Thermohaline structure around seamounts and islands off North-Eastern Brazil

The influences of current and topography on the thermohaline structure around seamounts and islands off North-Eastern Brazil were investigated. Changes in the thermohaline structure were observed close to seamounts located in the western part of the Fernando de Noronha chain and throughout the North Brazilian Chain. The main observed features were an uplifting of the isotherms and isohalines and a step-wise gradient in vertical temperature profiles, providing evidence of seamount-induced perturbations. These patterns were more pronounced above seamounts with summits located just below the thermocline base. At one seamount in the North Brazilian Chain, a pronounced upwelling cone was found, suggesting the formation of a Taylor column. Consisting of a diameter of 20 km and a height of 90 m, this dome extended into the euphotic zone and presented the greatest potential for enrichment of the surface layers. There was no evidence to show that any of the upwellings extended to the surface.