Hydrographic Structure of Overflow Water Passing through the Denmark Strait

Dana Mastropole1, Robert S Pickart1, Hedinn Valdimarsson2, Kjetil Våge3, Kerstin Jochumsen4, Detlef R Quadfasel5, Gerd Krahmann6, Bert Rudels7 and James B Girton8, (1)Woods Hole Oceanographic Institution, Physical Oceanography, Woods Hole, MA, United States, (2)Marine Research Institute, Reykjavik, Iceland, (3)University of Bergen, Gephysical Institute, Bergen, Norway, (4)University of Hamburg, Institute of Oceanography, Hamburg, Germany, (5)University of Hamburg, Hamburg, Germany, (6)GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, (7)Finnish Meteorological Institute, Helsinki, Finland, (8)University of Washington, Applied Physics Laboratory, Seattle, WA, United States
Abstract:
Denmark Strait Overflow Water (DSOW) constitutes the densest portion of North Atlantic Deep Water, which feeds the lower limb of the Atlantic Meridional Overturning Circulation. As such, it is critical to understand how DSOW is transferred from the upstream basins in the Nordic Seas, across the Greenland-Scotland Ridge, and to the North Atlantic Ocean. Here we characterize the hydrographic structure of the different DSOW constituents at the sill before the water descends into the Irminger Sea. Temperature and salinity (T/S) data are used from 111 shipboard sections in the vicinity of the sill carried out between 1990 and 2012. The individual realizations indicate that weakly stratified "boluses" of DSOW frequent the sill and supply the densest water to the overflow. We also characterize the structure, size, and location of the boluses and relate them to the T/S modes found at the sill. Lastly, historical hydrographic data from the Nordic Seas are used to make inferences regarding the origin of the boluses.
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