Climate-driven variability of the Southern Ocean CO2 sink

Mayot, N. ORCID:, Le Quéré, C. ORCID:, Rödenbeck, C., Bernardello, R., Bopp, L., Djeutchouang, L. M., Gehlen, M., Gregor, L., Gruber, N., Hauck, J., Iida, Y., Ilyina, T., Keeling, R. F., Landschützer, P., Manning, A. C. ORCID:, Patara, L., Resplandy, L., Schwinger, J., Séférian, R., Watson, A. J., Wright, R. M. ORCID: and Zeng, J. (2023) Climate-driven variability of the Southern Ocean CO2 sink. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 381 (2249). ISSN 1364-503X

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The Southern Ocean is a major sink of atmospheric CO2, but the nature and magnitude of its variability remains uncertain and debated. Estimates based on observations suggest substantial variability that is not reproduced by process-based ocean models, with increasingly divergent estimates over the past decade. We examine potential constraints on the nature and magnitude of climate-driven variability of the Southern Ocean CO2 sink from observation-based air-sea O2 fluxes. On interannual time scales, the variability in the air-sea fluxes of CO2 and O2 estimated from observations is consistent across the two species and positively correlated with the variability simulated by ocean models. Our analysis suggests that variations in ocean ventilation related to the Southern Annular Mode are responsible for this interannual variability. On decadal time scales, the existence of significant variability in the air-sea CO2 flux estimated from observations also tends to be supported by observation-based estimates of O2 flux variability. However, the large decadal variability in air-sea CO2 flux is absent from ocean models. Our analysis suggests that issues in representing the balance between the thermal and non-thermal components of the CO2 sink and/or insufficient variability in mode water formation might contribute to the lack of decadal variability in the current generation of ocean models. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.

Item Type: Article
Additional Information: Funding Information: N.M., C.L.Q., R.B., N.G., L.G. and A.C.M. acknowledge the funding from the European Commission through the H2020 project 4C (grant no. 821003). J.H., L.G., M.G. and N.G. acknowledge the funding from the European Commission through the H2020 project COMFORT project (grant no. 820989). C.L.Q. was funded by the UK Royal Society (grant no. RPR1191063). N.M. and R.M.W. were funded by UK's Natural Environment Research Council (SONATA: grant no. NE/P021417/1). J.S. received funding from the Research Council of Norway through project INES (grant no. 270061) and HPC resources provided by the National Infrastructure for HPC and Data Storage in Norway, UNINETT Sigma2 (grant no. nn/ns2980k). L.R. acknowledges the Princeton University Catalysis Initiative. N.G. and L.G. acknowledge funding from ETH Zürich. M.G. and R.S. acknowledge the ESM2025 project under the grant agreement number 101003536. M.G. also acknowledges funding from the European Union's Horizon 2020 Blue Growth research and innovation programme under grant agreement number 862923 (project AtlantECO). J.H. acknowledges support by the Initiative and Networking Fund of the Helmholtz Association (Helmholtz Young Investigator Group Marine Carbon and Ecosystem Feedbacks in the Earth System [MarESys], grant number VH-NG-1301). The integration of the ORCA025-GEOMAR experiment was performed at the North German Supercomputing Alliance (HLRN) and was financially supported by the German Research Foundation (project PA 3075/2-1). The APO measurements were supported by a series of grants to the Scripps Institution of Oceanography from the US NSF and NOAA, most recently OPP-1922922 and NA20OAR4320278. Acknowledgements Funding Information: Thanks to Erik Buitenhuis and David Willis for their work on the NEMO-PlankTOM12 model development. The research presented in this paper was carried out on the High Performance Computing Cluster supported by the Research and Specialist Computing Support service at the University of East Anglia. Publisher Copyright: © 2023 The Authors.
Uncontrolled Keywords: carbon sink,climate,decadal,interannual,oxygen,southern ocean,mathematics(all),engineering(all),physics and astronomy(all),sdg 13 - climate action ,/dk/atira/pure/subjectarea/asjc/2600
UEA Research Groups: Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
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Depositing User: LivePure Connector
Date Deposited: 03 Aug 2023 15:32
Last Modified: 07 Aug 2023 00:49
DOI: 10.1098/rsta.2022.0055


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