Surface circulation variability in the Balearic Basin

The Balearic Basin is defined as a wide region of the western Mediterranean located in between the Liguro-Provencal and Algerian basins. The dynamics of the Liguro-Provencal Basin, in the north, is dominated by the dense water formation process associated with a permanent circulation along the continental slope: the Northern Current. The Algerian Basin, in the south, is dominated by intense mesoscale eddies and their interactions with the unstable Algerian Current. The Balearic Basin is a transition region between these two different dynamic regimes. It includes the Catalan Sea, located between the Balearic Islands and the Iberian peninsula, and the wide Gulf of Valencia in the south of this sea. Some new ideas about the surface circulation variability have been inferred from a series of NOAA satellite advanced very high resolution radiometer images, taken mainly from the autumn-winter period during 1981–1988, and also from various in situ data. The Northern Current, which flows southward along the Iberian peninsula slope, is covered in summer by a warm surface layer spreading over the whole Catalan Sea. This local warming creates one of the most intense thermal fronts in the western Mediterranean, the Pyrenees Front. Near the Balearic Islands, the flow through the sills of recent Atlantic water, partially deflected by anticyclonic eddies from the Algerian Current, creates the Balearic Front and contributes to its mesoscale variability. This variability appears to be much more intense than previously described. The Balearic Front is clearly recognized as the westward continuation of the North Balearic Front, already defined in the open sea as the northern limit of the recent Atlantic water reservoir. Finally, the Gulf of Valencia is frequently influenced by water entering from the Algerian Basin, which appears to be important in the disruption of the Northern Current and the formation of the Balearic Current, the geostrophic flow associated with the Balearic Front.