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Piola, A.R., Valla, D., Guerrero, R.A., Fenco, H., Möller, O.O., Matano, R.P., Combes, V., Chao, Y., Palma, E.D., Ruiz Etcheverry, L.A., Strub, P.T., and Saraceno, M. (14-Nov-13)

The freshwater discharge from the La Plata River generates a sea surface salinity anomaly (SSSa) that characterizes the local outflow of shelf waters into the deep ocean. In complimentary presentations we show that this shelf water outflow is a robust feature of salinity, altimeter and in-situ observations (R. Guerrero and A. Piola). Here, we discuss the kinematics and dynamics of the observed SSSa using the results of a suite of process-oriented numerical simulations. These simulations were conducted in a double nested model that includes the entire southern hemisphere but retains a very high resolution (1/36˚) in the southwestern Atlantic region. The model was forced with daily values of the La Plata River discharge and with climatological winds, monthly winds and daily winds. Our experiments indicate that the fate of the La Plata River plume is largely insensitive to the magnitude of the river discharge and it is mostly controlled by the local wind forcing in the inner and middle portions of the shelf and the influence of the neighboring western boundary currents in the outer shelf. The seasonal and interannual variations of the SSSa in the region are also discussed.