Sedimentary records of the evolution of the Melville Bugt ice stream

Understanding the temporal evolution of the Greenland Ice Sheet is crucial to making informed predictions of future environmental change in a warming world. Despite already being one of the largest contributors to sea-level rise and perturbation of oceanic circulation via meltwater release, the north-west sector of the ice sheet and adjoining ocean are relatively understudied in terms of their history from deglaciation to the present. During the Last Glacial Maximum, large ice streams filled major cross-shelf troughs on the north-west Greenland continental shelf in Melville Bugt and the Uummannaq region, comparable in size and configuration to large Antarctic ice streams. These ice streams subsequently retreated and the ice sheet and ocean were subjected to warm Holocene Thermal Maximum conditions. The evolution of these ice streams and the proximal ocean is at present uncertain; developing improved knowledge of ice sheet retreat dynamics and palaeoceanographic evolution has implications for regional glacial understanding and for feeding into numerical modelling of ice sheet behaviour. Ice sheet and oceanographic behaviour was investigated utilising proxy records from a suite of sediment cores collected from the continental shelf in north-west Greenland. Radiocarbon dating combined with sedimentological analysis have determined that the Melville Bugt Ice Stream retreated rapidly from a large mid-shelf grounding zone wedge tentatively dated to the Younger Dryas, reaching the modern coastline at approximately 11.4 cal. ka. This rapid retreat was conditioned by high atmospheric temperatures, the width of the ice stream, the presence of a reverse bed slope, and the penetration of warm West Greenland Current waters to its grounding zone. Fully ice distal conditions were established by 9.3 cal. ka. Subsequent oceanographic evolution as recorded by XRF and foraminiferal proxies - were controlled by variation in inputs of Arctic Water through the Canadian Arctic Archipelago, meltwater efflux, and the West Greenland Current.