GEOSTROPHIC VELOCITY AND TRANSPORT VARIABILITY IN THE BRAZIL MALVINASCONFLUENCE

This paper presents the results from a study of the dynamics of the Br azil-Malvinas Confluence in the southwestern Atlantic based on data co llected with an array of inverted echo sounders. Dynamic height series were obtained at 10 different sites for a period of 15 months. The da ta are analyzed in terms of dynamic height, geostrophic velocities and transports. The large variability previously inferred from satellite observations is observed in the dynamic height field of the surface, r elative to 100 m, and is attributed to changes in the latitude of sepa ration, the meandering of the Confluence front towards the east, and e ddy generation. The eddy circulation observed is both cyclonic and ant icyclonic. These eddies are observed both between the southward edge o f the Brazil Current and the northward edge of the Malvinas Current an d superimposed to the main flows. The diameter of the eddies is two to three times the Rossby Radius of deformation. The highest observed va lues of the geostrophic velocities (102 cm s-1 at 36.5-degrees-S and - 61 to -62 cm s-1 at 37.6-degrees-S) are associated with the large shea r in frontal situations. The northward penetration of the Malvinas Cur rent occurs during 1988 and 1990 during the southern hemisphere winter . This is in agreement with results from a previous deployment, satell ite observations and model results. The Brazil Current transport is at 35.2 and 36.5-degrees-S, -24 Sv towards the south and -20 Sv between 37.7 and 38-degrees-S (reference 1000 m). The transport of the Brazil Current return at 35.2-degrees-S is of the same value as the southward flow: 24 Sv. For the Malvinas Current, the estimates indicate a north ward transport of 5 Sv at 37.7-degrees-S (reference 1000 m). These val ues are considered as a lower limit. The array captured only about hal f the flow due to the location of the deployments, and only the barocl inic component. The transport should be at least doubled to compensate the value obtained for the Malvinas return flow at the same latitudes , -24 Sv.