Sea spray driven CO2 efflux: modeling the effect of sea spray evaporation on carbonate chemistry and air-sea gas exchange

The air-sea interface is a major climate control for our planet. At high winds this boundary layer becomes turbulent and challenging to parameterize. Sea spray is only now emerging as an important but unaccounted for parameter in air-sea models. Here we apply state-of-the-art air-sea surface sea spray generation models coupled to a carbonate system model to predict the spray-driven flux of carbon dioxide (CO2) gas between the atmosphere and ocean at various wind speeds and sea states. When these droplets are injected into air, they experience gas exchange affected by both temperature equilibration and evaporation. The latter process leads to a super-saline and acidic droplet that removes dissolved inorganic carbonate and bicarbonate, chemically converting them to additional CO2 and thereby evading more CO2 than is predicted by traditional models that do not consider this process. At 40% evaporation, the droplet evicts all its dissolved inorganic carbon, which is a 100-fold increase in potential CO2 evasion. Evaporating sea spray acts as a significant feedback to ocean CO2 uptake and could serve important roles in episodic storm events and over longer planetary timescales.