"Warming of the surface of the Arctic is matched by a colder polar vortex high in the atmosphere, which is speeding the breakdown of the Earth’s shield against ultraviolet rays."
"After sampling the atmosphere above the Arctic for more than a year during the MOSAiC research voyage, climate scientists say the ozone layer, Earth’s protection against intense ultraviolet radiation, is at risk, despite the progress made in protecting atmospheric ozone by the 1987 Montreal Protocol, the global treaty that banned ozone-harming chemicals.
As greenhouse gases heated the surface of the planet, the researchers said, they have also, during the past 50 years, cooled the upper layers of the atmosphere over the Arctic. In the colder stratosphere, long-lived pollutants like chlorofluorocarbons and halons from refrigerants and industrial solvents break down and release chlorine and bromine, which react with sunlight to destroy ozone.
Concentrations of those pollutants in the atmosphere have decreased by about 10 percent since the ban, allowing the ozone layer above Antarctica to heal over the past 20 years, but progressively colder temperatures in the stratosphere above the Arctic are increasing the destruction of ozone in that region."