Study on air-sea CO2 exchange with wave breaking

Hydrodynamic processes at air-sea interface play a significant role on air-sea CO₂ gas exchange, which further affects global carbon cycle and climate change. CO₂ gas transfer velocity (K_CO2) is generally parameterized with wind speed but ocean surface waves have direct impact on the gas exchange. Thus, the relationship between wave breaking and CO₂ gas exchange was studied through laboratory experiments and by utilizing field campaign data. The results from laboratory show that wave breaking plays a significant role in CO₂ gas exchange in all experiments while wind forcing can also influence K_CO2. A non-dimensional empirical formula is established in which K_CO2 is expressed as the product of wave breaking probability, transformed Reynolds number and an enhancement factor of wind speed. The parameterization is then improved by considering the bubble-mediated gas transfer based on both laboratory and ship campaign data sets. In the end, the formula is employed in the estimation of global CO₂ uptake by ocean and the result is found consistent with reported values.