Ž . Chemometrics and Intelligent Laboratory Systems 47 1999 289–297 Oceanographic characterization of northern Sao Paulo Coast: ˜ a chemometric study Marcia M.C. Ferreira a, ) , Cristiano Gomes Faria a , Eduardo T. Paes b ´ a Instituto de Quımica, UniÕersidade Estadual de Campinas-UNICAMP, Campinas SP, 13081-970, Brazil ´ b Departamento de Biologia Marinha, UniÕersidade Federal Fluminense-UFF, Niteroi, RJ, 24220-970, Brazil ´ Abstract A study of the northern Sao Paulo Brazilian coast was carried out by four survey cruises during the summers of 1985r1986 ˜ and winters of 1986r1987. In this work, the seasonal variations of physical parameters and chemical composition of marine Ž . waters collected during these four cruises are investigated through the multivariate approaches of principal component PCA Ž . and hierarchical cluster analysis HCA , besides the application of the traditional thermohaline analysis. The ‘island effect’, 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 penetra- Ž . tion 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 NO y , PO 3y and O should be taken into account especially when biological processes are im- 3 4 2 portant. q 1999 Elsevier Science B.V. All rights reserved. Ž . Ž . Keywords: Principal component analysis PCA ; Hierarchical cluster analysis HCA ; Chemometrics; Oceanography; Water masses; Up- welling 1. Introduction The northern coast of Sao Paulo State is a rich en- ˜ vironment, which has attracted attention from geolo- gists and oceanographers. In this paper, a data analy- sis of the water samples collected during four survey cruises in this region is carried out. As a whole, the phenomena happening in this region are very inter- esting and peculiar, especially the intense upwelling observed during the summertime. In order to have a better understanding of these data sets, a brief intro- ) Corresponding author. E-mail: marcia@iqm.unicamp.br duction about the nature and general circulation of water masses at the Southern Atlantic Ocean will be presented. The surface circulation of the oceans is intimately tied to the prevailing wind circulation of the atmo- sphere. The horizontal movement of surface waters in the southern Atlantic is counterclockwise and oppo- wx site to its movement in the Northern Hemisphere 1 . The composition of those waters and also their den- sity, which is basically a function of temperature and salinity, are subjected to different environmental conditions such as temperature, sunlight radiation, pluvial influxes and melting of polar ices among other factors. Such differences in density promote the strat- 0169-7439r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-7439 98 00216-0