The largest Arctic ozone hole ever measured is hovering over the North Pole
A curious confluence of atmospheric events has produced the largest ozone hole ever measured over the Arctic. A powerful polar vortex has trapped especially frigid air in the atmosphere above the North Pole, allowing high-altitude clouds to form in the stratosphere, where the ozone layer also sits. Within those clouds, chlorofluorocarbons and hydrochlorofluorocarbons already high in the atmosphere — gases used as refrigerants — react with ultraviolet rays from the sun to release chlorine and bromine atoms, which in turn react with and deplete the ozone. Such conditions are more often seen over Antarctica, leading to a more frequent and much larger ozone hole in the Southern Hemisphere (SN: 12/14/16). The ozone layer sits in the stratosphere, an atmospheric layer between about 10 and 50 kilometers above the ground, where it protects life on Earth from UV radiation from the sun. During the Southern Hemisphere’s spring, as much as 70 percent of the ozone can disappear; in some places, the ozone concentration drops...