A numerical study of the Southwestern Atlantic Shelf circulation: Stratified ocean response to local and offshore forcing

Abstract

[1] This article discusses the results of a suite of numerical simulations of the oceanic circulation in the Southwestern Atlantic Shelf region that are aimed to characterize its mean circulation and seasonal variability and to determine the dynamical mechanisms controlling them. Our experiments indicate that south of 40°S the mean circulation is dominated by a general northeastward flow in the southern portion of the shelf, which is controlled by the discharges from the Magellan Straits, tidal mixing, wind forcing, and the offshore influence of the Malvinas Current farther north. The region from 40°S to 33°S presents the highest seasonal variability, with intrusions of cold sub-Antarctic waters and the northward expansion of mixtures of the Río de la Plata waters in late fall and a slower retraction of the plume during spring-summer. Wind stress variability seems to be the primarily forcing mechanism for the plume dynamics. These model results are in reasonable agreement with observations and previous model results. The present solutions also reveal important additional features of the shelf response. The along-shelf circulation, for example, is largely driven by the western boundary currents in the middle and outer shelf, with induced transports that are 3 times larger than in experiments forced by winds and tides. The analysis also indicates that the upstream influence of the Malvinas Current is felt well beyond its retroflection point in the form of a northward middle-shelf current and that the interaction of the Brazil Current with the Brazilian shelf topography is primarily responsible for inducing steady shelf break upwelling.

Seasonal and Inter-Annual Analysis of Chlorophyll-a and Inherent Optical Properties from Satellite Observations in the Inner and Mid-Shelves of the South of Buenos Aires Province (Argentina)

“…The Colorado River is the second source of freshwater, with peak discharge in late spring (215 m 3 · s −1 ) [1,6]. The oceanic circulation is characterized by the development of an anticlockwise gyre during winter and its dissolution during spring and summer [7] ( Figure 1c). Cuadrado et al [8] described the northward propagation of the Colorado River plume, from the river mouth to the mouth of the Bahí a Blanca Estuary.…”

Trophic ecology of Mugil liza at the southern limit of its distribution (Buenos Aires, Argentina)

“…On the other hand, large concentrations of silt-clay are found in the coastal region at the southern site between Bahia Blanca and San Blas Bay, known as Anegada Bay (Figure 1), due to the contribution of the Colorado River and Bahia Blanca estuary, while coarse sediments were located between the Negro River mouth and San Blas Bay, since this area is affected by an intense coastal drift from the southern region (ALIOTTA et al, 1999). The hydrological dynamics of the study area often create a potential retention area which displays an average top-to-bottom integrated anticlockwise gyre (PIOLA & RIVAS, 1997;PALMA et al, 2008). These environmental characteristics determined differences between the benthic communities, on which M. liza feeds, of the two sites (BREMEC; LASTA, 1998).…”

Growth and reproduction investment of the young of the year of the squat lobster <em>Munida gregaria</em> (Crustacea: Anomura) in the Patagonian coast

“…Its maximum depth is approximately 100 m. The water in the San Jorge Gulf is a mixture of sub-Antarctic water from the Cape Horn Current and low-salinity water of the Magellan plume. The latter, which originated from the discharge from the Strait of Magellan, extends along the inner shelf of southern Patagonia (Palma et al 2008). In coastal areas, the minimum surface temperature is 7.6°C and the maximum is 17.3°C.…”