Alongshore winds force warm Atlantic water toward Helheim Glacier in Southeast Greenland

Abstract

Enhanced transport of warm subsurface Atlantic Water (AW) into Greenland fjords has driven glacier mass loss, but the mechanisms transporting AW to the fjords remain poorly characterized. Here, we provide the first direct satellite-based observations of rapid (∼0.2 m/s) AW intrusion toward Sermilik Fjord abutting Helheim Glacier, one of Greenland's largest glaciers. The intrusions arise when coastal upwelling—through interactions with Sermilik's bathymetric trough on the continental shelf—triggers enhanced AW upwelling and inflow that can travel tens of kilometers along the trough within hours. A weakening or reversal of northeasterly alongshore winds stimulates the intrusions and is often associated with the passing of cyclones and subsequent sea surface lowering. Mooring data show that these intrusions produce subsurface ocean warming both at Sermilik Fjord mouth and within the fjord and that the warming signal in the fjord does not diminish during subsequent coastal downwelling events. Satellite imagery captures near-synchronous AW intrusions at multiple troughs rimming southeast Greenland suggesting that these wind-driven processes may play a substantial role in ocean heat transport toward the Greenland Ice Sheet.