Etude de la dynamique de la couche de surface et des interactions surface/océan dans l'océan Austral sous la glace de mer

Abstract : The Southern Ocean is a key region for the understanding of the global ocean circulation and for the climate as a whole. In this region, a large majority of the ocean’s water masses are ventilated in the surface layer, before being sent back to the deep ocean. The surface layer of the Southern Ocean is therefore a central element for understanding the global ocean circulation. Despite their fundamental role in the global ocean circulation and climate, the structure and characteristics of the mixed-layer are still poorly understood in the Antarctic Polar Region due to a significant lack of in-situ observations.However, the international MEOP program (2004) has led to the deployment of thousands of hydrological sensors on Elephant Seals and offers a unique spatial coverage of new data that cover the entire seasonal cycle. In this thesis, we exploit this dataset and other more conventional data, to bring a new perspective on this unknown region. Based on these observations, we describe the climatological properties and dynamics of the mixed-layer under Antarctic sea-ice. The vertical transfers between the mixed-layer and the deep ocean, associated with the meridional overturning circulation, and the hydrographic variations of the water masses in the mixed-layer, are described at seasonal and inter-annual time scales. The results highlight the critical role of freshwater fluxes, induced by sea-ice and precipitations, on the transformation of water masses under the sea-ice. Our findings suggest that changes in the intensity of these freshwater fluxes would directly affect the buoyancy budgets of the mixed-layer and impact the large-scale overturning circulation.
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Violaine Pellichero. Etude de la dynamique de la couche de surface et des interactions surface/océan dans l'océan Austral sous la glace de mer. Océanographie. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS029⟩. ⟨tel-01910121v2⟩

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