New marine geological and geophysical evidence for the extent, flow, and retreat of a West Antarctic palaeo-ice stream offshore from the Hobbs Coast

• Main Authors: Klages, Johann Philipp, Kuhn, Gerhard, Hillenbrand, Claus-Dieter, Graham, Alastair G. C., Smith, James A., Larter, Robert D., Gohl, Karsten
• Format: Conference Object
• Language: unknown
• Published: 2013
• Subjects: Amundsen Sea; Antarc*; Antarctic; Hobbs coast; Ice Sheet; Iceberg*
• Online Access: https://epic.awi.de/id/eprint/32217/; https://hdl.handle.net/10013/epic.40854

Palaeo-ice stream beds that are exposed today on polar continental shelves provide unique archives of conditions at the base of ice sheets that are difficult to assess beneath their modern counterparts. During the last decade, several of these palaeo-ice stream beds have been studied in detail to reconstruct the extent of the West Antarctic Ice Sheet (WAIS) at the Last Glacial Maximum (LGM), the patterns of ice drainage, and the timing of grounding-line retreat during the last deglaciation. However, despite significant advances, such information still remains poorly constrained in numerous drainage sectors of the WAIS. In particular, the maximum extent of ice at the LGM remains ambiguous for key drainage basins of the ice sheet. Whether the WAIS extended to the shelf break in the entire Pacific sector, or it advanced, at least locally, only to a middle or outer shelf position, is a crucial piece of information required for reconstructing and modeling patterns of ice-sheet change from past to present. Here we present new marine geological and geophysical data that we collected on R/V “Polarstern” expedition ANT-XXVI/3 in early 2010 to investigate the extent, flow, and retreat of the WAIS from an especially poorly studied part of the West Antarctic shelf, offshore from the Hobbs Coast in the western Amundsen Sea. Here, a landward deepening palaeo-ice stream trough is incised into the shelf. The seafloor within the western-central part of the trough is characterized by a large grounding zone wedge (GZW), ~70 m thick and ~17 km long, which overlies a high of seaward dipping sedimentary strata. Directly seaward of the GZW a ~20 km wide 80±10 m deep relatively flat basin is mapped. The back-slope of the GZW is characterized by highly elongate streamlined bedforms suggesting fast palaeo-ice flow towards NW. In contrast, the outer shelf seafloor offshore from the GZW is predominantly smooth, at numerous locations scoured by icebergs and characterized by a distinct and ~2 m-deep subbottom reflector. As in other Antarctic ...