Ocean surface waves impact on global air-sea CO 2 flux

Ocean surface gravity waves facilitate gas exchanges primarily in two ways: (1) the formation of bubbles during wave breaking increases the surface area available for gas exchange, promoting CO $_2^{}$ transfer, and (2) wave-current interaction processes alter the sea surface partial pressure of CO $_2^{}$ and gas solubility, consequently affecting the CO $_2^{}$ flux. This study tests these influences using a global ocean-ice-biogeochemistry model under preindustrial conditions. The simulation results indicate that both wave-current interaction processes and the sea-state-dependent gas transfer scheme-which explicitly accounts for bubble-mediated gas transfer velocity-influence the air-sea CO $_2^{}$ flux, with substantial spatial and seasonal variations. In the equatorial region (10 $_{}^{\circ }$ S-10 $_{}^{\circ }$ N), both processes enhance the CO $_2^{}$ outgassing flux, with comparable magnitudes (more than 10% on average). However, in the region between approximately 10 $_{}^{\circ }$ and 35 $_{}^{\circ }$ , the impact of ocean surface waves on the air-sea CO $_2^{}$ flux via the sea-state-dependent gas transfer velocity is greater than that of the wave-current interaction processes, with opposing directions of influence. During winter, the sea-state-dependent gas transfer velocity enhances the CO $_2^{}$ uptake flux, while in the summer season, it increases the CO $_2^{}$ outgassing flux. In regions poleward of 35 $_{}^{\circ }$ , the impact of wave-current interaction processes on CO $_2^{}$ exchange dominates over that of the sea-state-dependent gas transfer velocity. It is worth noting that the impact of wave-current interaction processes on air-sea CO $_2^{}$ flux is primarily driven by changes in the ratio between the concentrations of dissolved inorganic carbon and total alkalinity, with variations in sea surface temperature exerting an opposite influence on pCO $_2^{}$ , albeit with a smaller magnitude. Overall, wave-related processes should be considered in Earth System Models to better model the carbon cycle.

The online version contains supplementary material available at 10.1007/s10533-025-01267-y.