Northward migration of Cape São Tomé rings, Brazil

Abstract

In the present work, nine years of altimetry data are analyzed in combination with sea surface temperature and ocean color images in order to track Brazil Current eddies generated at Cape São Tomé, Brazil. Direct evidences are presented that at least six eddies detach from the main current during this period giving rise to isolated rings. Two rings move southward, bordering the current, while four migrate northward, and translate in the direction of the Tubarão Bight. These rings eventually reach the bight, leading to a cyclonic circulation in that region that is analogous, at surface levels, to what would be observed during formation of the Vitória Eddy. For one ring, the observations are complemented by in situ measurements: a Lagrangian surface drifter, an expandable bathythermograph section during the ring formation at Cape São Tomé, and acoustic Doppler current profiler data during the ring formation and inside the bight. The cyclonic circulation within the bight in this occasion reaches levels much deeper than those previously reported for locally-generated eddies. These results indicate that properties of shelf and slope waters near Cape São Tomé can be carried upstream the Brazil Current, eventually influencing the coastal waters further north, with possible ecological and environmental implications.