Dynamic simulations of Icelandic ice cap evolution constrained by observations

Like most ice caps and glaciers worldwide, Icelandic glaciers are losing mass and retreating as a result of a warming climate. Here, we link satellite observations and dynamic ice-flow modeling to produce robust long-term projections of the five largest Icelandic ice caps—Vatnajökull, Langjökull, Hofsjökull, Mýrdalsjökull, and Eyjafjallajökull—until 2300 under the RCP 8.5 scenario. The simulations are conducted using the Parallel Ice Sheet Model (PISM), forced by climatic mass balance fields from a regional climate model.

PISM is initialized by constraining ice-flow parameters using satellite-derived surface velocities from Sentinel-1 for the period 2015–2020. Simulated velocities are compared to observations to identify the best-fitting parameter set, and simulated thickness and area changes are evaluated against available geodetic measurements and glacier outlines. These observational constraints are used to improve confidence in subsequent long-term projections.

The calibrated ice-flow model is then used to simulate glacier evolution until 2100, and then the 2081–2100 climatic mass balance forcing is repeated to extend the simulations to 2300. The ice caps are projected to lose 15–30% of their volume and 7–22% of their area by 2100, increasing to 50–70% volume loss and 30-60% area loss by 2300.