A census of North Brazil Current rings observed from TOPEX/POSEIDON altimetry: 1992-1998

Six years of TOPEX/POSEIDON altimeter data are used to investigate the form ation of rings and eddies shed by the North Brazil Current. Upper layer thi ckness maps were used to identify 34 of these features formed in the North Brazil Current retroflection region, an average of more than 5 rings and ed dies per year. The ensemble of ring trajectories closely parallels the 500 m isobath, and one out of six rings penetrate into the Caribbean Sea throug h the southern Lesser Antilles. The rest of the rings and eddies follow a n orthern trajectory past Barbados once they reach 58W. Their estimated mean translation speed is 14 km/day and their mean length scale is approximately 100 km. Our results suggest that the formation rate of NBC rings and eddie s is nearly twice that previously thought, and that they may account for mo re than 1/3 of the interhemispheric transport within the Atlantic meridiona l overturning cell.