The Lofoten Vortex of the Nordic Seas

The Lofoten Basin is the largest reservoir of ocean heat in the Nordic Seas. A particular feature of the basin is 'the Lofoten Vortex', a most anomalous mesoscale structure in the Nordic Seas. The vortex resides in one of the major winter convection sites in the Norwegian Sea, and is likely to influence the dense water formation of the region. Here, we document this quasi-permanent anticyclonic vortex using hydrographic and satellite observations. The vortex' uniqueness in the Nordic Seas, its surface characteristics on seasonal, inter-annual, and climatological time-scales, are examined together with the main forcing mechanisms acting on it. The influence of the vortex on the hydrography of the Lofoten Basin is also shown. We show that the Atlantic Water in the Nordic Seas penetrate the deepest inside the Lofoten Vortex, and confirm the persistent existence of the vortex in the deepest part of the Lofoten Basin, its dominant cyclonic drift and reveal seasonality in its eddy intensity with maximum during late winter and minimum during late autumn. Eddy merging processes are studied in detail, and mergers by eddies from the slope current are found to provide anticyclonic vorticity to the Lofoten Vortex.