While the global ocean is a net sink of atmospheric CO₂, the tropical Atlantic is generally a source with strong interannual variability driven largely by physical processes (Le Quéré et al., 2018; Padin et al., 2010). PIRATA sites were equipped with CO₂ sensors from 2006 (Lefèvre et al., 2008), providing the first sustained time series of fCO₂, SST, and oxygen in the region, contributing to the Integrated Carbon Observation System. PIRATA cruises also provided key spatial coverage: underway fCO₂ and carbonate samples revealed strong zonal and meridional gradients, including CO₂ drawdown near the Congo River plume and enhanced outgassing in coastal upwelling areas (Bonou et al., 2016; Koffi et al., 2010). In the western basin, Brazilian cruises confirmed the dominant role of physical drivers in shaping fCO₂ variability (Lefèvre et al., 2014).
