Rio de la Plata estuary response to wind variability in synoptic to intraseasonal scales: 2. Currents' vertical structure and its implications for the salt wedge structure

Abstract

[1] The first acoustic Doppler current profiler current data collected at two locations of the Río de la Plata salt wedge during a period of around 6 months and salinity profiles gathered at and around those locations are used to study the vertical structure of currents' response to wind variability in synoptic to intraseasonal timescales and its implications for stratification. Results indicate that the estuary rapidly responds to prevailing southwesterlies/northeasterlies with currents that decay toward the bottom with only little rotation in depth. For the less frequent southeasterlies/northwesterlies the estuary develops a strong vertical structure with a defined inversion in current direction between surface and bottom layers. These patterns derive from the estuary's geometry and bathymetry. Results have important implications for the salinity vertical structure that are verified on the analyzed profiles. First, the combination of the bathymetry and coastline with the prevailing wind variability is highly favorable to the maintenance of a salt wedge structure in this estuary. Second, weakening and eventually breakdown of stratification can only occur for intense and/or persistent southeasterly winds, which even can be very strong, are not frequent. This can explain why the Río de la Plata displays the unusual feature of being an area of spawning and a nursery for a number of coastal species that use the wedge as an essential element for their reproduction. Results show that stratification is highly affected by short-term wind variability, which is its major characteristic in the area, changing the classical concept of summer-winter seasonality as the main feature of estuarine variability.Citation: Simionato, G. C., V. L. Meccia, R. Guerrero, W. C. Dragani, and M. Nuñez (2007), Rio de la Plata estuary response to wind variability in synoptic to intraseasonal scales: 2. Currents' vertical structure and its implications for the salt wedge structure,

Population Structure of the SW Atlantic Estuarine Crab Neohelice granulata Throughout Its Range: a Genetic and Morphometric Study

“…1). Coastal marine waters in this region are strongly influenced by the Río de la Plata, one of the largest estuaries in the world with a watershed of 35,000 km 2 (Simionato et al 2007). This system drains the waters of the Paraná and Uruguay rivers Fig.…”

“…Major ocean currents (heavy black lines), presumptive direction of shelf circulation (dashed lines), schematic extension of Plata Plume Waters (PPW, shadow area), and 200-m isobath (grey dotted line); compiled from Huret et al (2005), Palma et al (2008), and NOAA's Global Drifter Program (courtesy R. Lumpkin, NOAA/AOML). MA Maricá, FL Florianópolis, RG Río Grande, AS Arroyo Solís, BS Bahía Samborombón, MC Mar Chiquita, BB Bahía Blanca, SB San Blas, SA San Antonio, RN Río Negro, RSJ Riacho San José discharging an average 23,000 m 3 s −1 of freshwater onto the SW Atlantic shelf at 35°S, reaching maximum values as high as 50,000 m 3 s −1 under extreme conditions (Simionato et al 2007;Piola et al 2008). Such discharge levels produce a large, low salinity plume that plays a major role in the dynamics of the inner shelf by modifying the vertical structure of water masses (Huret et al 2005).…”

Phenotypic variation of south-western Atlantic clamMactra isabelleana(Bivalvia: Mactridae)

“…There are several publications about the relationship between shell morphology and environmental factors such as latitude, temperature, currents, depth and type of sediment (e.g. Stramma & Peterson, 1990;Guerrero et al, 1997;Framiñan et al, 1999;Simionato et al, 2007). In our study, the seasonal cycle of temperature, with cold and warm periods, affected similarly the four localities sampled (Guerrero et al, 1997).…”

A trans-ecosystem fishery: Environmental effects on the small-scale gillnet fishery along the Río de la Plata boundary

“…The RdP discharge,~23,000 m 3 s À1 of freshwater to the western South Atlantic shelf at 35 S (Jaime et al, 2002), results in a estuarine region that encompasses approximately 35,000 km 2 (Framiñan et al, 1999) and the meridional extension of the plume of low salinity extends northeastward (beyond 26 S) in fallewinter and southwestward (reaching 37 S, Punta M edanos, Fig. 1) in springesummer as a result of the changes in the along-shore wind stress and freshwater discharge (Piola et al, 2005;Simionato et al, 2007;Jaureguizar et al, 2007). In shallower waters, the seasonal and inter-annual variation in RdP freshwater inputs modifies the spatial extents of estuarine conditions (along-shore salinity gradient) influencing the distributions of marine and estuarine fish species (Prionotus punctatus vs Prionotus nudigula, Jaureguizar et al, 2007) and their ontogenetic stages (Cynoscion guatucupa, Jaureguizar and Guerrero, 2009;Jaureguizar et al, 2006a;Micropogonias furnieri, Jaureguizar et al, 2003a), thereby affecting fish assemblage composition along the coast (Jaureguizar et al, 2003b(Jaureguizar et al, , 2006bGarcía et al, 2010;Barletta et al, 2010).…”