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Matano, R.P., Combes, V., and Strub, P.T. (26-Feb-14)

The freshwater discharge from the La Plata River - the fifth largest river of the world - spreads along the coasts of Argentina, Uruguay and Brazil forming a low-salinity plume that is modulated by the effect of local wind forcing, tides and the offshore flows of the Brazil and Malvinas Currents. Previous attempts to characterize this plume have been strongly constrained by data availability and therefore have been largely focused on the shelf region. We use Aquarius sea surface salinity (SSS) data to document, for the first time, the excursions of the La Plata River plume into the deep ocean. These excursions generate the largest SSS variance of the subtropical and subpolar portions of the South Atlantic Ocean. Concurrent analysis of altimeter data indicates that the detrainment of the low salinity waters from the La Plata River is controlled by the confluence of the Brazil and Malvinas Currents. Numerical simulations indicate that the fate of the plume over the shelf is largely controlled by the local winds. Ancillary studies using passive tracers suggest that SSS data could be used to assess the outflow of shelf waters into the deep ocean.