THE RIO DE LA PLATA ESTUARY RESPONSE TO WIND VARIABILITY IN SYNOPTIC TIME SCALE: SALINITY FIELDS AND BREAKDOWN AND RECONSTRUCTION OF THE SALT WEDGE STRUCTURE

MECCIA V. L.; SIMIONATO, C. G.; GUERRERO, R. A.

JOURNAL OF COASTAL RESEARCH

COASTAL EDUCATION & RESEARCH FOUNDATION

Lugar: Royal Palm Beach, Florida; Año: 2012

0749-0208

The Río de la Plata estuary response to wind variability in synoptic time scale is studiedwith the Estuary, Coastal and Ocean Model forced by tides, runoff and idealized winds. AncillaryCTD data from synoptic oceanographic cruises are used to validate the conclusions extractedfrom the simulations. Results show that the estuary response to wind variability can be explainedin terms of four characteristic patterns associated with winds that blow with a dominantcomponent either along or across the estuary axis. Cross-estuary winds from the southwest(northeast) produce a northward displacement (southwestwards retraction) of the surface salinityfront towards (from) the Uruguayan coast and cause downwelling (upwelling) betweenMontevideo and Punta del Este. Along-estuary winds with a downstream (upstream) componentproduce a net outflow (inflow) of continental surface waters and inflow (outflow) of bottom shelfwaters, resulting in an intensification (weakening) of the vertical structure. Stratification can becompletely destroyed by strong or persistent southeasterly winds, which are not frequent in theregion, and it completely recovers in a relatively short period of time (10 - 15 days) after windrelaxation. Consequently the salt wedge structure is present in the Río de la Plata during most ofthe year. This implies that significant vertical mixing events producing exchanges of water andproperties between the surface and bottom waters occur only a few times along the year. As aresult, the Río de la Plata shows strong retentive features favoring biota by retaining eggs andlarvae, but also favoring pollutant accumulation.