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1 May 2007 Multiannual and Seasonal Variability of Water Masses and Fronts Over the Uruguayan Shelf
Leonardo Ortega, Ana Martínez
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Seasonal (autumn and spring) and multiannual (1991, 1995, 1996, 1997, 1998, and 2001) variability in the composition of water masses on the Uruguayan shelf were analyzed. The main difference between seasons was the presence of Tropical Water (TW) and a relative dominance of Subtropical Water (STW) over Subantartic Water (SAW) in autumn, whereas spring was characterized by a dominance of SAW and the absence of TW. Changes in the composition of water masses, surface temperature distributions, and front positions and strengths are discussed in regards to biological implications. Our results reveal seasonal changes in the frontal zone position and suggest an enhaced migration during El Niño Southern Oscillation (ENSO) warm and cold episodes, reaching higher latitudes during the former (e.g., autumn of 1998). During cold episodes, the position of the frontal zone reached lower latitudes, with prevailing cold waters over the shelf. Higher frontal strength was observed during ENSO episodes, mainly because of the haline component of CW at the surface. The combination of highly variable freshwater inputs and the occurrence of shelf convergences produced a distinctive hydrographic system with a high degree of seasonal and interannual variation and an evident impact on ecological processes.

Leonardo Ortega and Ana Martínez "Multiannual and Seasonal Variability of Water Masses and Fronts Over the Uruguayan Shelf," Journal of Coastal Research 2007(233), 618-629, (1 May 2007).
Received: 15 October 2004; Accepted: 3 January 2005; Published: 1 May 2007
Río de la Plata
shelf convergence
thermohaline fronts
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