A Net Sink for Atmospheric CH3Br in the East Pacific Ocean

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Science  17 Feb 1995:
Vol. 267, Issue 5200, pp. 1002-1005
DOI: 10.1126/science.267.5200.1002


Surface waters along a cruise track in the East Pacific Ocean were undersaturated in methyl bromide (CH3Br) in most areas except for coastal and upwelling regions, with saturation anomalies ranging from + 100 percent in coastal waters to –50 percent in open ocean areas, representing a regionally weighted mean of –16 (–13 to –20) percent. The partial lifetime of atmospheric CH3Br with respect to calculated oceanic degradation along this cruise track is 3.0 (2.9 to 3.6) years. The global, mean dry mole fraction of CH3Br in the atmosphere was 9.8 ± 0.6 parts per trillion, with an interhemispheric ratio of 1.31 ± 0.08. These data indicate that ∼8 percent (0.2 parts per trillion) of the observed interhemispheric difference in atmospheric CH3Br could be attributed to an uneven global distribution of oceanic sources and sinks.