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Modélisation de la dynamique océanique barotrope dans l'estuaire et le plateau amazoniens

Yoann Le Bars 1
1 ECOLA - Echanges Côte-Large
LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
Abstract : The vast majority of material flows (solid and dissolved, organic and inorganic) coming from continent into ocean happens in continental margin, as it is the interface between continents and oceans. Continental margin also exchange materials and elements with ocean water. One of the main sources of chemical elements in the ocean is erosion and transport by rivers, material from continent to ocean being promoted by re-suspension of sediments and important water mixtures. The AMANDES project aims to study transports from the Andean mountains to the Atlantic Ocean through the Amazon system. Three complementary disciplines - continental and marine geochemistry, physical oceanography, and hydrodynamic modeling (including data assimilation) -- are combined to achieve these goals. None of the available models of this area can be used in AMANDES project. Therefore, the purpose of the thesis has been to establish a new model, with which it will be possible to explore in depth the problem of transport, i.e. the moving of the whole water column and what it contains, such as sediments. However, establishing a new hydrodynamical model in order to study the transport of materials by the Amazon River in the Atlantic Ocean was a subject too ambitious for just one thesis. As a consequence, we have established the foundations for a model to be extended thereafter. In order to meet its modelling needs, the AMANDES project has chosen the unstructured grids model T-UGOm. Unstructured grids are very flexible, and thus can be closely adapted to the specific geographical area being modeled. In the case of the Amazon estuary, where the geography can be complex, this characteristic is a critical advantage. To apply T-UGOm to the case of the Amazon river, we have clarify some numerical schemes. Also, as the estuary is an area of strong tides, large shallow waters, and subject to strong currents, bottom friction has a major influence. As a consequence, we have made a major effort to refine the inclusion of friction in this model. Moreover, shallow waters and complex geography induce a strong influence of coastlines and bathymetry, so a significant effort has been dedicated to establish a digital coastline and bathymetry database as fine and accurate as possible. As tide is the hydrodynamic phenomenon of greatest amplitude in the area, we focused on its modelling. Comparing our best solution with in situ and satellite data, the developments mentioned above have significantly improved the tidal modeling. Also, this solution is closer to the collected data than those already published. This opens the way for a more complete hydrodynamic modeling, especially transport.
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Submitted on : Tuesday, June 22, 2010 - 2:45:33 PM
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Yoann Le Bars. Modélisation de la dynamique océanique barotrope dans l'estuaire et le plateau amazoniens. Planète et Univers [physics]. Université Paul Sabatier - Toulouse III, 2010. Français. ⟨tel-00494238⟩

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