Evolution of Air-Sea CO2 Flux during ARAMIS, EGEE and ROAM

Abstract

The aim of this study is to compare evolution of the CO2 in two different areas of the tropical Atlantic Ocean. We investigate the spatial and temporal variability of CO2 fluxes, Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC) and hydrological parameters (Salinity and Temperature) in the western and eastern tropical Atlantic for three years (2005-2006-2007), using the data collected during the ARAMIS 7, 8 and 10, EGEE and ROAM cruises (2019-2020). Our results showed that Sea Surface Salinity (SSS), Sea Surface Temperature (SST), TA and DIC are higher on average in the western area than in the eastern tropical Atlantic, except the oceanic CO2 fugacity (fCO2sw). A north-south gradient is observed with high values in the south of the Equator and low values in the north. This gradient is due to the Equatorial upwelling, which upwelled CO2-rich deep water to the surface; in addition, the Guinea current (GC) transports low salinity and parameters of carbon in the eastern area and Amazon outflow at West decreases the concentration of these parameters. On average, the western area was a sink of 0.34 mmol.m-2.d-1 and the eastern basin a source of 1.15 mmol.m-2.d-1. During ROAM cruises, air-sea CO2 flux was ten times higher than during all the EGEE cruises and more for all ARAMIS cruises.