Atmos. Chem. Phys., 13, 8915-8934, 2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Global sea-to-air flux climatology for bromoform, dibromomethane and methyl iodide
F. Ziska1, B. Quack1, K. Abrahamsson2, S. D. Archer3,*, E. Atlas4, T. Bell5, J. H. Butler6, L. J. Carpenter7, C. E. Jones7,**, N. R. P. Harris8, H. Hepach1, K. G. Heumann9, C. Hughes10, J. Kuss11, K. Krüger1, P. Liss12, R. M. Moore13, A. Orlikowska11, S. Raimund14,***, C. E. Reeves12, W. Reifenhäuser15, A. D. Robinson8, C. Schall16, T. Tanhua1, S. Tegtmeier1, S. Turner12, L. Wang17, D. Wallace13, J. Williams18, H. Yamamoto19,****, S. Yvon-Lewis20, and Y. Yokouchi19
1GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany
2Department of Analytical and Marine Chemistry, Chalmers University of Technology and Gothenburg University, Gothenburg, Sweden
3Plymouth Marine Laboratory, Plymouth, PMI, Plymouth, UK
4Marine and Atmospheric Chemistry, Rosenstiel School of Marine and Atmospheric Science, University of Miami, MAC, Miami, USA
5Department of Earth System Science, University of California, UCI, Irvine, USA
6Earth System Research Laboratory, Global Monitoring Division, ESRL/NOAA, Boulder, USA
7Department of Chemistry, University of York, York, YO10 5DD, UK
8Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK, Cambridge, UK
9Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, JGU, Mainz, Germany
10Laboratory for Global Marine and Atmospheric Chemistry, University of East Anglia, LGMAC/UEA, Norwich, UK
11Institut für Ostseeforschung Warnemünde, IOW, Rostock-Warnemünde, Germany
12School of Environmental Science, University of East Anglia, Norwich, UK
13Department of Oceanography, Dalhousie University, Halifax, B3H 4R2, Canada
14CNRS, UMR7144, Equipe Chim Marine, Stn Biol Roscoff, 29680 Roscoff, France
15Bayerisches Landesamt für Umwelt, Augsburg, Germany
16Fresenius Medical Care Deutschland GmbH, Frankfurterstraße 6–8, 66606 St. Wendel, Germany
17Rutgers State University of New Jersey, New Brunswick, USA
18Max Planck Institute for Chemistry, Air Chemistry Department, MPI, Mainz, Germany
19National Institute for Environmental Studies, Tsukuba, Ibaraki 305-0053, Japan
20Department of Oceanography, Texas A&M University, College Station, USA
*now at: Bigelow Laboratory of Ocean Sciences, Maine, USA
**now at: Graduate School of Global Environmental Studies, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan
***now at: GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany
****now at: Marine Works Japan, Ltd., Oppamahigashi, Yokosuka 237-0063, Japan

Abstract. Volatile halogenated organic compounds containing bromine and iodine, which are naturally produced in the ocean, are involved in ozone depletion in both the troposphere and stratosphere. Three prominent compounds transporting large amounts of marine halogens into the atmosphere are bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I). The input of marine halogens to the stratosphere has been estimated from observations and modelling studies using low-resolution oceanic emission scenarios derived from top-down approaches. In order to improve emission inventory estimates, we calculate data-based high resolution global sea-to-air flux estimates of these compounds from surface observations within the HalOcAt (Halocarbons in the Ocean and Atmosphere) database ( Global maps of marine and atmospheric surface concentrations are derived from the data which are divided into coastal, shelf and open ocean regions. Considering physical and biogeochemical characteristics of ocean and atmosphere, the open ocean water and atmosphere data are classified into 21 regions. The available data are interpolated onto a 1°×1° grid while missing grid values are interpolated with latitudinal and longitudinal dependent regression techniques reflecting the compounds' distributions. With the generated surface concentration climatologies for the ocean and atmosphere, global sea-to-air concentration gradients and sea-to-air fluxes are calculated. Based on these calculations we estimate a total global flux of 1.5/2.5 Gmol Br yr−1 for CHBr3, 0.78/0.98 Gmol Br yr−1 for CH2Br2 and 1.24/1.45 Gmol Br yr−1 for CH3I (robust fit/ordinary least squares regression techniques). Contrary to recent studies, negative fluxes occur in each sea-to-air flux climatology, mainly in the Arctic and Antarctic regions. "Hot spots" for global polybromomethane emissions are located in the equatorial region, whereas methyl iodide emissions are enhanced in the subtropical gyre regions. Inter-annual and seasonal variation is contained within our flux calculations for all three compounds. Compared to earlier studies, our global fluxes are at the lower end of estimates, especially for bromoform. An under-representation of coastal emissions and of extreme events in our estimate might explain the mismatch between our bottom-up emission estimate and top-down approaches.

Citation: Ziska, F., Quack, B., Abrahamsson, K., Archer, S. D., Atlas, E., Bell, T., Butler, J. H., Carpenter, L. J., Jones, C. E., Harris, N. R. P., Hepach, H., Heumann, K. G., Hughes, C., Kuss, J., Krüger, K., Liss, P., Moore, R. M., Orlikowska, A., Raimund, S., Reeves, C. E., Reifenhäuser, W., Robinson, A. D., Schall, C., Tanhua, T., Tegtmeier, S., Turner, S., Wang, L., Wallace, D., Williams, J., Yamamoto, H., Yvon-Lewis, S., and Yokouchi, Y.: Global sea-to-air flux climatology for bromoform, dibromomethane and methyl iodide, Atmos. Chem. Phys., 13, 8915-8934, doi:10.5194/acp-13-8915-2013, 2013.
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