Pre-Holocene to recent deglaciation of the Amundsen Sea Embayment, West Antarctica

gerhard.kuhn [ at ]


Ice loss from the marine-based, inherently unstable West Antarctic Ice Sheet (WAIS) contributes to the currently observed rise in sea-level and may raise it by up to 3.3-5 metres in the future. Over the last few decades, glaciers draining the WAIS into the Amundsen Sea Embayment (ASE), in particular into Pine Island Bay, have shown thinning, grounding-line retreat and ice-flow acceleration at dramatic rates. These changes are mainly attributed to significant ice-shelf melting by upwelling warm deep water. A critical unknown, limiting our ability to accurately predict future WAIS behaviour, is the poorly constrained long-term context of ice-sheet retreat in the ASE. Here we present a new pre-Holocene to present chronology for WAIS retreat in Pine Island Bay (PIB) based on radiocarbon dating of marine sediment cores. The dates give evidence that grounded ice had retreated close to its modern-day position by ~10 ka BP. Maximum average retreat rates calculated from the deglaciation ages suggest, that the current rapid WAIS retreat in Pine Island Bay is unprecedented over the last ~10 ka and originates in recent changes in regional climate, ocean circulation or ice-sheet dynamics. However, our data and previously published ages for grounding-line retreat from the wider ASE further demonstrate, that, other than in the Ross Sea, the WAIS did not retreat continuously since the LGM. A unique assemblage of glacial morphological features mapped on the eastern ASE shelf suggest a more complex deglacial history, with ice masses slowly flowing and/or stagnating on topographic highs (’Inter-ice stream ridges’) adjacent to main palaeo-ice stream troughs. The incorporation of our results into ice-sheet models will improve predictions of future sea-level rise.

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Conference (Poster)
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Event Details
Planet Under Pressure 2012, 26 Mar 2012 - 29 Mar 2012, London, England.
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Kuhn, G. , Hillenbrand, C. D. , Klages, J. P. , Smith, J. A. , Graham, A. G. C. , Larter, R. D. and Gohl, K. (2012): Pre-Holocene to recent deglaciation of the Amundsen Sea Embayment, West Antarctica , Planet Under Pressure 2012, London, England, 26 March 2012 - 29 March 2012 .

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