Geochemical and geological evidence for a palaeo-subglacial lake in Pine Island Bay, Antarctica


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gerhard.kuhn [ at ] awi.de

Abstract

Subglacial meltwater facilitates rapid ice flow beneath concurrent ice sheets, and there is widespread evidence for a dynamic subglacial water system beneath the Antarctic ice sheet. It steers and affects the pattern of ice flow and is a direct result from boundary processes acting at the base of the ice sheet, i.e. pressure-induced basal melting. Consequently, the occurrence of subglacial meltwater plays an important role in bedrock erosion, subsequent resedimentation, and in shaping the topography of ice-sheet beds. Here we present new geological and geochemical data from sediments recovered on the West Antarctic continental shelf in Pine Island Bay that we interpret as reliable indicators for deposition in a palaeo-subglacial lake beneath the formerly expanded West Antarctic ice sheet, presumably during or following the Last Glacial Maximum. Characteristic changes of sedimentary facies and geochemical profiles within these cores taken on RV Polarstern expeditions ANTXXIII/ 4 (2006) and ANT-XXVI/3 (2010) support the presence of an active subglacial lake system during the late stages of the last glacial period. These findings have important implications for palaeo ice-sheet dynamics, suggesting there was considerable water available to lubricate the bedrock–ice interface and deposit water-saturated subglacial sediments (soft tills). Based on our investigations performed so far, we suggest that the transition from subglacial lake to contact with the ocean took place in the early Holocene. During this time we speculate that the ice sheet thinned and successively transformed into an ice shelf with sub-ice cavities flushed by tidal currents. Based on bathymetric maps and relative sealevel curves we will aim to estimate ice thickness as the grounding line retreated across the subglacial lake threshold further inland. Our findings may also have implications for ice-sheet models, which have to consider the predominantly non-linear effects related to subglacial hydrology.



Item Type
Conference (Talk)
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Primary Division
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Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
International Symposium on Hydrology of Glaciers and Ice Sheets, 21 Jun 2015 - 27 Jun 2015, Höfn, Island.
Eprint ID
38968
Cite as
Kuhn, G. , Hillenbrand, C. D. , Kasten, S. , Smith, J. A. , Nitsche, F. O. and Klages, J. P. (2015): Geochemical and geological evidence for a palaeo-subglacial lake in Pine Island Bay, Antarctica , International Symposium on Hydrology of Glaciers and Ice Sheets, Höfn, Island, 21 June 2015 - 27 June 2015 .


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