Ozone depletion and the air-sea exchange of greenhouse and chemically reactive trace gases

One of the most important aspects of global change is that of stratospheric ozone depletion and the resulting increase in UV radiation reaching the surface of the Earth. Some 70% of the Earth surface is covered by water containing an extremely complicated milieu of organic and inorganic chemical species. The photochemical production and transformation of various greenhouse and chemically reactive gases in the ocean has been a focus of much study over the last century. We assess the implications of increased UV radiation on aquatic and marine boundary layer bio-geochemistry with a focus on trace gases that exchange between the ocean and the atmosphere. CO₂, DMS, CO, OCS, CH₄, N₂O, non-methane hydrocarbons (NMHCs) and organohalogens are considered within the context of changing surface ocean UV fluxes and various feedbacks upon the integrated climate system. Links between the upper ocean photochemical environment and the lower atmosphere are stressed. Once in the atmosphere, these gases each play a different role in modulating several aspects of atmospheric chemistry and by implication atmospheric circulation and climate dynamics such as precipitation patterns, surface temperatures and surface-atmosphere substance exchange. We augment the conceptual models proposed with new observational data on surface ocean concentrations from the southern hemisphere obtained under a range of UV exposures. (C) 2000 Elsevier Science Ltd.