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). In this study, we implement the sea state dependent bubble gas transfer formulation of Deike and Melville (2018) into a spectral wave model (WAVEWATCH III) incorporating the spectral modeling of the wave breaking distribution from Romero (2019). 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, Yang et al. (2022)). 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.