Distribution and circulation of water masses in the Gulf of Cadiz from in situ observations

From data collected during GOLFO 2001 survey, a study was conducted on the circulation and distribution of water masses in the Gulf of Cadiz in the spring of 2001. The general surface circulation in the Gulf of Cadiz is anticyclonic with short-term, meteorologically induced variations. North Atlantic Central Water (NACW) ( γ t = 26.6 – 27.3 kg m - 3 ) is a representative water mass of the upper 1000 m of the water column. To the north, the lower part of the NACW layer ( γ t = 27.3 kg m - 3 ) is entrained by Mediterranean Water (MW) towards the open ocean while the upper layer ( γ t = 26.6 kg m - 3 ) forms part of the anticyclonic surface circulation of the Gulf of Cadiz. NACW mainly upwells in the vicinity of Capes St. Vincent and St. Maria. The upwelling off Cape St. Vincent is an open-sea process linked to a positive wind curl over the area, whereas the upwelling off Cape St. Maria is a more likely coastal process with a short time response to changes in the wind regime. The waters upwelled off Cape St. Vincent move eastwards following the main current until reaching ∼7.5 °W, where they form the filament of Cape St. Maria, whose core flows at about 40–50 m. Wind changes from westerlies to easterlies produce important temporal variability in some spatial features (the upwelling off Cape St. Maria, the surface signature of the Huelva Front or the region of warm coastal waters) in a relatively shallow layer. Below this surface layer, the hydrological characteristics are fairly independent of meteorological forcing.