A Sea State Dependent Gas Transfer Velocity for CO2 Unifying Theory, Model, and Field Data.

Wave breaking induced bubbles contribute a significant part of air‐sea gas fluxes. Recent modeling of the sea state dependent CO2 flux found that bubbles contribute up to ∼40% of the total CO2 air‐sea fluxes (Reichl & Deike, 2020, https://doi.org/10.1029/2020gl087267). In this study, we implement the sea state dependent bubble gas transfer formulation of Deike and Melville (2018, https://doi.org/10.1029/2018gl078758) into a spectral wave model (WAVEWATCH III) incorporating the spectral modeling of the wave breaking distribution from Romero (2019, https://doi.org/10.1029/2019gl083408). We evaluate the accuracy of the sea state dependent gas transfer parameterization against available measurements of CO2 gas transfer velocity from 9 data sets (11 research cruises, see Yang et al. (2022, https://doi.org/10.3389/fmars.2022.826421)). The sea state dependent parameterization for CO2 gas transfer velocity is consistent with observations, while the traditional wind‐only parameterization used in most global models slightly underestimates the observations of gas transfer velocity. We produce a climatology of the sea state dependent gas transfer velocity using reanalysis wind and wave data spanning 1980–2017. The climatology shows that the enhanced gas transfer velocity occurs frequently in regions with developed sea states (with strong wave breaking and high significant wave height). The present study provides a general sea state dependent parameterization for gas transfer, which can be implemented in global coupled models. Plain Language Summary: The atmosphere‐ocean gas exchange influences Earth's climate, including local and global sinks and sources of CO2. We implement a physics based bubble mediated gas exchange model using state of the art gas transfer velocity models dependent on wind and waves, together with the various gases physicochemical parameters to better constrain the trend of the ocean‐atmosphere gas fluxes, validated against extensive field measurements of CO2 fluxes. In current climate models, the CO2 air‐sea fluxes are parameterized solely based on wind speed, and we discuss the high frequency variability induced by the waves. The climatology of gas transfer velocity for both a simple bulk formula and a complete sea state models are provided for the community and can be used in global ocean or climate models. Key Points: The sea state dependent CO2 gas transfer velocity models that are evaluated against existing data setsTwo models are examined that are consistent with the observations, with differences at low wind speed due to the representation of swellA database of both sea state dependent gas transfer velocities for the period 1980–2017 are archived for future CO2 studies [ABSTRACT FROM AUTHOR]