Using a record of bedload transport from Leverett glacier in western Greenland to understand proglacial sediment transport processes from the ice sheet

Increased glacier melt leads to a change in sediment transport capacity below glaciers, which impacts the sediment transport within proglacial areas as well as downstream ecosystems and geomorphology. Previous work on Alpine glaciers shows that strong diurnal discharge variations lead to fluctuations in sediment transport capacity such that deposition and erosion can occur in the proglacial area over the course of the melt season. However, the exact processes controlling sediment transport at the outlet glaciers of ice sheet margins and in their proglacial areas remain uncertain. Data suggest that the diurnal discharge variations are substantially reduced and baseflow discharge is much greater, likely capable of maintaining significant sediment transport throughout the melt season. This difference in the hydrological regime as compared with Alpine glacial systems may drive different rates and variations in sediment transport and, ultimately, in proglacial braid plain morphodynamics.

We measure proglacial sediment transport at Leverett glacier, a land-terminating glacier located at the western margin of the Greenland Ice Sheet. As bedload transport is exceptionally difficult to measure in situ, two seismic stations were installed to evaluate bedload transport in the glacial meltwater stream in the summer of 2022. The first station is located close to the current glacier terminus, and the second one is about 2 km from the current glacier terminus. These two stations allow for the examination of the sediment transport processes within the proglacial area. By using a Fluvial Inversion Model the recorded seismic data is converted into bedload flux. The model is calibrated using active seismic surveys and statistical approaches to evaluate the physical parameters. Outputs of the Fluvial Inversion Model are validated with available water stage data.  The results provide insight as to whether the proglacial area is aggrading or eroding as sediment transport in the two locations at Leverett glacier evolves over the summer season. We discuss the relationship between bedload transport and level of the proglacial river, as well as the seasonal variations in proglacial sediment transport and deposition in Leverett glacier’s proglacial area.