Importance of water mass formation regions for the air-sea CO 2 flux estimate in the Southern Ocean

• Published in: Global Biogeochemical Cycles
• Main Authors: Barbero, Leticia, Boutin, Jacqueline, Merlivat, Liliane, Martin, Nicolas, Takahashi, Taro, Sutherland, Stewart C., Wanninkhof, Rik H.
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL), 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)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: CCSD 2011
• Subjects: [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; Pacific; Southern Ocean
• Online Access: https://hal.science/hal-00758307; https://hal.science/hal-00758307v1/document; https://hal.science/hal-00758307v1/file/2010GB003818.pdf; https://doi.org/10.1029/2010GB003818

International audience CARIOCA drifters and ship data from several cruises in the Subantarctic Zone (SAZ) of the Pacific Ocean, approximately 40°S-55°S, have been used in order to investigate surface CO 2 partial pressure (pCO 2 ) and dissolved inorganic carbon (DIC) patterns. The highest DIC values were determined in regions of deep water formation, characterized by deep mixed layer depths (MLD) as estimated from Argo float profiles. As a result, these areas act as sources of CO 2 to the atmosphere. Using an empirical linear relationship between DIC, sea surface temperature (SST), and MLD, we then combine DIC with AT based on salinity and compute pCO 2 . Finally, we derive monthly fields of air-sea CO 2 flux in the SAZ. Our fit predicts the existence of a realistic seasonal cycle, close to equilibrium with the atmosphere in winter and a sink when biological activity takes place. It also reproduces the impact that deep water formation regions close to the Subantarctic Front (SAF) and in the eastern part of the SAZ have on the uptake capacity of the area. These areas, undersampled in previous studies, have high pCO 2 , and as a result, our estimates (0.05 ± 0.03 PgC yr -1 ) indicate that the Pacific SAZ acts as a weaker sink of CO 2 than suggested by previous studies which neglect these source regions.