Assessing the extent of the West Antarctic Ice Sheet on the eastern Amundsen Sea shelf during the last glacial period

• Main Authors: Klages, Johann Philipp, Kuhn, Gerhard, Hillenbrand, Claus-Dieter, Graham, Alastair G. C., Smith, James A., Nitsche, Frank O., Larter, Robert D., Gohl, Karsten, Wacker, Lukas
• Format: Conference Object
• Language: unknown
• Published: 2014
• Subjects: Amundsen Sea; Antarc*; Antarctic; Ice Sheet; Ice Shelf
• Online Access: https://epic.awi.de/id/eprint/37239/; https://epic.awi.de/id/eprint/37239/1/Poster_small.pdf; https://hdl.handle.net/10013/epic.44950; https://hdl.handle.net/10013/epic.44950.d001

High-resolution swath bathymetry data collected during several research cruises over the past two decades reveal a palaeo-ice stream trough (Abbot Glacial Trough) crossing the middle and outer shelf of the easternmost Amundsen Sea Embayment, east of the main Pine Island Trough. Regions of both fast palaeo-ice flow (within the central trough) and slow palaeo-ice flow (on adjacent seafloor highs referred to as inter-ice stream ridges) bear glacial landforms indicative of phases of grounding-line stabilization of the ice sheet. We associate a grounding-zone wedge situated within the outer Abbot Glacial Trough with a grounding-zone wedge in outer Pine Island Trough and suggest a synchronous grounding-line halt in both troughs. New sediment echosounder and sediment core data collected from outer Abbot Glacial Trough, between the seaward limit of the grounding-zone wedge and the shelf edge, reveal an up to 6 m-thick well stratified drape that is composed of unconsolidated glaciomarine sediments occasionally bearing calcareous microfossils. In order to decipher whether this unusually thick sediment drape might indicate sub-ice shelf and/or seasonal-open marine deposition throughout or since the Last Glacial Maximum, we used a multi-proxy approach to characterize its lithofacies and applied radiocarbon dating of calcareous microfossils. Here we present our initial results and discuss since when the outer shelf in the eastern Amundsen Sea has been free of grounded-ice. Such information will 1) improve ice sheet models that aim to reconstruct the flow and extent of the West Antarctic Ice Sheet during the Last Glacial Maximum, 2) help to quantify the ice volume of the West Antarctic Ice Sheet during this time, and 3) prove or reject the possibility that Antarctic benthic biota endured glacial periods in outer shelf refugia.