THE EDDY FIELD OF THE SOUTH-EAST ATLANTIC OCEAN: A STATISTICAL CENSUS FROM THE BEST PROJECT

C.M. Duncombe Rae,1,2 S.L. Garzoli 2 and A.L. Gordon 2

1. Sea Fisheries Research Institute, P.Bag X2, Rogge Bay, 8012 Cape Town, SOUTH AFRICA. 2. Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, U.S.A.

ABSTRACT

Data collected during the Benguela Sources and Transports project were examined to determine some statistical properties of the eddy field observed in the Cape Basin. Seven anticyclonic eddies were encountered during the hydrographic surveys. Two of these were shown to be of Brazil Current origin (this paper and Smythe-Wright et al. [1995]). Inverted echo-sounder records of acoustic travel time were scaled to the depth of the thermocline, represented in the Cape Basin by the 10 C isotherm. These records indicate that a minimum of four to six eddies, assumed to be of Agulhas origin, entered the Cape Basin per year during the sampling period. They were associated with depressions in the 10oC isotherm records ranging from 100 to 400 m and of a duration between 30 and 100 days. The thermocline appears to shallow appreciably after the passage of an eddy before relaxing to the local mean. Estimates of the heat and salt contents of the hydrographically surveyed eddies indicated that the mean available heat and salt anomalies of the eddies were 0.55 x 1020 J and 3.5 x 1012 kg respectively. Extrapolating the hydrographic data to the eddies detected in the IES record shows the eddy field responsible for the transfer of 2.2 to 3.3 x 1020 J per year (0.007 PW), 14 to 21 x 1012 kg salt per year, and 2.6 to 3.8 x 106 m3.s-1.