| Summary: | participant The North Atlantic climate variability is influenced by natural atmospheric forcing like the North Atlantic Oscillation. In recent decades this climate is also influenced by the global warming. Both natural variability and anthropogenic pressure interact and impact on oceanic physical processes and we suppose through these processes on production regimes and carbon dynamics. The objectives of this PhD are to determine, in the North Atlantic Ocean during the last 50 years, the impact of oceanic circulation on production regimes and carbon export fluxes, and the carbon fate in the mesopelagic layer. After establishing a biogeography in term of production regimes, the links between dynamical oceanic processes (mixing, vertical transport, horizontal advection) and production regionalisation will be analysed. Variabilities of the intensity and repartition of the production 5 regimes, associated with climate forcing, will be studied at seasonal, inter annual and decennial scales. The impact of the variability of these regimes on tracer export flux will also be estimated. Parametrisation of the carbon fate will be improved in order to investigate the influence of carbon regulation processes in the mesopelagic layer, vertical transport (diel variations) and horizontal transport (thermohaline transport) in the carbon sequestration. For this study a 3D coupled physicalbiogeochemical model, NEMOPISCES is used. The configuration is based on that of ORCA0.25 of DRAKKAR project. Simulations use a realistic atmospheric forcing for the last 50 years (ERA40ECMW).
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