Glacial plumes drive widespread subsurface warming in northwest Greenland’s fjords

Greenland’s glacial fjords modulate the exchange of heat and freshwater between the ice sheet and ocean, with the ocean properties adjacent to tidewater glaciers influencing the rate of submarine glacier melting and the properties of glacially modified waters exported to the shelf. Here we use a numerical plume model in conjunction with observations from close to 14 glaciers in northwest Greenland to assess the impact of subglacial-runoff-driven plumes on near-glacier ocean properties. We find that at depths where plumes most commonly find neutral buoyancy (~75-300m), intruded plume waters frequently make up the largest component of the near-glacier water composition. These plume waters register predominantly as a warm anomaly relative to waters of equivalent density on the shelf, and will thus serve to increase submarine melting at intermediate depths. Our findings demonstrate the key role played by plumes in driving water modification in Greenland’s fjords, the importance of accounting for this process when studying ice-sheet/ocean interactions, and the potential for simple models to capture these impacts across a range of settings.