A description of the physical oceanography of the coastal ocean around Cape Sao Vicente is presented. This region of the Iberian Peninsula, where the west and south coasts meet at right angles, forms part of the eastern boundary of the North Atlantic. The description is based on four data sets: 1. The historical hydrographic data base recorded between 1900 and 1990; 2. Sea level, meteorology, and nearshore sea surface temperature time series, from 1981 to 1992, at coastal sites within 200 km of Cape Sao Vicente; 3. Over 1200 advanced very high resolution (AVHRR) satellite images of sea surface temperature (SST) from 1981 to 1995; 4. in situ data from June 1994, which include underway meteorology, acoustic doppler current profiler (ADCP) and conductivity-temperature-depth probe (CTD) surveys.
The large scale hydrography shows a marked seasonality of the surface fields. Though rather uniform in winter, they show strong gradients in summer when the isolines tend to parallel the coastline as a result of upwelling of cooler and fresher water inshore. A mean alongshore pressure gradient, stronger in summer and off the southern coast, tends to force the flow westward along the southern coast and northward around the Cape. During upwelling favourable winds the alongshore flow can be reversed, at least in the upper layers, more easily off the western coast. Upwelling and non-upwelling patterns of SST are investigated. Cold waters upwelled off the western coast are observed primarily to turn cyclonically around the Cape, but also to feed the equatorward development of the Cape Sao Vicente filament, which at times develops a westward branch by meandering of the upwelling jet. A coastal warm countercurrent is observed during upwelling unfavourable winds. The cruise principally observed the region during such a relaxation period. Remnants of the previous upwelling episode, advecting cold low spiciness water cyclonically around the Cape from regions further north, and an inshore warm counterflow, turning poleward around the Cape with speeds up to 0.4 m/s were identified in the data. No cold filament feature was present in the region at the time. The wind stress and the alongshore pressure gradient are the major forcings acting in the region. The relative strength of these mechanisms dictates the alongshore circulation of the upper coastal ocean.