One air mass after another enters the polar darkness and soon emerges back into low sunshine. Thus, a bit of ozone is lost from each parcel of air, rather than a large amount from one parcel as in the southern hemisphere. The end result is that we are losing ozone in both hemispheres. Ozone levels in the atmosphere have been monitored from the ground since the 1950s and by satellite since the 1970s. Since ozone is created and destroyed by solar UV radiation, there is some correlation of ozone concentration with 11-year sunspot cycles.
Sunspots emit high levels of electromagnetic radiation.
The increased UV radiation contributes to ozone production. Natural cycles in ozone variation are also associated with the quasi-biennial oscillation in which tropical winds switch from easterly to westerly every 26 months.