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

Iole Orselli1, Felippe Galdino1, José Luiz Azevedo2, Rodrigo Kerr Sr.3 and Catherine Goyet4, (1)FURG, Rio Grande, Brazil, (2)Federal University of Rio Grande, Instituto de Oceanografia, Rio Grande, Brazil, (3)Universidade Federal do Rio Grande, Instituto de Oceanografia, Rio Grande, Brazil, (4)University of Perpignan Via Domitia, Perpignan, France
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.