Processos de ressurgência na porção Norte da plataforma continental Leste brasileira e seus fluxos de troca com a Baía de Todos os Santos

Abstract

Upwelling and shelf-estuary exchange processes were studied based on a high resolution regional model (ROMS) outputs near Todos os Santos Bay (13ºS). Climate Forecast System Reanalysis (CFSR) wind data were used to complement the model results. Upwelling and exchange flow processes were studied based on high-resolution regional model (ROMS) outputs near Todos os Santos bay (13ºS). Upwelling and uplift events from 2008 to 2012 were analyzed at the South Equatorial Current bifurcation region and in the Salvador Canyon near 13ºS. Upwelling and uplift events occurred predominantly during spring and summer. Previous studies have suggested upwelling implications for fisheries and fish diversity in the region. Uplift events were, on average, longer than upwelling events. Spatially, the strongest events were found over the adjacent shelf of Todos os Santos Bay and Salvador Canyon. This was also the region with the most frequent events. Analysis of forcing mechanisms revealed that wind-driven upwelling, mainly due to upward Ekman pumping, is dominant, with current-driven upwelling providing an additional contribution. Connectivity between Salvador Canyon and Todos os Santos Bay upwelling processes was observed in 20 events, preferentially during the austral summer. This connectivity was linked to a northward coastal undercurrent, which, in turn, advected upwelled/uplifted water from the canyon to the bay-adjacent shelf area. Connectivity occurred under two conditions: i) intense canyon upwelling and ii) low influence of the Brazil Current flow on the shelf. The results of this study demonstrate that wind-driven upwelling contributes directly to the connectivity phenomenon, whereas Brazil Current encroachment inhibits this process. Shelf-estuary exchange pulses from 2008 to 2014. Exchange pulses occurred under 2 distinct circulation patterns, namely Circ+ and Circ pulses. The connectivity between Jaguaripe river and Todos os Santos bay entrance was observed. The increase in river discharge in association with up-estuary winds promoted the northward advection of the river plume toward the main entrance of the estuary, creating a horizontal density gradient over the western shoal. Finally, our results demonstrate that studies at higher latitudes are quite applicable to low latitude estuaries when depth and/or basin's width indicate that Earth's rotation effect is relevant.