Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment

• Published in: Quaternary Science Reviews
• Main Authors: Smith, James A., Hillenbrand, Claus-Dieter, Kuhn, Gerhard, Larter, Robert D., Graham, Alastair G.C., Ehrmann, Werner, Moreton, Steven G., Forwick, Matthias
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2011
• Subjects: Glaciology; Amundsen Sea; Antarctic; West Antarctic Ice Sheet; Antarc*; Ice Sheet; Iceberg*
• Online Access: http://nora.nerc.ac.uk/id/eprint/14112/; https://nora.nerc.ac.uk/id/eprint/14112/1/Smith_et_al__REVISION_JQSR-D-10-00259%2BSuppl_low_res.pdf

The Amundsen Sea Embayment (ASE) drains approximately 35% of the West Antarctic Ice Sheet (WAIS) and is one of the most rapidly changing parts of the cryosphere. In order to predict future ice sheet behaviour, modellers require long-term records of ice-sheet melting to constrain and build confidence in their simulations. Here, we present detailed marine geological and radiocarbon data along three palaeo-ice stream tributary troughs in the western ASE to establish vital information on the timing of deglaciation of the WAIS since the Last Glacial Maximum (LGM). We have undertaken multi-proxy analyses of the cores (core description, shear strength, x-radiographs, magnetic susceptibility, wet bulk density, total organic carbon/nitrogen, carbonate content and clay mineral analyses) in order to: (1) characterise the sedimentological facies and depositional environments; and (2) identify the horizon(s) in each core that would yield the most reliable age for deglaciation. In accordance with previous studies we identify three key facies, which offer the most reliable stratigraphies for dating deglaciation by recording the transition from a grounded ice sheet to open marine environments. These facies are: i) subglacial, ii) proximal grounding line, and iii) seasonal open marine. In addition, we incorporate ages from other facies (e.g., glaciomarine diamictons deposited at some distance from the grounding line, such as glaciogenic debris flows and iceberg-rafted diamictons and turbates) into our deglacial model. In total, we have dated 78 samples (mainly the acid insoluble organic (AIO) fraction, but also calcareous foraminifers), which include 63 downcore and 15 surface samples. Through careful sample selection prior to dating, we have established a robust deglacial chronology for this sector of the WAIS. Our data show that deglaciation of the western ASE was probably underway as early as 22,351 calibrated years before present (cal yr BP), reaching the mid-shelf by 13,837 cal yr BP and the inner shelf to within c.10-12 km ...