SACC IAI CNR 2 2076


Setting

The continental shelf of the southwestern Atlantic (SWA) is an irregularly shaped platform that extends from the tropic of Capricorn to the southern tip of South America. With a total area of 2.7 million km2 this broad and relatively smooth submarine terrace is the largest continental shelf in the southern hemisphere. Located along its western margin are some of the most important industrial and commercial centers of Latin America: Rio de Janeiro, Sao Paulo, Montevideo, and Buenos Aires.

The SW Atlantic

Along its eastern margin, the strong Brazil and Malvinas currents flow in opposition and collide, creating one of the most energetic regions in the world ocean, namely the Brazil/Malvinas Confluence (BMC). The oceanic circulation over the SWA shelf is characterized by exceptionally large tidal amplitudes, substantial freshwater discharges, high wind speeds and intrusions from the neighboring western boundary currents. All these mechanisms are believed to be significant in the development of the region’s outstanding biological activity. The high biological activity causes high CO2 fluxes between the coastal seas, the atmosphere and the adjacent open oceans. By linking the terrestrial, oceanic and atmospheric carbon reservoirs the SWA plays an important role in the global carbon cycle and climate. Given these remarkable characteristics it is surprising the little that we know about its circulation and its influence on the marine ecosystems and the regional climate.

Schematic circulation in the western South Atlantic shelf, adapted from Piola and Matano (2001)

Schematic circulation in the western South Atlantic shelf, adapted from Piola and Matano (2001)

Schematic circulation in the western South Atlantic shelf, adapted from Piola and Matano (2001)

SeaWIFs January chl-a climatology depicting the biologically important regions, which are

SeaWIFs January chl-a climatology depicting the biologically important regions, which are

Problems

The accelerated rates of coastal urbanization and industrial development of recent decades, combined with the necessity to account for the influence of the SWA on global problems (e.g., the thermohaline circulation, the assessment of the carbon fluxes into the deep ocean, the evaluation of climate change on the coastal region, etc), has lead national and international funding agencies to promote the study of region. During the upcoming years, for example, the World Bank and national funding agencies from Argentina, Brazil, France and the United States will support research projects aimed to collect physical and biological information over the SWA. Most of these projects, however, are either focused on a specific region (e.g., the Patagonia shelf, the South Brazil Bight, the Plata River, etc) or are confined to a relative small group of investigators (usually from a single institution).

SACC – CRN2

In this project the IAI sponsors the collaboration and coordination among several existing groups. With previous support from the IAI and other agencies our group has already began carried out multinational and multidisciplinary collaborations involving 13 institutions form 4 5 IAI member countries. In this new stage we will expand the scientific scope and geographic composition of the network. Our goal is to advance our understanding of the physical mechanisms that influence the biological processes in highly productive regions of the western South Atlantic

Project Goal

To determine the physical mechanisms that control biological processes in highly productive regions of the western South Atlantic and their variability from intra- to interannual times scales.

Project Objectives

3.3.1 Evaluate the role of thermohaline fronts in the enhancement of biological production.

  • Study the effect of the circulation and mixing on the distribution of early life stages of species of economic importance (i.e. shrimp, squids, fish).
  • Study changes in biological properties associated to mesoscale oceanographic features, such as fronts, eddies and upwelling.
  • Produce scenarios of biological production under different oceanographic conditions.

3.2.2 Identify the physical mechanisms that control the mass, vorticity, energy and biogeochemical (species, nutrients, CO2, sediments) exchanges between the deep ocean and the continental shelf, and their variability from the subseasonal to interannual time scales.

  • Explore the role of western boundary currents mesoscale variability on the nutrient enrichment of the outer shelf and shelf break via eddy pumping and shelf/deep ocean exchanges.

3.2.3 Determine the influence of buoyant inflows on the production and biodiversity of the marine environment.

  • Evaluate the buoyancy and nutrient supply from the Straits of Magellan, the Plata and Patos Lagoon, and their variability from synoptic to interannual time scales
  • Characterize the paleo-environmental conditions of continental discharges based on a sedimentological study of the continental shelf.
Ongoing and funded observations in the SWA high productivity regions. The black open

Ongoing and funded observations in the SWA high productivity regions. The black open