Impact of Varying Greenland Surface Melt on the West Greenland Shelf and the Labrador Sea

James Holte and Fiammetta Straneo, Scripps Institution of Oceanography, La Jolla, CA, United States
In recent years, freshwater input to the North Atlantic has increased due to the accelerated melting of Greenland's glaciers. By increasing the buoyancy of the surface layer, this freshwater could potentially impact biogeochemical cycles, marine ecosystems, and the overturning circulation in the North Atlantic. In this study, we use underway observations collected by the container ship Nuka Arctica since 2002 and estimates of Greenland melt to investigate the link between surface salinity variability over the West Greenland shelf and Greenland freshwater discharge. We find that both the seasonal cycle and the interannual variability of the shelf salinity are strongly linked to Greenland melt. Seasonally, the shelf begins freshening in May just as Greenland melt commences. The freshest surface layers occur in August, coinciding with the melt peak, and extend across the shelf. Interannually, the shelf salinity during summer is highly correlated with estimates of cumulative melt from Southwest Greenland. Two summers characterized by extreme melt in Southwest Greenland, 2010 and 2012, feature the freshest observations on the shelf. Lastly, we examine the extent to which these melt-driven fresh surface layers on the West Greenland shelf can be linked to observations of anomalously fresh summer mixed layers in the Labrador Sea. We find that summers characterized by high-melt/fresh shelf salinities do not directly correspond to fresh summer mixed layers in the Labrador Sea, suggesting that an interplay between both shelf freshwater and transport mechanisms influences how much Greenland melt reaches the Labrador Sea.