THE USE OF THERMAL IMAGES TO INFER MARINE CIRCULATION FEATURES: MEDITERANEAN EXAMPLES

The overall functioning of the Mediterranean Sea, which transforms Atlantic Water (AW) into Mediterranean Waters (MW), has been comprehended for decades now, and so is the process of dense water formation, which leads AW to sink in specific offshore northern zones of both basins. However, some circulation features are still being debated in the western basin, while a similar debate is currently being initiated in the eastern one. One main reason for these controversies lies in the fact that most studies do not take into account the large spatio-temporal variability induced by the mesoscale dynamics, which is intense in the whole Mediterranean, especially in the southern parts of both basins. The flow of AW forms unstable currents that generate meanders and eddies along the Algerian and the Libyo-Egyptian slopes, respectively. These eddies have diameters ranging from 50 to 150 km (up to 250 km), vertical extents from 100s to1000s of metres (down to the bottom: ~3000m), and lifetimes from month to year (up to 3 years at least). These eddies propagate alongslope downstream (eastward) at a few km/day, can detach from the current to drift in the open sub-basin, and can have an impact on the general circulation. In order to interpret correctly the in situ observations, it is thus of the utmost importance to locate and track these phenomena with a fine spatio-temporal interval. The medium-resolution satellite images (pixel ~ 1km, ~1 pass/day) are an extremel