Study of anthropogenic carbon in the Southern Indian Ocean: Distribution and decadal variability

• Main Author: Lo Monaco, Claire
• 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), Université Pierre et Marie Curie - Paris VI, Nicolas Metzl, Alain Poisson
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2006
• Subjects: anthropogenic carbon; ocean observation; Southern Ocean; Indian Ocean; mode waters; decadal variability; CO2; carbone anthropique; observation océanique; Océan Austral; Océan Indien; eaux de mode; variabilité décennale; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere
• Online Access: https://theses.hal.science/tel-00121242; https://theses.hal.science/tel-00121242/document; https://theses.hal.science/tel-00121242/file/These_LoMonaco.pdf

The Southern Ocean where mode, deep and bottom water are formed has a high capacity for sequestrating anthropogenic carbon. In this study the distribution of anthropogenic carbon in the Southern Ocean was analyzed using different data-based methods. Results deduced from observations collected at the Indian-Atlantic boundary (WOCE/CIVA2) show higher anthropogenic carbon inventories than previous estimates deduced from either observations or ocean models. In addition to the invasion of anthropogenic carbon, the ocean carbon cycle is subjected to the impact of climate change through the modification of dynamical and biogeochemical processes. The analysis of data collected between 1978 and 2001 (GEOSECS, INDIGO, WOCE and OISO) shows that the increase in dissolved inorganic carbon (DIC) in Mode Waters (300-800m) is significant over the two decades. Over the period 1985-2001, it is shown that the variations of DIC observed in these water masses are lower than the increase in anthropogenic carbon. The difference, which is associated with a decrease in oxygen mean concentrations, could be explained by a change primary production in the circumpolar frontal region. The results obtained in our study suggests that there is a need, firstly, to re-evaluate anthropogenic carbon inventories at the scale of the Southern Ocean and, secondly, to better account for the coupling between biogeochemical cycles and climate forcing in order to separate natural variability and anthropogenic impacts in the ocean. L'Océan Austral est le siège de processus de formation d'eaux modales, profondes et de fond, ce qui en fait un acteur d'importance dans la séquestration du carbone anthropique. Dans cette étude la distribution de carbone anthropique dans l'Océan Austral a été analysée en employant différentes méthodes diagnostiques. Les résultats déduits d'observations collectées à la frontière Indien-Atlantique (WOCE/CIVA2) montrent des inventaires de carbone anthropique plus élevés que les précédentes estimations basées sur les observations ...