Speaker: Isabela Le Bras (SIO)
Title: Seasonality of Freshwater in the East Greenland Current System
The Greenland ice sheet and Arctic sea ice store freshwater which has the potential to alter global ocean circulation and climate. Notably, freshwater flowing into the ocean east of Greenland is likely to spread to the ocean interior and impact the sinking of surface waters. I will present the first year-round observations of the East Greenland Current system (August 2014 - August 2016) which were collected as part of OSNAP (Overturning in the Subpolar North Atlantic Program) [Le Bras et al. 2018].
Using a set of eight moorings southeast of Greenland at 60N, we find two distinct, persistent velocity cores on the shelf and slope. These are the East Greenland Coastal Current (EGCC), which carries cold, fresh water from the Arctic and Greenland along the shelf, and the East Greenland/Irminger Current (EGIC) over the slope, which includes cold, fresh waters as well as warm, salty waters of Atlantic origin. We find that these currents carry 70% of the freshwater transport across the subpolar North Atlantic east of Greenland. The freshwater transport is approximately equipartitioned between the coastal current (EGCC) and the fresh portion of the slope current (EGIC). The coastal and slope current freshwater transports have staggered seasonality, peaking in December and March respectively, suggesting that summer surveys underestimate freshwater transport in this region, particularly over the slope. We find that the continental slope is freshest in the winter, when we hypothesize that surface cooling mixes freshwater off the shelf. This previously unmeasured freshwater is likely to enter the Labrador Sea downstream, where it can impact deep convection.