LGM ice sheet extent in the Weddell Sea: evidence for diachronous behavior of Antarctic Ice Sheets

Inaccessibility due to harsh weather conditions and perennial sea ice has resulted in the Weddell Sea being one of the more under-studied regions of Antarctica. Re-examination of existing cores and unpublished multibeam bathymetric data provide new insight into the LGM configuration of the ice sheet in the region. Sediment cores from the eastern continental shelf, where the East Antarctic Ice Sheet (EAIS) drains, display a retreat stratigraphy with distal glacimarine sediments overlying proximal glacimarine sediments and till. The distinction between distal and proximal glacimarine sediments is based on degrees of marine influence based on grain-size distributions and foraminiferal abundance and diversity. Glacimarine sediments yielded AMS radiocarbon ages that span the past 30,476 cal yr BP, indicating that retreat of the EAIS from the continental shelf occurred prior to the LGM. Multibeam swath bathymetry data show mega-scale glacial lineations in two troughs on the southern continental shelf, which indicates the existence of two ice streams draining the West Antarctic Ice Sheet (WAIS). More subtle lineations within Filchner Trough imply more sluggish flow across bedrock and older strata within this trough. Although there are no radiocarbon ages to absolutely constrain the timing of this grounding event on the southern continental shelf, we interpret the lineations as LGM age based on their pristine nature. This interpretation is consistent with results from other sectors of the West Antarctic continental shelf where compelling evidence for significant WAIS advance during the LGM exists. In the Weddell Sea, this apparent diachronous behavior of the EAIS and WAIS is consistent with results from onshore studies.

► Grounding line retreat in the Weddell Sea is constrained by radiocarbon dates.
► The East Antarctic Ice Sheet has not appreciably advanced in the last 30,000 years.
► Identification of a previously unknown glacial trough (named Hughes Trough).
► Mega-scale glacial lineations identified in Ronne and Hughes Troughs.