Surface circulation and dynamics of the Balearic Sea

Abstract

The Balearic Sea forms the transition zone between two key regions in the western Mediterranean Sea having well-defined dynamics: the Liguro-Provenqal and the Algerian Basins. Studies of the large scale circulation during the seventies depicted a predominant cyclonic circulation. Later studies found that this circulation was actually associated with two permanent density fronts. ,One on the continental shelf slope and a second distinctly separated front located over the Balearic Islands shelf slope. Those fronts arise because of thermohaline differences between low salinity coastal waters, more saline, offshore MAW in the central part of the basin and less saline, coastal waters of the Balearic Islands. More recently, intensive field experiments that have included current meter moorings, radio tracked drifters, satellite imagery and high resolution CTD and ADCP sampling, revealed the importance of mesoscale variability, one of the most representative topics of the western Mediterranean dynamics. These field studies indicate strong temporal and spatial variability in the area. In several studies, energetic eddies and filaments associated with the slope fronts have been observed. These rapidly evolving instabilities, characterized by velocities almost an order of magnitude higher than the mean large scale current, have a significant effect on the shelf/slope exchange processes and as a result strongly affect the biomass distribution in the Balearic Sea. There are several physical mechanisms that could account for this important mesoscale variability. The relationship between these instabilities and bottom topography has been suggested in several studies. Local wind forcing has been also shown to play an important role as an input of energy in the inertial range affecting upper layer circulation and internal-near inertial oscillations at the thermocline. Frequent changes of water inflows from the north and south also modify and characterize the seasonal circulation. Seasonal and Interannual Variability of the Western Mediterranean Sea Coastal and Estuarine Studies, Volume 46, Pages 73-91 Copyright 1994 by the American Geophysical Union