| Summary: | Observations of record-breaking ozone depletion during the Arctic spring of 2011 were made at 76° N in Thule, Greenland. The ozone total column amount of 290 DU measured on 18 March 2011 is the lowest value from the 12-year observation record and represents an ozone depletion of up to 48% of a typical March column. The unique 2010 - 11 vortex was characterized by sustained low stratospheric temperatures and stability that resisted breakup through March. Simultaneous observations of O3, HF, HCl, HNO3, and ClONO2 demonstrate strong subsidence and substantial conversion of chlorine from its normal reservoirs.
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