NEAR-SURFACE CIRCULATION OVER THE YERMAK PLATEAU IN NORTHERN FRAM STRAIT

Using hydrographic data collected over an 11-year period, a view of the circulation pattern existing in the upper 40 m over the Yermak Plateau of northern Fram Strait is presented. Past work has indicated that the primary influx of Atlantic Water into the central Arctic Ocean is accomplished via a single narrow current that borders the northern coast of Svalbard. Volumetric analysis of the available hydrographic data has shown the presence of a shallow, previously undocumented plume of Atlantic-derived water entering the Arctic Ocean directly over the Litke Trough. This plume represents one part of a large, near-surface (predominant in the upper 20 m) mushroom-shaped salinity-defined dipole structure that has a lateral extent of some 450 km. The eastern vortex of this dipole is poorly documented due to a lack of data-coverage but, the better documented western limb of the dipole, which is the central topic of this paper, represents a recirculated filament of modified Atlantic Water that moves cyclonically around the periphery of the Yermak Plateau. T-S analysis of the original data and the use of a simplified model depicting the evolving T-S properties of Atlantic Water as it interacts with the atmosphere and ice cover support this view. Additionally, over the larger-scale distribution fields of salinity (which primarily defines density) and dynamic height, a well defined front in both salinity and dynamic height is observed 200-500 km north of Svalbard trending east northeast.