Why unprecedented ozone loss in the Arctic in 2011? Is it related to climate change?
- ISSN: 16807316
- DOI: 10.5194/acp-13-5299-2013
An unprecedented ozone loss occurred in the Arctic in spring 2011. The\ndetails of the event are revisited from the twice-daily total ozone and\nNO2 column measurements of the eight SAOZ/NDACC (Systeme d'Analyse par\nObservation Zenithale/Network for Detection of Atmospheric Composition\nChanges) stations in the Arctic. It is shown that the total ozone\ndepletion in the polar vortex reached 38% (approx. 170 DU) by the end\nof March, which is larger than the 30% of the previous record in 1996.\nAside from the long extension of the cold stratospheric NAT PSC period,\nthe amplitude of the event is shown to be resulting from a record daily\ntotal ozone loss rate of 0.7% d(-1) after mid-February, never seen\nbefore in the Arctic but similar to that observed in the Antarctic over\nthe last 20 yr. This high loss rate is attributed to the absence of NOx\nin the vortex until the final warming, in contrast to all previous\nwinters where, as shown by the early increase of NO2 diurnal increase,\npartial renoxification occurs by import of NOx or HNO3 from the outside\nafter minor warming episodes, leading to partial chlorine deactivation.\nThe cause of the absence of renoxification and thus of high loss rate,\nis attributed to a vortex strength similar to that of the Antarctic but\nnever seen before in the Arctic. The total ozone reduction on 20 March\nwas identical to that of the 2002 Antarctic winter, which ended around\n20 September, and a 15-day extension of the cold period would have been\nenough to reach the mean yearly amplitude of the Antarctic ozone hole.\nHowever there is no sign of trend since 1994, either in PSC (polar\nstratospheric cloud) volume (volume of air cold enough to allow\nformation of PSCs), early winter denitrification, late vortex\nrenoxification, and vortex strength or in total ozone loss. The\nunprecedented large Arctic ozone loss in 2011 appears to result from an\nextreme meteorological event and there is no indication of possible\nstrengthening related to climate change.