Aspects of dissolved inorganic carbon dynamics in the upwelling system off the Galician coast

In the present paper, we report data on the partial pressure of CO2 (pCO(2)) in surface seawater off the Galician coast, obtained during four cruises carried out in summer (upwelling conditions). Over the continental shelf, two processes that have opposite effects control pCO(2) in surface waters: (a) the input from upwelling of deep cold water with high CO2 content that causes oversaturation of CO2 and (b) primary production that tends to decrease pCO(2). In offshore waters, the distribution of pCO(2) is mainly controlled by temperature change. In two distinct hydrographic coastal regions, the Rias Baixas area (RBA) and the Cape Finisterre area (CFA), the patterns of the distribution of pCO(2) are complex but, in the Rias Baixas area, the averaged pCO(2) values are systematically lower and temperature values higher. These differences between the two hydrographic regions are mainly related to the combination of outwelling from the Rias and the width of the continental shelf In the Rias Baixas area, outwelling affects significantly the adjacent inner continental shelf but to a much lesser extent the outer continental shelf In the Cape Finisterre area, the continental shelf is narrower and the ratio between the surface area of the shelf to the length of the shelf break is lower, inducing during an upwelling event, lower temperature and higher pCO(2) values in surface waters than in the Rias Baixas area. (C) 2002 Elsevier Science B.V All rights reserved.