An ice‐water vortex at the edge of the East Greenland Current

Abstract

During the Y mer‐80 cruise in August 1980 we observed an ice feature of 60‐km diameter having the shape of a breaking wave. It lay at the edge of the East Greenland drift ice in Fram Strait with its center at 79°15′N, 00°38′E, and the wave was breaking upstream relative to the East Greenland Current. Two conductivity, temperature, and depth sections across the feature in N‐S and E‐W directions revealed warm (up to 4.3°C) water some 60 km inside the polar front, in lenses centered at 40‐m depth but with an effect to beyond 600 m. The temperature anomalies were accompanied by salinity anomalies so that there was little net effect on the density profile. The form of the sections, together with the ice distribution (observed by vertical photography from a helicopter) and surface motion (observed by tracking four radar transponders) all suggest that the feature is a vortex produced by an instability in the polar front. It has similar characteristics to vortices investigated experimentally and theoretically by Griffiths and Linden (1981a, b, 1982) and observationally by Wadhams et al. (1979).