The effects of mixing on traces relationships in the polar vortices

We review recent analyses of tracer observations within the Arctic vortex, showing anomalous tracer-tracer relationships which indicate the mixing of outside air into the vortex. Similar anomalous relationships have previousl y been observed in vortex fragments, following breakdown of the Arctic vort ex, and interpreted as indicative of mixing within the filamentary fragment s. In the light of other observations we conclude that this interpretation is incorrect: the mixing took place into the vortex prior to breakdown. We discuss the effects of mixing on tracer relationships within the vortex, il lustrated by results both from a simple conceptual model and from two three -dimensional chemical transport models. These models indicate that continuo us mixing across the vortex edge produces entirely changed tracer relations inside the vortex and that separate, compact vortex relationships can deve lop. In general, tracer relationships should not be used to estimate denitr ification or chemical ozone loss unless the effects of mixing can be quanti fied; this may be possible using information from other tracers, but one ca nnot assume that the effects of anomalous mixing are manifested as simple m ixing lines on tracer-tracer diagrams.