Constraints on N2O sinks inferred from observed tracer correlations in thelower stratosphere

Recent isotopic studies have suggested that the trace gas N2O has a missing stratospheric sink of potentially major significance. While these studies have raised interesting questions, the constraints on N2O photochemistry im posed by correlations between N2O, total reactive nitrogen, and other trace rs measured in situ in the lower stratosphere also should be considered. Me asured tracer correlations, when compared to the results of models using st andard photochemistry, provide evidence in support of conventional N2O sink s. Stratospheric tracer correlations, however, cannot be used to preclude a new atmospheric source of N2O in the troposphere or to argue against an un discovered stratospheric sink that contributes less than similar to 20% of the total sink.