Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history.

The Greenland ice sheet has been one of the largest contributors to global sea-level rise over the past 20 years, accounting for 0.5 mm yr−1 of a total of 3.2 mm yr−1. A significant portion of this contribution is associated with the speed-up of an increased number of glaciers in southeast and northwest Greenland. Here, we show that the northeast Greenland ice stream, which extends more than 600 km into the interior of the ice sheet, is now undergoing sustained dynamic thinning, linked to regional warming, after more than a quarter of a century of stability.