IMAU Colloquium - Brice Noël (University of Liège) - in person/ online

Resilience of the Greenland ice sheet firn layer in a future warming climate

Brice Noël¹

1 Department of Climatology and Topoclimatology, University of Liège, Liège, Belgium.

Firn, the compressed snow layer covering 90% of the Greenland ice sheet (GrIS), currently retains about half of rain and meltwater through refreezing, hence mitigating mass loss from surface runoff. The loss of firn refreezing could mark a tipping point for sustained GrIS mass loss as decades to centuries of cold summers would be required to rebuild a healthy firn buffer. The GrIS has not passed such a tipping point yet, at least not since the beginning of the satellite era. In contrast, Greenland peripheral ice caps, detached from the main ice sheet, and other neighbouring Arctic glaciers have progressively lost their firn buffer since the mid-1990s.

In this talk, we first identify the drivers of reduced firn refreezing capacity for these Arctic glaciers and investigate the impact on contemporary mass loss. Next, we explore the resilience of GrIS firn in a future warming climate using multiple long-term scenario projections covering the period 1850-2300. We predict that GrIS firn refreezing could peak and permanently decline in the early 22^nd century under high-end warming trajectories, strongly accelerating the ice sheet contribution to global sea-level rise.