On the East Greenland Shelf, downwelling-favorable northerly winds confine the freshest water masses to the inner shelf, creating a strong cross-shelf salinity gradient. This wedge of fresh water supports a southward East Greenland Coastal Current (EGCC) that flows continuously from Fram Strait (80°N) to Cape Farewell at the southern tip of Greenland (60°N). What happens to this freshwater as it rounds Cape Farewell is not well understood. Here, we present results from a Lagrangian experiment in which we deployed 50 Surface Velocity Program (SVP) drifters and 8 profiling floats in the EGCC on the southeast Greenland shelf in August/September 2021 and 2022. The SVP drifters were drogued at 15 m and the profiling floats drifted at 100 m for 6 hours and profiled to the surface every 6 hours. We find that the vast majority of the EGCC continues on the shelf around Cape Farewell and supplies the northward West Greenland Coastal Current (WGCC). Local winds exert strong control on the coastal current’s cross-shelf position, but there is little evidence of shelf-basin exchange there. Investigation of the winds during the deployments revealed that they were similar to the mean conditions, and thus our instruments likely captured the typical ocean circulation. However, the lack of sampling during a strong Greenland tip jet event leaves open the possibility that the shelf-basin exchange in this region is intermittent in response to large wind events.

Denmark Strait, the channel located between Greenland and Iceland, is a critical gateway between the Nordic Seas and the North Atlantic. Mesoscale features crossing the strait regularly enhance the volume transport of the Denmark Strait overflow. They interact with the dense water masses descending into the subpolar North Atlantic and therefore are important for the Atlantic Meridional Overturning Circulation. Using a realistic numerical model, we find new evidence of the causal relationship between overflow surges (i.e., mesoscale features associated with high-transport events) and overflow cyclones observed downstream. Most of the cyclones form at the Denmark Strait sill during overflow surges and, because of potential vorticity conservation and stretching of the water column, grow as they move equatorward. A fraction of the cyclones form downstream of the sill, when anticyclonic vortices formed during high-transport events start collapsing. Regardless of their formation mechanism, the cyclones weaken starting roughly 150 km downstream of the sill, and potential vorticity is only materially conserved during the growth phase.

Export from the Arctic and meltwater from the Greenland Ice Sheet together form a southward-flowing coastal current along the East Greenland shelf. This current transports enough fresh water to substantially alter the large-scale circulation of the North Atlantic, yet the coastal current’s origin and fate are poorly known due to our lack of knowledge concerning its north-south connectivity. Here, we demonstrate how the current negotiates the complex topography of Denmark Strait using in situ data and output from an ocean circulation model. We determine that the coastal current north of the strait supplies half of the transport to the coastal current south of the strait, while the other half is sourced from offshore via the shelfbreak jet, with little input from the Greenland Ice Sheet. These results indicate that there is a continuous pathway for Arctic-sourced fresh water along the entire East Greenland shelf from Fram Strait to Cape Farewell.

Initial results are presented from a yearlong, high-resolution (~2 km) numerical simulation covering the east Greenland shelf and the Iceland and Irminger Seas. The model hydrography and circulation in the vicinity of Denmark Strait show good agreement with available observational datasets. This study focuses on the variability of the Denmark Strait overflow (DSO) by detecting and characterizing boluses and pulses, which are the two dominant mesoscale features in the strait. The authors estimate that the yearly mean southward volume flux of the DSO is about 30% greater in the presence of boluses and pulses. On average, boluses (pulses) are 57.1 (27.5) h long, occur every 3.2 (5.5) days, and are more frequent during the summer (winter). Boluses (pulses) increase (decrease) the overflow cross-sectional area, and temperatures around the overflow interface are colder (warmer) by about 2.6°C (1.8°C). The lateral extent of the boluses is much greater than that of the pulses. In both cases the along-strait equatorward flow of dense water is enhanced but more so for pulses. The sea surface height (SSH) rises by 4–10 cm during boluses and by up to 5 cm during pulses. The SSH anomaly contours form a bowl (dome) during boluses (pulses), and the two features cross the strait with a slightly different orientation. The cross streamflow changes direction; boluses (pulses) are associated with veering (backing) of the horizontal current. The model indicates that boluses and pulses play a major role in controlling the variability of the DSO transport into the Irminger Sea.