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Buenos Aires, Argentina

Matano R.P.,Oregon State University | Palma E.D.,National University of the South | Palma E.D.,CONICET | Piola A.R.,Servicio de Hidrografia Naval | Piola A.R.,University of Buenos Aires
Ocean Science | Year: 2010

The oceanic circulation over the southwestern Atlantic shelf is influenced by large tidal amplitudes, substantial freshwater discharges, high wind speeds and - most importantly - by its proximity to two of the largest western boundary currents of the world ocean: the Brazil and Malvinas currents. This review article aims to discriminate the dynamical processes controlling the interaction between this extensive shelf region and the deep-ocean. The discussion is focused on two broad regions: the South Brazil Bight to the north, and Patagonia to the south. The exchanges between the Brazil Current and the South Brazil Bight are characterized by the intermittent development of eddies and meanders of the Brazil Current at the shelfbreak. However, it is argued that this is not the only - nor the most important - influence of the Brazil Current on the shelf. Numerical simulations show that the thermohaline structure of the South Brazil Bight can be entirely ascribed to steady state, bottom boundary layer interactions between the shelf and the Brazil Current. The Malvinas Current does not show the development of eddies and meanders, but its influence on the Patagonian shelf is not less important. Models and observations indicate that the Malvinas Current not only controls the shelfbreak dynamics and cross-shelf exchanges but also influences the circulation in the shelf's interior. © Author(s) 2010.

Arndt J.E.,Alfred Wegener Institute for Polar and Marine Research | Schenke H.W.,Alfred Wegener Institute for Polar and Marine Research | Jakobsson M.,University of Stockholm | Nitsche F.O.,Lamont Doherty Earth Observatory | And 12 more authors.
Geophysical Research Letters | Year: 2013

The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 is a new digital bathymetric model (DBM) portraying the seafloor of the circum-Antarctic waters south of 60°S. IBCSO is a regional mapping project of the General Bathymetric Chart of the Oceans (GEBCO). The IBCSO Version 1.0 DBM has been compiled from all available bathymetric data collectively gathered by more than 30 institutions from 15 countries. These data include multibeam and single-beam echo soundings, digitized depths from nautical charts, regional bathymetric gridded compilations, and predicted bathymetry. Specific gridding techniques were applied to compile the DBM from the bathymetric data of different origin, spatial distribution, resolution, and quality. The IBCSO Version 1.0 DBM has a resolution of 500 × 500 m, based on a polar stereographic projection, and is publicly available together with a digital chart for printing from the project website (www.ibcso.org) and at http://dx.doi.org/10.1594/PANGAEA.805736. Key Points The first regional bathymetric compilation covering the entire Southern Ocean A new keystone dataset for Antarctic research The southern equivalent to IBCAO is now released ©2013. American Geophysical Union. All Rights Reserved.

Campos P.C.,Grande Rio University | Moller Jr. O.O.,Grande Rio University | Piola A.R.,Servicio de Hidrografia Naval | Piola A.R.,University of Buenos Aires | And 3 more authors.
Journal of Geophysical Research: Oceans | Year: 2013

The Santa Marta Grande Cape (CSM) area, a relatively steep and narrow continental shelf off southeast Brazil, is under the influence of the Brazil Current and intense seasonal variations of the wind field that affect the composition of water masses and their circulation. Hydrographic data, satellite-derived wind stress, and numerical simulations are used to characterize the seasonal and shorter period variability of the oceanographic conditions off CSM, in the area between 27°S and 30°S. The study is focused on the upwelling episodes and the dynamical mechanisms associated with these events. Field data and numerical results indicate significant seasonal changes in the oceanographic structure, the water mass composition, and the dynamical balance. During fall and winter, when southwesterly winds prevail and the frequency of meteorological frontal systems increases, the region is characterized by waters of continental origin, the Plata Plume Water (PPW). During spring and summer, deeper waters reach the surface layer due to the action of northeasterly winds. Coastal upwelling events are revealed by surface temperature minima observed south of CSM. Synoptic data show that these events occur in pulses associated with changes in the wind direction. Analysis of the numerical results shows that this particular location of the upwelling band results from the synergy between shelf-break upwelling and the regional shelf circulation induced by the northeasterly winds, both of which are modulated by changes in the coastline orientation and shelf width. © 2013. American Geophysical Union. All Rights Reserved.

Lantzsch H.,University of Bremen | Hanebuth T.J.J.,University of Bremen | Chiessi C.M.,University of Sao Paulo | Schwenk T.,University of Bremen | Violante R.A.,Servicio de Hidrografia Naval
Quaternary Research (United States) | Year: 2014

The continental margin off the La Plata Estuary (SE South America) is characterized by high fluvial sediment supply and strong ocean currents. High-resolution sediment-acoustic data combined with sedimentary facies analysis, AMS-14C ages, and neodymium isotopic data allowed us to reconstruct late Quaternary sedimentary dynamics in relation to the two major sediment sources, the La Plata Estuary and the Argentine margin. Sediments from these two provinces show completely different dispersal patterns. We show that the northward-trending La Plata paleo-valley was the sole transit path for the huge volumes of fluvial material during lower sea levels. In contrast, material from the Argentine margin sector was transported northwards by the strong current system. Despite the large sediment volumes supplied by both sources, wide parts of the shelf were characterized by either persistent non-deposition or local short-term depocenter formation. The location and formation history of these depocenters were primarily controlled by the interplay of sea level with current strength and local morphology. The high sediment supply was of secondary importance to the stratigraphic construction, though locally resulting in high sedimentation rates. Thus, the shelf system off the La Plata Estuary can be considered as a hydrodynamic-controlled end-member. © 2014 University of Washington.

Boltovskoy D.,University of Buenos Aires | Boltovskoy D.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Correa N.,Servicio de Hidrografia Naval | Bordet F.,Area Ecologia | And 4 more authors.
Freshwater Biology | Year: 2013

Toxic cyanobacterial blooms and biological invasions are major threats to freshwater systems worldwide. While usually dealt with independently, the two threats can interact to produce synergistic or antagonistic outcomes. The aim of this survey is to analyse interactions between the cyanobacterium Microcystis spp. and the Asian invasive mussel Limnoperna fortunei. On the basis of 9 years of observational data in a large subtropical reservoir (Salto Grande, Argentina-Uruguay), we analyse causal relationships between recurring summer-early autumn blooms of Microcystis spp. and recruitment by L. fortunei. Reproduction of the mussel was interrupted during dry summers (January-April), coinciding with periods of peak Microcystis spp. growth and low water discharge (which favours build-up of algal biomass). On the other hand, wet summers with high discharge rates were characterised by low Microcystis spp. densities and high numbers of L. fortunei larvae in the water column. Of the seven South American waterbodies investigated, Salto Grande was the only one with very marked cyanobacterial blooms and where larval numbers decrease to near zero during January-April; in all others, reproduction peaks in January-April. The assumption that microcystin-producing algae are responsible for these troughs during periods when elsewhere larvae are very abundant was reinforced by experimental results indicating that microcystin-LR is highly toxic to the mussel's larvae, eliminating 58-100% of animals in 48 h at 10-20 μg L-1. Paradoxically, high concentrations of microcystin in water are probably partly due to L. fortunei's own activity, which enhances growth of Microcystis spp. through modification of nutrient concentrations, selective grazing of solitary Microcystis spp. cells over colonial ones and production of chemical cues that trigger the formation of colonies. These interactions have important implications for the management of biofouling of industrial raw cooling water facilities by the byssate mussels, as well as policies oriented at curtailing the spread of the invasive bivalve. © 2013 John Wiley & Sons Ltd.

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