Water mass and coastal current variability near Barbados, West Indies

Abstract

Moored current meter observations complimented by conductivity‐temperature‐depth (CTD) profiles and shipboard acoustic Doppler current profiler measurements have revealed two distinctly different coastal circulation patterns south of the island of Barbados, West Indies, in the springs of 1990 and 1991. In the first year an abrupt increase in speed and change in direction of the currents south of the island was found to be associated with a large, anticyclonic, horizontally sheared circulation and a marked variation in temperature‐salinity characteristics. The shift in currents was also accompanied by the incursion of a shallow pool of low‐salinity water, a strong internal semidiurnal tidal signal, and a change in the location of larval fish assemblages west of the island. Rapid variations in current speed and direction were also observed in 1991, though less persistent than in the previous year. In this year the island was at one time completely surrounded by a large, shallow pool of low‐salinity water. A comparison was made of the 1990 hydrographic observations with CTD data from the National Oceanographic Data Center archive for the region 0°–20°N, 40°–60°W. This suggests that the variation in hydrographic characteristics was due to the intrusion of a water mass of North Brazil Current origin which displaced the ambient North Atlantic Subtropical Underwater around the island. Several recent studies have demonstrated that mesoscale anticyclonic eddies formed near the retroflection region of the North Brazil Current can be advected toward the eastern Caribbean before being dissipated. It is concluded that the most likely cause of the observed high‐energy event in 1990 was the passage of such an eddy past Barbados.