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Abstract

According to the NOAA Arctic Report Card 2021 (https://arctic.noaa.gov/Report-Card/Report-Card-2021) the ice cap over the Arctic is shrinking. Ozone depleting events (ODEs) are here defined as the fraction of hours in a given month that fall below 15ppb, a level that is highly suggestive of the halogen chemistry that occurs in the arctic springtime and deplete the ozone near the surface. ODEs have been measured during the springtime at NOAA’s NOAA GML’s Barrow Observatory since its founding in the early 1970s. Because the ODEs at the Barrow site are a major driver of the climatology of ozone in the springtime, changes in ODEs frequency or severity will affect the overall trend. The overall trend in the frequency of ODE has been increasing in the months of February and March and decreasing during April and May. However, recently (since 2014), the ODEs have been decreasing and therefore the monthly mean ozone has been increasing. In March, where the source region of the air masses used to be primarily from over the frozen arctic ocean, now there is an increasing component coming from the continental landmass. Using the trajectories and arctic sea ice data from the National snow and ice data center, we will show the link between the ozone depleting events and the source of air masses with enhanced levels of halogens and how changing circulation patterns in the arctic may be the driving factor of the ozone trends.