Southern Ocean is Likely a Stronger CO2 Sink Than Previous Thought

The Southern Ocean plays a major role in absorbing carbon dioxide (CO₂) emitted by human activities, a process vital for controlling the Earth's climate. We collected direct air-sea CO₂ flux observations by the eddy covariance (EC) method from seven scientific cruises in the Southern Ocean. These flux data suggest that the summer Southern Ocean is likely to be a strong CO₂ sink, challenging the much weaker estimates based on float data and model simulations. In addition, we find that the EC data support the shipboard observations (Surface Ocean CO₂ Atlas, SOCAT)-based flux estimates, but the upper ocean temperature gradients and the sufficient temporal resolution should be considered. Noting that our data only covers some part of the Southern Ocean in summer, continued efforts towards high-quality EC flux and surface ocean CO₂ fugacity (fCO_2w) observations are essential to improve the estimate of air-sea CO₂ fluxes. In addition, refined resolutions in the fCO_2w reconstruction and model simulation should be a focus of future work.

Reference: Dong, Y., Bakker, D.C.E., Bell, T.G., et al. (2024). Direct observational evidence of strong CO₂ uptake in the Southern Ocean. Sci. Adv., 10(30), eadn5781. https://doi.org/10.1126/sciadv.adn5781