The surface salinity maximum of the South Atlantic

Like most other ocean basins, the maximum sea surface salinity region (MSR) in the South Atlantic shows a large displacement from the region of maximum difference between evaporation and precipitation (E-P), suggesting that ocean processes play a key role in determining the location of the MSR. We use outputs from a general circulation model (ECCO v4r3) to analyze the mixed layer salinity balance and disentangle the interaction of atmospheric forcing and oceanic processes in both regions. The MSR balance is dominated by evaporative surface fluxes and entrainment, while advection and diffusion play a secondary role. On the other hand, in the region of maximum E-P, the high surface freshwater loss is partially compensated by horizontal advection of low salinity waters, which is responsible for decreasing the salinity below that observed in the MSR. Using a particle tracking model, we find that MSR waters originate mostly from re-circulation in the Tropical South Atlantic and from the Tropical North Atlantic and Indian Oceans. After reaching the MSR, most of those waters flow southward in austral summer along the Brazil Current (1.6 Sv, 1 Sv = 106 m3 s−1), and northward in winter along the North Brazil Current (3.5 Sv). This seasonal variability in the fate of the salty water is modulated by the seasonal migration of the South Equatorial Current bifurcation region. Tracking of particles released at the base of the MSR mixed layer shows a subducted salt river with an estimated transport of 2.6 Sv on the 25.2 kg m−3 neutral density surface that flows northward along the North Brazil Current and retroflects just north of the equator as part of the Equatorial Undercurrent. These high-salinity waters are a significant contributor to the upper limb of the Atlantic meridional overturning circulation and the eastern Tropical Atlantic and their variability.Fil: Aubone, N.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; ArgentinaFil: Palma, Elbio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Piola, Alberto Ricardo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Instituto Franco-argentino sobre Estudios del Clima y sus Impactos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Physical changes recorded by a deep diving seal on the Patagonian slope drive large ecological changes

International audienceThe Patagonian slope is the region where Subantarctic waters and bathymetry give raise to physical and ecological processes that support a rich biodiversity and a large-scale industrial fisheries. Unique among the species that depend on this region is the deep diving southern elephant seal, Mirounga leonina. We report here on changes in the foraging behavior of a female seal explained by the combined effect of a cold and high salinity water mass and a decrease in surface chlorophyll-a concentration. Behavioral and oceanographic data from about 5000 profiles of temperature, conductivity, pressure, light and prey encounters were collected within an area ranging 59.5–61°W and 46–47.5°S, at depths of 300–700 m, on the Patagonian slope, during November–December 2018. A decrease in temperature (0.15 °C) and an increase in salinity (0.03) was found below the mixed layer, during December. Light data revealed a significant increase of irradiance in December (almost reaching the ocean bottom) associated with a decrease of chlorophyll-a in the upper levels. Concomitantly, the seal had a different diving behavior in December, foraging near the surface at night and close to the bottom during daylight hours. Also, the seal doubled the prey capture attempts in December compared to November. This study reveals the importance of ocean physical properties on seal's diving and foraging behavior, and how this changes, although small, can impact on seals diet and body composition during their post-breeding trips

Physical changes recorded by a deep diving seal on the Patagonian slope drive large ecological changes

The Patagonian slope is the region where Subantarctic waters and bathymetry give raise to physical and ecological processes that support a rich biodiversity and a large-scale industrial fisheries. Unique among the species that depend on this region is the deep diving southern elephant seal, Mirounga leonina. We report here on changes in the foraging behavior of a female seal explained by the combined effect of a cold and high salinity water mass and a decrease in surface chlorophyll-a concentration. Behavioral and oceanographic data from about 5000 profiles of temperature, conductivity, pressure, light and prey encounters were collected within an area ranging 59.5–61°W and 46–47.5°S, at depths of 300–700 m, on the Patagonian slope, during November–December 2018. A decrease in temperature (0.15 °C) and an increase in salinity (0.03) was found below the mixed layer, during December. Light data revealed a significant increase of irradiance in December (almost reaching the ocean bottom) associated with a decrease of chlorophyll-a in the upper levels. Concomitantly, the seal had a different diving behavior in December, foraging near the surface at night and close to the bottom during daylight hours. Also, the seal doubled the prey capture attempts in December compared to November. This study reveals the importance of ocean physical properties on seal's diving and foraging behavior, and how this changes, although small, can impact on seals diet and body composition during their post-breeding trips.Fil: Aubone Videla, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Saraceno, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Torres Alberto, María Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Campagna, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Ster, L. Le. La Rochelle Université; Francia. Centre National de la Recherche Scientifique. Observatoire Océanologique de Villefranche Sur Mer; FranciaFil: Picard, B.. La Rochelle Université; FranciaFil: Hindell, M.. University of Tasmania; AustraliaFil: Campagna, Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Wildlife Conservation Society; Estados UnidosFil: Guinet, C. R.. La Rochelle Université; Franci

On the complementary information provided by satellite images, Lagrangian drifters and a regional numerical model: a case study in the San Matias Gulf, Argentina

Satellite images are of great help to understand the ocean circulation. In coastal regions, high-resolution images of chlorophyll-a (chl-a) concentration deliver a very accurate picture of the coastal currents and jets that are often transient features difficult to track otherwise. In this paper we combine clear-sky 750-m-resolution chl-a images with the trajectories of five Lagrangian drifters that have been deployed in the San Matías Gulf (SMG), Argentina, and outputs from a regional numerical model, with the objective to improve the knowledge of the surface circulation in the region. Improving the knowledge of the circulation in SMG is very important to determine critical areas for spawning and recruitment of fishing resources and the distribution of marine biodiversity. However, knowledge of the region is limited because of the scarce observations. The trajectories obtained with the drifters follow, at first order, isobath contours, confirming the presence of a closed circulation cell of approximately 70 km in diameter centered at 41.4°S, 64.5°W, in good agreement with previous studies based on hydrographic data and numerical models. The drifters also highlighted the dominant role of the tidal currents and showed speeds of up to 82 cm/s, suggesting that the dissipation of kinetic energy in the gulf is very high. Near the west coast the trajectories displayed complex circulation patterns that are in very good agreement with the high-resolution satellite images of chl-a. The joint analysis of the satellite images and drifter trajectories shows a strong jet that separates from the coast and tilts from a N-S direction to a SW-NE direction, probably due to persistent northerly winds. These features were not described before and could have important consequences for the ecology of local species.Fil: Saraceno, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Tonini, Mariano Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales. Universidad Nacional del Comahue. Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales; ArgentinaFil: Williams, Gabriela Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Aubone, N.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; ArgentinaFil: Olascoaga, J.. University of Miami; Estados UnidosFil: Beron Vera, F.. University Of Miami. Rosenstiel School Of Marine Atmospheric Science; Estados UnidosFil: González, Raul Alberto Candido. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentina. Universidad Nacional del Comahue. Escuela de Ciencias Marinas; ArgentinaFil: Soria, Mariano Valentin. Universidad Nacional del Comahue. Escuela de Ciencias Marinas; ArgentinaFil: Saad, Juan Francisco. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentina. Universidad Nacional del Comahue. Escuela de Ciencias Marinas; ArgentinaFil: Svendsen, Guillermo. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin