Coastal upwelling in the San Jorge Gulf (Southwestern Atlantic) from remote sensing, modelling and hydrographic data

Abstract

Coastal upwelling is a known mechanism that generates favorable conditions for marine life. In this paper, we evaluate the conditions for the development of coastal upwelling in the San Jorge Gulf, on the west coast of the South Atlantic Ocean. The wind-based upwelling indices were calculated for 4 years (2003–2006) in three coastal regions of the gulf with different orientations. Monthly images of sea surface temperature, chlorophyll-a and wind and numerical simulations were used to analyze upwelling conditions. In addition, results of daily images, numerical simulations with daily forcings and CTD sections in the southwestern region of the gulf during the spring of 2016 and 2017 were described. The upwelling indices clearly highlight the differences between the three regions, linked to the basin geometry. Using an average of daily indices in the southwestern part of the gulf, thirteen upwelling events were detected during the warm season (November to March, 2003–2006). Numerical simulations suggest that the drop in surface temperature generated by an upwelling event in the SW region remains cold for more than a week. The wind pattern and CTD profiles during spring 2016 suggested favorable conditions for coastal upwelling compared to the profiles performed in 2017, in which wind do not appear to be upwelling-favorable.