Extension of Greenland Ice Sheet outlets to the shelf edge bordering Baffin Bay during the last glacial cycle

Despite much research seeking to understand recent dynamic changes to the Greenland Ice Sheet our understanding of the longer-term history of the ice sheet remains surprisingly poor for many sectors. This is particularly the case on the central west Greenland continental margin bordering Baffin Bay. In this region, several major fast flowing outlets, including Jakobshavns Isbrae, drain the ice sheet today. Marine geological and geophysical records recently acquired from the continental shelf and slope offshore of central west Greenland provide new evidence for the extension of ice sheet outlets to the shelf edge during the last glaciation. Bathymetric troughs extend from the mouths of Umanak Fjord and Disko Bugt to the shelf edge. Streamlined subglacial bedforms imaged on geophysical records and subglacial tills recovered in cores from these troughs record the flow of grounded ice sheet outlets along these troughs to the shelf edge during the last glaciation. Major submarine fans deposited at the mouths of the troughs record associated glacigenic sediment delivery to the continental slope. Cores and geophysical records from the fans show significant differences between them in terms of the nature of sediment delivery and slope morphology, with examples of both low gradient debris-flow dominated fans and much steeper channelized fans. These differences imply marked spatial variations in the nature of continental slope sedimentation in front of fast flowing ice sheet outlets. Over thirty AMS radiocarbon dates provide new chronological control on the timing and rate of glacigenic sediment delivery to the continental slope and the timing of subsequent ice sheet retreat from the shelf edge. These new landform, sediment and chronological records from the central west Greenland shelf and slope will be presented and the wider implications for Greenland Ice Sheet history at and following the LGM discussed.