Presented at the 2013 Aquarius/SAC-D Science Team MeetingThe largest variance in sea surface salinity in the subtropical South Atlantic is observed at the western flank of the basin, off the Río de la Plata. The salinity distribution in this area is controlled by the confluence of the Malvinas and the Brazil currents as well as the export of diluted waters from the neighboring shelf. We show that SAC-D/Aquarius data can be used to document the surface expression of the interaction between the shelf and the deep-ocean in this region. Mesoscale features and their variability are identified using SSSaq along-track and gridded data by us using a 3-week weighted moving average. Our analysis shows plumes of low-salinity waters extending offshore from the shelf and interacting with warm and cold eddies spawned by the Brazil and Malvinas currents; validated with ARGO and SST (AQUA-MODIS) data. We focus on two particular events, which are further analyzed using time series of river discharge, scatterometer winds and altimetry data. A comparison between Aquarius and OSCAR data shows a remarkable agreement between the time evolution of the salinity distributions observed by Aquarius and the surface velocity field inferred from altimetry. The evolution surface salinity during a 4-week period presents low-salinity plumes extending 500 km into the open ocean where they are advected by the swift currents that characterize the Confluence.