Bloom phenology, mechanisms and future change in the Southern Ocean.

• Main Author: Llort, Joan
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), 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-PSL), 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), Bourse de thèse ED129 - UPMC, BIOCOSM : observer, modéliser et comprendre les interactions physico-biogéochimiques dans l'océan australProjet CNES (J.LeSommer et M.Lévy), Université Pierre et Marie Curie - Paris 6, Marina Lévy, Julien LeSommer, ANR-10-BLAN-0614,KEOPS 2,Kerguelen : Comparaison plateau Ocean2(2010)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2015
• Subjects: Sverdrup; Behrenfeld; primary production; climate; biogeochemical oceanography; CMIP5; Southern Ocean; HNLC; Bloom; phytoplankton; production primaire; Océan Austral; climat; biogeochimie de l'océan; floraison; [SDE.MCG]Environmental Sciences/Global Changes; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
• Online Access: https://hal.science/tel-01140801; https://hal.science/tel-01140801/document; https://hal.science/tel-01140801/file/Thesis_HAL.pdf

DOI:10.13140/RG.2.1.1922.0003 Primary production (PP) in the Southern Ocean (SO) plays a crucial role on atmospheric carbon uptake. PP in this ocean is highly iron-limited and presents a marked seasonal cycle. Such a seasonal cycle has a strong productive phase in late winter, called bloom, which distribution and intensity is highly variable. My PhD focus on two specific aspects of the PP in the SO: first, the mechanisms that drive such a bloom and its dynamics and, second, the elements able to control the bloom intensity at present and in the future. The first aspect (bloom phenology and mechanisms) was addressed by setting up a mechanistic approach based on a novel model configuration: a complex biogeochemical model (PISCES) forced by a 1D idealised physical framework. This methodology allowed me to conciliate the different bloom formation theories and to identify the SO bloom specificities. Moreover, I proposed how to use different bloom detection criteria to properly identify bloom from observations. Such criteria were then tested in a complementary observation-based approach (with satellite and in-situ data) to characterise different bloom phenologies and its spatial distribution in the SO. The second aspect (bloom intensity and future change) was also addressed by a twofold approach. First, using the 1D model, I studied how seasonal variability of vertical mixing combine light and Fe limitation to drive PP. Secondly, I used such an analysis to interpret PP trends observed in 8 coupled model climatic projections (CMIP5 models). My PhD thesis results allow for a better understanding of the physical and biological processes controlling phytoplankton growth. My conclusions also suggest how an alteration of these processes by Climate Change may influence PP in the whole SO, a key region for future climate evolution. La production primaire (PP) dans l’Océan Austral joue un rôle crucial dans la capacité des océans à absorber le carbon atmosphérique. Elle est caract éris ée par une forte limitation en Fer et ...