Impact du changement climatique et l’acidification des océans sur le cycle océanique de l’azote

Abstract : The marine nitrogen cycle is responsible for two climate feedbacks in the Earth System. Firstly, it modulates thefixed nitrogen pool available for phytoplankton growth and hence it modulates in part the strength of thebiological pump, one of the mechanisms contributing to the oceanic uptake of anthropogenic CO2. Secondly, thenitrogen cycle produces a powerful greenhouse gas and ozone (O3) depletion agent called nitrous oxide (N2O).Future changes of the nitrogen cycle in response to global warming, ocean deoxygenation and oceanacidification are largely unknown. Processes such as N2-fixation, nitrification, denitrification and N2Oproduction will experience changes under the simultaneous effect of these three stressors. Global oceanbiogeochemical models allow us to study such interactions. Using NEMO-PISCES and the CMIP5 modelensemble we project changes in year 2100 under the business-as-usual high CO2 emissions scenario in globalscale N2-fixation rates, nitrification rates, N2O production and N2O sea-to-air fluxes adding CO2 sensitivefunctions into the model parameterizations. Second order effects due to the combination of global warming intandem with ocean acidification on the fixed nitrogen pool, primary productivity and N2O radiative forcingfeedbacks are also evaluated in this thesis.
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Jorge Martinez-Rey. Impact du changement climatique et l’acidification des océans sur le cycle océanique de l’azote. Météorologie. Université de Versailles-Saint Quentin en Yvelines, 2015. Français. ⟨NNT : 2015VERS009V⟩. ⟨tel-01241404⟩

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