POSSIBLE ROLE OF ICE CRYSTALS IN OZONE DESTRUCTION OF THE LOWER ARCTIC ATMOSPHERE

Recent observations have highlighted ozone destruction in the lower Arctic atmosphere during spring, as the Sun rises. The ozone destruction occurs in the surface radiation inversion layer and has been linked to the presence of bromine. The purely gas-phase mechanisms that have been previously proposed are inadequate to explain the observations of rapid destruction of boundary layer ozone. In view of the widespread occurrence of lower tropospheric ice crystals in the Arctic, heterogeneous chemical reactions occurring on the surfaces of ice crystals are proposed here as a mechanism to explain the rapid ozone destruction. Heterogeneous reactions have the potential to modulate the ozone destruction both through the production of BrOx and also by depleting the atmosphere of NOx. Using data obtained from the University of Washington research aircraft, observational evidence is presented for the coincidence of ozone destruction and the presence of ice crystals in the Arctic troposphere. The ozone destruction is hypothesized to be modulated by the availability of sufficient sunlight and Br-x. The proposed mechanism has the advantage of potentially explaining the observed rate of ozone destruction in the lower Arctic troposphere, while at the same time being consistent with the dynamics and thermodynamics of the Arctic troposphere.