Deglaciation of the ancestral Kangerlussuaq Glacier from the continental shelf offshore of SE Greenland following the LGM

Marine geophysical data and sediment cores were collected from the continental shelf and slope offshore of SE Greenland during cruise SD041 of the UK research vessel the RRS Sir David Attenborough in 2024. The cruise collected a range of geological, geophysical, oceanographic and biological data. The cruise was part of the ‘Kang-Glac’ project, the aim of which is to investigate the response of the Greenland Ice Sheet to ocean warming during the last 11,700 years. Marine geophysical data and radiocarbon-dated sediment cores provide a clear record of an extensive Greenland Ice Sheet which expanded and retreated across the continental shelf offshore of SE Greenland during, and following, the last glacial maximum. An ancestral Kangerlussuaq Glacier flowed along Kangerlussuaq Trough, a cross shelf bathymetric trough which extends from the mouth of Kangerlussuaq Fiord to the edge of the continental shelf, where it terminates in a trough-mouth fan. Streamlined subglacial bedforms record convergent ice flow into the trough. Sediment cores from along the trough recovered subglacial tills recording a grounded ice sheet. The tills are overlain by a range of deglacial, glacimarine facies recording ice sheet retreat by melting and iceberg calving. A suite of new radiocarbon dates were obtained on foraminifera and shells from the deglacial facies in a transect of cores extending from the trough-mouth fan to the inner shelf. The dates constrain the timing of initial retreat from the outer shelf and allow the position of the grounding-line to be tracked during retreat. The new radiocarbon dates significantly improve the offshore temporal constraints on the post-LGM deglaciation for this sector of the Greenland Ice Sheet and, allied with core sedimentology and foraminferal assemblage data, allow assessment of the role of ocean warming in driving retreat of the ancestral Kangerlussuaq Glacier.