University of Cambridge > Talks.cam > Scott Polar Research Institute - Physical Sciences Seminar > The central-west sector of the Greenland Ice Sheet since the LGM - the story from offshore evidence

The central-west sector of the Greenland Ice Sheet since the LGM - the story from offshore evidence

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Recent reconstructions of the Greenland Ice Sheet (GrIS) during the LGM still have large uncertainties along much of the ice sheet’s margin, particularly for the NW, NE and central-W sectors of the ice sheet. This is partly due to the scarcity of information from the offshore record that could confirm maximum ice-sheet extent and date the start of deglaciation in these areas. Here we present recent work that uses a variety of seismic data to investigate sediments deposited by ice masses retreating in to Disko Bay and, ultimately, the Jakobshavn and Torssukatak fjord systems. The sub-bottom profiles show rapid ice-margin retreat through bathymetric troughs and embayments until topographic pinning points close to the present coastline. Once the ice margins were pinned at fjord mouths large volumes of sediment were deposited via rainout from turbid meltwater plumes and calculated subglacial sediment fluxes are relatively high when compared with existing estimates from West Antarctic ice streams. Using existing marine and terrestrial dates we place these standstills in a chronologic framework that support an earlier ice-margin retreat in northern Disko Bay (Torssukatak) than in southern Disko Bay (Jakobshavn). Using the newest radiocarbon dates available from the offshore record we can now present a deglacial chronology for the GrIS from the shelf break several hundred kilometres west of Disko Bay, through the bay to the fjord mouth, and then into the fjord itself at c. 7.8-7.6 cal ka BP. We will also present dates from Umanak Trough to the north for which there is an emerging picture of retreat from the shelf edge followed by a significant stillstand or readvance before c. 10 cal ka BP.

This talk is part of the Scott Polar Research Institute - Physical Sciences Seminar series.

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