Evolution of the Northeast Greenland glaciers in a warming world

The Northeast Greenland Ice Stream (NEGIS) drains through two major outlet glaciers: the 79 North Glacier (79NG) and Zachariae Isstrøm (ZI). Since the 2000s, these glaciers have exhibited contrasting behavior: while the ZI ice shelf has retreated dramatically and transitioned to a tidewater glacier, the 79NG ice tongue has remained relatively stable in extent despite significant thinning. The retreat and thinning of both glaciers have accelerated the upstream ice stream, with important implications for global sea level rise.

We present a novel coupled model that integrates the Ice-sheet and Sea-level System Model (ISSM) with the Finite volumE Sea Ice-Ocean Model version 2 (FESOM2). The ice sheet model domain encompasses the NEGIS region, while the global ocean model features enhanced mesh resolution on the Northeast Greenland continental shelf and explicitly resolves the ice shelf cavities of both 79NG and ZI. This coupling enables dynamic representation of ice sheet-ocean-sea ice interactions, including grounding line migration and ice geometry evolution.

A hindcast simulation spanning 2008-2023, forced by atmospheric reanalysis data, reproduces the observed calving front retreat at ZI with good fidelity, validating our modeling approach. Beyond validation, this experiment reveals that the rapid ZI retreat is driven primarily by internal ice dynamics rather than changes in oceanic forcing. We extend our analysis through climate projection simulations using atmospheric forcing from CMIP6 scenarios. Applying both low and high emission scenarios (SSP126 and SSP585), we are able to  assess the possible future evolution of these glaciers until the end of this century.