Late Neogene to Quaternary climate and ice sheet history of West Antarctica

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The West Antarctic Ice Sheet (WAIS) holds an ice volume of 2.2 million km3 and thereby contributes ~10% to the ice volume of Antarctica. Rates of mass loss from the WAIS have dramatically accelerated in the recent past and at present the WAIS is the fastest melting region of the Antarctic continent. Current estimates suggest that the WAIS contributed about 86% to the total ice mass loss of Antarctica over the last two decades and if melting continues at its present pace, it may lead to a global sea level rise by up to one meter until the end of this century. A complete collapse of the WAIS may result in a global sea level rise of up to 6 m. Model predictions indicate that such collapses may have occurred repeatedly since the late Miocene and unfold within a geologically relative short timespan of only several hundreds of years. Such model simulations also suggest that a threshold leading to the collapse of the WAIS may have been crossed already and that much of the ice sheet could be lost even under relatively moderate greenhouse gas emission scenarios. These model predictions, however, show large uncertainties in terms of timing and absolute volume of ice sheet loss. Proxy records that yield information on the past waxing and waning of the WAIS may help in improving our understanding on the future behaviour of this very vulnerable but globally important region of our planet. Such proxy records may specifically be used for constraining and testing ice sheet models that aim to predict future WAIS behaviour and the potential contribution of the WAIS to global sea level rise. Yet proxy records defining the deep time ice sheet history of the WAIS are largely lacking at present. Sediments obtained from the continental rise of the Amundsen Sea during IODP Expedition 379: “Amundsen Sea West Antarctic Ice Sheet History” provide the first continuous records of climate and ice sheet dynamics of the WAIS that date back to ~6.8 Ma and will allow reconstructing spatiotemporal variations of the ice sheet extent in an as yet unprecedented resolution. In the project proposed here, we plan to employ a multi-proxy approach, combining bulk-geochemical, isotope and lipid biomarker techniques, to investigate the response of the WAIS to changing environmental conditions and determine to which extent partial to full collapses of the WAIS have occurred previously and on which time scales. In particular, we aim to generate the first continuous late Miocene to Quaternary paleotemperature record for this region of the global oceans and test the hypothesis that the retreat of the ice sheet is directly controlled by incursions of relatively warm circumpolar deep water onto the West Antarctic shelf. In addition, we plan to determine the response of the aquatic and terrestrial ecosystems to advances and retreats of ice masses and explore whether these systems will act as sources or sinks of carbon under future scenarios of global warming.