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Environnements et Paléoenvironnements
Océaniques et Continentaux
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Séminaire


L'Océan Austral – un rôle clé dans l'évolution climatique passée, présente (et future ?)

Date
le 22-04-2013 à 10:45

Lieu
Salle Stendhal, DGO, Bâtiment B18

Intervenant(s)
Samuel JACCARD, ETH Zürich, Geologisches Institut, Suisse

Résumé
Sedimentary proxies of ocean productivity reveal that the export of sinking organic carbon from surface waters of the Antarctic zone of the Southern Ocean decreased into ice ages, coinciding with declining atmospheric CO2 concentrations, signaling reduced exchange between deep and surface layers of the ocean. Antarctic zone export production decreased most strongly during the first cooling step following peak interglacial conditions. In the Subantarctic Zone, on the other hand, export production increased into ice ages. This occurred later in the glacial inception than the Antarctic productivity decline, coinciding with rising dust fluxes and thus suggesting iron fertilization of Subantarctic phytoplankton. This contrasting pattern of export in the two regions suggests a bimodal mechanism by which the Southern Ocean regulates the transfer of carbon between the abyssal ocean and the atmosphere, with progressive CO2 sequestration during glacial cooling, terminated abruptly by CO2 release during deglaciations.
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