The potential effect of oceanic biological degradation on the lifetime of atmospheric CH3Br

We use a global, coupled, ocean-atmosphere box model to examine the potential effect that biological degradation and its distribution can have on the lifetime of atmospheric CH3Br. The results of this study show that both the value of the oceanic degradation rate constant and its geographic distribution are important in determining the calculated atmospheric lifetime. The best estimate of the partial lifetime of atmospheric CH3Br with respect to oceanic loss now comes to 1.8 - 1.9 y with a full possible range of 1.1 - 3.9 y, which, together with other, non-oceanic losses, yields a total atmospheric lifetime of 0.7 y (0.6 - 0.9 y). A subsequent revision of the budget for atmospheric CH3Br indicates that estimated sinks of CH3Br today exceed estimated sources by about 70 Gg y(-1).