Scales of spatial and temporal variation for the pelagic processes in the Gulf of Cadiz (Spanish text)

The goal of this PhD Thesis is to analyze the variability in phytoplankton distribution in the gulf of Cadiz in relation to the oceanographic processes that affect the basin. In order to undertake this study, different methodologies have been implemented as remote sensing analysis and data obtained in situ along different oceanographic cruises carried out in the zone. The results derived from processing sea surface temperature (SST) and colour images between 1998 and 2002 show that more productive waters appear during the months of spring and autumn and are mainly located in the proximities of the coastal region, whereas the minima of surface chlorophyll take place over the summer. An Empirical Orthogonal Functions analysis has been performed on the weekly chlorophyll composites in order to identify different dynamical areas near cape San Vicente, Huelva Front, a coastal area between Cadiz and Huelva and cape Trafalgar. Spatial variability of the chlorophyll in these zones is markedly related to meteorological forcing.; The process of formation of North Atlantic Surface Water (NASW) has a direct influence on the depth where the deep chlorophyll maximum (DCM) occurs. An isopycnal of 26.66 kg/m3, that indicates the interface between the deep limit of the ASW (Atlantic Surface Water) and the shallow limit of the NACW (North Atlantic Central Water) behaves as a tracer of the nutrient gradient and consequently reveals the DCM position. The intensity of the DCM depends on the diffusive and advective flows acting in the surroundings of the isopycnal. Westerly winds generate a rise of the isopycnal around cape Santa Maria which favours the input of nutrients into the photic layer. The opposite effect is observed with easterlies. As a novel contribution, combined information of remote sensing of SST and colour images in conjunction with the application of lagrangian models for phytoplankton growth are used to estimate vertical velocities in upwelling areas.