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Spring will bring thinner ozone layer, predict experts

Record cold temperatures in the Arctic's upper atmosphere have scientists predicting the loss of the protective layer of ozone over the Arctic as spring approaches, reports Doug Schneider for Arctic Science Journeys Radio. Experts predict the thinning will most likely have the greatest impact on northern Europe.

It can get really cold in the Arctic, especially in the layer of the upper Arctic atmosphere called the stratosphere. That’s the relatively thin layer about 36 to 50 miles above the earth that contains ozone.

Ozone is important because it blocks the sun’s harmful ultraviolet rays from reaching the earth where they can cause skin cancer and other ailments. But when the stratosphere becomes too cold, chemicals in the layer, such as nitrogen and chlorine, freeze and form polar stratospheric clouds. And this January, temperatures in the stratosphere plummeted to 125 degrees below zero.

Within the thin, wispy clouds caused under such cold conditions, a complex chemical chain reaction can occur that destroys ozone, say atmospheric scientists.

Paul Newman, an atmospheric physicist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, says conditions are shaping up for a significant loss of ozone in the weeks ahead—with the addition of one more important ingredient: sunlight.

“We are still a few weeks away from knowing how things are going to evolve,” said Newman. For much of the winter, the high Arctic has been cloaked in darkness. But now the sun is returning. And sunlight is the catalyst that drives the chemical reactions that break down ozone.

Adding to the problem are industrial chemicals such as chlorine and chlorofluorocarbons, or CFCs, that make their way into the Arctic stratosphere. Although CFCs are banned in many countries, including the United States, they are still used elsewhere. Cathy Cahill, an atmospheric scientist at the University of Alaska Fairbanks, explains that CFCs contain the chemicals that destroy ozone.

“Chlorofluorocarbon is a compound that has chlorine and fluorine,” says Cahill. “And when it hits the stratosphere, the sunlight breaks it apart and releases chlorine atoms, which will then cycle and destroy ozone.”

Almost every year, conditions occur in the Arctic that destroy at least some ozone. But some years, a great deal of ozone is lost. In 2000, a record amount of ozone was lost over Greenland, England and northern Europe. In 1997, an area of ozone the size of Texas thinned over the Russian high Arctic.

But just as the sun triggers the destruction of ozone, it also helps create it. Sunlight in the warmer mid- and lower latitudes cause another chemical reaction that produces ozone. The ozone is carried to the poles on upper atmosphere wind currents, where it replenishes the protective ozone layer.

Scientists predict that most of this year’s ozone losses will occur over northern Europe. Experts there are keeping a close eye on things, and getting ready to warn people to wear sunglasses and sunblock to prevent skin cancer.

The ozone layer is not expected to become thinner over other parts of the Arctic, such as Canada and Alaska.

[Read more at Arctic Science Journeys radio]

| Posted 03.08.05 at 5:18 pm

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