Atmospheric Chemistry and Physics Discussions Antarctic ozone loss in 1989–2010: evidence for ozone recovery?

Abstract

We present a detailed estimation of chemical ozone loss in the Antarctic polar vor-tex from 1989 to 2010. The analyses include ozone loss estimates for 12 Antarctic ground-based (GB) stations. All GB observations show minimum ozone in the late September–early October period. Among the stations, the lowest minimum ozone val-5 ues are observed at South Pole and the highest at Dumont d'Urville. The ozone loss starts by mid-June at the vortex edge and then progresses towards the vortex core with time. The loss intensifies in August–September, peaks by the end of September–early October, and recovers thereafter. The average ozone loss in the Antarctic is revealed to be about 33–50 % in 1989–1992 in agreement with the increase in halogens dur-10 ing this period, and then stayed at around 48 % due to saturation of the loss. The ozone loss in the warmer winters (e.g. 2002, and 2004) is lower (37–46 %) and in the colder winters (e.g. 2003, and 2006) is higher (52–55 %). Because of small inter-annual variability, the correlation between ozone loss and the volume of polar stratospheric clouds yields ∼0.51. The GB ozone and ozone loss values are in good agreement with 15 those found from the space-based observations of the Total Ozone Mapping Spec-trometer/Ozone Monitoring Instrument (TOMS/OMI), the Global Ozone Monitoring Ex-periment (GOME), the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and the Aura Microwave Limb Sounder (MLS), where the differences are within ±5 % and are mostly within the error bars of the measure-20 ments. The piece-wise linear trends computed from the September–November vortex average GB and TOMS/OMI ozone show about −4 to −5.6 DU (Dobson Unit) yr −1 in 1989–1996 and about +1 DU yr −1 in 1997–2010. The trend during the former period is significant at 95 % confidence intervals, but the trend in 1997–2010 is significant only at 85 % confidence intervals. Our analyses suggest a period of about 9–10 yr to get the 25 first detectable ozone recovery signal at the 95 % confidence intervals with the current ozone trends in the Antarctic. Thus, this study reveals that the recovery of the Antarctic ozone is well on course.