Chlorine peroxide reaction explains observed wintertime hydrogen chloride in the Antarctic vortex

Abstract It is well established that the drastic ozone loss in the Antarctic stratosphere, commonly known as the ozone hole, is primarily driven by gas-phase and heterogeneous chemical processes. While chemistry transport models generally reproduce observed ozone depletion well, they fail to capture the rapid early-winter decline of hydrogen chloride. We here examine the impact of the heterogeneous reaction between chlorine peroxide and hydrogen chloride forming HOOCl, followed by its photolysis. Incorporating this reaction and an additional hypochlorous acid loss pathway into a chemical mechanism significantly improves model agreement with observed levels of several chlorine compounds in the lower polar vortex stratosphere. This revised mechanism increases simulated ozone partial column depletion by over 15% between early July and mid-September 2011. Laboratory confirmation of these proposed reactions is needed to validate the mechanism.