RECENT ADVANCES IN THE KNOWLEDGE OF THE RÍO DE LA PLATA ESTUARY CIRCULATION, FORCINGS AND VARIABILITY

SIMIONATO, C. G.; MECCIA, V. L.; DRAGANI, W. C.; GUERRERO, R. A.; NUÑEZ, M. N.

Foz do Iguazú, Brasil

Conferencia; 8th International Conference on Southern Hemisphere Meteorology and Oceanography; 2006

AMS

The Río de la Plata, located in the eastern coast of Southern South America, approximately at 35º S, is one of the largest estuaries of the world. With an estuarine area of 35000 Km2, a drainage area of 3.5´106 Km2 and a mean discharge of 25000 m3s-1, it ranks 4th and 5th worldwide in fresh water discharge and drainage area, respectively. Besides its geographical extension, the estuary is of great social and economical importance for the countries on its shores. The capital cities of both countries and a number of harbors, resorts and industrial centers are located there. The estuary constitutes the main source of drinking water for the millions of inhabitants in the region, for whom it is also an important amusement zone. The estuary has important fisheries and possesses the unusual feature of being a spawning and nursery area for several coastal species. Because of these reasons the estuary is being impacted by anthropogenic actions, which consequences have not been completely evaluated yet. Due to the intense discharge, when the fresh river water meets the open ocean, an intense and active salinity front followed by a fresh water plume, which influence can be tracked up to 23º S, is formed. This front is important not only for fisheries, but also modifies the coastal circulation and the mixing and convection conditions with important oceanographic implications. Despite of its social and oceanographic importance, not much was known about the Río de la Plata circulation, its variability and forcings a few years ago. Recently, in the context of National and International Projects -as UNDP/GEF Project “Environmental Protection of the Río de la Plata and its Maritime Front” (FREPLATA), and “Estudio de la dinámica oceánica y atmosférica del Estuario del Río de la Plata mediante un sistema de modelado numérico integral” (PROPLATA) funded by the Agencia Nacional de Promoción Científica of Argentina- important advances in our understanding of the physical oceanography of this system were done. This improvement is in a large extent the result of the collection, by the first time, of long term ADCP current data that allowed the study of current variability from very high frequencies to intra-seasonal time scales, and its connection to wind variability. Also, the application of numerical models contributed to the understanding of the mechanisms that control estuarine motions and the effect of their variability. As a result, our view of the behavior of this system has essentially enhanced and in many aspects has changed. In this sense, the aim of this presentation will be to discuss what we learned during the last few years and the main gaps that must be fulfilled in order to allow for an adequate representation of the system to permit its forecasting, management and control.