Sulfur in the western North Atlantic Ocean atmosphere: Results from a summer 1988 ship/aircraft experiment

Authors

  • James N. Galloway,

  • William C. Keene,

  • Alexander A. P. Pszenny,

  • Douglas M. Whelpdale,

  • Herman Sievering,

  • John T. Merrill,

  • Joe F. Boatman


Abstract

To investigate the relative importance of anthropogenic versus marine sources of sulfur in the North Atlantic Ocean troposphere, sulfur species were measured from aircraft, ship, and island based platforms as part of the Global Change Expedition/Coordinated Air-Sea Experiment/Western Atlantic Ocean Experiment conducted during the summer of 1988. Four synoptic meteorological cases were examined: flow from highly populated North America, lightly populated North America, tropical oceanic regions, and polar oceanic regions. Literature values suggest that 2–10 μmol m−2 day−1 of (CH3)2S are emitted from the ocean to the atmosphere in marine regions associated with the first three synoptic cases. Data from this experiment indicate that 36, 16, and 14 μmol m−2 day−1, for the highly populated North America, lightly populated North America, and tropical oceanic regions synoptic cases, respectively, were deposited to the ocean's surface. Differences between previously estimated natural emissions and calculated deposition suggest that anthropogenic sources of sulfur contribute significantly to sulfur deposition for these cases. The sulfur deposition rate for the polar oceanic regions synoptic case was 20 μmol m−2 day−1 . Given the larger range of literature values for the corresponding (CH3)2S emission rate (1–14 μmol m−2 day−1 ) , however, the relative importance of the nonmarine S source is less certain in this case.

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