On the dynamics of surface cold filaments in the Mediterranean Sea

Thermal NOAA/AVHRR satellite images relative to the years 1997–2000 are analyzed in this study, in order to obtain a first systematic identification of the sites of highest frequency in cold filaments in the Mediterranean Sea, as well as their properties. These sites are characterised by upwelling and/or the funnelling of strong cold winds by a somewhat irregular coastal orography. Indeed, intense air–sea interaction in the coastal zone generates a particularly strong input of potential vorticity into the sea. This in turn gives origin to cold filaments and jets. In the Mediterranean Sea, the geographical zones with a higher frequency in these jets are the two lobes of the southern Sicilian coast, the sea off eastern Sardinia, that south of the island of Crete, where a particularly intense mesoscale field is evident, and the Balkan coast of the Adriatic Sea. A chosen subset of the examined images is here used to obtain an estimate of a bulk coefficient M for mass exchange between filaments and ambient water, in order to explain the along-flow warming observed in most of the satellite images, at each filament site.