Trends in sea surface temperature and air-sea heat fluxes over the South Atlantic Ocean

The understanding of latent and sensible heat fluxes (LHF and SHF, respectively) is essential to improve our knowledge on how the atmosphere and oceans interact. In this work we identified trends of LHF and SHF in the South Atlantic (SA) Ocean from 1982 to 2015 and evaluated the potential drivers that contribute to those trends. Based on the Objectively Analyzed air-sea Fluxes (OAFlux) dataset, the European Centre for Medium Range Weather Forecasts (ERA-Interim) and the Optimum Interpolation sea surface temperature (SST) Analysis Version 2 we analyze trends and interannual variability of seasonal heat fluxes and variables influencing them. Heat fluxes trends in the SA have a strong regional and seasonal dependence. The highest increase of heat fluxes is found over the region delimited to the West and to the South by the Brazil Current Front (referred to as the Extended Brazil Current Region; ExtBCR).The humidity (temperature) differences and -U10m in the ExtBCR only contributed to explain trends of LHF (SHF) in winter. Other mechanisms should be considered to explain the LHF and SHF trend observed in summer and in the rest of the SA. The close correspondence found between the trends in temperature and humidity differences and the trend in SST, indicates that the largest driver of trends in heat fluxes over the ExtBCR are the SST trends. We argue that the expansion and intensification of the South Atlantic Subtropical High causes an increase of wind speed which intensifies the western boundary current, leading to an increase of SST and therefore an intensification of heat fluxes.