Continuous pCO₂ measurements in surface water of the Northeastern tropical Atlantic

Abstract

The partial pressure of CO₂ in the area of the northeastern tropical Atlantic influenced by the Mauritanian upwelling is highly variable in time and space. Partial pressures between 300 and 450 μatm were observed in autumn 1991 and spring 1992. In the oceanic region off the Mauritanian coast, the range of spatial variations in pCO₂ was low (between 365 and 395 μatm, in autumn, and between 332 and 353 μatm in spring). In this area, the seasonal pCO₂ variations were mainly due to temperature effects. Even in the upwelling region, where the biomass was high, there was not a single relationship valid for the whole area between chlorophyll fluorescence and pCO₂. On the other hand, pCO₂ at a constant temperature was, on an average, decreasing with temperature. A comparison with older data shows that pCO₂ in the surface seawater of the open ocean has evolved as the atmospheric pCO₂ the last twenty years.