Observations of coastal upwelling off Uruguay downshelf of the Plata estuary, South America

Abstract

We analyze hydrographic and current observations of an upwelling center off eastern South America on the Uruguayan coast (ϳ35S) and downshelf from the Rio de la Plata estuary. Our observations show that the buoyancy-driven subtidal alongshore circulation is modulated by winds. During the winter, strong upwelling-favorable local winds forced the Rio de la Plata buoyant plume poleward. In the summer, the plume detached from the coast with warm and saline subtropical waters intruding from the north. These waters bounded the upwelling of cold waters in the nearshore area off Uruguay. A shallow submarine canyon cutting obliquely across the shelf facilitates the advection of cold waters into the coastal upwelling domain. An upwelling jet was detected off Uruguay for summer conditions, while for winter the plume configuration generated strong horizontal shear of along-shelf currents. Cross-shelf circulation was dependent on the coastal stratification. Under low stratification (summer) a two-layer circulation developed, with thick surface and bottom mixed layers flowing in opposite directions. High stratification levels (winter) modified this pattern by allowing circulation along a thick stratified interior.The existence of upwelling was linked to the history of wind events and shelf stratification. During the winter, downwelling winds frequently restore the plume, so the upwelling efficiency is very low. In the summer, downwelling events are less frequent and intense, so that the cumulative effect of upwelling events act to export the Plata freshwaters offshore. The reduction of inner-shelf stratification increases the likelihood of a full upwelling to the surface. Analysis of the wind-induced Ekman transport suggests that the Uruguay upwelling system reflects a seasonal wind pattern modulated by significant interannual variability.

The Imprint of the Geological Inheritance and Present Dynamics on Uruguayan Inner Shelf Sediments (South-Western Atlantic)

“…In this regard, the summer SST climatology favoured an upwelling phenomenon (SST < 22°C) affecting stations S15 to S18. This correlates to the coastal bands of negative sea surface temperature anomalies observed along the southern coast of Uruguay and indicators of upwelling associated with strong easterly and northeasterly winds (e.g., Palma et al, 2008;Pimenta et al, 2008;Simionato et al, 2010, Trinchín et al, 2019.…”

“…Another essential feature of the UCM is the occurrence of coastal upwelling events. These events occur along the estuarine and oceanic coasts and are more frequent during the summer season, when NE winds prevail (Framiñan et al 1999;Pimenta et al 2008;Simionato et al 2009Simionato et al , 2010Meccia et al, 2013;Trinchín et al, 2019).…”

Range extension of the mud crab Eurypanopeus depressus (Smith, 1869) (Decapoda, Panopeidae): A new record for the coastal south of Brazil

“…More than an expansion of distribution, this can be interpreted as a record of a new geographic locality. The occurrence in the Patos Lagoon indicates that the La Plata River, which has been considered as a significant biogeographical barrier on the southwest Atlantic coast, might have allowed the expansion of the range of the species, possibly through larval transport due to advances from the river plume northward (Pimenta et al 2008).…”

Determinação do grau da influência terrestre versus marinha ao longo da transição Río de La Plata - Oceano Atlântico Sul, através de proxies bióticos e abióticos

“…(2013) na região de estudo (sendo neste caso, relativamente menores para o C org ). para regiões próximas (SE brasileiro) e RdlP (Mahiques et al, 2009;Burone et al, 2013) (Framiñán et al, 1999;Framiñán, 2005;Pimenta, 2008;Simonato, 2009;Luz et al, 2013). Estes são mais frequentes na primavera e no verão do que no inverno e outono, e são produto dos ventos de NE e N (mais intensos e frequentes no período de primavera-verão austral) os quais deslocam a água superficial da pluma do Martins e Urien, 2004).…”

“…Esta maior influência da vazão continental na AC, e a existência de ressurgências de margem de plataforma, provocadas pelas frentes (Framiñán et al, 1999;Pimenta, 2008;Luz et al, 2013), aporta material orgânico e nutrientes os quais se refletem em uma elevada concentração de clorofila-a, produção primária, grande número de foraminíferos bentônicos e espécies relacionadas com recursos pesqueiros economicamente muito importantes na área (Ciotti et al, 1995;Muelbert e Sinque, 1996;Longhurst, 1998;Sunyé e Servain, 1998, Brandini et al, 2000Saraceno et al, 2005;Eichler et al, 2008). Assim mesmo, condiciona diretamente todos os processos sedimentológicos Mahiques et al, 2008;Möller et al, 2008).…”