A seamless ensemble-based reconstruction of surface ocean <i>p</i>CO<sub>2</sub> and air–sea CO<sub>2</sub> fluxes over the global coastal and open oceans - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Biogeosciences Année : 2022

A seamless ensemble-based reconstruction of surface ocean pCO2 and air–sea CO2 fluxes over the global coastal and open oceans

Résumé

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 Oscillation climate variability is reconfirmed.
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hal-03599212 , version 1 (07-03-2022)

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Thi Tuyet Trang Chau, Marion Gehlen, Frederic Chevallier, Thi Chau. A seamless ensemble-based reconstruction of surface ocean pCO2 and air–sea CO2 fluxes over the global coastal and open oceans. Biogeosciences, 2022, 19 (4), pp.1087 - 1109. ⟨10.5194/bg-19-1087-2022⟩. ⟨hal-03599212⟩
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