On the recovery of Antarctic ozone

We examine monthly mean time series of ozone column, ozone profiles, temperature, and EESC (Effective Equivalent Stratospheric Chlorine) within the Antarctic vortex core and collar regions, for September and October, from 1979 to present. The ozone data are from the Brewer/Dobson network, SAGE II, HALOE, and ozonesondes. Year-to-year variations in column ozone are correlated with temperature fluctuations. Accounting for this ozone/temperature relation results in smoothly varying time series of ozone column in the core and collar regions, for both September and October. For the vortex core and collar in September, these resulting time series are well described by variations in EESC. From 1979 to 1996, the ozone abundance in these regions followed a near linear, monotonic decline. Since 1997, we show that ozone has deviated from this prior decline in a statistically significant manner that is clearly related to changes in EESC. Hence, during September, Antarctic ozone has entered its first stage of recovery due to the ban of ozone depleting substances that resulted from the Montreal Protocol and its amendments. The time series analysis is more complicated for October, because: a) ozone is almost completely removed between ~380 to 500 K in the core of the vortex (“loss saturation”); b) recent year-to-year variations in column ozone are clearly controlled by dynamics. We shall discuss these results in the context of various meanings of “recovery” and the severe conditions that took place within the Antarctic ozone during 2006.