Carbonate system parameters during the propagation of Agulhas eddies through the South Atlantic Ocean: inferences from satellite data

The Agulhas eddies are the largest mesoscale structures of the world’s oceans. Some studies suggested that these structures influence the Atlantic Meridional Overturning Circulation, due to the amount of heat and salt they transport. Agulhas eddies also influence ocean-atmosphere interactions. They are anticyclonic structures, associated to regions with positive heat flux anomalies, what tend to warm the atmospheric boundary layer. Even admitting that these mesoscale eddies play a vital role on ocean-atmosphere interactions, their impact on the changes of the marine carbonate system are not yet constrained. Recent studies pointed out that Agulhas eddies play a significant role on atmospheric CO₂ uptake and contain higher anthropogenic carbon concentrations than their surrounding waters. Thus, they are able to enhance the acidification of the South Atlantic Central Water. As these previous studies were conducted using cruise data (i.e., considering a snapshot of a period of the Agulhas eddies lives) we aimed here to characterize the CO₂ system behaviour of 25 eddies shed by the Agulhas retroflection during their propagation through the South Atlantic Ocean. We used the mesoscale eddy AVISO product and the satellite data of sea surface salinity, sea surface temperature, and chlorophyll considering their trajectories. We applied regression models in those satellite data to recreate the superficial seawater pCO₂ and total alkalinity of these Agulhas eddies as a function of those environmental parameters along their trajectories. The other carbonate system parameters were derived using the CO2SYS software. Preliminary results of satellite-derived pCO₂ indicate that the observed Agulhas eddies behaved as CO₂ sinking structures during their entire lives. As expected, the CO₂ uptake was mainly driven by temperature. The next step of this work is to investigate the drivers of the CO₂ sink behaviour along the propagation of Agulhas eddies throughout the South Atlantic Ocean.