Reconstructing Jakobshavn Isbræ's evolution from 1958 to 2025 with ISSM constrained by multi-mission observations

Over the past decade, Greenland’s major outlet glaciers have more than doubled their contribution to global sea-level rise. Among these, Jakobshavn Isbræ, located in West Greenland, is the largest outlet glacier by drainage area, accounting for approximately 6.5% of the Greenland Ice Sheet. The pronounced acceleration of Jakobshavn Isbræ around 2000 has been widely attributed to the collapse of a substantial portion of its floating ice tongue and the retreat of its terminus. This collapse is thought to be linked to enhanced basal melting beneath the ice shelf, driven by the intrusion of warm ocean waters, as well as the increased calving activity associated with a reduction in sea ice within the fjord. Estimates of the rate of retreat and mass loss from 1950 to 2000 remain very uncertain due to the sparsity of data throughout that timeframe.
In this study, we develop a new high-resolution model of the region that is constrained by available observations to reconstruct the retreat, acceleration, and thinning of the glacier during this time period. We use Ice-sheet and Sea-level System Model (ISSM) to simulate Jakobshavn Isbræ from 1958 to 2025. Our analysis integrates a comprehensive set of observational data, including ice front positions derived from Landsat imagery, ice velocity variations, and surface elevation changes. The simulations are performed on an unstructured, adaptively refined mesh with a model resolution reaching 100 m within the first few kilometers around the terminus position. The resulting transient simulations document the temporal evolution of glacier mass balance from 1958 to the present. Model performance is evaluated by comparing simulated ice volume changes with independent volume estimates derived from CryoSat-2, Envisat,  ICESat, ICESat-2, and NASA’s Operation IceBridge Airborne Topographic Mapper, as well as digital elevation models from 1964 and 1985, providing a robust reconstruction of Jakobshavn's recent history.