Greenland Subglacial Discharge as a Driver of Hotspots of Increasing Coastal Chlorophyll Since the Early 2000s

Subglacial discharge emerging from the base of Greenland's marine-terminating glaciers drives upwelling of nutrient-rich bottom waters to the euphotic zone, which can fuel nitrate-limited phytoplankton growth. Here, we use buoyant plume theory to quantify this subglacial discharge-driven nutrient supply on a pan-Greenland scale. The modeled nitrate fluxes were concentrated in a few critical systems, with half of the total modeled nitrate flux anomaly occurring at just 14% of marine-terminating glaciers. Increasing subglacial discharge fluxes results in elevated nitrate fluxes, with the largest flux occurring at Jakobshavn Isbræ in Disko Bay, where subglacial discharge is largest. Subglacial discharge and nitrate flux anomaly also account for significant temporal variability in summer satellite chlorophyll a (Chl) within 50 km of Greenland's coast, particularly in some regions in central west and northwest Greenland.