Springtime Ozone Loss

By George Grow

This is the VOA Special English SCIENCE REPORT.

Information gathered one year ago shows large areas of Earth's lower atmosphere with very little ozone over northern Canada. Instruments on airplanes measured the ozone loss over Hudson Bay, Baffin Bay and parts of the Arctic Ocean.

Scientists say the measurements were the first to confirm ozone loss over large areas just south of the Arctic Circle. They say the lack of surface ozone has been observed each spring since the Nineteen-Eighties at a research station in northern Canada.

Scientists from the National Center for Atmospheric Research led the experiment. University researchers and the American space agency NASA assisted with the project.

Ozone is a form of oxygen. It is found in the air we breathe and in Earth's atmosphere. The ozone layer in the upper atmosphere protects life on Earth. The ozone there blocks harmful radiation from the sun. Near Earth, ozone is a common pollutant. It can harm people, crops and other plants.

Having less ozone near the surface of the Earth may sound like a good thing. However, scientists are concerned. Although ozone is a pollutant, it also produces a chemical that removes pollutants from the atmosphere.

Brian Ridley was involved on the research flights last year. He says the ozone losses over the Arctic are not threatening. He says they show that scientists still have a lot to learn about the chemistry of the atmosphere.

Last April, one research airplane flew almost seven-hundred-forty kilometers through an area over Hudson Bay with little or no ozone. Ozone levels in most areas in the northern part of the world are normally thirty to forty-five parts per one-thousand-million. Over Hudson Bay, the ozone levels dropped to less than one part per one-thousand-million. Scientists suspect the ozone loss ends quickly with the arrival of ozone-rich air from other areas.

Scientists say surface ozone loss happens during the spring when sunlight returns to the Arctic. This starts chemical processes that do not happen during the dark winter months.

Scientists say a possible cause of ozone destruction is the chemical bromine. Satellites orbiting Earth have measured large amounts of bromine high in the atmosphere. But scientists do not know what starts and continues bromine production through the spring.

This VOA Special English SCIENCE REPORT was written by George Grow.