Regionalized global budget of the CO 2 exchange at the air‐water interface in continental shelf seas

• Published in: Global Biogeochemical Cycles
• Main Authors: Laruelle, Goulven, G, Lauerwald, Ronny, Pfeil, Benjamin, Regnier, Pierre
• Other Authors: Université libre de Bruxelles (ULB), Universiteit Utrecht / Utrecht University Utrecht, 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), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), University of Bergen (UiB)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: [SDE]Environmental Sciences; Arctic; Sea ice
• Online Access: https://hal.science/hal-04686915; https://hal.science/hal-04686915/document; https://hal.science/hal-04686915/file/Global%20Biogeochemical%20Cycles%20-%202014%20-%20Laruelle%20-%20Regionalized%20global%20budget%20of%20the%20CO2%20exchange%20at%20the%20air%E2%80%90water%20interface.pdf; https://doi.org/10.1002/2014gb004832

International audience Over the past decade, estimates of the atmospheric CO2 uptake by continental shelf seas were constrained within the 0.18–0.45 Pg C yr−1 range. However, most of those estimates are based on extrapolations from limited data sets of local flux measurements (n < 100). Here we propose to derive the CO2 air-sea exchange of the shelf seas by extracting 3 · 106 direct surface ocean CO2 measurements from the global database SOCAT (Surface Ocean CO2 Atlas), atmospheric CO2 values from GlobalVIEW and calculating gas transfer rates using readily available global temperature, salinity, and wind speed fields. We then aggregate our results using a global segmentation of the shelf in 45 units and 152 subunits to establish a consistent regionalized CO2 exchange budget at the global scale. Within each unit, the data density determines the spatial and temporal resolutions at which the air-sea CO2 fluxes are calculated and range from a 0.5° resolution in the best surveyed regions to a whole unit resolution in areas where data coverage is limited. Our approach also accounts, for the first time, for the partial sea ice cover of polar shelves. Our new regionalized global CO2 sink estimate of 0.19 ± 0.05 Pg C yr−1 falls in the low end of previous estimates. Reported to an ice-free surface area of 22 · 106 km2, this value yields a flux density of 0.7 mol C m−2 yr−1, ~40% more intense than that of the open ocean. Our results also highlight the significant contribution of Arctic shelves to this global CO2 uptake (0.07 Pg C yr−1).