Ozone loss over Arctic set new record

Ozone loss over Arctic sets new record
By John Heilprin
Associated Press / April 6, 2011

GENEVA — The protective ozone layer in the Arctic that keeps out the sun’s most damaging rays — ultraviolet radiation — has thinned about 40 percent this winter, a record drop, the UN weather agency said.

The Arctic’s damaged stratospheric ozone layer isn’t the best known “ozone hole’’ — that would be Antarctica’s, which forms when sunlight returns in spring there each year. But the Arctic’s situation is due to similar causes: ozone-munching compounds in air pollutants that are chemically trigged by a combination of extremely cold temperatures and sunlight.

The losses this winter in the Arctic’s fragile ozone atmospheric layer strongly exceeded the previous seasonal loss of about 30 percent, the UN’s World Meteorological Organization in Geneva said yesterday.

It blamed the combination of very cold temperatures in the stratosphere, the second major layer of the Earth’s atmosphere, just above the troposphere, and ozone-eating CFCs from aerosol sprays and refrigeration.

“This is pretty sudden and unusual,’’ said Bryan Johnson, a US atmospheric chemist in Boulder, Colo.

Atmospheric scientists concerned about global warming focus on the Arctic because that is where the effects are expected to be felt first.

Ozone losses occur over the polar regions when temperatures drop below -108 Fahrenheit and iridescent ice clouds form. Sunlight on icy surfaces triggers ozone-eating reactions in chlorine and bromine that come from air pollutants such as chlorofluorocarbons.

As of late March, the UN said, the thinning ozone was shifting away from the pole and covering Greenland and Scandinavia.

For the planet, Johnson said, there’s the concern that “if this were to happen every year — even though the ozone naturally regenerates itself — you might see a trending downward of the atmospheric ozone layer.’’

Because of changing weather and temperatures that some Arctic winters experience, there have been times where there is almost no ozone loss, and others when cold stratospheric conditions led to substantial ozone depletion, UN scientists said.

This year, the Arctic winter was warmer than average at ground level but colder than normal in the stratosphere.