A seamless ensemble-based reconstruction of surface ocean p CO 2 and air–sea CO 2 fluxes over the global coastal and open oceans

• Published in: Biogeosciences
• Main Authors: Chau, Thi Tuyet Trang, Gehlen, Marion, Chevallier, Frederic, Chau, Thi
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Modélisation INVerse pour les mesures atmosphériques et SATellitaires (SATINV), This research has been supported by the European Copernicus Marine Environment Monitoring Service (CMEMS) for the MOB TAC project in 2018–2021 (83-CMEMSTAC-MOB contract, https://marine.copernicus.eu/about/producers/ mob-tac, last access: 27 July 2021).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Arctic; Southern Ocean
• Online Access: https://hal.science/hal-03599212; https://hal.science/hal-03599212/document; https://hal.science/hal-03599212/file/bg-19-1087-2022.pdf; https://doi.org/10.5194/bg-19-1087-2022

International audience We have estimated global air-sea CO 2 fluxes (fgCO 2) from the open ocean to coastal seas. Fluxes and associated uncertainty are computed from an ensemble-based reconstruction of CO 2 sea surface partial pressure (pCO 2) maps trained with gridded data from the Surface Ocean CO 2 Atlas v2020 database. The ensemble mean (which is the best estimate provided by the approach) fits independent data well, and a broad agreement between the spatial distribution of model-data differences and the ensemble standard deviation (which is our model uncertainty estimate) is seen. Ensemble-based uncertainty estimates are denoted by ±1σ. The space-time-varying uncertainty fields identify oceanic regions where improvements in data reconstruction and extensions of the observational network are needed. Poor reconstructions of pCO 2 are primarily found over the coasts and/or in regions with sparse observations, while fgCO 2 estimates with the largest uncertainty are observed over the open Southern Ocean (44 • S southward), the subpolar regions, the Indian Ocean gyre, and upwelling systems. Our estimate of the global net sink for the period 1985-2019 is 1.643 ± 0.125 PgC yr −1 including 0.150 ± 0.010 PgC yr −1 for the coastal net sink. Among the ocean basins, the Subtropical Pacific (18-49 • N) and the Subpolar Atlantic (49-76 • N) appear to be the strongest CO 2 sinks for the open ocean and the coastal ocean, respectively. Based on mean flux density per unit area, the most intense CO 2 drawdown is, however, observed over the Arctic (76 • N poleward) followed by the Subpolar Atlantic and Subtropical Pacific for both open-ocean and coastal sectors. Reconstruction results also show significant changes in the global annual integral of all open-and coastal-ocean CO 2 fluxes with a growth rate of +0.062 ± 0.006 PgC yr −2 and a temporal standard deviation of 0.526 ± 0.022 PgC yr −1 over the 35-year period. The link between the large interannual to multi-year variations of the global net sink and the El Niño-Southern ...