Cause of Odd Arctic Ozone 'Hole' Found

Cold temperatures, chlorine and a stagnant atmosphere caused a thinning in the ozone layer over the Arctic in 2011, a new NASA study finds.

This ozone loss is not the more famous ozone hole, found seasonally over Antarctica, which has been shrinking since the phase-out of chlorofluorocarbons, or CFCs, that interact with ozone molecules in the atmosphere. These ozone molecules are made of three oxygen atoms bound together. Their high concentration in the stratosphere about 12 miles to 19 miles (20 to 30 kilometers) above the Earth's surface blocks harmful ultraviolet light from the sun.

Arctic ozone depletion is typically not as severe as that in the Antarctic. Over the South Pole, the sun barely or never sets around Christmas, creating a confluence of sunlight and cold in the atmosphere. Under these conditions, chlorine from CFCs eats away at ozone molecules.

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