Winter oceanographic conditions in the Fram Strait‐Yermak Plateau region

Abstract

Temperature, salinity and currents were measured in the Yermak Plateau and northern Fram Strait region during March–April 1989. An isothermal upper layer was near the freezing point everywhere except seaward of the ice edge near western Svalbard. Temperatures in the underlying Atlantic Water layer decreased in general toward the northwest from maximum values in the West Spitsbergen Current west of Svalbard. Mesoscale features were superimposed on this trend, and the most apparent of these was a middepth (200–300 m) warm filament overlying the northwestern flank of the plateau. Currents in the warm filament were northward, at 2–4 cm/s, for a 10‐day period in April, providing a possible advective explanation for presence of the filament. The mechanism for these currents may involve topographic control over a western extension of the north flowing West Spitsbergen Current or, alternately, rectification of diurnal currents which are enhanced by the bottom topography of the plateau. Our data favor the tidal rectification mechanism. A warm core, anticyclonic eddy associated with the filament contained Atlantic Water which was virtually unmodified from that occurring more than 200 km farther south. Characteristics of this eddy were consistent with an origin in the West Spitsbergen Current. In the upper layer, a generally cyclonic baroclinic circulation was present about the plateau. Measured upper layer current speeds were greatest (∼8 cm/s) in the southward flowing East Greenland Current, where they exceeded the baroclinic currents by approximately 1 cm/s, which may represent a southward barotropic component. Farther to the northeast, both measured and baroclinic upper layer currents were weak and variable.