Seasonality of freshwater in the east Greenland current system from 2014 to 2016

Abstract

The initial 2 years of Overturning in the Subpolar North Atlantic Program mooring data (2014–2016) provide the first glimpse into the seasonality of freshwater in the complete East Greenland Current system. Using a set of eight moorings southeast of Greenland at 60∘ N, we find two distinct, persistent velocity cores on the shelf and slope. These are the East Greenland Coastal Current, which carries cold, fresh water from the Arctic and Greenland along the shelf, and the East Greenland/Irminger Current over the slope, which is a combination of cold, fresh waters and warm, salty waters of Atlantic origin. Together, these currents carry 70% of the freshwater transport across the subpolar North Atlantic east of Greenland. The freshwater transport referenced to a salinity of 34.9 is approximately equipartitioned between the coastal current (East Greenland Coastal Current) and the fresh portion of the slope current (East Greenland Current), which carry 42 ± 6 and 32 ± 6 mSv, respectively. The coastal and slope current freshwater transports have staggered seasonality during the observed period, peaking in December and March, respectively, suggesting that summer surveys have underestimated freshwater transport in this region. We find that the continental slope is freshest in the winter, when surface cooling mixes freshwater off the shelf. This previously unmeasured freshwater over the slope is likely to enter the Labrador Sea downstream, where it can impact deep convection.

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