Sources and Controls on Oceanic Emission of Volatile Iodinated Compounds

Volatile iodinated compounds (VICs) influence tropospheric and stratospheric chemistry and have globally significant impacts on the concentrations and lifetimes of climatically active gases. The atmospheric lifetimes of VICs vary substantially, reflecting not only the relative reactivity of each chemical species but also how far they may be transported vertically in the atmosphere. Semi-lagrangian, open ocean experiments allowed the rates of net change of several VICs to be determined in the sub-tropical open ocean. When combined with measured and modeled rates of loss from the water column, including photolysis, chemical transformation and air-sea exchange, the ';gross' production rates of several VICs can be estimated. We compare the production rates of polyhalogenated versus monohalogenated compounds in the open-ocean environments, in part to examine whether they may be derived from contrasting primary sources. Estimates of air-sea flux based on water-column measurements of concentration and wind-based transfer velocity parameterizations from several field campaigns allow the dominant VIC vectors of iodine to the marine boundary layer to be determined. How this water-column derived VIC air-sea flux compares in magnitude and composition to emissions of reactive iodine potentially generated by processes at the air-sea interface involving ozone and iodide is assessed.