Distribution of CO2 parameters in the Western Tropical Atlantic Ocean

Abstract The variability of sea surface Total Alkalinity (TA) and sea surface Total Inorganic Carbon (C T ) is examined using all available data in the western tropical Atlantic (WTA: 20°S-20°N, 60°W-20°W). Lowest TA and C T are observed for the region located between 0°N-15°N/60°W-50°W and are explained by the influence of the Amazon plume during boreal summer. In the southern part of the area, 20°S-10°S/40°W-60°W, the highest values of TA and C T are linked to the CO 2 –rich waters due to the equatorial upwelling, which are transported by the South Equatorial Current (SEC) flowing from the African coast to the Brazilian shore. An increase of C T of 0.9 ± 0.3 μmol kg −1 yr −1 has been observed in the SEC region and is consistent with previous published estimates. A revised C T -Sea Surface Salinity (SSS) relationship is proposed for the WTA to take into account the variability of C T at low salinities. This new C T -SSS relationship together with a published TA-SSS relationship allow to calculate p CO 2 values that compare well with observed p CO 2 (R 2  = 0.90).