The origins of the East Greenland Coastal Current on the Northeast Greenland Shelf: a comparison of two reanalysis products

Abstract

The East Greenland Coastal Current (EGCC) carries some of the freshest outflow from the Arctic southward along the East Greenland Shelf and into the Nordic Seas and subpolar North Atlantic. How this fresh water initially flows onto the Northeast Greenland Shelf (NEGS) and feeds the EGCC is not well known due in part to the lack of observations in the region. In this thesis, I use two ocean reanalyses, the Regional Arctic Ocean/sea-ice Reanalysis (RARE) and Global Ocean Physics Reanalysis (GLORYS) to explore the structure and dynamics of the ocean circulation on the NEGS. To validate the use of these products in the region, I compare the reanalysis products to the Fram Strait Arctic Outflow Observatory for the period of 2003-2019. In the mean, RARE is too warm and salty compared to the moorings, while the properties in GLORYS track more closely to the observations. However, the observed velocity field is better represented in RARE than GLORYS. From there, I analyze the cross-shelfbreak flow from 74°N to 81.5°N in the two reanalysis products, and conclude that transport onto the NEGS of waters fresher than 34 salinity is driven by an Ekman circulation that arises from along-shelfbreak winds and a widening shelf south of 81.5°N. The enhanced transport of fresh water also shifts the isohalines across the shelfbreak, directing a geostrophic flow onshelf between 81°N and 79°N. The convergence of fresh water on the NEGS initiates the EGCC as an identifiable and distinct feature around 80°N in RARE, uniting the EGCC along the southwest coast of Greenland and its northern counterpart, the Polar Surface Water (PSW) Jet. In GLORYS, the EGCC is not present throughout the domain, though there is a weak net southward flow on the NEGS. The EGCC in RARE is primarily buoyancy-driven, though the along-coast winds likely play a major role in maintaining the density front that supports the EGCC. Results from this thesis have implications for the transport and fate of Arctic and Greenland-sourced fresh water, and stratification in the high latitude North Atlantic and Nordic Seas.