Fate of Arctic ozone remains up in the air.

Fate of Arctic ozone remains up in the air

Using two instrument-laden airplanes flying from a base in Stavenger, norway, a team of 150 U.S. and European scientists is surveying the dubios health of stratospheric ozone over the Arctic. The six-week project, which will continue through Feb. 15, is aimed at determining how human-made chemicals called chlorofluorocarbons are harming the protective layer of ozone in the North.

Despite earlier projections that the Arctic stratosphere might be too warm this year for certain parts of the project, weather has cooperated with the experimenters, says Michael Kurylo, program manager of NASA's Upper Atmosphere Research Program in Washington, D.C. "The low temperatures are there and the PSCs [polar stratospheric clouds] are there," he told SCIENCE NEWS in a telephone interview frm Norway.

Polar stratospheric clouds are composed of frozen water and nitric acid crystals that form when stratospheric temperatures drop below about 85[deg.]C. In past studies of the dramatic ozone losses over Antarctica, scientists have learned that PSCs help chlorine destroy ozone by fostering certain chemical reactions (SN: 10/15/88, p.249).

Sponsored principally by NASA, the present Arctic project reunites many scientists and instruments from a similar airborned campaign over the Antarctic last year. Both studies rely on a high-altitude ER-2 and a medium-altitude, long-range DC-8. The ER-2 can fly into the stratosphere to take direct measurements and samples, while the DC-8 carries an airborne laboratory of remote-sensing instruments that probe that stratosphere from beneath.

Researchers say there is no Arctic ozone "hole" comparable to the one detected over the Antarctic each September and October since the late 1970s. Warm temperatures and strong weather variations in the North do not create the same kind of conditions that allow the Antarctic-scale destruction of ozone molecules.

Long-term records, however, show that ozone levels in the high northern latitudes have dropped roughly 5 percent over the last 17 years, says Kurylo. This trend concerns scientists because, while the Antarctic remains virtually unpopulated, people do live in the northern areas that appear to be suffering ozone loss. Stratospheric ozone protects humans and other life forms by absorbing ultraviolet radiation from the sun.

Last year, researchers stationed in Thule, Greenland, measured elevated levels of reactive chlorine compounds -- an indication that chlorine is destroying ozone in the region, although the severity of this process is still unclear. Scientists say they need to detail what is taking place in the Arctic in order to create realistic models forecasting how quickly ozone levels will drop in the future.