Montes de Oca, Argentina
Montes de Oca, Argentina

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Hernandez-Molina F.J.,University of Vigo | Paterlini M.,Servicio de Hidrografia Naval SHN | Somoza L.,Instituto Geologico Y Minero Of Espana Igme | Violante R.,Servicio de Hidrografia Naval SHN | And 6 more authors.
Marine and Petroleum Geology | Year: 2010

Partially buried giant drifts are located in the southern-most sector of the Argentine continental margin, generating a bathymetric jump at the base of the slope. They are characterised as giant, asymmetrical elongated, mounded contourite drifts, and are described in detail here for the first time. This description is mainly based on the bathymetric and multichannel seismic reflection profiles data. Their origin and evolution in the Argentine Basin are decoded and their implications in an area crucial for geologic and palaeoceanographic reconstruction between the Atlantic and Antarctica are discussed. The buried giant drifts are divided into two zones by a large seamount. The major giant-drift (50. km wide, 300. km long, and having a sedimentary thickness of nearly 1. km) is located to the south of this seamount and oriented to the north, where its summit outcrops at present seafloor. Here, its asymmetric external shape is characterised by a steep, western side and a gently dipping, smooth eastern side, with internal reflections prograding eastward. Based on its position, morphology and internal characteristics, it has been deduced that this giant-drift was generated in the Argentine Basin by the southward branch of a confined large loop of the Antarctic Bottom Deep Water, from the Eocene-Oligocene boundary (coevally with the Drake Passage opening) until the middle Miocene. However, after a major palaeoceanographic change in the mid-to-late Miocene a new oceanographic scenario was established that fossilised these giant drifts. These changes produced a new depositional style in the margin, resulting in initiation of the present contourite depositional system and morphologic features over the slope. Extension of North Atlantic Deep Water circulation into the Southern Hemisphere and deepening of Antarctic Bottom Water circulation in the Argentine Basin are herein postulated as the factors that controlled said changes. These giant drifts show strong seismic evidence of hydrates and free gas that are ripe for energy resources exploration, thus demonstrating the economic potential of contourite deposits in deep marine environments. © 2010 Elsevier Ltd.


Mauna A.C.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero Inidep | Lomovasky B.J.,CONICET | Lomovasky B.J.,University of the Sea | Franco B.C.,Servicio de Hidrografia Naval SHN | And 8 more authors.
Journal of Shellfish Research | Year: 2010

Oceanographic fronts and their associated physical processes create strong spatial patterns of food availability that may influence the metabolic processes of bivalves located within these areas. To investigate this prediction, we used mass-size relationships, condition indices, and carbon (C) and nitrogen (N) stable isotopes to evaluate how the biological characteristics of the Patagonian scallop (Zygochlamys patagonica) are influenced by the Shelf Break Front (SBF) and the surrounding chlorophyll a concentration (CSAT). Scallops from 2 transects across the front (38-39°S, 55-56°W, southwest Atlantic Ocean) were sampled with a nonselective dredge in October 2005. The results show that the SBF position, estimated from satellite-derived sea surface temperature, was more stable than the CSAT maximum concentrations. If muscle tissue is considered a better indicator of food shifts as previous studies indicate, scallops located far from the front have lower C isotopic signatures and C/N ratios than scallops located near the front. However, the lack of a shift in scallop organ conditions suggest that spatial differences in food supply are not strong enough during the time of year we sampled to impact scallop development, as may happen at a seasonal scale. Our results show that complicated interactions exist between oceanographic structures, food supply, and scallop life history characteristics.


Voigt I.,University of Bremen | Henrich R.,University of Bremen | Preu B.M.,University of Bremen | Preu B.M.,Chevron | And 5 more authors.
Marine Geology | Year: 2013

The Mar del Plata Canyon is located at the continental margin off northern Argentina in a key intermediate and deep-water oceanographic setting. In this region, strong contour currents shape the continental margin by eroding, transporting and depositing sediments. These currents generate various depositional and erosive features which together are described as a Contourite Depositional System (CDS). The Mar del Plata Canyon intersects the CDS, and does not have any obvious connection to the shelf or to an onshore sediment source. Here we present the sedimentary processes that act in the canyon and show that continuous Holocene sedimentation is related to intermediate-water current activity. The Holocene deposits in the canyon are strongly bioturbated and consist mainly of the terrigenous "sortable silt" fraction (10-63. μm) without primary structures, similarly to drift deposits. We propose that the Mar del Plata Canyon interacts with an intermediate-depth nepheloid layer generated by the northward-flowing Antarctic Intermediate Water (AAIW). This interaction results in rapid and continuous deposition of coarse silt sediments inside the canyon with an average sedimentation rate of 160. cm/kyr during the Holocene. We conclude that the presence of the Mar del Plata Canyon decreases the transport capacity of AAIW, in particular of its deepest portion that is associated with the nepheloid layer, which in turn generates a change in the contourite deposition pattern around the canyon. Since sedimentation processes in the Mar del Plata Canyon indicate a response to changes of AAIW contour-current strength related to Late Glacial/Holocene variability, the sediments deposited within the canyon are a great climate archive for paleoceanographic reconstructions. Moreover, an additional involvement of (hemi) pelagic sediments indicates episodic productivity events in response to changes in upper ocean circulation possibly associated with Holocene changes in intensity of El Niño/Southern Oscillation. © 2013 Elsevier B.V.


Folch A.,Barcelona Supercomputing Center | Mingari L.,Servicio de Hidrografia Naval SHN | Mingari L.,CONICET | Osores M.S.,CONICET | Collini E.,Servicio de Hidrografia Naval SHN
Natural Hazards and Earth System Sciences | Year: 2014

Volcanic fallout deposits from the June 2011 Cordón Caulle eruption on central Patagonia were remobilized in several occasions months after their emplacement. In particular, during 14-18 October 2011, an intense outbreak episode generated widespread volcanic clouds that were dispersed across Argentina, causing multiple impacts in the environment, affecting the air quality and disrupting airports. Fine ash particles in volcanic fallout deposits can be resuspended under favorable meteorological conditions, particularly during strong wind episodes in arid environments with low soil moisture and poor vegetation coverage. As opposed to eruption-formed ash clouds, modeling of resuspension-formed ash clouds has received little attention. In consequence, there are no emission schemes specially developed and calibrated for resuspended volcanic ash, and few operational products exists to model and forecast the formation and dispersal of resuspension ash clouds. Here we implement three dust emission schemes of increasing complexity in the FALL3D tephra dispersal model and use the 14-18 October 2011 outbreak episode as a model test case. We calibrate the emission schemes and validate the results of the coupled WRF-ARW (Weather Research and Forecasting - Advanced Research WRF)/FALL3D modeling system using satellite imagery and measurements of visibility (a quantity related to total suspended particle concentration at the surface) and particulate matter (PM10) concentration at several meteorological and air quality stations located at Argentina and Uruguay. Our final goal is to test the capability of the modeling system to become, in the near future, an operational forecast product for volcanic ash resuspension events.©Author(s) 2014.


Hernandez-Molina F.J.,Royal Holloway, University of London | Soto M.,ANCAP | Piola A.R.,Servicio de Hidrografia Naval SHN | Piola A.R.,University of Buenos Aires | And 9 more authors.
Marine Geology | Year: 2015

For the first time, a multidisciplinary approach to evaluate the influence of bottom currents in the Uruguayan continental margin is presented. Bathymetric data and multichannel 2D and 3D seismic reflection profiles were used to construct a morphosedimentary map to interpret and decode sedimentary and oceanographic processes along the Uruguayan continental margin. Based on these results, an extensive contourite depositional system on the margin is described, which contains an impressive array of large erosive, depositional (drifts) and mixed (terrace) features, which have been generated primarily by the near-bottom flows associated with water masses of Antarctic and subantarctic origin. From the Eocene-Oligocene boundary up to present time, the long-term influence of water masses from higher southern latitudes, in combination with down-slope sedimentary processes have strongly controlled the overall margin morphology. Most of the features described here, were formed during the middle/late Miocene epoch due to paleoceanographic shifts that include the arrival of Antarctic Intermediate Water along the margin, which in combination with deeper Antarctic Bottom Water are fundamental in the margin evolution. In combination with Quaternary climatic and eustatic changes in sea level, fluctuations of the Brazil-Malvinas Confluence influenced subsequently glacial and interglacial stages as recognized in sedimentary features defined here. These paleoceanographic changes controlled the sedimentary stacking pattern and the locations of high amplitude reflections along the contourite terraces, which could be associated with sandy deposits. A more detailed understanding of the margin will improve interpretations of variations in the South Atlantic subtropical gyre and further constrain general climatic and ocean circulation models. © 2015 The Authors.


Mauna A.C.,Institute Nacional Of Investigacion Y Desarrollo Pesquero Inidep | Botto F.,CONICET | Franco B.,Servicio de Hidrografia Naval SHN | Schwartz J.M.,Institute Nacional Of Investigacion Y Desarrollo Pesquero Inidep | And 4 more authors.
Journal of Sea Research | Year: 2011

Marine benthic trophic relationships and food web structures may be influenced by benthic-pelagic coupling processes, which could also be intensified by the physical dynamics of marine fronts. In this work, we employed stable isotope (δ13C and δ15N) analysis to investigate the influence of the Southwest (SW) Atlantic shelf-break front (SBF; 38-39°S, 55-56°W; Argentina) on an epibenthic trophic web. Epibenthic organisms were sampled, at depths of ~100m, with a non-selective dredge from a sandy bottom community located in frontal (F) and marginal (M) areas. The SBF position and the chlorophyll-a (chl-a) concentrations were inferred using satellite data of the sea surface temperature (SST) and satellite chl-a concentration, respectively. The most noticeable shifts in stable isotopes between the sampled areas were those of the Patagonian scallop, Zygochlamys patagonica (δ13C), and those of the sea urchin, Sterechinus agassizi (δ15N). Diet analyses inferred from stable isotopes and mixing models demonstrated that the dominant component of this community, Z. patagonica, had variable contributions to higher trophic levels between areas. More importantly, the epibenthic assemblage in F areas showed δ13C-enriched and δ15N-depleted isotopic signatures with respect to the M areas. Collectively, this evidence suggests that frontal dynamics promotes the accumulation of δ13C-enriched phytoplankton in the seabed in F areas, while in M areas the more degraded organic matter becomes more important in the trophic web, decreasing the δ15N isotopic signature of the assemblage. Therefore, the trophic web was sustained by fresher food in F areas than in M areas, demonstrating the role of frontal dynamics in the shaping of these communities. © 2011 Elsevier B.V.


Grings F.,University of Buenos Aires | Bruscantini C.A.,University of Buenos Aires | Smucler E.,University of Buenos Aires | Carballo F.,University of Buenos Aires | And 4 more authors.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2015

In this paper, an evaluation strategy for two-candidate satellite-derived SM products is presented. In particular, we analyze the performance of two candidate algorithms [soil moisture ocean salinity (SMOS)-based soil moisture (SM) and advanced scatterometer (ASCAT)-based SM] to monitor SM in Pampas Plain. The difficulties associated with commonly used evaluation techniques are addressed, and techniques that do not require ground-based observations are presented. In particular, we introduce comparisons with a land-surface model (GLDAS) and SM anomalies and triple collocation analyses. Then, we discuss the relevance of these analyses in the context of end-users requirements, and propose an extreme events-detection analysis based on anomalies of the standardized precipitation index (SPI) and satellite-based SM anomalies. The results show that: 1) both ASCAT and SMOS spatial anomalies data are able to reproduce the expected SM spatial patterns of the area; 2) both ASCAT and SMOS temporal anomalies are able to follow the measured in situ SM temporal anomalies; and 3) both products were able to monitor large SPI extremes at specific vegetation conditions. © 2008-2012 IEEE.

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