Evolution of the Freshwater Coastal Current at the Southern Tip of Greenland

Abstract

Shipboard hydrographic and velocity measurements collected in summer 2014 are used to study the evolution of the freshwater coastal current in southern Greenland as it encounters Cape Farewell. The velocity structure reveals that the coastal current maintains its identity as it flows around the cape and bifurcates such that most of the flow is diverted to the outer west Greenland shelf, while a small portion remains on the inner shelf. Taking into account this inner branch, the volume transport of the coastal current is conserved, but the freshwater transport decreases on the west side of Cape Farewell. A significant amount of freshwater appears to be transported off the shelf where the outer branch flows adjacent to the shelfbreak circulation. It is argued that the offshore transposition of the coastal current is caused by the flow following the isobaths as they bend offshore because of the widening of the shelf on the west side of Cape Farewell. An analysis of the potential vorticity shows that the subsequent seaward flux of freshwater can be enhanced by instabilities of the current. This set of circumstances provides a pathway for the freshest water originating from the Arctic, as well as runoff from the Greenland ice sheet, to be fluxed into the interior Labrador Sea where it could influence convection in the basin.

An Updated View on Water Masses on the pan‐West Greenland Continental Shelf and Their Link to Proglacial Fjords

“…In the southern slope section we observe the presence of a thick layer (0–600 m) of warm and saline water (Figures a and c), which is identified as uSPMW and dSPMW (Figure , lower left). SPMW is transported northward as part of the WGC (Lin et al, ). As SPMW reaches 64°N it is joined by CW in the upper 200 m of the water column (Figures a and c) resulting in a distinct temperature and salinity decrease.…”

“…When dSPMW enters the northern slope section its T and S properties are close to 4°C and 34.7. In the literature, SPMW has been referred to as Atlantic Water, Atlantic-origin Water, Irminger Water, and West Greenland Irminger Water (e.g., Curry et al, 2011;Myers et al, 2009;Gladish et al, 2014;Lin et al, 2018). The interactions of these three water masses shape the hydrographic conditions on the west Greenland continental shelf of which we focus on in three cases below.…”

Seasonality of Freshwater in the East Greenland Current System From 2014 to 2016

“…Sutherland and Pickart () estimated 50–70 mSv of freshwater transport (referenced to 34.8) in the coastal current at CF in summer 2004. The most recent estimates, calculated from shipboard data during the OSNAP deployment cruise in August 2014 are 1.0/1.09 Sv of volume transport and 40.95/68.45 mSv of freshwater transport (referenced to 34.8), where the larger estimates are for a section just upstream of the moored array that covered a larger portion of the shelf (Lin et al, ). Note that previous studies use reference salinities ranging from 34.8 to 35, but such changes do not impact our coastal current freshwater transport estimates by more than 4 mSv.…”

“…Synoptic summer measurements of coastal current volume and freshwater transport range from 0.5 to 2 Sv and 50 to 70 mSv, respectively (Bacon et al, ; Lin et al, ; Pickart et al, ; Sutherland & Pickart, ; Wilkinson & Bacon, ). Sutherland and Pickart () hypothesized that the coastal current's variability is driven by downwelling‐favorable winds, which steepen the freshwater density front on the shelf.…”

Water Mass Evolution and Circulation of the Northeastern Chukchi Sea in Summer: Implications for Nutrient Distributions

“…The peak magnitude of the vertically integrated reversed flow is 0.75 m s −1 (compared to 0.9 m s −1 for the down‐canyon flow in the background state). Interestingly, the reversed current appears to bifurcate downstream in the vicinity of Icy Cape (162–163°W), which is likely associated with the widening topography (e.g., Lin, Pickart, Torres, et al, ). The composite of Figure b indicates that wind from any other direction only slightly modulates the background coastal flow.…”