Impact of oceanic eddy activity on the variability of CO2 air-sea fluxes in the Southern Ocean.

• Main Author: Dufour, Carolina
• Other Authors: Laboratoire des Écoulements Géophysiques et Industriels Grenoble (LEGI), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Grenoble, Bernard Barnier, Marion Gehlen, Julien Le Sommer, James Wilder Orr
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2011
• Subjects: Numerical dynamics-biogeochemistry model; Southern Annular Mode; Eddies; Air-sea CO2 fluxes; Southern Ocean; Océan Austral; Flux air-mer de CO2; Tourbillons; Mode Annulaire Austral; Modèle numérique dynamique-biogéochimie; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Antarctic; Austral; The Antarctic; Antarc*
• Online Access: https://tel.archives-ouvertes.fr/tel-00679918; https://tel.archives-ouvertes.fr/tel-00679918/document; https://tel.archives-ouvertes.fr/tel-00679918/file/24331_DUFOUR_2011_archivage1.pdf

By taking up large amounts of atmospheric CO2, the Southern Ocean helps to regulate the climate system. Southern Ocean carbon sink is poorly constrained, in part because data coverage is sparse and also because ocean models that have been used in such assessments fail to explicitly resolve key physical features such as mesoscale eddies. In recent decades, the growth of the Southern Ocean carbon sink may have been partly counteracted due to a loss of natural CO2 from the ocean driven by an intensification of westerlies, related to a positive trend in the Southern Annular Mode (SAM). This thesis focuses on documenting and understanding recent spatial and temporal variability of air-sea CO2 fluxes in the Southern Ocean. Sensitivity to positive phases of the SAM are tested by making simulations with a regional model of the Southern Ocean (south of 30°S) that couples biogeochemistry to the dynamics, is forced by atmosphere reanalysis data, and partially resolves the mesoscale. The resulting response of Southern Ocean CO2 fluxes to the SAM is dominated by a strong CO2 efflux to the atmosphere from the Antarctic Zone due to an increase in surface dissolved inorganic carbon (DIC). This increase is driven by the mixed-layer dynamics and is supplied by a meridional transport of DIC, a competition between the wind-driven circulation and the standing eddy-induced circulation. This work discusses the effect of increasing model resolution on simulated air-sea CO2 fluxes. L'océan Austral joue un rôle crucial dans la régulation du système climatique en absorbant de grandes quantités de CO2 atmosphérique. Toutefois de nombreuses incertitudes demeurent quant à l'évolution récente du puits de carbone austral notamment en raison du manque d'observations et des lacunes des modèles océaniques dans la représentation de processus dynamiques comme les tourbillons. Depuis quelques décennies notamment, l'efficacité du puits de carbone austral diminuerait en raison d'une intensification des vents liée à une tendance positive du Mode ...