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  • 1.
    Arndt, Jan Erik
    et al.
    Alfred Wegener Inst Polar & Marine Res, Bremerhaven, Germany..
    Schenke, Hans Werner
    Alfred Wegener Inst Polar & Marine Res, Bremerhaven, Germany..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Nitsche, Frank O.
    Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY USA..
    Buys, Gwen
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Goleby, Bruce
    Geosci Australia, Canberra, ACT, Australia..
    Rebesco, Michele
    Ist Nazl Oceanog & Geofis Sperimentale, Sgonico, Italy..
    Bohoyo, Fernando
    Inst Geol & Minero Espana, Madrid, Spain..
    Hong, Jongkuk
    Korean Polar Res Inst, Inchon, South Korea..
    Black, Jenny
    Inst Geol & Nucl Sci, Lower Hutt, New Zealand..
    Greku, Rudolf
    Ukrainian Acad Sci, Inst Geol Sci, Kiev, Ukraine..
    Udintsev, Gleb
    Vemadsky Inst Geochem & Analyt Chem, Moscow, Russia..
    Barrios, Felipe
    Serv Hidrog & Oceanog, Valparaiso, Chile..
    Reynoso-Peralta, Walter
    Serv Hidrog Naval, Buenos Aires, DF, Argentina..
    Taisei, Morishita
    Japan Coast Guard, Hydrog & Oceanog Dept, Tokyo, Japan..
    Wigley, Rochelle
    Univ New Hampshire, Ctr Coastal & Ocean Mapping, Joint Hydrog Ctr, Durham, NH 03824 USA..
    The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0-A new bathymetric compilation covering circum-Antarctic waters2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 12, p. 3111-3117Article in journal (Refereed)
    Abstract [en]

    The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 is a new digital bathymetric model (DBM) portraying the seafloor of the circum-Antarctic waters south of 60 degrees S. IBCSO is a regional mapping project of the General Bathymetric Chart of the Oceans (GEBCO). The IBCSO Version 1.0 DBM has been compiled from all available bathymetric data collectively gathered by more than 30 institutions from 15 countries. These data include multibeam and single-beam echo soundings, digitized depths from nautical charts, regional bathymetric gridded compilations, and predicted bathymetry. Specific gridding techniques were applied to compile the DBM from the bathymetric data of different origin, spatial distribution, resolution, and quality. The IBCSO Version 1.0 DBM has a resolution of 500 x 500 m, based on a polar stereographic projection, and is publicly available together with a digital chart for printing from the project website (www.ibcso.org) and at .

  • 2.
    Bentley, Michael J.
    et al.
    Univ Durham, Dept Geog, Sci Labs, Durham DH1 3LE, England..
    Cofaigh, Colm O.
    Univ Durham, Dept Geog, Sci Labs, Durham DH1 3LE, England..
    Anderson, John B.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Conway, Howard
    Univ Washington, Dept Earth & Space Sci, Seattle, WA 98195 USA..
    Davies, Bethan
    Aberystwyth Univ, Dept Geog & Earth Sci, Ctr Glaciol, Aberystwyth SY23 3DB, Dyfed, Wales..
    Graham, Alastair G. C.
    Univ Exeter, Coll Life & Environm Sci, Exeter EX4 4RJ, Devon, England..
    Hillenbrand, Claus-Dieter
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Hodgson, Dominic A.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Jamieson, Stewart S. R.
    Univ Durham, Dept Geog, Sci Labs, Durham DH1 3LE, England..
    Larter, Robert D.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Mackintosh, Andrew
    Victoria Univ Wellington, Antarctic Res Ctr, Wellington, New Zealand..
    Smith, James A.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Verleyen, Elie
    Univ Ghent, Dept Biol, Lab Protistol & Aquat Ecol, B-9000 Ghent, Belgium..
    Ackert, Robert P.
    Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA..
    Bart, Philip J.
    Louisiana State Univ, Dept Geol & Geophys, Baton Rouge, LA 70803 USA..
    Berg, Sonja
    Univ Cologne, Inst Geol & Mineral, D-50674 Cologne, Germany..
    Brunstein, Daniel
    Univ Paris 01, CNRS, Lab Geog Phys, F-92195 Meudon, France..
    Canals, Miguel
    Univ Barcelona, Fac Geol, Dept Stratig Paleontol & Marine Geosci, CRG Marine Geosci, E-08028 Barcelona, Spain..
    Colhoun, Eric A.
    Univ Newcastle, Sch Environm & Life Sci, Callaghan, NSW 2308, Australia..
    Crosta, Xavier
    Univ Bordeaux 1, UMR 5805, F-33405 Talence, France..
    Dickens, William A.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Domack, Eugene
    Univ S Florida, Coll Marine Sci, St Petersburg, FL 33701 USA..
    Dowdeswell, Julian A.
    Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England..
    Dunbar, Robert
    Stanford Univ, Stanford, CA 94305 USA..
    Ehrmann, Werner
    Univ Leipzig, Inst Geol & Geophys, D-04103 Leipzig, Germany..
    Evans, Jeffrey
    Univ Loughborough, Dept Geog, Loughborough LE11 3TU, Leics, England..
    Favier, Vincent
    UJF CNRS, UMR5183, LGGE, F-38402 St Martin Dheres, France..
    Fink, David
    Australian Nucl Sci & Technol Org, Inst Environm Res, Menai, NSW 2234, Australia..
    Fogwill, Christopher J.
    Univ New S Wales, Climate Change Res Ctr, Sydney, NSW, Australia..
    Glasser, Neil F.
    Aberystwyth Univ, Dept Geog & Earth Sci, Ctr Glaciol, Aberystwyth SY23 3DB, Dyfed, Wales..
    Gohl, Karsten
    Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, D-27568 Bremerhaven, Germany..
    Golledge, Nicholas R.
    Victoria Univ Wellington, Antarctic Res Ctr, Wellington, New Zealand..
    Goodwin, Ian
    Macquarie Univ, Dept Geog & Environm, N Ryde, NSW 2109, Australia..
    Gore, Damian B.
    Macquarie Univ, Dept Geog & Environm, N Ryde, NSW 2109, Australia..
    Greenwood, Sarah L.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Hall, Brenda L.
    Univ Maine, Sch Earth & Climate Sci, Orono, ME USA..
    Hall, Kevin
    Univ No British Columbia, Geog Programme, Prince George, BC V2N 479, Canada..
    Hedding, David W.
    Univ S Africa, Dept Geog, ZA-1710 Florida, South Africa..
    Hein, Andrew S.
    Univ Edinburgh, Sch Geosci, Edinburgh EH8 9XP, Midlothian, Scotland..
    Hocking, Emma P.
    Northumbria Univ, Dept Geog, Newcastle Upon Tyne NE1 8ST, Tyne & Wear, England..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Johnson, Joanne S.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Jomelli, Vincent
    Univ Paris 01, CNRS, Lab Geog Phys, F-92195 Meudon, France..
    Jones, R. Selwyn
    Victoria Univ Wellington, Antarctic Res Ctr, Wellington, New Zealand..
    Klages, Johann P.
    Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, D-27568 Bremerhaven, Germany..
    Kristoffersen, Yngve
    Univ Bergen, Dept Earth Sci, N-5014 Bergen, Norway..
    Kuhn, Gerhard
    Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, D-27568 Bremerhaven, Germany..
    Leventer, Amy
    Colgate Univ, Dept Geol, Hamilton, NY 13346 USA..
    Licht, Kathy
    Indiana Univ Purdue Univ, Dept Earth Sci, Indianapolis, IN 46202 USA..
    Lilly, Katherine
    Univ Otago, Dept Geol, Dunedin, New Zealand..
    Lindow, Julia
    Colgate Univ, Dept Geol, Hamilton, NY 13346 USA.;Univ Bremen, Dept Geosci, D-28359 Bremen, Germany..
    Livingstone, Stephen J.
    Univ Sheffield, Dept Geog, Sheffield S10 2TN, S Yorkshire, England..
    Masse, Guillaume
    Univ Paris 06, CNRS, IRD, MNHN,LOCEAN,UMR7159, F-75252 Paris, France..
    McGlone, Matt S.
    Landcare Res, Lincoln 7640, New Zealand..
    McKay, Robert M.
    Victoria Univ Wellington, Antarctic Res Ctr, Wellington, New Zealand..
    Melles, Martin
    Univ Cologne, Inst Geol & Mineral, D-50674 Cologne, Germany..
    Miura, Hideki
    Natl Inst Polar Res, Tokyo 1908518, Japan..
    Mulvaney, Robert
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Nel, Werner
    Univ Ft Hare, Dept Geog & Environm Sci, ZA-5700 Alice, South Africa..
    Nitsche, Frank O.
    Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY USA..
    O'Brien, Philip E.
    Macquarie Univ, Dept Geog & Environm, N Ryde, NSW 2109, Australia..
    Post, Alexandra L.
    Geosci Australia, Canberra, ACT 2601, Australia..
    Roberts, Stephen J.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Saunders, Krystyna M.
    Univ Bern, Inst Geog, CH-3012 Bern, Switzerland.;Univ Bern, Oeschger Ctr Climate Change Res, CH-3012 Bern, Switzerland..
    Selkirk, Patricia M.
    Macquarie Univ, Dept Biol Sci, N Ryde, NSW 2109, Australia..
    Simms, Alexander R.
    Univ Durham, Dept Geog, Sci Labs, Durham DH1 3LE, England.;Univ Calif Santa Barbara, Dept Earth Sci, Santa Barbara, CA 93106 USA..
    Spiegel, Cornelia
    Univ Bremen, Dept Geosci, D-28359 Bremen, Germany..
    Stolldorf, Travis D.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Sugden, David E.
    Univ Edinburgh, Sch Geosci, Edinburgh EH8 9XP, Midlothian, Scotland..
    van der Putten, Nathalie
    Lund Univ, Dept Geol, SE-22362 Lund, Sweden..
    van Ommen, Tas
    Australian Antarctic Div, Hobart, Tas 7001, Australia.;Antarctic Climate & Ecosyst Cooperat Res Ctr, Hobart, Tas 7001, Australia..
    Verfaillie, Deborah
    UJF CNRS, UMR5183, LGGE, F-38402 St Martin Dheres, France..
    Vyverman, Wim
    Univ Ghent, Dept Biol, Lab Protistol & Aquat Ecol, B-9000 Ghent, Belgium..
    Wagner, Bernd
    Univ Cologne, Inst Geol & Mineral, D-50674 Cologne, Germany..
    White, Duanne A.
    Univ Canberra, Inst Appl Ecol, Canberra, ACT 2601, Australia..
    Witus, Alexandra E.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Zwartz, Dan
    Victoria Univ Wellington, Antarctic Res Ctr, Wellington, New Zealand..
    A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 100, p. 1-9Article in journal (Refereed)
    Abstract [en]

    A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse la. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community. (C) 2014 The Authors. Published by Elsevier Ltd.

  • 3.
    Colleoni, Florence
    et al.
    Ist Nazl Geofis & Vulcanol, Ctr Euromediterraneo Cambiamenti Climatici, Bologna, Italy.;UJF, CNRS, Lab Glaciol & Geophys Environm, St Martin Dheres, France.;Stockholm Univ, Dept Geol Sci, S-10691 Stockhlom, Sweden..
    Liakka, Johan
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden..
    Krinner, Gerhard
    UJF, CNRS, Lab Glaciol & Geophys Environm, St Martin Dheres, France..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockhlom, Sweden..
    Masina, Simona
    Ist Nazl Geofis & Vulcanol, Ctr Euromediterraneo Cambiamenti Climatici, Bologna, Italy..
    Peyaud, Vincent
    UJF, CNRS, Lab Glaciol & Geophys Environm, St Martin Dheres, France..
    The sensitivity of the Late Saalian (140 ka) and LGM (21 ka) Eurasian ice sheets to sea surface conditions2011In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, no 3-4, p. 531-553Article in journal (Refereed)
    Abstract [en]

    This work focuses on the Late Saalian (140 ka) Eurasian ice sheets' surface mass balance (SMB) sensitivity to changes in sea surface temperatures (SST). An Atmospheric General Circulation Model (AGCM), forced with two preexisting Last Glacial Maximum (LGM, 21 ka) SST reconstructions, is used to compute climate at 140 and 21 ka (reference glaciation). Contrary to the LGM, the ablation almost stopped at 140 ka due to the climatic cooling effect from the large ice sheet topography. Late Saalian SST are simulated using an AGCM coupled with a mixed layer ocean. Compared to the LGM, these 140 ka SST show an inter-hemispheric asymmetry caused by the larger ice-albedo feedback, cooling climate. The resulting Late Saalian ice sheet SMB is smaller due to the extensive simulated sea ice reducing the precipitation. In conclusion, SST are important for the stability and growth of the Late Saalian Eurasian ice sheet.

  • 4.
    Darby, Dennis A.
    et al.
    Old Dominion Univ, Dept Ocean Earth & Atmospher Sci, Norfolk, VA 23529 USA..
    Myers, Wesley B.
    Old Dominion Univ, Dept Ocean Earth & Atmospher Sci, Norfolk, VA 23529 USA..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, SE-10691 Stockholm, Sweden..
    Rigor, Ignatius
    Univ Washington, Appl Phys Lab, Seattle, WA 98105 USA..
    Modern dirty sea ice characteristics and sources: The role of anchor ice2011In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, ISSN 2169-9275, Vol. 116, article id C09008Article in journal (Refereed)
    Abstract [en]

    Extensive dirty ice patches with up to 7 kg m(-2) sediment concentrations in layers of up to 10 cm thickness were encountered in 2005 and 2007 in numerous areas across the central Arctic. The Fe grain fingerprint determination of sources for these sampled dirty ice floes indicated both Russian and Canadian sources, with the latter dominating. The presence of benthic shells and sea weeds along with thick layers (2-10 cm) of sediment covering 5-10 m(2) indicates an anchor ice entrainment origin as opposed to suspension freezing for some of these floes. The anchor ice origin might explain the dominance of Canadian sources where only narrow flaw leads occur that would not favor suspension freezing as an entrainment process. Expandable clays, commonly used as an indicator of a Kara Sea origin for dirty sea ice, are present in moderately high percentages (>20%) in many circum-Arctic source areas, including the Arctic coasts of North America. Some differences between the Russian and the North American coastal areas are found in clay mineral abundance, primarily the much higher abundance of chlorite in North America and the northern Barents Sea as opposed to the rest of the Russian Arctic. However, sea ice clay mineralogy matched many source areas, making it difficult to use as a provenance tool by itself. The bulk mineralogy (clay and non-clay) does not match specific sources possibly due to reworking of the sediment in dirty floes through summer melting or the failure to characterize all possible source areas.

  • 5.
    Freire, Francis
    et al.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Gyllencreutz, Richard
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Jafri, Rooh Ullah
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Acoustic evidence of a submarine slide in the deepest part of the Arctic, the Molloy Hole2014In: Geo-Marine Letters, ISSN 0276-0460, E-ISSN 1432-1157, Vol. 34, no 4, p. 315-325Article in journal (Refereed)
    Abstract [en]

    The western Svalbard continental margin contains thick sediment sequences with areas known to contain gas hydrates. Together with a dynamic tectonic environment, this makes the region prone to submarine slides. This paper presents results from geophysical mapping of the deepest part of the high Arctic environment, the Molloy Hole. The mapping includes multibeam bathymetry, acoustic backscatter and sub-bottom profiling. The geophysical data reveal seabed features indicative of sediment transport and larger-scale mass wasting. The large slide scar is here referred to as the Molloy Slide. It is located adjacent to the prominent Molloy Hole and Ridge system. The slide is estimated to have transported >65 km(3) of sediments over the deep axial valley of the Molloy Ridge, and further into the Molloy Hole. A unique feature of this slide is that, although its run-out distance is relatively short (<5 km), it extends over an enormous vertical depth (>2,000 m) as a result of its position in a complex bathymetric setting. The slide was most likely triggered by seismic activity caused by seafloor spreading processes along the adjacent Molloy Ridge. However, gas-hydrate destabilization may also have played a role in the ensuing slide event.

  • 6.
    Hanslik, Daniela
    et al.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Backman, Jan
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Björck, Svante
    Sellén, Emma
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    O'Regan, Matt
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Fornaciari, Eliana
    Univ Padua, Dept Geosci, I-35100 Padua, Italy..
    Skog, Göran
    Lund Univ, Dept Earth & Ecosyst Sci, Div Geol, Radiocarbon Dating Lab, Lund, Sweden..
    Quaternary Arctic Ocean sea ice variations and radiocarbon reservoir age corrections2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, p. 3430-3441Article in journal (Refereed)
    Abstract [en]

    A short sediment core from a local depression forming an intra basin on the Lomonosov Ridge, was retrieved during the Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX). It contains a record of the Marine Isotope Stages (MIS) 1-3 showing exceptionally high abundances of calcareous microfossils during parts of MIS 3. Based on radiocarbon dating, linear sedimentation rates of 7-9 cm/ka persist during the last deglaciation. The Last Glacial Maximum (LGM) is partly characterized by a hiatus. Planktic foraminiferal abundance variations of Neogloboquadrina pachyderma sinistral and calcareous nannofossils reflect changes in Arctic Ocean summer sea ice coverage and probably inflow of subpolar North Atlantic water. Calibration of the radiocarbon ages, using modeled reservoir corrections from previous studies and the microfossil abundance record of the studied core, results in marine reservoir ages of 1400 years or more, at least during the last deglaciation. Paired benthic-planktic radiocarbon dated foraminiferal samples indicate a slow decrease in age difference between surface and bottom waters from the Lateglacial to the Holocene, suggesting circulation and ventilation changes. (C) 2010 Elsevier Ltd. All rights reserved.

  • 7.
    Hell, Benjamin
    et al.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Gridding heterogeneous bathymetric data sets with stacked continuous curvature splines in tension2011In: Marine Geophysical Researches, ISSN 0025-3235, E-ISSN 1573-0581, Vol. 32, no 4, p. 493-501Article in journal (Refereed)
    Abstract [en]

    Gridding heterogeneous bathymetric data sets for the compilation of Digital bathymetric models (DBMs), poses specific problems when there are extreme variations in source data density. This requires gridding routines capable of subsampling high-resolution source data while preserving as much as possible of the small details, at the same time as interpolating in areas with sparse data without generating gridding artifacts. A frequently used gridding method generalizes bicubic spline interpolation and is known as continuous curvature splines in tension. This method is further enhanced in this article in order to specifically handle heterogeneous bathymetric source data. Our method constructs the final grid through stacking several surfaces of different resolutions, each generated using the splines in tension algorithm. With this approach, the gridding resolution is locally adjusted to the density of the source data set: Areas with high-resolution data are gridded at higher resolution than areas with sparse source data. In comparison with some of the most widely used gridding methods, our approach yields superior DBMs based on heterogeneous bathymetric data sets with regard to preserving small bathymetric details in the high-resolution source data, while minimizing interpolation artifacts in the sparsely data constrained regions. Common problems such as artifacts from ship tracklines are suppressed. Even if our stacked continuous curvature splines in tension gridding algorithm has been specifically designed to construct DBMs from heterogeneous bathymetric source data, it may be used to compile regular grids from other geoscientific measurements.

  • 8. Jakobsson, M
    et al.
    Macnab, R
    A comparison between GEBCO sheet 5.17 and the International Bathymetric Chart of the Arctic Ocean (IBCAO) version 1.02006In: Marine Geophysical Researches, ISSN 0025-3235, E-ISSN 1573-0581, Vol. 27, no 1, p. 35-48Article in journal (Refereed)
    Abstract [en]

    In 1979, the General Bathymetric Chart of the Oceans (GEBCO) published Sheet 5.17 in the Fifth Edition of its series of global bathymetric maps. Sheet 5.17 covered the northern polar region above 64 degrees N, and was for long the authoritative portrayal of Arctic bathymetry. The GEBCO compilation team had access to an extremely sparse sounding database from the central Arctic Ocean, due to the difficulty of mapping in this permanently ice covered region. In the past decade, there has been a substantial increase in the database of central Arctic Ocean bathymetry, due to the declassification of sounding data collected by US and British Navy nuclear submarines, and to the capability of modern icebreakers to measure ocean depths in heavy ice conditions. From these data sets, evidence has mounted to indicate that many of the smaller (and some larger) bathymetric features of Sheet 5.17 were poorly or wrongly defined. Within the framework of the project to construct the International Bathymetric Chart of the Arctic Ocean (IBCAO), all available historic and modern data sets were compiled to create a digital bathymetric model. In this paper, we compare both generally and in detail the contents of GEBCO Sheet 5.17 and version 1.0 of IBCAO, two bathymetric portrayals that were created more than 20 years apart. The results should be helpful in the analysis and assessment of previously published studies that were based on GEBCO Sheet 5.17.

  • 9.
    Jakobsson, Martin
    et al.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Anderson, John B.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Nitsche, Frank O.
    Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA..
    Dowdeswell, Julian A.
    Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England..
    Gyllencreutz, Richard
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Kirchner, Nina
    Stockholm Univ, Dept Phys Geog & Quaternary, S-10691 Stockholm, Sweden..
    Mohammad, Rezwan
    O'Regan, Matthew
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Alley, Richard B.
    Penn State Univ, Dept Geosci, University Pk, PA 16802 USA..
    Anandakrishnan, Sridhar
    Penn State Univ, Dept Geosci, University Pk, PA 16802 USA..
    Eriksson, Bjorn
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Kirshner, Alexandra
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Fernandez, Rodrigo
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Stolldorf, Travis
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Minzoni, Rebecca
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Majewski, Wojciech
    Polish Acad Sci, Inst Paleobiol, PL-00818 Warsaw, Poland..
    Geological record of ice shelf break-up and grounding line retreat, Pine Island Bay, West Antarctica2011In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 39, no 7, p. 691-694Article in journal (Refereed)
    Abstract [en]

    The catastrophic break-ups of the floating Larsen A and B ice shelves (Antarctica) in 1995 and 2002 and associated acceleration of glaciers that flowed into these ice shelves were among the most dramatic glaciological events observed in historical time. This raises a question about the larger West Antarctic ice shelves. Do these shelves, with their much greater glacial discharge, have a history of collapse? Here we describe features from the seafloor in Pine Island Bay, West Antarctica, which we interpret as having been formed during a massive ice shelf break-up and associated grounding line retreat. This evidence exists in the form of seafloor landforms that we argue were produced daily as a consequence of tidally influenced motion of mega-icebergs maintained upright in an iceberg armada produced from the disintegrating ice shelf and retreating grounding line. The break-up occurred prior to ca. 12 ka and was likely a response to rapid sea-level rise or ocean warming at that time.

  • 10.
    Jakobsson, Martin
    et al.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Long, Antony
    Univ Durham, Dept Geog, Durham DH1 3LE, England..
    Ingolfsson, Olafur
    Univ Iceland, Fac Earth Sci, IS-101 Reykjavik, Iceland..
    Kjaer, Kurt H.
    Univ Copenhagen, Nat Hist Museum, Ctr GeoGenet, DK-1350 Copenhagen, Denmark..
    Spielhagen, Robert F.
    IFM GEOMAR, Leihniz Inst Marine Sci, D-24148 Kiel, Germany.;Acad Sci Humanities & Literature, Mainz, Germany..
    New insights on Arctic Quaternary climate variability from palaeo-records and numerical modelling2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, p. 3349-3358Article in journal (Refereed)
    Abstract [en]

    Terrestrial and marine geological archives in the Arctic contain information on environmental change through Quaternary interglacial-glacial cycles. The Arctic Palaeoclimate and its Extremes (APEX) scientific network aims to better understand the magnitude and frequency of past Arctic climate variability, with focus on the "extreme" versus the "normal" conditions of the climate system. One important motivation for studying the amplitude of past natural environmental changes in the Arctic is to better understand the role of this region in a global perspective and provide base-line conditions against which to explore potential future changes in Arctic climate under scenarios of global warming. In this review we identify several areas that are distinct to the present programme and highlight some recent advances presented in this special issue concerning Arctic palaeo-records and natural variability, including spatial and temporal variability of the Greenland Ice Sheet, Arctic Ocean sediment stratigraphy, past ice shelves and marginal marine ice sheets, and the Cenozoic history of Arctic Ocean sea ice in general and Holocene oscillations in sea ice concentrations in particular. The combined sea ice data suggest that the seasonal Arctic sea ice cover was strongly reduced during most of the early Holocene and there appear to have been periods of ice free summers in the central Arctic Ocean. This has important consequences for our understanding of the recent trend of declining sea ice, and calls for further research on causal links between Arctic climate and sea ice. (C) 2010 Elsevier Ltd. All rights reserved.

  • 11. Jakobsson, Martin
    et al.
    Mayer, Larry
    Coakley, Bernard
    Dowdeswell, Julian A.
    Forbes, Steve
    Fridman, Boris
    Hodnesdal, Hanne
    Noormets, Riko
    Pedersen, Richard
    Rebesco, Michele
    Schenke, Hans Werner
    Zarayskaya, Yulia
    Accettella, Daniela
    Armstrong, Andrew
    Anderson, Robert M.
    Bienhoff, Paul
    Camerlenghi, Angelo
    Church, Ian
    Edwards, Margo
    Gardner, James V.
    Hall, John K.
    Hell, Benjamin
    Hestvik, Ole
    Kristoffersen, Yngve
    Marcussen, Christian
    Mohammad, Rezwan
    Mosher, David
    Nghiem, Son V.
    Teresa Pedrosa, Maria
    Travaglini, Paola G.
    Weatherall, Pauline
    The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.02012In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 39, article id L12609Article in journal (Refereed)
    Abstract [en]

    The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded bathymetric compilation in 1999. The IBCAO bathymetric portrayals have since supported a wide range of Arctic science activities, for example, by providing constraint for ocean circulation models and the means to define and formulate hypotheses about the geologic origin of Arctic undersea features. IBCAO Version 3.0 represents the largest improvement since 1999 taking advantage of new data sets collected by the circum-Arctic nations, opportunistic data collected from fishing vessels, data acquired from US Navy submarines and from research ships of various nations. Built using an improved gridding algorithm, this new grid is on a 500 meter spacing, revealing much greater details of the Arctic seafloor than IBCAO Version 1.0 (2.5 km) and Version 2.0 (2.0 km). The area covered by multibeam surveys has increased from similar to 6% in Version 2.0 to similar to 11% in Version 3.0. Citation: Jakobsson, M., et al. (2012), The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 3.0, Geophys. Res. Lett., 39, L12609, doi:10.1029/2012GL052219.

  • 12. Jakobsson, Martin
    et al.
    Nilsson, Johan
    Anderson, Leif
    Backman, Jan
    Bjork, Goran
    Cronin, Thomas M.
    Kirchner, Nina
    Koshurnikov, Andrey
    Mayer, Larry
    Noormets, Riko
    O'Regan, Matthew
    Stranne, Christian
    Ananiev, Roman
    Macho, Natalia Barrientos
    Cherniykh, Denis
    Coxall, Helen
    Eriksson, Bjorn
    Floden, Tom
    Gemery, Laura
    Gustafsson, Orjan
    Jerram, Kevin
    Johansson, Carina
    Khortov, Alexey
    Mohammad, Rezwan
    Semiletov, Igor
    Evidence for an ice shelf covering the central Arctic Ocean during the penultimate glaciation2016In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 10365Article in journal (Refereed)
    Abstract [en]

    The hypothesis of a km-thick ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of ice shelves should, however, exist where ice grounded along their flow paths. Here we present new evidence of ice-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an ice shelf extending over the entire central Arctic Ocean during at least one previous ice age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions41-km thick, central Arctic Ocean ice shelf dated to marine isotope stage 6 (similar to 140 ka). Bathymetric highs were likely critical in the ice-shelf development by acting as pinning points where stabilizing ice rises formed, thereby providing sufficient back stress to allow ice shelf thickening.

  • 13.
    Jakobsson, Martin
    et al.
    Stockholm Univ, Dept Geol & Geochem, SE-10691 Stockholm, Sweden..
    Spielhagen, Robert F.
    Acad Sci Human & Literature, DE-55131 Mainz, Germany.;Univ Kiel, Leibniz Inst Marine Sci, DE-24148 Kiel, Germany..
    Thiede, Joern
    Alfred Wegener Inst Polar & Marine Res, DE-27568 Bremerhaven, Germany.;Univ Copenhagen, Dept Geog & Geol, DK-1350 Copenhagen, Denmark..
    Andreasen, Claus
    Greenland Natl Museum & Archives, DK-3900 Nuuk, Greenland..
    Hall, Brenda
    Univ Maine, Bryand Global Sci Ctr, Dept Earth Sci, Orono, ME 04469 USA.;Univ Maine, Climate Change Inst, Orono, ME 04469 USA..
    Ingolfsson, Olafur
    Univ Iceland, Dept Earth Sci, IS-101 Reykjavik, Iceland..
    Kjaer, Kurt H.
    Univ Copenhagen, Nat Hist Museum, DK-1350 Copenhagen K, Denmark..
    van Kolfschoten, Thijs
    Leiden Univ, Fac Archaeol, NL-2311 BE Leiden, Netherlands..
    Krinner, Gerhard
    Natl Ctr Sci Res, Lab Glaciol & Geophys Environm, FR-38402 St Martin Dheres, France..
    Long, Antony
    Univ Durham, Dept Geog, Durham DH1 3LE, England..
    Lunkka, Juha-Pekka
    Univ Oulu, Inst Geosci, FI-90014 Oulu, Finland..
    Subetto, Dmitry
    Alexander Herzen State Pedag Univ Russia, Dept Geog, RU-191186 St Petersburg, Russia..
    Svendsen, John Inge
    Univ Bergen, Dept Earth Sci, NO-5007 Bergen, Norway.;Univ Bergen, Bjerknes Ctr Climate Res, NO-5007 Bergen, Norway..
    Foreword to the special issue: Arctic Palaeoclimate and its Extremes (APEX)2008In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 27, no 2, p. 97-104Article in journal (Other academic)
  • 14.
    Kaufman, Darrell S.
    et al.
    No Arizona Univ, Sch Earth Sci & Environm Sustainabil, Flagstaff, AZ 86011 USA..
    Cooper, Katherine
    No Arizona Univ, Sch Earth Sci & Environm Sustainabil, Flagstaff, AZ 86011 USA..
    Behl, Richard
    Calif State Univ Long Beach, Dept Geol Sci, Long Beach, CA 90840 USA..
    Billups, Katharina
    Univ Delaware, Sch Marine Sci & Policy, Lewes, DE 19958 USA..
    Bright, Jordon
    Univ Arizona, Dept Geosci, Tucson, AZ 85721 USA..
    Gardner, Karleen
    No Arizona Univ, Sch Earth Sci & Environm Sustainabil, Flagstaff, AZ 86011 USA..
    Hearty, Paul
    Univ N Carolina, Dept Environm Studies, Wilmington, NC 28403 USA..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Mendes, Isabel
    Univ Algarve, CIMA, P-8005139 Faro, Portugal..
    O'Leary, Michael
    Curtin Univ, Dept Environm & Agr, Bentley, WA 6102, Australia..
    Polyak, Leonid
    Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA..
    Rasmussen, Tine
    Univ Tromso, Dept Geol, Tromso, Norway..
    Rosa, Francisca
    Univ Algarve, CIMA, P-8005139 Faro, Portugal..
    Schmidt, Matthew
    No Arizona Univ, Sch Earth Sci & Environm Sustainabil, Flagstaff, AZ 86011 USA..
    Amino acid racemization in mono-specific foraminifera from Quaternary deep-sea sediments2013In: Quaternary Geochronology, ISSN 1871-1014, E-ISSN 1878-0350, Vol. 16, p. 50-61Article in journal (Refereed)
    Abstract [en]

    The deep-sea environment is among the most stable on Earth, making it well suited for amino acid geochronology. Foraminifera with calcareous tests are distributed across the World Ocean and are often recovered in sufficient abundance from sediment cores to derive robust mean amino acid D/L values of multiple replicates from each stratigraphic level. The extent of racemization (D/L) can be compared with independent age control, which in most cases is based on correlation with global marine oxygen-isotope stages and radiocarbon ages from the same stratigraphic levels. In this study, we report the results of amino acid racemization analysis of multiple foraminifera species from well-dated sediment cores taken from the Pacific, Atlantic, and Arctic oceans. The composite of results analyzed to date (179 samples, each composed of an average of 8.6 subsamples = 1531 analyses) show that D/L values generally increase systematically down core, and are similar for samples of comparable ages from different deep-sea sites. Previously published equations that relate D/L values of aspartic and glutamic acids to post-depositional temperature and sample age for Pulleniatina obliquiloculata generally conform to the D/L trends for species analyzed in this study. Laboratory heating experiments were used to quantify the difference in the rate of racemization between P. obliquiloculata and other taxa. For example, aspartic acid in P. obliquiloculata racemizes an average of 12-16% faster than in the common high-latitude species, Neogloboquadrina pachyderma (s). Apparently, the unexpectedly high D/L values previously reported for N. pachyderma (s) older than 35 lea from the Arctic Ocean cannot be attributed to taxonomic effects. (C) 2012 Elsevier B.V. All rights reserved.

  • 15.
    Kirchner, Nina
    et al.
    Stockholm Univ, Dept Phys Geog & Quaternary Geol, S-10691 Stockholm, Sweden..
    Hutter, Kolumban
    Swiss Fed Inst Technol, Lab Hydraul Hydrol & Glaciol, CH-8092 Zurich, Switzerland..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Gyllencreutz, Richard
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Capabilities and limitations of numerical ice sheet models: a discussion for Earth-scientists and modelers2011In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 30, no 25-26, p. 3691-3704Article in journal (Refereed)
    Abstract [en]

    The simulation of dynamically coupled ice sheet, ice stream, and ice shelf-systems poses a challenge to most numerical ice sheet models. Here we review present ice sheet model limitations targeting a broader audience within Earth Sciences, also those with no specific background in numerical modeling, in order to facilitate cross-disciplinary communication between especially paleoglaciologists, marine and terrestrial geologists, and numerical modelers. The 'zero order' (Shallow Ice Approximation, SIA)-, 'higher order'-, and 'full Stokes' ice sheet models are described conceptually and complemented by an outline of their derivations. We demonstrate that higher order models are required to simulate coupled ice sheet-ice shelf and ice sheet-ice stream systems, in particular if the results are aimed to complement spatial ice flow reconstructions based on higher resolution geological and geophysical data. The zero order SIA model limitations in capturing ice stream behavior are here illustrated by conceptual simulations of a glaciation on Svalbard. The limitations are obvious from the equations comprising a zero order model. However, under certain circumstances, simulation results may falsely give the impression that ice streams indeed are simulated with a zero order SIA model. (C) 2011 Elsevier Ltd. All rights reserved.

  • 16.
    Kirshner, Alexandra E.
    et al.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Anderson, John B.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    O'Regan, Matthew
    Cardiff Univ, Sch Earth & Ocean Sci, Cardiff, S Glam, Wales..
    Majewski, Wojciech
    Polish Acad Sci, Inst Paleobiol, PL-00818 Warsaw, Poland..
    Nitsche, Frank O.
    Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA..
    Post-LGM deglaciation in Pine Island Bay, West Antarctica2012In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 38, p. 11-26Article in journal (Refereed)
    Abstract [en]

    To date, understanding of ice sheet retreat within Pine Island Bay (PIB) following the Last Glacial Maximum (LGM) was based on seven radiocarbon dates and only fragmentary seafloor geomorphic evidence. During the austral summer 2009-2010, restricted sea ice cover allowed for the collection of 27 sediment cores from the outer PIB trough region. Combining these cores with data from prior cruises, over 133 cores have been used to conduct a detailed sedimentological facies analysis. These results, augmented by 23 new radiocarbon dates, are used to reconstruct the post-LGM deglacial history of PIB. Our results record a clear retreat stratigraphy in PIB composed of, from top to base; terrigenous sandy silt (distal glacimarine), pebbly sandy mud (ice-proximal glacimarine), and till. Initial retreat from the outer-continental shelf began shortly after the LGM and before 16.4 k cal yr BP, as a likely response to rising sea level. Bedforms in outer PIB document episodic retreat in the form of back-stepping grounding zone wedges and are associated with proximal glacimarine sediments. A sub-ice shelf facies is observed in central PIB and spans similar to 12.3-10.6 k cal yr BR It is possible that widespread impingement of warm water onto the continental shelf caused an abrupt and widespread change from sub-ice shelf sedimentation to distal glacimarine sedimentation dominated by widespread dispersal of terrigenous silt between 7.8 and 7.0 k cal yr BP. The final phase of retreat ended before similar to 1.3 k cal yr BP, when the grounding line migrated to a location near the current ice margin. (C) 2012 Elsevier Ltd. All rights reserved.

  • 17.
    Lachner, Johannes
    et al.
    Swiss Fed Inst Technol, Lab Ion Beam Phys, Zurich, Switzerland..
    Christl, Marcus
    Swiss Fed Inst Technol, Lab Ion Beam Phys, Zurich, Switzerland..
    Synal, Hans-Arno
    Swiss Fed Inst Technol, Lab Ion Beam Phys, Zurich, Switzerland..
    Frank, Martin
    CAU Kiel, IFM Geomar, Kiel, Germany..
    Jakobsson, Martin
    Univ Stockholm, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Carrier free Be-10/Be-9 measurements with low-energy AMS: Determination of sedimentation rates in the Arctic Ocean2013In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 294, p. 67-71Article in journal (Refereed)
    Abstract [en]

    Using the TANDY AMS facility (600 kV) at ETH Zurich the seawater-derived (authigenic) Be-10/Be-9 ratio of marine sediment samples is measured without the addition of Be-9 carrier. This novel method reduces systematic uncertainties because the Be-10/Be-9 ratio of a sample is determined in only one (AMS) measurement. A challenge of carrier-free AMS is to avoid any contamination of the sample with Be-9 during the chemical preparation. Further, the leaching procedure has to be reproducible and ideally should attack the authigenic Be of the sediments only, leaving the detrital Be untouched. The low amount of stable Be-9 in the unspiked samples causes low currents during the AMS measurement. This requires a good stability and sensitivity of the AMS setup. Our first results show that the new preparation method is reliable and that background from stable Be-9 is avoided. For a comparison study, sediment samples from two cores located in the Arctic Ocean (HLY0503-09JPC, HLY0503-14JPC) were used. The authigenic Be-10/Be-9 ratio of these samples had been determined previously applying the conventional method where Be-10 and Be-9 concentrations are measured separately by AMS and ICP-MS, respectively. The resulting sedimentation rates are in discrepancy with values derived from biomarkers. To cross check the Be-10/Be-9 based age model two samples from each core were measured again with the new carrier-free method. The carrier-free results show systematically higher authigenic Be-10/Be-9 ratios. The calculated sedimentation rates of about 0.2 cm/kyr, however, are consistent for the carrier free and the conventional method. (C) 2012 Elsevier B.V. All rights reserved.

  • 18.
    Larter, Robert D.
    et al.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Anderson, John B.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Graham, Alastair G. C.
    British Antarctic Survey, Cambridge CB3 0ET, England.;Univ Exeter, Coll Life & Environm Sci, Exeter EX4 4RJ, Devon, England..
    Gohl, Karsten
    Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, D-27568 Bremerhaven, Germany..
    Hillenbrand, Claus-Dieter
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Johnson, Joanne S.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Kuhn, Gerhard
    Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, D-27568 Bremerhaven, Germany..
    Nitsche, Frank O.
    Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY USA..
    Smith, James A.
    British Antarctic Survey, Cambridge CB3 0ET, England..
    Witus, Alexandra E.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Bentley, Michael J.
    Univ Durham, Dept Geog, Durham DH1 3LE, England..
    Dowdeswell, Julian A.
    Univ Cambridge, Scott Polar Res Inst, Cambridge CB2 1ER, England..
    Ehrmann, Werner
    Univ Leipzig, Inst Geol & Geophys, D-04103 Leipzig, Germany..
    Klages, Johann P.
    Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, D-27568 Bremerhaven, Germany..
    Lindow, Julia
    Univ Bremen, Dept Geosci, D-28359 Bremen, Germany..
    Cofaigh, Colm O.
    Univ Durham, Dept Geog, Durham DH1 3LE, England..
    Spiegel, Cornelia
    Univ Bremen, Dept Geosci, D-28359 Bremen, Germany..
    Reconstruction of changes in the Amundsen Sea and Bellingshausen Sea sector of the West Antarctic Ice Sheet since the Last Glacial Maximum2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 100, p. 55-86Article in journal (Other academic)
    Abstract [en]

    Marine and terrestrial geological and marine geophysical data that constrain deglaciation since the Last Glacial Maximum (LGM) of the sector of the West Antarctic Ice Sheet (WAIS) draining into the Amundsen Sea and Bellingshausen Sea have been collated and used as the basis for a set of time-slice reconstructions. The drainage basins in these sectors constitute a little more than one-quarter of the area of the WAIS, but account for about one-third of its surface accumulation. Their mass balance is becoming increasingly negative, and therefore they account for an even larger fraction of current WAIS discharge. If all of the ice in these sectors of the WAIS were discharged to the ocean, global sea level would rise by ca 2 m. There is compelling evidence that grounding lines of palaeo-ice streams were at, or close to, the continental shelf edge along the Amundsen Sea and Bellingshausen Sea margins during the last glacial period. However, the few cosmogenic surface exposure ages and ice core data available from the interior of West Antarctica indicate that ice surface elevations there have changed little since the LGM. In the few areas from which cosmogenic surface exposure ages have been determined near the margin of the ice sheet, they generally suggest that there has been a gradual decrease in ice surface elevation since pre-Holocene times. Radiocarbon dates from glacimarine and the earliest seasonally open marine sediments in continental shelf cores that have been interpreted as providing approximate ages for post-LGM grounding-line retreat indicate different trajectories of palaeo-ice stream recession in the Amundsen Sea and Bellingshausen Sea embayments. The areas were probably subject to similar oceanic, atmospheric and eustatic forcing, in which case the differences are probably largely a consequence of how topographic and geological factors have affected ice flow, and of topographic influences on snow accumulation and warm water inflow across the continental shelf. Pauses in ice retreat are recorded where there are "bottle necks" in cross-shelf troughs in both embayments. The highest retreat rates presently constrained by radiocarbon dates from sediment cores are found where the grounding line retreated across deep basins on the inner shelf in the Amundsen Sea, which is consistent with the marine ice sheet instability hypothesis. Deglacial ages from the Amundsen Sea Embayment (ASE) and Eltanin Bay (southern Bellingshausen Sea) indicate that the ice sheet had already retreated close to its modern limits by early Holocene time, which suggests that the rapid ice thinning, flow acceleration, and grounding line retreat observed in this sector over recent decades are unusual in the context of the past 10,000 years. (C) 2014 The Authors. Published by Elsevier Ltd. All rights reserved.

  • 19.
    O'Regan, Matthew
    et al.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Kirchner, Nina
    Stockholm Univ, Dept Phys Geog & Quaternary Geol, S-10691 Stockholm, Sweden..
    Glacial geological implications of overconsolidated sediments on the Lomonosov Ridge and Yermak Plateau2010In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, no 25-26, p. 3532-3544Article in journal (Refereed)
    Abstract [en]

    With the coupled use of multibeam swath bathymetry, high-resolution subbottom profiling and sediment coring from icebreakers in the Arctic Ocean, there is a growing awareness of the prevalence of Quaternary ice-grounding events on many of the topographic highs found in present water depths of <1000 m. In some regions, such as the Lomonosov Ridge and Yermak Plateau, overconsolidated sediments sampled through either drilling or coring are found beneath seismically imaged unconformities of glacigenic origin. However, there exists no comprehensive analysis of the geotechnical properties of these sediments, or how their inferred stress state may be related to different glacigenic processes or types of ice-loading. Here we combine geophysical, stratigraphic and geotechnical measurements from the Lomonosov Ridge and Yermak Plateau and discuss the glacial geological implications of overconsolidated sediments. The degree of overconsolidation, determined from measurements of porosity and shear strength, is shown to result from consolidation and/or deformation below grounded ice and, with the exception of a single region on the Lomonosov Ridge, cannot be explained by erosion of overlying sediments. We demonstrate that the amount and depth of porosity loss associated with a middle Quaternary (similar to 790-950 thousand years ago - ka) grounding on the Yermak Plateau is compatible with sediment consolidation under an ice sheet or ice rise. Conversely, geotechnical properties of sediments from beneath late Quaternary ice-groundings in both regions, independently dated to Marine Isotope Stage (MIS) 6, indicate a more transient event commensurate with a passing tabular iceberg calved from an ice shelf. (C) 2010 Elsevier Ltd. All rights reserved.

  • 20.
    O'Regan, Matthew
    et al.
    Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA.;Univ Rhode Isl, Dept Ocean Engn, Narragansett, RI 02882 USA..
    St John, Kristen
    James Madison Univ, Dept Geol & Environm Sci, Harrisonburg, VA 22807 USA..
    Moran, Kathryn
    Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA.;Univ Rhode Isl, Dept Ocean Engn, Narragansett, RI 02882 USA..
    Backman, Jan
    Stockholm Univ, Dept Geol & Geochem, S-10691 Stockholm, Sweden..
    King, John
    Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA.;Univ Rhode Isl, Dept Ocean Engn, Narragansett, RI 02882 USA..
    Haley, Brian A.
    Leibniz Inst Marine Sci, IFM GEOMAR, D-24105 Kiel, Germany..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol & Geochem, S-10691 Stockholm, Sweden..
    Frank, Martin
    Leibniz Inst Marine Sci, IFM GEOMAR, D-24105 Kiel, Germany..
    Roehl, Ursula
    Univ Bremen, Ctr Marine Environm Sci, Bremen, Germany..
    Plio-Pleistocene trends in ice rafted debris on the Lomonosov Ridge2010In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 219, no 1-2, p. 168-176Article in journal (Refereed)
    Abstract [en]

    Although more than 700 sediment cores exist from the Arctic Ocean, the Plio-Pleistocene evolution of the basin and its marginal seas remains virtually unknown. This is largely due the shallow penetration of most of these records, and difficulties associated with deriving chronologies for the recovered material. The Integrated Ocean Drilling Program's (IODP) Expedition 302 (Arctic Coring Expedition, ACEX) recovered 197 m of Neogene/Quaternary sediment from the circumpolar regions of the Lomonosov Ridge. As detailed analyses of this material emerge, research is beginning to formulate a long-term picture of paleoceanographic changes in the central Arctic Ocean. This paper reviews the ACEX Plio-Pleistocene age model, identifies uncertainties, and addresses ways in which these may be eliminated. Within the established stratigraphic framework, a notable reduction in the abundance of ice rafted debris (IRD) occurs in the early part of the Pleistocene and persists until Marine Isotope Stage 6 (MIS 6). Therefore, while global oceanographic proxies indicate the gradual growth of terrestrial ice-sheets during this time, IRD delivery to the central Arctic Ocean remained comparatively low and stable. Within the resolution of existing data, the Pleistocene reduction in IRD is synchronous with predicted changes in both the inflow of North Atlantic and Pacific waters, which in modern times are known to exert a strong influence on sea ice stability. (C) 2009 Elsevier Ltd and INQUA. All rights reserved.

  • 21.
    O'Regan, Matthew
    et al.
    Cardiff Univ, Sch Earth & Ocean Sci, Cardiff, S Glam, Wales..
    Williams, Christopher J.
    Franklin & Marshall Coll, Dept Earth & Environm, Lancaster, PA 17604 USA..
    Frey, Karen E.
    Clark Univ, Grad Sch Geog, Worcester, MA 01610 USA..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, Stockholm, Sweden..
    A Synthesis of the Long-Term Paleoclimatic Evolution of the Arctic2011In: Oceanography, ISSN 1042-8275, Vol. 24, no 3, p. 66-80Article in journal (Refereed)
    Abstract [en]

    Since the Arctic Ocean began forming in the Early Cretaceous 112-140 million years ago, the Arctic region has undergone profound oceanographic and paleoclimatic changes. It has evolved from a warm epicontinental sea to its modern state as a cold isolated ocean with extensive perennial sea ice cover. Our understanding of the long-term paleoclimate evolution of the Arctic remains fragmentary but has advanced dramatically in the past decade through analysis of new marine and terrestrial records, supplemented by important insights from paleoclimate models. Improved understanding of how these observations fit into the long-term evolution of the global climate system requires additional scientific drilling in the Arctic to provide detailed and continuous paleoclimate records, and to resolve the timing and impact of key tectonic and physiographic changes to the ocean basin and surrounding landmasses. Here, we outline the long-term paleoclimatic evolution of the Arctic, with a focus on integrating both terrestrial and marine records.

  • 22.
    Sohn, Robert A.
    et al.
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Willis, Claire
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Humphris, Susan
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Shank, Timothy M.
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Singh, Hanumant
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Edmonds, Henrietta N.
    Univ Texas Austin, Inst Marine Sci, Port Aransas, TX 78373 USA..
    Kunz, Clayton
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Hedman, Ulf
    Swedish Polar Secretariat, S-10405 Stockholm, Sweden..
    Helmke, Elisabeth
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Jakuba, Michael
    Johns Hopkins Univ, Baltimore, MD 21218 USA..
    Liljebladh, Bengt
    Univ Gothenburg, S-40530 Gothenburg, Sweden..
    Linder, Julia
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Murphy, Christopher
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Nakamura, Ko-ichi
    AIST, Higashi, Tokyo, Japan..
    Sato, Taichi
    Univ Tokyo, Ocean Res Inst, Tokyo 1648639, Japan..
    Schlindwein, Vera
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Stranne, Christian
    Univ Gothenburg, S-40530 Gothenburg, Sweden..
    Tausenfreund, Maria
    Alfred Wegener Inst Polar & Marine Res, D-27570 Bremerhaven, Germany..
    Upchurch, Lucia
    Univ Texas Austin, Inst Marine Sci, Port Aransas, TX 78373 USA..
    Winsor, Peter
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol & Geochem, S-10691 Stockholm, Sweden..
    Soule, Adam
    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA..
    Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean2008In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 453, no 7199, p. 1236-1238Article in journal (Refereed)
    Abstract [en]

    Roughly 60% of the Earth's outer surface is composed of oceanic crust formed by volcanic processes at mid- ocean ridges. Although only a small fraction of this vast volcanic terrain has been visually surveyed or sampled, the available evidence suggests that explosive eruptions are rare on mid- ocean ridges, particularly at depths below the critical point for seawater ( 3,000 m)(1). A pyroclastic deposit has never been observed on the sea floor below 3,000 m, presumably because the volatile content of mid- ocean- ridge basalts is generally too low to produce the gas fractions required for fragmenting a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel ridge in the Arctic Basin at 856 E, to acquire photographic and video images of 'zero- age' volcanic terrain on this remote, ice- covered ridge. Here we present images revealing that the axial valley at 4,000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele)(2), covering a large ( > 10 km(2)) area. At least 13.5 wt% CO(2) is necessary to fragment magma at these depths(3), which is about tenfold the highest values previously measured in a mid- ocean- ridge basalt(4). These observations raise important questions about the accumulation and discharge of magmatic volatiles at ultraslow spreading rates on the Gakkel ridge(5) and demonstrate that large- scale pyroclastic activity is possible along even the deepest portions of the global mid- ocean ridge volcanic system.

  • 23.
    Stranne, Christian
    et al.
    Univ Gothenburg, Dept Earth Sci, S-41320 Gothenburg, Sweden..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Bjork, Goran
    Univ Gothenburg, Dept Earth Sci, S-41320 Gothenburg, Sweden..
    Arctic Ocean perennial sea ice breakdown during the Early Holocene Insolation Maximum2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 92, p. 123-132Article in journal (Refereed)
    Abstract [en]

    Arctic Ocean sea ice proxies generally suggest a reduction in sea ice during parts of the early and middle Holocene (similar to 6000-10,000 years BP) compared to present day conditions. This sea ice minimum has been attributed to the northern hemisphere Early Holocene Insolation Maximum (EHIM) associated with Earth's orbital cycles. Here we investigate the transient effect of insolation variations during the final part of the last glaciation and the Holocene by means of continuous climate simulations with the coupled atmosphere sea ice ocean column model CCAM. We show that the increased insolation during EHIM has the potential to push the Arctic Ocean sea ice cover into a regime dominated by seasonal ice, i.e. ice free summers. The strong sea ice thickness response is caused by the positive sea ice albedo feedback. Studies of the GRIP ice cores and high latitude North Atlantic sediment cores show that the Bolling Allerod period (c. 12,700-14,700 years BP) was a climatically unstable period in the northern high latitudes and we speculate that this instability may be linked to dual stability modes of the Arctic sea ice cover characterized by e.g. transitions between periods with and without perennial sea ice cover. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

  • 24.
    Thompson, Bijoy
    et al.
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Nycander, Jonas
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden..
    Nilsson, Johan
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Doos, Kristofer
    Stockholm Univ, Dept Meteorol, S-10691 Stockholm, Sweden..
    Estimating ventilation time scales using overturning stream functions2014In: Ocean Dynamics, ISSN 1616-7341, E-ISSN 1616-7228, Vol. 64, no 6, p. 797-807Article in journal (Refereed)
    Abstract [en]

    A simple method for estimating ventilation time scales from overturning stream functions is proposed. The stream function may be computed using either geometric coordinates or a generalized vertical coordinate, such as potential density (salinity in our study). The method is tested with a three-dimensional circulation model describing an idealized semi-enclosed ocean basin ventilated through a narrow strait over a sill, and the result is compared to age estimates obtained from a passive numerical age tracer. The best result is obtained when using the stream function in salinity coordinates. In this case, the reservoir-averaged advection time obtained from the overturning stream function in salinity coordinates agrees rather well with the mean age of the age tracer, and the corresponding maximum ages agree very well.

  • 25.
    Witus, Alexandra E.
    et al.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Branecky, Carolyn M.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Anderson, John B.
    Rice Univ, Dept Earth Sci, Houston, TX 77005 USA..
    Szczucinski, Witold
    Adam Mickiewicz Univ, Inst Geol, PL-61606 Poznan, Poland..
    Schroeder, Dustin M.
    Univ Texas Austin, Inst Geophys, Austin, TX USA..
    Blankenship, Donald D.
    Univ Texas Austin, Inst Geophys, Austin, TX USA..
    Jakobsson, Martin
    Stockholm Univ, Dept Geol Sci, S-10691 Stockholm, Sweden..
    Meltwater intensive glacial retreat in polar environments and investigation of associated sediments: example from Pine Island Bay, West Antarctica2014In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 85, p. 99-118Article in journal (Refereed)
    Abstract [en]

    Modern Pine Island and Thwaites Glaciers, which both drain into Pine Island Bay, are among the fastest changing portions of the cryosphere and the least stable ice streams in Antarctica. Here we show that the uppermost sediment unit in Pine Island Bay was deposited from a meltwater plume, a plumite, during the late stages of ice sheet retreat similar to 7-8.6 k cal yr BP and argue that this deposit records episodes of meltwater intensive sedimentation. The plumite is a hydraulically sorted, glacially sourced, draping deposit that overlies proximal glaci-marine sediments and thickens towards the modern grounding line. The uppermost sediment unit is interpreted as a product of non-steady-state processes in which low background sedimentation in large bedrock-carved basins alternates with episodic purging of sediment-laden water from these basins. The inner part of Pine Island Bay contains several basins that are linked by channels with a storage capacity on the order of 70 km(3) of stagnant water and significant sediment storage capacity. Purging of these basins is caused by changes in hydraulic potential and glacial reorganization. The sediment mobilized by these processes is found here to total 120 km3. This study demonstrates that episodes of meltwater-intensive sedimentation in Pine Island Bay occurred at least three times in the Holocene. The most recent episode coincides with rapid retreat of the grounding line in historical time and has an order of magnitude greater flux relative to the entire unit. We note that the final phase of ice stream retreat in Marguerite Bay was marked by a similar sedimentary event and suggest that the modern Thwaites Glacier is poised for an analogous meltwater-intensive phase of retreat. (C) 2013 Elsevier Ltd. All rights reserved.

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