On the physics, circulation and exchange processes of the Rio de la Plata Estuary and the adjacent shelf

The Rio de la Plata Estuary and the adjacent shelf located at 35°S on the eastern coast of South America constitute one of the major Regions Of Freshwater Influence (ROFI) in the world. Remote sensing information, historical hydrographic data, long-term records of forcings from coastal stations, and high-resolution velocity and density data collected during two research cruises from the RIOPLA project are combined to examine the physical characteristics and exchange processes of this large-scale estuarine-shelf system.; The study is divided in three parts: the analysis of the forcing mechanisms, the study of the transition zone, and the investigation of the fate of the buoyant plume and development of coastal upwelling.; The dynamical boundaries of the system were delimited based on remote sensing information, analyzing the variability of the frontal zones. The estuarine turbidity front was established as the dynamical boundary between the freshwater outflow and the brackish water, constituing the transition between the inner and outer estuary. The large spatio-temporal variability across the estuary is associated with distinct dynamics controlling the northern, central and southern parts. The importance of intratidal processes contributes to the enhanced estuarine characteristics of the central and southern area, while long time-scale variability associated with buoyancy, wind and ambient flow contributes to shelf-like dynamics along the northern coast. Strong seasonality characterizes the buoyant plume as the result of complex interaction of buoyancy, winds and ambient flow. The plume is surface-advected, and the shelf is strongly stratified. The roles of a newly discovered topographically steered jet, the Pozo de Fango Current, as well as an important coastal upwelling region are discussed.