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 po tential effect that biological degradation and its distribution can ha ve on the lifetime of atmospheric CH3Br. The results of this study sho w that both the value of the oceanic degradation rate constant and its geographic distribution are important in determining the calculated a tmospheric lifetime. The best estimate of the partial lifetime of atmo spheric CH3Br with respect to oceanic loss now comes to 1.8 - 1.9 y wi th a full possible range of 1.1 - 3.9 y, which, together with other, n on-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 ind icates that estimated sinks of CH3Br today exceed estimated sources by about 70 Gg y(-1).