A catalytic cycle is a series of reactions in which a chemical family or a particular species is depleted, leaving the catalyst unaffected. The net result of the two reactions is the depletion of ozone and atomic oxygen. The suspected cause of the depletion was catalytic cycles involving chlorine and nitrogen. Depletions of greater than 50 percent of total atmospheric ozone have been observed over the Antarctic continent. Similar processes lead to depletion in the Arctic, but to a lesser degree.
Temperatures are higher due to the variability of the polar vortex, which limits formation of PSCs.
The potential for significant depletion in the Arctic does exist, however. The breakup of the polar vortex following polar springtime leads to mixing of ozone-poor air parcels down to lower latitude regions. Brune et al. Multiphase reactions involving aerosol particles are another source of ozone loss that can occur at all latitudes. Hofmann et al.