Tracking eddies in the subtropical North-Western Atlantic Ocean

Abstract

Anticyclonic eddies generated in the North Brazil Current retroflection area are traced along the coast of North Brazil and into the Caribbean Sea using TOPEX/ POSEIDON altimetric observations and a 1/6°eddy-resolving ocean general circulation model simulation. About 16 to 20 anticyclonic eddies were identified during the period from October 1992 to June 1997. These eddies propagate northwestward along the continental shelf. As these eddies approach the Lesser Antilles island chain, their amplitudes decrease. Most of these eddies were able to penetrate the narrow passages of the Windward Islands. Once they enter the Caribbean Sea, their amplitudes increase, probably due to the strong meridional shear of the Caribbean Current. It takes more than a year for these eddies to travel from the North Brazil coast, through the Caribbean Sea and eventually to the Yucatan Peninsula. The observed eddy sizes range from 200 to 600 km, their average amplitude is about 15 cm, their average propagation speed is around 14 cm/s, and their time scale is about 80 to 100 days. In contrast to the tropical instability waves which are only present in the autumn season, no seasonal dependence is observed in the generation of these anticyclonic eddies.