The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Numerical simulations

Published in Journal of Geophysical Research: Oceans, v. 119(11):7949-7968 
Authors

Matano, R.P., Combes, V., Piola, A.R., Guerrero, R.A., Palma, E.D., Strub, P.T., James, C., Fenco, H., Chao, Y. and Saraceno, M.
Publication year 2014
DOI https://doi.org/10.1002/2014JC010116
Affiliations
  • College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA
  • Departamento Oceanografía, Servicio de Hidrografía Naval and Departamento de Ciencias de la Atmósfera y los Océanos, Universidad de Buenos Aires, and UMI/IFAECI, CONICET, Buenos Aires, Argentina
  • Instituto Nacional de Investigacíon y Desarrollo Pesquero, Mar del Plata, Argentina
  • Departamento de Física, Universidad Nacional del Sur and Instituto Argentino de Oceanografía, Bahía Blanca, Argentina
  • Remote Sensing Solutions, Inc., Barnstable, Massachusetts, USA
  • Centro deInvestigaciones del Mar y la Atmósfera, and Departamento de Ciencias de la Atmósfera y los Océanos, Universidad de Buenos Aires, and UMI/IFAECI, CONICET, Buenos Aires, Argentina

 
IAI Program

CRN3
IAI Project CRN3070
Keywords
sea surface salinity
SSS variability
Southwestern Atlantic Ocean

Highlights

  • Cross-shelf exchanges in the SW Atlantic are characterized by SSS anomalies
  • Cross-shelf exchanges are partially controlled by local winds
  • Seasonal variations of the cross-shelfexchanges are small

Abstract

A high‐resolution model is used to characterize the dominant patterns of sea surface salinity (SSS) variability generated by the freshwater discharges of the Rio de la Plata (RdlP) and the Patos/Mirim Lagoon in the southwestern Atlantic region. We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the austral winter (JJA), the plumes leave the shelf region north of the BMC. During the austral summer (DJF), the plumes are entrained more directly into the BMC. A sensitivity study indicates that the high‐frequency component of the wind stress forcing controls the vertical structure of the plumes while the low‐frequency component of the wind stress forcing and the interannual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross‐shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross‐shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.