Impact of paleoclimatic and paleoceanographic changes on the stability of the late Miocene to present West Antarctic Ice Sheet

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West Antarctica is the fastest melting region of the Antarctic continent and the West Antarctic Ice Sheet (WAIS) currently contributes about 90% to the total ice loss. The unique geological setting with a landward dipping shelf in combination with the upwelling of warm circumpolar deep water (CDW) that is trapped below the ice sheet, which is grounded several hundred meters below sea level, results in increased basal melting and is considered primarily responsible for the rapidly accelerating ice loss observed in West Antarctica over the recent past. There is particular concern that this process - within two to three decades after initiation - is irreversible and will result in the partial to full collapse of the WAIS within the next centuries. Given that the WAIS holds about 10% of Antarctica’s ice volume, this will equal a global sea level rise of 3.3 to 4.3 m. While recent instrumental and satellite-derived observations clearly demonstrate that the WAIS is particularly vulnerable to rapid melting, proxy records that can be employed to (1) establish causal and temporal links between the upwelling of warm CDW and ice sheet melting and (2) ground truth model simulations of ice sheet advances and retreats under different climate scenarios are entirely missing from this most vulnerable region of our planet. Sediments recovered during IODP Expedition 379 "West Antarctic Ice Sheet History" can close this gap. They provide the first continuous and undisturbed sedimentary sequence, spanning the late Miocene to present, from the continental rise of the Amundsen Sea; an area that is most strongly affected by ice melting and key to investigate the WAIS history. The here proposed project will, for the first time, investigate the complex interplay between paleoclimatic and paleoceanographic changes in West Antarctica and their impetus for the ice sheet dynamic of the WAIS using a multi-proxy approach consisting of bulk-geochemical and lipid biomarker investigations that are complemented by the application of organic temperature proxies. Specifically, the project will establish the first long-term paleotemperature record from the West Antarctic (covering the past ~6.8 Ma), which will allow a differential comparison of West Antarctic climate variability with those of other Antarctic regions. Through high-resolution studies of intervals considered to have experienced a partial to full collapse of the WAIS, including the mid-Pliocene Warm Period and Marine Isotope Stage 31, the project will also provide first temporal constraints on the velocity and extent of ice sheet retreat in response to climate warming and/or the upwelling of CDW onto the Amundsen Sea shelf. The here proposed research will thus provide important new insights into the climate and ice sheet dynamics of an area of the Antarctic continent that is most susceptible for ice sheet loss but for which rates and magnitudes of ice loss are largely terra incognita.