A submesoscale coherent eddy in the Greenland Sea in 2003

Submesoscale Coherent Vortices (SCVs) have been observed earlier in the Greenland Sea, but their overall characteristics, the formation and the dissolution mechanisms, and the effects on the large-scale hydrodynamics were not well understood. In order to improve the understanding of these features, a simultaneous investigation of hydrography, chemical tracers, and full-depth velocity profiles in a SCV was employed in September 2003. The observed eddy had a homogeneous cold core from 500 m to 2500 m depth with a radius of 8 similar to 15 km. The velocity field of the eddy was higher than in the previous years, and the eddy was in strong anticyclonic rotation in the intermediate layer ( 1000 similar to 2000 m). The high velocity field led to the estimate of eddy vorticity twice as high as previous observations, and this was accounted for the eddy migration while the earlier observed eddies were rather stationary around 75 degrees N 0 degrees E. The eddy migrated northeast ward with a speed of 3 km/day driven by the background mean flow under the strong effects of the background shear, which tilted the rotation axis in the upper layer. The concentrations of sulphur hexafluoride (SF6) and chlorofluorocarbons (CFCs) in the eddy provided firm information about the source water end-members. The Greenland Sea Arctic Intermediate Water and winter cold surface water were determined as the principal eddy source waters. This differs from the earlier conception of eddies being sourced from intermediate waters at the periphery of the Greenland Basin.