You are looking for aqua blue colors right at the north pole as they indicate a lower concentration in Dobson units as indicated by the color bar on the bottom. Again a black hole is just a lack of data and is NOT an ozone hole. The inactive forms of chlorine in hydrochloric acid and chlorine nitrate can react with ice crystals and nitric acid trihydrate crystals in very high cold clouds in the stratosphere over Antarctica. This reaction on the surface produces diatomic chlorine molecule and nitric acid, which quickly dissociate into chlorine atoms in the sunlight of the Antarctic spring. The reactive chlorine atoms start a cycle of destruction of ozone.
Chlorine atoms react with ozone to make chlorine monoxide molecules and oxygen molecules.
Chlorine monoxide reacts with atomic oxygen to make diatomic oxygen and reactive chlorine atoms to cycle over again. Since there are few gaseous water molecules and virtually no nitrogen dioxide molecules to react with and inactivate the chlorine, the reactive chlorine builds up as chlorine monoxide.