Surface CO 2 parameters and air–sea CO 2 flux distribution in the eastern equatorial Atlantic Ocean

Abstract

Six cruises have been carried out in the eastern equatorial Atlantic between June 2005 and September 2007 to study the distribution of the surface total alkalinity (TA) and dissolved inorganic carbon (DIC). During these cruises a strong north–south gradient is observed in sea surface temperature (SST), sea surface salinity (SSS), DIC and TA. Low surface salinity waters are associated with low TA and low DIC. They are observed north of the equator (0°–6°N) in the Guinea current, whereas higher concentrations are observed south of the equator. TA–SSS and DIC–SST–SSS relationships are determined and are used to calculate surface fCO 2. Monthly maps of fCO 2 are obtained, on a one degree grid, using SST and SSS fields for the region 10°W–10°E, 6°N–10°S from June to November. The monthly mean flux of CO 2 ranges from 1.69 ± 1.94 mmol m − 2 day − 1 in November to 2.78 ± 1.65 mmol m − 2 day − 1 in August over the region. Using the same gas exchange coefficient, the CO 2 flux was calculated with the climatological ΔfCO 2. Our estimates show a stronger gradient between northern and southern waters than the climatology, probably due to a lack of data in the climatology as well as its 4° latitude by 5° longitude resolution.