Deep structure of an open sea eddy in the Algerian Basin

The Algerian Basin dynamics is dominated by the presence of very energetic mesoscale structures. Deep open sea eddies are key features that influence the regional circulation of water masses at all depths. In May 1998, an open sea eddy was sampled near 38°N 2°E by means of CTD, Acoustic Doppler Current Profiler (ADCP) and surface Lagrangian drifters. For the first time, it has been possible to characterise one of these mesoscale structures in its full depth, down to 2800 m. The density distribution indicated the presence of lighter water in the centre of the eddy from the surface to the bottom. The direct velocity measurements in the surface layer, plus the determination of the baroclinic shear from CTD data, evidenced that the anticyclonic motion was present in the whole water depth.