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Near-surface ozone depletion in the Arctic spring affected by the Northern-Hemispheric climate variability

In the Arctic spring, near-surface ozone can decrease to extremely low levels due to chemical removal catalyzed by halogen radicals. These ozone depletion events (ODEs) are usually accompanied by greatly enhanced surface deposition of reactive gaseous mercury. Here we show the effects of regional climate variability on Arctic ODE frequencies by analyzing surface ozone measurements at three monitoring sites (Barrow, Alert, and Zeppelinfjellet) in the past 30 years. Among the various climate variability indices, the Western Pacific (WP) index has the most significant impact. In years with high ODE frequencies at Barrow and Alert in April, the WP teleconnection pattern tends to be in its negative phase with a weakened storm track from the western Pacific to the Arctic and a strengthened subtropical jet across the Pacific, reducing transport of ozone-rich air masses from mid-latitudes to the Arctic. Analysis of the observations at Zeppelinfjellet indicates a much stronger influence of WP pattern in the 2000s than 1990s. Consequently, the WP index may be used as a proxy to assess ODE frequencies and subsequent environmental impacts in future climate projections.