EGU General Assembly 2022
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Origin and magnitude of interannual variabilities in Southern Ocean air-sea O2 and CO2 fluxes

Nicolas Mayot1, Corinne Le Quéré1, Andrew Manning1, David Willis1, Nicolas Gruber2, Jörg Schwinger3, Roland Séférian4, Tatiana Ilyina5, Judith Hauck6, Laure Resplandy7, Laurent Bopp8, Ralph Keeling9, and Christian Rödenbeck10
Nicolas Mayot et al.
  • 1University of East Anglia, School of Environmental Sciences, Norwich, United Kingdom of Great Britain – England, Scotland, Wales (
  • 2ETH Zurich, Zürich, Switzerland
  • 3Norwegian Research Centre, Bergen, Norway
  • 4Centre National de Recherches Météorologiques, Toulouse, France
  • 5Max Planck Institute for Meteorology, Hamburg, Germany
  • 6Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
  • 7Princeton University, Department of Geosciences, Princeton, United States
  • 8Institut Pierre-Simon Laplace, Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France
  • 9Scripps Institution of Oceanography, La Jolla, United States
  • 10Max Planck Institute for Biogeochemistry, Jena, Germany

The Southern Ocean plays a major role in both the global oceanic uptake of anthropogenic CO2 and its interannual variations. The size and origin of the interannual variability in the Southern Ocean CO2 fluxes is debated. Observation-based estimates suggest a large variability (+/- 0.11 PgC/yr) while Global Ocean Biogeochemistry Models (GOBMs) simulate almost no variability. Studying the air-sea fluxes of O2 can provide independent information that help resolve this data-model inconsistency. Oceanic O2 is influenced by the same physical and biogeochemical processes as CO2, but unlike CO2, its variability is not masked by a large anthropogenic flux. Here, we used 26 years (1994-2019) of monthly O2 fluxes from 9 GOBMs. These model outputs were compared to air-sea O2 fluxes inferred from an atmospheric inversion of precisely quantified changes in atmospheric O2 and CO2 levels. The 26-year time series of air-sea O2 fluxes from all GOBMs and the atmospheric inversion exhibited similar temporal variations. This could be linked to the Southern Annular Mode and its influence on air-sea heat flux forcing that induced large-scale changes in observed wintertime Mixed Layer Depth (MLD). However, the amplitude of the interannual variability in air-sea O2 fluxes was two times higher in the atmospheric inversion than in GOBMs. It possible that this was induced by the general overestimation of the mean wintertime MLD by the GOBM and subsurface vertical gradients in oxygen saturation lower than observed. Implications of these results for the variability in air-sea fluxes of CO2 will be discussed.

How to cite: Mayot, N., Le Quéré, C., Manning, A., Willis, D., Gruber, N., Schwinger, J., Séférian, R., Ilyina, T., Hauck, J., Resplandy, L., Bopp, L., Keeling, R., and Rödenbeck, C.: Origin and magnitude of interannual variabilities in Southern Ocean air-sea O2 and CO2 fluxes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12773,, 2022.