Remotely sensed sea surface thermal patterns in the Gulf of Cadiz and the Strait of Gibraltar: Variability, correlations, and relationships with the surface wind field

Satellite image sequences (covering periods of a few days throughout the annual cycle) of the waters off southern Iberia have been analyzed in conjunction with concurrent surface wind speed data from coastal stations. Qualitative analysis reveals a large degree of temporal and spatial variability in the thermal signature of the sea surface over periods of both a few days and several months. During the summer, a cool seasurface temperature signature extends from the western Iberian coast around Cape St. Vincent and eastward as far as Fare. At the same time, a warm signature originating on the Iberian coast between Faro and Cadiz extends into the Strait of Gibraltar. These two features are shown to sometimes adopt more westerly positions, and the strait experiences regions of cool thermal signature originating at its southern side. During winter, the surface flow into the Mediterranean through the Strait of Gibraltar is anomalously warm and appears to come from the interior of the Gulf of Cadiz. Quantitative measurements show that temporal variability over timescales of a few days at individual sites is maximum in midsummer. Spatial thermal variability over the whole region is found to peak toward the end of the summer. Statistical analyses of the data reveal the coupling between the surface wind field in the Gulf of Cadiz and the surface thermal pattern (especially during the summer). Wind-induced, across-stream upwelling in the Strait of Gibraltar, although dynamically subordinate to tidal and density-driven processes, is shown to occasionally dominate the surface thermal signature.