HR: 09:30h
AN: OS21A-04    [Abstracts]
TI: Effects of the Seasonal Wind Variations on the Shelf Waters off Southeastern South America
AU: * Moller, O
EM: o.moller@terra.com.br
AF: Fundacao Universidade do Rio Grande, Av. Italia, Campus Carreiros, Rio Grande, RS 96201-900 Brazil
AU: Piola, A
EM: apiola@hidro.gov.ar
AF: Servicio de Hidrografia Naval, A. Montes de Oca 2124, Buenos Aires, BA C1270ABU Argentina
AU: Freitas, A C
EM: anacf@furg.br
AF: Fundacao Universidade do Rio Grande, Av. Italia, Campus Carreiros, Rio Grande, RS 96201-900 Brazil
AU: Campos, E J
EM: edmo@io.usp.br
AF: Instituto Oceanografico da Universidade de Sao Paulo, Pra‡a do Oceanografico 191, Sao Paulo, SP 05508-900 Brazil
AB: The impact of Rio de la Plata derived waters along the Uruguayan and southern Brazilian shelves has been recognized since the first oceanographic surveys were carried out in this region. These waters form a low salinity tongue that affects the circulation and stratification as well as the distribution of nutrients and biological species. The coastal low salinity plume presents a seasonal meridional displacement reaching lower latitudes (28o S) during winter and 32 o S during summer months. Historical data suggests that the seasonal plume fluctuations are a response to the variations in the along-shore wind stress. To provide a synoptic view of these processes and to establish the connection between wind and outflow variations on the distribution of the coastal waters, two oceanographic cruises were carried out in late August 2003 and February 2004. The surveys covered the continental shelf and slope of southeastern South America, between Mar del Plata, Argentina and the northern coast of Santa Catarina, Brazil. On each cruise about 90 stations were occupied, distributed in 11 cross-shelf profiles using a Seabird 911 CTD. The observations show how the Plata plume alters the circulation and property distributions causing the dominant environmental variations on the continental. The seasonal wind variations are the most important factor for the plume dynamics in the sense that: A) SW winds prevailing in winter force the northward spreading of the plume to low latitudes even during low river discharge periods. In the winter of 2003 mixtures of about 5% of Plata river waters were found at the northernmost section, located 1300 km from the Plata estuary; B) NE winds retain the plume in the southern area and spread it over the entire width of the continental shelf east of the estuary. Another effect of the summer NE winds that inhibit the northward plume penetrations is the development of coastal upwelling near Cabo de Santa Marta. Wind action also influences the dynamics and water masses variations along the continental shelf area. In this case, in areas influenced by the river discharge, Subtropical Shelf waters are kept away from the coastal region. When the influence of freshwater decreases, NE winds induce coastal upwelling cells such as observed near Cabo de Santa Marta.
DE: 1860 Runoff and streamflow
DE: 4219 Continental shelf processes
DE: 4271 Physical and chemical properties of seawater
DE: 4283 Water masses
DE: 4528 Fronts and jets
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly