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  1. Abstract

    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.

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  2. Coastal waters off west Greenland are strongly influenced by the input of low salinity water from the Arctic and from meltwater from the Greenland Ice Sheet. Changes in freshwater content in the region can play an important role in stratification, circulation, and primary production; however, investigating salinity variability in the region is challenging because in situ observations are sparse. Here, we used satellite observations of sea surface salinity (SSS) from the Soil Moisture and Ocean Salinity mission produced by LOCEAN and by the Barcelona Expert Center (SMOS LOCEAN and SMOS BEC) and from the Soil Moisture Active Passive mission produced by the Jet Propulsion Laboratory (SMAP JPL) as well as by Remote Sensing Systems (SMAP RSS) to investigate how variability in a narrow coastal band off west Greenland is captured by these different products. Our analyses revealed that the various satellite SSS products capture the seasonal freshening off west Greenland from late spring to early fall. The magnitudes of the freshening and of coastal salinity gradients vary between the products however, being attenuated compared to historical in situ observations in most cases. The seasonal freshening off southwest Greenland is intensified in SMAP JPL and SMOS LOCEAN near the mouth of fjords characterized by large inputs of meltwater near the surface, which suggests an influence of meltwater from the Greenland Ice Sheet. Synoptic observations from 2012 following large ice sheet melting revealed good agreement with the spatial scale of freshening observed with in situ and SMOS LOCEAN data. Our analyses indicate that satellite SSS can capture the influence of meltwater input and associated freshwater plumes off coastal west Greenland, but those representations differ between products.

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