Modelling of the present-day state and future evolution of CH Ostenfeld glacier, northern Greenland, using new subglacial topography observations

Among components of the cryosphere, the Greenland Ice Sheet (GrIS) is currently the largest contributor to global mean sea-level rise, driven by both enhanced surface melt and dynamic ice loss to the ocean. Evidence from the Holocene suggests that the GrIS can undergo substantial deglaciation under climatic conditions only slightly warmer than at present day. However, projections of its future evolution remain highly uncertain, largely due to the heterogeneous response of individual outlet glaciers to ocean forcing, particularly in the relatively understudied and sparsely sampled northern GrIS.

In this project, we investigate the present-day state and future evolution of the northern GrIS, with a specific focus on CH Ostenfeld Glacier. This glacier lost its floating extension completely decades ago, which could be a precursor of the fate of the nearby Ryder and Petermann glacier. We use the Ice-sheet and Sea-level System Model (ISSM) for this purpose. We integrate new ice-penetrating radar observations of the subglacial topography in the grounding zone of Ostenfeld Glacier, collected during the GEOEO 2024 North of Greenland Expedition aboard the ice breaker Oden. Together with existing subglacial topography datasets these data are used to assess the sensitivity of modelled glacier behaviour to variations in subglacial topography. Using the updated subglacial topography dataset, we furthermore investigate the subglacial hydrological network. Modelled freshwater fluxes from this network will be used to investigate the interaction between the marine-terminating ice sheet and fjord circulation, in collaboration with researchers from the Tracing How Atlantic Water Influences Northern Greenland (THAWING) project. This coupling governs the delivery of warm Atlantic Water to the glacier grounding zone and, consequently, the magnitude of frontal melt at CH Ostenfeld Glacier. The freshwater released from the CH Ostenfeld glacier through this frontal melting or from the subglacial hydrological network, will influence the fjord circulation and thereby the availability of Atlantic Water at the front of the glacier.