Oceanographic characterization of northern Sمo Paulo Coast: a chemometric study

A study of the northern São Paulo Brazilian coast was carried out by four survey cruises during the summers of 1985/1986 and winters of 1986/1987. In this work, the seasonal variations of physical parameters and chemical composition of marine waters collected during these four cruises are investigated through the multivariate approaches of principal component (PCA) and hierarchical cluster analysis (HCA), besides the application of the traditional thermohaline analysis. The `island effectʹ, coastal and shelf break upwelling phenomena and its influence in the phytoplankton community are clearly visualized through the spatial interpolation of PCA scores and of chlorophyll concentration for the column water profiles. The intense penetration of tropical water mass (TW) over the continental shelf towards the coast observed during the winter 1987 cruise, can also be visualized through the scores contour plots. Complementing the usual thermohaline analysis, chemometrics has shown that other elements such as NO3−, PO43− and O2 should be taken into account especially when biological processes are important.