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Modélisation du cycle océanique du néodyme

Thomas Arsouze 1
1 GEOMAR LEGOS
LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
Abstract : Neodymium isotopic composition (Nd IC, currently noted as "Nd) is a tracer of oceanic circulation and lithogenic inputs to the ocean. The current work aims to validate the "Boundary Exchange" hypothesis (BE, Bundary Scavenging associated with important inputs along the continental margin) as the main source/sink term of Nd to the oceanic reservoir, using an oceanic global circulation model. First, considering the only BE term for Nd IC sources/sinks, we successfully simulated the main distribution's characteristics (inter basin gradient, isotopic signature of the main water masses) both at global and regional scale. This result confirms BE as an important process in the element's oceanic cycle. The same parameterization of BE has been used at Last Glacial Maximum. Results show that this input varies both with a change in forcings, and a change in circulation. Comparison with data suggest a circulation scenario in the Atlantic with a predominance of southern deep waters and a vigorous mderidional cell from surface to 2000m depth. In a second place, we used a coupled dynamical/biogeochemical model to explicitely represent Nd IC and Nd concentrations, for studying the "Nd Paradox" (resulting from the decoupling of both parameters) and quantify the Nd sources to the ocean. Results suggest that dissolve/particulate interactions must be invoked to conciliate both distributions, and that oceanic margins are the main sources of Nd to the ocean (1:1:1010 g(Nd)/year), representing inputs up to 25 times higher than other external sources (dissolved river discharge and atmospheric dusts).
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https://tel.archives-ouvertes.fr/tel-00606365
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Submitted on : Wednesday, July 6, 2011 - 11:17:38 AM
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  • HAL Id : tel-00606365, version 1

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Thomas Arsouze. Modélisation du cycle océanique du néodyme. Planète et Univers [physics]. Université Paul Sabatier - Toulouse III, 2008. Français. ⟨tel-00606365⟩

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