modified to include Landsat 4 and Background 5 MSS and Thematic Mapper (TM) (and in some areas Landsat 7 Changes in the area and volume of polar ice sheets are Enhanced Thematic Mapper Plus (ETM+)), RADARSAT images, intricately linked to changes in global climate, and the resulting and other data where available, to compare changes during a changes in sea level may severely impact the densely populated 20- to 25- or 30-year time interval (or longer where data were coastal regions on Earth. Melting of the West Antarctic part available, as in the Antarctic Peninsula). The results of the analy- alone of the Antarctic ice sheet could cause a sea-level rise of sis are being used to produce a digital database and a series of approximately 6 meters (m). The potential sea-level rise after USGS Geologic Investigations Series Maps (I–2600) consisting of melting of the entire Antarctic ice sheet is estimated to be 65 23 maps at 1:1,000,000 scale and 1 map at 1:5,000,000 scale, m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). in both paper and digital format (Williams and others, 1995; In spite of its importance, the mass balance (the net volumetric Williams and Ferrigno, 1998; Ferrigno and others, 2002) (avail- gain or loss) of the Antarctic ice sheet is poorly known; it is not able online at http://www.glaciers.er.usgs.gov).
    [Show full text]
  • Sensitivity of the Weddell Sea Sector Ice Streams to Sub-Shelf Melting and Surface Accumulation
    The Cryosphere, 8, 2119–2134, 2014 www.the-cryosphere.net/8/2119/2014/ doi:10.5194/tc-8-2119-2014 © Author(s) 2014. CC Attribution 3.0 License. Sensitivity of the Weddell Sea sector ice streams to sub-shelf melting and surface accumulation A. P. Wright1, A. M. Le Brocq1, S. L. Cornford2, R. G. Bingham3, H. F. J. Corr4, F. Ferraccioli4, T. A. Jordan4, A. J. Payne2, D. M. Rippin5, N. Ross6, and M. J. Siegert7 1Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK 2Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol BS8 1SS, UK 3School of Geosciences, University of Edinburgh, Edinburgh EH8 9XP, UK 4British Antarctic Survey, Madingley Road, High Cross, Cambridge, Cambridgeshire CB3 0ET, UK 5Environment Department, University of York, Heslington, York YO10 5DD, UK 6School of Geography, Politics and Sociology, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK 7Grantham Institute and Department of Earth Science and Engineering, Imperial College London, South Kensington, London SW7 2AZ, UK Correspondence to: S. L. Cornford ([email protected]) Received: 4 July 2013 – Published in The Cryosphere Discuss.: 19 November 2013 Revised: 16 July 2014 – Accepted: 18 September 2014 – Published: 24 November 2014 Abstract. A recent ocean modelling study indicates that pos- 1 Introduction sible changes in circulation may bring warm deep-ocean wa- ter into direct contact with the grounding lines of the Filch- A recent geophysical survey (see e.g. Ross et al., 2012) ner–Ronne ice streams, suggesting the potential for future has highlighted the potential for a marine ice sheet instabil- ice losses from this sector equivalent to ∼0.3 m of sea- ity (e.g.
    [Show full text]
  • Ice-Flow Structure and Ice Dynamic Changes in the Weddell Sea Sector
    PUBLICATIONS Journal of Geophysical Research: Earth Surface RESEARCH ARTICLE Ice-flow structure and ice dynamic changes 10.1002/2014JF003291 in the Weddell Sea sector of West Antarctica Key Points: from radar-imaged internal layering • RES-sounded internal layers in Institute/Möller Ice Streams show Robert G. Bingham1, David M. Rippin2, Nanna B. Karlsson3, Hugh F. J. Corr4, Fausto Ferraccioli4, fl ow changes 4 5 6 7 8 • Ice-flow reconfiguration evinced in Tom A. Jordan , Anne M. Le Brocq , Kathryn C. Rose , Neil Ross , and Martin J. Siegert Bungenstock Ice Rise to higher 1 2 tributaries School of GeoSciences, University of Edinburgh, Edinburgh, UK, Environment Department, University of York, York, UK, • Holocene dynamic reconfiguration 3Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark, 4British Antarctic occurred in much of IIS/MIS as ice Survey, Natural Environment Research Council, Cambridge, UK, 5Geography, College of Life and Environmental Sciences, thinned University of Exeter, Exeter, UK, 6Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, UK, 7School of Geography, Politics and Sociology, Newcastle University, Newcastle, UK, 8Grantham Institute and Department of Supporting Information: Earth Science and Engineering, Imperial College London, London, UK • Sections S1–S4 and Figure S1 Correspondence to: Abstract Recent studies have aroused concerns over the potential for ice draining the Weddell Sea R. G. Bingham, sector of West Antarctica to figure more prominently in sea level contributions should buttressing from [email protected] the Filchner-Ronne Ice Shelf diminish. To improve understanding of how ice stream dynamics there evolved through the Holocene, we interrogate radio echo sounding (RES) data from across the catchments of Citation: Institute and Möller Ice Streams (IIS and MIS), focusing especially on the use of internal layering to Bingham, R.
    [Show full text]
  • Reconstruction of Changes in the Weddell Sea Sector of the Antarctic Ice Sheet Since the Last Glacial Maximum
    Quaternary Science Reviews xxx (2013) 1e26 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Reconstruction of changes in the Weddell Sea sector of the Antarctic Ice Sheet since the Last Glacial Maximum Claus-Dieter Hillenbrand a,*,1, Michael J. Bentley b,1, Travis D. Stolldorf c, Andrew S. Hein d, Gerhard Kuhn e, Alastair G.C. Graham f, Christopher J. Fogwill g, Yngve Kristoffersen h, James. A. Smith a, John B. Anderson c, Robert D. Larter a, Martin Melles i, Dominic A. Hodgson a, Robert Mulvaney a, David E. Sugden d a British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK b Department of Geography, Durham University, South Road, Durham DH1 3LE, UK c Department of Earth Sciences, Rice University, 6100 Main Street, Houston, TX 77005, USA d School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK e Alfred-Wegener-Institut Hemholtz-Zentrum für Polar- und Meeresforschung, Am Alten Hafen 26, D-27568 Bremerhaven, Germany f College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK g Climate Change Research Centre, University of New South Wales, Sydney, Australia h Department of Earth Science, University of Bergen, Allegate 41, Bergen N-5014, Norway i Institute of Geology and Mineralogy, University of Cologne, Zülpicher Strasse 49a, D-50674 Cologne, Germany article info abstract Article history: The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for Received 4 December 2012 about one fifth of Antarctica’s continental ice volume.
    [Show full text]
  • (ASPA) No. 119 DAVIS VALLEY and FORLIDAS POND
    Measure 6 (2010) Annex Management Plan for Antarctic Specially Protected Area (ASPA) No. 119 DAVIS VALLEY AND FORLIDAS POND, DUFEK MASSIF, PENSACOLA MOUNTAINS (51° 05' W, 82° 29' S) Introduction Davis Valley and Forlidas Pond Antarctic Specially Protected Area (ASPA) is situated within the Dufek Massif, Pensacola Mountains at 51°4'53"W, 82°29'21"S. Approximate area: 57.3 km2. The primary reason for the designation of the Area is that it contains some of the most southerly freshwater ponds with plant life known to exist in Antarctica, which represent unique examples of near-pristine freshwater ecosystems and their catchments. The geomorphology of the Area represents a unique scientific resource for the reconstruction of previous glacial and climatic events. As a consequence of its extreme remoteness and inaccessibility, the Area has experienced very little human activity and with the total number of visitors estimated to be less than 50 people. As a result, the Area has outstanding potential as a scientific reference site. Furthermore, the Area possesses outstanding wilderness and aesthetic values. The Area is one of the most southerly ‘dry valley’ systems in Antarctica and, as of March 2010, is the most southerly Antarctic Specially Protected Area (ASPA) in Antarctica. The Area was originally proposed by the United States of America and adopted through Recommendation through Recommendation XVI-9 (1991, SPA No. 23) and included Forlidas Pond (82°27'28"S, 51°16'48"W) and several ponds along the northern ice margin of the Davis Valley. The boundaries of the Area were extended to include the entire ice-free region centered on the Davis Valley through Measure 2 (2005).
    [Show full text]
  • Cosmogenic-Nuclide Exposure Ages from the Pensacola Mountains Adjacent to the Foundation Ice Stream, Antarctica
    [American Journal of Science, Vol. 316, June, 2016,P.542–577, DOI 10.2475/06.2016.02] COSMOGENIC-NUCLIDE EXPOSURE AGES FROM THE PENSACOLA MOUNTAINS ADJACENT TO THE FOUNDATION ICE STREAM, ANTARCTICA GREG BALCO*,†, CLAIRE TODD**, KATHLEEN HUYBERS***, SETH CAMPBELL§, MICHAEL VERMEULEN**, MATTHEW HEGLAND**, BRENT M. GOEHRING§§, AND TREVOR R. HILLEBRAND*** ABSTRACT. We describe glacial-geological observations and cosmogenic-nuclide exposure ages from the Schmidt, Williams, and Thomas Hills in the Pensacola Mountains of Antarctica adjacent to the Foundation Ice Stream (FIS). Our aim is to learn about changes in the thickness and grounding line position of the Antarctic Ice Sheet in the Weddell Sea embayment between the Last Glacial Maximum (LGM) and the present. Glacial-geological observations from all three regions indicate that currently- ice-free areas were covered by ice during one or more past ice sheet expansions, and that this ice was typically frozen to its bed and thus non-erosive, permitting the accumulation of multiple generations of glacial drift. Cosmogenic-nuclide exposure- age data from glacially transported erratics are consistent with this interpretation in that we observe both (i) samples with Holocene exposure ages that display a systematic age-elevation relationship recording LGM-to-present deglaciation, and (ii) samples with older and highly scattered apparent exposure ages that were deposited in previous glacial-interglacial cycles and have experienced multiple periods of surface exposure and ice cover. Holocene exposure ages at the Thomas and Williams Hills, upstream of the present grounding line of the FIS, show that the FIS was at least 500 m thicker prior to 11 ka, and that 500 m of thinning took place between 11 and 4 ka.
    [Show full text]
  • Ice-Free Valleys in the Neptune Range of the Pensacola Mountains, Antarctica: Glacial Geomorphology, Geochronology and Potential
    Antarctic Science 33(4), 428–455 (2021) © The Author(s), 2021. Published by Cambridge University Press on behalf of Antarctic Science Ltd. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http:// creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. doi:10.1017/S0954102021000237 Ice-free valleys in the Neptune Range of the Pensacola Mountains, Antarctica: glacial geomorphology, geochronology and potential as palaeoenvironmental archives DAVID SMALL 1, MICHAEL J. BENTLEY 1, DAVID J.A. EVANS1, ANDREW S. HEIN 2 and STEWART P.H.T. FREEMAN 3 1Department of Geography, Durham University, Durham, DH1 3LE, UK 2School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK 3Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF, UK [email protected] Abstract: We describe the glacial geomorphology and initial geochronology of two ice-free valley systems within the Neptune Range of the Pensacola Mountains, Antarctica. These valleys are characterized by landforms associated with formerly more expanded ice sheet(s) that were at least 200 m thicker than at present. The most conspicuous features are areas of supraglacial debris, discrete debris accumulations separated from modern-day ice and curvilinear ridges and mounds. The landsystem bears similarities to debris-rich cold-based glacial landsystems described elsewhere in Antarctica and the Arctic where buried ice is prevalent. Geochronological data demonstrate multiple phases of ice expansion. The oldest, occurring > 3 Ma, overtopped much of the landscape. Subsequent, less expansive advances into the valleys occurred > 2 Ma and > ∼1 Ma.
    [Show full text]