Six years of continuous observations of the Deep Western Boundary Current from Cape Farewell

Abstract

<p>Since 2014, the Overturning in the Subpolar North Atlantic Program (OSNAP) has maintained the first continuous Eulerian array across the North Atlantic Subpolar Gyre to monitor changes in the Atlantic Meridional Overturning Circulation (AMOC).  The deep limb of the AMOC – the Deep Western Boundary Current (DWBC) – forms in the North Atlantic subpolar gyre from the combination of cold, dense waters of Norwegian Sea origin with the ambient waters within the gyre.  Norwegian Sea Water enters the gyre by crossing southward over the Greenland Scotland Ridge as Denmark Strait Overflow Water to the west of Iceland and Iceland Scotland Overflow Water to the east.  As these waters descend into the Irminger and Iceland Basins (respectively), they entrain the surrounding waters, which are primarily comprised of Labrador Sea Water and Subpolar Mode Water, to increase their transport.  These waters mostly flow cyclonically along the bathymetry of the gyre before merging along the eastern flank of Greenland.  At the eastern tip of Greenland, near Cape Farewell, OSNAP maintains moorings consisting of current meters, acoustic doppler current profilers and temperature-salinity recorders to capture the transport of the DWBC.  This presentation will give new estimates of the DWBC from 6 years of OSNAP observations and shed new light into the current’s variability and long-term trend.  Previous observations at this location found 9-13 Sv of transport, including 10.8 Sv from the first two years of OSNAP data. </p>