Deglacial Chronology of the Northern Scott Coast from Relative Sea-Level Curves

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9909104 HallThis award provides support for three years for a project to develop a radiocarbon chronology for recession of grounded ice from the northwestern Ross Sea Embayment (northern Scott Coast) since the Last Glacial Maximum (LGM). A key unresolved question in Antarctic glaciology concerns the stability of the marine-based West Antarctic ice sheet (WAIS). One way to gain insight into present and future stability is to examine its past behavior. In particular, the timing of deglaciation from the LGM position on the continental shelf is critical for isolating the mechanisms (sea level, climate, ocean temperature, and internal dynamics) that control WAIS dynamics. The northern Scott Coast was likely the first area to become free of grounded ice and hence is critical for isolating triggering mechanisms. Initial retreat from the Ross Sea Embayment was thought to have begun as early as 17,000 years ago; corresponding to the rise in sea level see in the Barbados coral record. In contrast, recent glacial geologic mapping and relative sea-level work from the southern Scott Coast suggests that deglaciation of the Ross Sea Embayment was a Holocene event, with southward grounding-line migration past Ross Island shortly before 6500 14C yr. B.P. This chronology suggests that rising sea level could not have driven grounding-line retreat to the Siple Coast, because deglacial sea-level rise essentially was accomplished by mid-Holocene. One deficiency in the southern Scott Coast work is that it cannot differentiate among the possible triggering mechanisms that initiated retreat because it is 450 km from the LGM grounding-line position. In this project, relative sea level (RSL) curves will be constructed on a transect along the northern Scott Coast from accelerator mass spectrometer 14C dates of seal skin and shells within raised beaches. These curves will provide information concerning the timing of the uploading of grounded ice from the northwestern Ross Sea Embayment. This study should help to evaluate those factors which could have triggered deglaciation and hence controlled the extent of the West Antarctic ice sheet (WAIS).