Role of the Southern Annular Mode (SAM) in Southern Ocean CO 2 uptake

• Published in: Global Biogeochemical Cycles
• Main Authors: Lenton, Andrew, Matear, Richard J.
• 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)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-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)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-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)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC), European Project: GOCE-511176-1
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: Global Change: Biogeochemical cycles; Atmospheric Processes: Ocean/atmosphere interactions (0312 4504); Oceanography: Biological and Chemical: Biogeochemical cycles processes and modeling (0412 0414 0793 1615 4912); [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Southern Ocean
• Online Access: https://hal.science/hal-00770696; https://hal.science/hal-00770696/document; https://hal.science/hal-00770696/file/2006GB002714.pdf; https://doi.org/10.1029/2006GB002714

International audience A biogeochemical ocean general circulation model, driven with NCEP-R1 and observed atmospheric CO 2 history, is used to investigate and quantify the role that the Southern Annular Mode (SAM), identified as the leading mode of climate variability, has in driving interannual variability in Southern Ocean air-sea CO 2 fluxes between 1980 and 2000. Our simulations show the Southern Ocean to be a region of decreased CO 2 uptake during the positive SAM phase. The SAM induces changes in Southern Ocean CO 2 uptake with a 2-month time lag explaining 42% of the variance in the total interannual variability in air-sea CO 2 fluxes. Our analysis shows that the response of the Southern Ocean to the SAM is primarily governed by changes in $\Delta$pCO 2 (67%), and that this response is driven by changes in ocean physics that control the supply of nutrients to the upper ocean, primarily Dissolved Inorganic Carbon (DIC). The SAM is predicted to become stronger and more positive in response to climate change and our results suggest this will decrease the Southern Ocean CO 2 uptake by 0.1 PgC/yr per unit change in the SAM.