Anthropogenic CO 2 in the Southern Ocean: distribution and inventory at the Indo-Atlantic boundary (WOCE line I6)

• Published in: Journal of Geophysical Research
• Main Authors: Lo Monaco, Claire, Metzl, Nicolas, Poisson, Alain, Brunet, Christian, Schauer, Bernard
• 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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Antarc*; Antarctic; Antarctica; North Atlantic; Prydz Bay; Southern Ocean; Weddell Sea
• Online Access: https://hal.science/hal-00122328; https://hal.science/hal-00122328/document; https://hal.science/hal-00122328/file/2004JC002643.pdf; https://doi.org/10.1029/2004JC002643

International audience The Southern Ocean, where various water masses are formed (mode, intermediate, deep, and bottom waters), has a high potential to absorb anthropogenic CO 2 (Cant). However, most data-based and model estimates indicate low Cant inventories south of 50°S. In order to investigate this paradox, the distribution of Cant is estimated between South Africa and Antarctica (World Ocean Circulation Experiment (WOCE) line I6) based on a back-calculation technique previously used in the North Atlantic (Körtzinger et al., 1998) and adapted here for application in the Southern Ocean. At midlatitudes (30°-50°S), formation and spreading of mode and intermediate waters results in a deep penetration of Cant (down to 2000 m). South of 50°S, significant concentrations of Cant were estimated in Circumpolar Deep Water (>10 μmol/kg) and Antarctic Bottom Water (AABW) (20-25 μmol/kg). Higher concentrations are detected along the continental slope in AABW presumably formed in Prydz Bay compared to AABW of Weddell Sea origin. The distribution of Cant obtained north of 50°S compares well with previous data-based and model estimates, but large disagreements are found in the south. However, although transient tracers are not used in the back-calculation technique employed here, the distribution of Cant is remarkably well correlated with CFCs. We reevaluated the column inventories of Cant for the Southern Ocean and found higher values at high latitudes (70-90 mol/m 2 ) compared to the subtropical/subantarctic region (40-80 mol/m 2 ). These results support the idea that deep and bottom water formation in the Southern Ocean is a key process in the natural sequestration of anthropogenic CO 2 .