Editing Polar vortex (section)

==Ozone depletion==
[[File:Srnhemozoneconcentration.gif|thumb|Southern Hemisphere ozone concentration, February 22, 2012]]

The chemistry of the Antarctic polar vortex has created severe [[ozone depletion]], although the effect has been weakening since the 2000s. It is expected to return to 1980 levels in about 2075. <ref>{{cite web |url=https://svs.gsfc.nasa.gov/30602 |title=The Antarctic Ozone Hole Will Recover|date=June 4, 2015|publisher=NASA |access-date=2017-08-05 }}</ref> The nitric acid in [[polar stratospheric cloud]]s reacts with [[chlorofluorocarbon]]s to form [[chlorine]], which [[catalysis|catalyzes]] the photochemical destruction of [[ozone]].<ref>{{cite book|pages=42–44|title=The Arctic and environmental change|author=J.A. Pyle|date=1997|publisher=CRC Press|isbn=978-90-5699-020-6|url=https://books.google.com/books?id=CSH2CU3eqNUC&pg=PA41}}</ref> Chlorine concentrations build up during the polar winter, and the consequent ozone destruction is greatest when the sunlight returns in spring.<ref>{{cite book|url=https://books.google.com/books?id=hXH-LO4iTZAC&pg=PA49|page=47|year=2010|title=Tracer-tracer Relations as a Tool for Research on Polar Ozone Loss|author=Rolf Müller|publisher=Forschungszentrum Jülich|isbn=978-3-89336-614-9}}</ref> These clouds can only form at temperatures below about {{Convert|-80|C|F}}.

Since there is greater air exchange between the Arctic and the mid-latitudes, ozone depletion at the north pole is much less severe than at the south.<ref>{{cite book|url=https://books.google.com/books?id=B93SSQrcAh4C&pg=PA34|page=34|title=Stratosphere troposphere interactions: an introduction|author=K. Mohanakuma|isbn=978-1-4020-8216-0|publisher=Springer|year=2008}}</ref> Accordingly, the seasonal reduction of ozone levels over the Arctic is usually characterized as an "ozone dent", whereas the more severe ozone depletion over the Antarctic is considered an "ozone hole". That said, chemical ozone destruction in the 2011 Arctic polar vortex attained, for the first time, a level clearly identifiable as an Arctic "[[ozone hole]]".<ref name="bbc">{{cite news|title=Arctic ozone loss at record level|url=https://www.bbc.co.uk/news/science-environment-15105747|publisher=BBC News Online|access-date=October 3, 2011|archive-url=https://web.archive.org/web/20111003182807/http://www.bbc.co.uk/news/science-environment-15105747|archive-date=October 3, 2011|url-status=live|date=October 2, 2011}}</ref>