Ocean-atmosphere CO2 exchanges at the Brazil Malvinas-Confluence Region

Oceans are responsible for sequestering approximately 1/4 of anthropogenic carbon emissions annually. The Southwest Atlantic Ocean (SAO) is one of the largest global carbon sink areas. The main objective of this study is to investigate how the intense horizontal sea surface temperature (SST) gradient and the atmospheric stability condition modulate CO₂ fluxes at SAO. A combination of in-situ, satellite, and reanalysis data set were used from October 14 to 27, 2018 to achieve this objective. The in-situ data were collected during the scientific cruise on board the Brazilian Navy polar vessel Almirante Maximiano which is part of the Brazilian Antarctic Program. The ocean-atmosphere CO₂ fluxes exhibited a complex behavior during the experiment. The Brazilian Coastal Current (BCC) behaved as a CO₂ sink due to the biochemical parameters (e.g. salinity, and chlorophyll). The confluence areas between waters from BCC and Brazil Current (BC), and BC and Malvinas Current (MC) were the areas with the highest CO₂ absorption during the study period. This result is mainly because of the proximity to the Chlorophyll-rich and less saline waters of the La Plata River and the cold and fresh waters of the MC. Moreover, this is owing to the intense wind speed, which increases the CO₂ flux between the ocean and atmosphere. The Brazil Malvinas Confluence (BMC) behaved as a CO₂ sink, and the modulation of CO₂ fluxes was due to the intense horizontal gradient of SST combined with the moderate surface wind and turbulence. During the experiment, the MC sequestered less carbon than other regions because of the influence of high-pressure atmospheric systems near the region, which inhibited mass exchange between the ocean and atmosphere. This research emphasizes how data collection efforts should be continued to expand our knowledge of the importance of the SAO in the global carbon balance.