Quantifying the contribution of marine organic gases to atmospheric iodine

Charlotte E. Jones, Karen E. Hornsby, Roberto Sommariva, Rachel M. Dunk, Roland von Glasow, Gordon McFiggins, Lucy J. Carpenter

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Oceanic emissions of gaseous organic iodine-atom precursors have the potential to significantly affect atmospheric chemistry and climate, however there is currently considerable uncertainty associated with quantifying their sources. We present sea-air fluxes calculated from simultaneous air and seawater measurements of a comprehensive range of volatile organic iodine compounds (VOICs), including CH3I and the less commonly reported dihalomethanes CH2ICl, CH2IBr and CH2I2, made during two cruises in the Atlantic Ocean between 15-58N. The combined dihalomethane flux provides a global iodine source (~0.33 0.19 Tg I y -1) comparable to that of CH3I, and a surface iodine atom source 3-4 times higher. However, a 1D atmospheric model reveals that, in the tropical east Atlantic Ocean in the vicinity of Cape Verde, even these combined VOIC fluxes are capable of supporting only ~10-25% of the observed IO levels, and suggests that a substantial (340-640 nmol I m-2 d -1) additional photochemical source of iodine is required.
Original languageEnglish
JournalGeophysical Research Letters
Issue number18
Publication statusPublished - 2010

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