Arctic Ozone Loss
INTRO: About 10 miles above us, in the stratosphere, there exists a layer filled with a chemical called ozone that shields us from the sun's harmful ultraviolet rays. For years, scientists have documented how human pollution is slowly destroying this protective layer. As Doug Schneider reports in this week's Arctic Science Journeys Radio, this spring brought some of the worst ozone destruction in 40 years in the stratosphere over Europe.
STORY: Dr. Paul Newman is one of several NASA scientists who led the U.S.-European study of ozone losses over northern Europe. He's quick to point out that the ozone losses measured this spring don't constitute an actual ozone hole--such as seen over Antarctica in recent years--but rather a dramatic thinning of the ozone layer.
NEWMAN: "The total ozone loss, between the surface and space, was about 16 percent. This is about the second worst that we've had; 1997 was the worst."
For ozone to be destroyed, several things have to happen at about the same time. First, it has to be extremely cold in the stratosphere--that's the layer from about 6 to 30 miles above the earth where ozone is found. Secondly, you need sunlight and a chemical called chlorine. In the presence of sunlight and extremely cold temperatures, chlorine destroys ozone faster than it can be replaced. These conditions came together this spring within some 14 million square miles over northern Europe.
NEWMAN: "It covered all of Greenland, and extended as far south as Great Britain, and cut across northern Russia. But didn't extend over Alaska or Siberia. So all of the North Atlantic."
Newman says so much ozone was lost because much of the stratosphere over northern Europe remained unusually cold throughout late winter and into the spring. Temperatures of 130 degrees below zero caused the formation of crystalline clouds, called polar stratospheric clouds. These clouds concentrated airborne chlorine, and in the presence of sunlight, triggered a chemical reaction that destroyed ozone.
NEWMAN: "Well, there are a few factors here. The first factor is that it didn't really get to record cold levels. But the region of cold temperatures was at a record size this year. That is, the region that was cold enough to form polar stratospheric clouds was really large. In fact, on January 28, it was the largest region of very cold temperatures we've ever seen in 40 years of observing stratospheric temperatures with balloons and satellites. It was a record size, and that meant that since you had a huge coverage of polar stratospheric clouds, you activated lots of chlorine. So that was happening quite a bit through the January, February, and March period."
The chlorine itself comes from chemicals called chloroflorocarbons, or CFCs. Although CFCs are being used less and less in things like air conditioners, there's still plenty of them making their way into the upper atmosphere.
NEWMAN: "I can say that about 75 to 80 percent of the chlorine we see in the stratosphere is man-made."
Newman doesn't know why the stratosphere became so cold this year but he says it could be because of shifts in global climate patterns.
OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider.
To learn more about the NASA study and Arctic ozone loss, visit these web pages:
Thanks to the following individual for help preparing this script:
Dr. Paul Newman
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.