System analysis of polar ozone depletion

Abstract

The sudden onset of catastrophic ozone losses over Antarctica a decade ago evokes the response of a feedback system under a steady perturbation. In this paper an explicit feedback mechanism is proposed and incorporated into a kinetic model that mimics observable trends for major variables. The essence of the proposal is that the extent and time profile of seasonal ozone depletion actually imply the coupling of [O_3], radiative heating, cloud persistence and heterogeneous regeneration of photochemically active chlorine species. The model seeks insight into the phenomenon as a paradigm of unanticipated amplification of human activity, strives for clarity and relevance and complies with fundamental principles and with global constraints such as ozone levels and decay rates, chlorine monoxide and nitrogen dioxide concentrations and cloud sightings. Two main conclusions emerge: 1) the local regeneration of active chlorine mediated by nitrogen dioxide on ice clouds after sunrise is a key factor, and 2) local ozone losses become highly sensitive to initial conditions, and to slight perturbations of the catalytic activity of clouds, above critical levels of active chlorine.