The ozone in the Arctic has depleted by about 40 per cent from the winter's start through to late March -- exceeding the previous seasonal loss of about 30 per cent, the World Meteorological Organization said.
The group said it appears that two factors are at play: a very cold winter in the stratosphere over the region; and the continuing presence of ozone-destroying chemicals in the atmosphere, such as fire retardants and coolants.
Arctic ozone conditions can vary greatly from year to year. Depending on the weather and temperatures, some Arctic winters experience almost no ozone loss while others – like this one – see substantial depletion.
This year, the Arctic winter was warmer than average at ground level, but it was colder than normal in the stratosphere, which is the second major layer of the Earth's atmosphere and starts at about 10 km altitude, reaching up to an altitude of about 50 km.
Although the scope of the Arctic ozone destruction this year is unprecedented, it is not unexpected, WMO scientists said. (read more)