Abstract. Ozone depletion events (ODEs) in the Arctic are primarily controlled by a bromine radical-catalyzed destruction mechanism that depends on the efficient production and recycling of Br atoms. Numerous laboratory and modeling studies have suggested the importance of heterogeneous recycling of Br through HOBr reaction with bromide on saline surfaces. However, the gas-phase regeneration of bromine atoms through BrO-BrO radical reactions has been assumed to be an efficient, if not dominant, pathway for Br reformation and thus ozone destruction. Indeed, it has been estimated that the rate of ozone depletion is approximately equal to twice the rate of the BrO self-reaction. Here, we use a zero-dimensional, photochemical model, largely constrained to observations of stable atmospheric species from the 2009 OASIS campaign in Barrow, Alaska, to investigate gas-phase bromine radical propagation and heterogeneous recycling of bromine for a seven-day period during late March. We find that the gas-phase bromine chain length is quite small, at <1.5, and is highly dependent on ambient O3 concentrations. As a result, ozone depletion rates estimated from only gas-phase BrO-radical reactions may significantly underestimate the rate of ozone loss. Furthermore, we find that Br atom production from primary surface emission of Br2 and BrCl can account for between 30 – 90% of total Br atom production. This analysis suggests that heterogeneous recycling of bromine is at least as important as, and at times greater than, gas-phase recycling for the occurrence of Arctic ODEs.;
