Greenland Ice Sheet Rainfall, Heat and Albedo Feedback Impacts From the Mid‐August 2021 Atmospheric River

Abstract

AbstractRainfall at the Greenland ice sheet Summit 14 August 2021, was delivered by an atmospheric river (AR). Extreme surface ablation expanded the all‐Greenland bare ice area to near‐record‐high with snowline climbing up to 788 ± 90 m. Ice sheet wet snow extent reached 46%, a record high for the 15–31 August AMSR data since 2003. Heat‐driven firn deflation averaged 0.14 ± 0.05 m at four accumulation area automatic weather stations (AWSs). Energy budget calculations from AWS data indicate that surface heating from rainfall is much smaller than from either the sensible, latent, net‐longwave or solar energy fluxes. Sensitivity tests show that without the heat‐driven snow‐darkening, melt at 1,840 m would have totaled 28% less. Similarly, at 1,270 m elevation, without the bare ice exposure, melting would have been 51% less. Proglacial river discharge was the highest on record since 2006 for late August and confirms the melt‐sustaining effect of the albedo feedback.