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Chemical data derived from air and precipitation samples collected during the Global Change Expedition/Coordinated Air-Sea Experiment/ Western Atlantic Ocean Experiment (GCE/CASE/WATOX) over the North Atlantic Ocean (NAO) are interpreted using simple box models. Estimated total sulfur (S) deposition fluxes from air masses with tropical oceanic, African, clean North American, and polluted North American origins are 4.4, 16, 33, and 70 μmol m−2 day−1, respectively, with associated uncertainties of at least factors of 2 to 3. Crude estimates of the fractions of deposition attributable to marine biogenic versus anthropogenic S sources suggest that the latter may be enhancing the natural NAO atmospheric S cycle by a factor of 0.5 to 0.8. Combination with similar estimates for the North Pacific region [Savoie and Prospero, 1989] yields an overall, area-weighted enhancement factor of approximately 0.3 for northern hemisphere ocean areas, consistent with estimates by Wigley [1989] based on climate modeling studies.

During the summer of 1988, a team of scientists aboard the NOAA ship Mt. Mitchell and the NOAA King Air aircraft investigated the spatial distributions of sulfur, nitrogen, and related species and their interactions over the North Atlantic Ocean. In support of these measurements, meteorological data from the National Meteorological Center and from rawinsonde data obtained from the ship were archived and back trajectories were calculated. A summary of the meteorological conditions during the cruise is presented using synoptic maps, soundings, cross sections, and isobaric and isentropic back trajectories. Since day-to-day variability of the synoptic situation was generally small, one representative day was chosen to illustrate the overall meteorology. During the cruise, three synoptic regimes were encountered: (1) north of the polar front, (2) under the Bermuda/Azores high, and (3) under the Intertropical Convergence Zone (ITCZ). Soundings from three different days illustrate these regimes. Boundary layer depth and cloud layers were also estimated from all the soundings. Cross sections of temperature, wind, and relative humidity describing the vertical structure of the atmosphere along the cruise show the general day-to-day uniformity except near the polar front and near the ITCZ boundary. The back trajectories show general air flow patterns and the land mass source regions of air reaching the ship within three days. For parts of the cruise, air reached the ship from North America, Iceland or Greenland, Africa, and South America.