Rain-induced changes in sea surface salinity and pCO2: Implications for global air-sea CO2 fluxes

Measurements from the eastern Equatorial Pacific have shown that rain decreases sea surface dissolved inorganic carbon (DIC) and pCO₂ in proportion to decreases in sea surface salinity. However, this change in carbonate chemistry is not normally observed from research vessels because the uncontaminated seawater intakes of these ships are usually too deep to capture the phenomenon, and therefore measurements made under certain conditions may not reflect the true biogeochemistry of the upper ocean. To assess the potential bias in air-sea CO₂ flux calculations, the duration and magnitude of rain-induced changes in salinity and hence dissolved inorganic carbon and pCO₂ was determined by using a model that considers sensible heat flux, freshwater flux, and wind and rain-induced mixing. The rain-induced pCO₂ changes were then used to examine the effect of rain on air-sea CO₂ fluxes, and the resulting CO₂ fluxes were compared with cases where the rain effect was not included.