Intra-Seasonal Variability of Southern Ocean Primary Production : the Role of Storms and Mesoscale Turbulence

• Main Author: Nicholson, Sarah-Anne
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris VI, University of Cape Town, Marina Lévy, Pedro Monteiro
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2016
• Subjects: Southern Ocean; Primary production; Storms; Océan Austral; Production primaire; Tempêtes; Diffusion verticale; Mésoéchelle; Ondes inertielles; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Austral
• Online Access: https://tel.archives-ouvertes.fr/tel-01336297; https://tel.archives-ouvertes.fr/tel-01336297/document; https://tel.archives-ouvertes.fr/tel-01336297/file/2016PA066675.pdf

The Southern Ocean is one of the stormiest places on earth; here strong mid-latitude storms frequently traverse large distances of this ocean. The presence of the passage of intense storms and meso to sub-mesoscale eddy variability has the potential to strongly impact the intra-seasonal variability of the upper ocean environment where phytoplankton live. Yet, exactly how phytoplankton growth rates and its variability are impacted by the dominance of such features is not clear. Herein, lies the problem addressed by the core of this thesis, which seeks to advance the understanding of intra-seasonal variability of Southern Ocean primary production. Model experiments have suggested that intra-seasonal storm-linked physical supplies of dissolved iron (DFe) during the summer played a considerably more active and influential role in explaining the sustained summer productivity in the surface waters of the Southern Ocean than what was thought previously. This was through two important insights: 1. Storm-eddy interactions may strongly enhance the magnitude and extent of upper-ocean vertical mixing in both the surface mixed layer as traditionally understood as well as in the subsurface ocean. These two mixing regimes have different dynamics but act in concert to amplify the DFe fluxes to the surface ocean. 2. Storm initiated inertial motions may, through interaction with eddies, greatly reinforce w and thus, enhance the vertical advection of DFe to the surface ocean, an effect that may last several days after the storm. Such storm-eddy dynamics may greatly increase the intra-seasonal variability of primary production. L'océan Austral aux moyennes latitudes est l'un des endroits les plus tempétueux sur Terre. On peut donc supposer que le passage de ces tempêtes intenses sur cette variabilité océanique intense peut avoir un impact fort sur la variabilité intra-saisonnière des couches de surface où vit le phytoplancton. Pour autant, cet impact sur le taux de croissance du phytoplancton et sa variabilité reste encore très ...