RELATED INFORMATION Background USATODAY.com: Understanding ozone September 2002 report: ozone hole filling in early USATODAY.com: Science in the Earth's cold regions

This year's Antarctic ozone hole confirmed as smallest since 1988

By Melanie Conner, The Antarctic Sun

MCMURDO STATION, Antarctica — Earth donned a heavier layer of sunscreen this year over the Southern Hemisphere. The active ingredient: ozone.

		Seth White prepares ozone measuring instruments on the rooftop of a building at Arrival Heights, near McMurdo.
		Melanie Conner/The Antarctic Sun (

Scientists confirmed that the 2002 ozone hole was the smallest since 1988, after abnormal weather patterns in Earth's upper atmosphere interfered with the chemical reactions that break down ozone molecules in the stratosphere.

In 2002, the hole covered an area of about 6 million square miles, about the size of Antarctica, down from 9 million to 10 million square miles seen during the last six years.

Observations from all three U.S. science stations indicated comparatively high concentrations of ozone and lower levels of ultra violet (UV) in September. Palmer Station experienced record-low UV levels until mid-October. South Pole Station's UV levels are usually lower than other stations during September because it is the last to receive the spring sunrise; however, UV levels dropped even further on Sept. 25, when the hole stunned observers once again by splitting into two.

"The split was unprecedented and is clearly documented in satellite data," said researcher Germar Bernhard, who maintains the National Science Foundation's UV monitoring network in Antarctica. Bernhard explained that one part of the hole traveled close to South America, mixed with warmer air and disappeared by the first of October. The second part was located off the Antarctic Coast, facing Africa. During the first two weeks of October, it moved again toward the South Pole and gained strength.

"The splitting occurred because extensive troposphere activity pumped energy into the stratosphere," said researcher Terry Deshler of the University of Wyoming. "The energy deposited in the stratosphere reduced the size and strength of the polar vortex. This is the situation frequently observed in the Arctic, but seldom in the Antarctic."

Scientists agree that this year's peculiar weather pattern should not be viewed as a long-term trend. However, it appears that Mother Nature sought self recovery following last year's record-high ozone hole, which was larger than the combined area of the United States, Canada and Mexico.

"It is not possible to make predictions for next year," said Bernhard. "The depth and size of the ozone hole depend very much on meteorological conditions, e.g. the strength of the polar vortex – and those cannot be forecasted with sufficient accuracy one year ahead."

Measured continuously with a combination of ground, balloon and satellite-based instruments, the small ozone hole in 2002 is a result of instability in the annually occurring, strong polar vortex during the Antarctic winter night.

Laser tracks ozone When winter residents at McMurdo Station see a green streak in the sky, they know the science technician has turned on the Light Detection and Ranging System or Lidar. Built in 1991 by the Italian Institute of Atmospheric and Climate Science, the Lidar collects data on the composition of polar stratospheric clouds. Also known as nacreous clouds, these colorful clouds appear in the otherwise dark sky in the polar spring. As nacreous clouds form, the Lidar’s green laser beam shoots like a beacon from the Crary Lab roof. The laser beam is reflected back from the clouds that rest 14 to 16 miles above Earth, where ozone is located. The Lidar’s telescope component amplifies the reflected light rays and records the cloud’s altitude, surface area and composition – liquid or solid. The Lidar’s cloud composition information allows scientists to determine whether the clouds contain the correct chemicals needed to increase or decrease chlorine dispersal. Chlorine is a key component in the destruction of ozone, and the creation of the ozone hole over Antarctica each year.

After wafting into the atmosphere from Asia, Europe, Africa and the Americas and circling Earth, decades-old pollutants known as chlorofluorocarbons or CFCs migrate to the stratosphere, the upper atmosphere, where airplanes travel and Mt. Everest crests. Eventually the pollutants wind up in the polar vortex, a weather pattern that encircles and isolates Antarctica from warmer temperatures.

"It needs to be cold in the stratosphere to form a hole, otherwise there would be a hole around the world," said Bernhard. The cold stratosphere over Antarctica promotes the formation of ice clouds upon which the chain of chemical reactions of ozone destruction depends.

On the surface of ice clouds, which form inside the cold, dark polar vortex, inert chlorine from man-made pollutants transform into active forms of chlorine. The first rays of sunlight appear at the end of the Antarctic night, continuing the chain reaction and these chlorine attack and destroy ozone.

"The ozone hole months are sunrise in August to late November or early December," said Bernhard. The harmful UV rays are most dangerous in November, when the sun is high in the sky, allowing rays to cut directly through the thin stratosphere where ozone is depleted. During September and October when the sun is low on the horizon, the rays travel a longer path and thus through more ozone.

Ultraviolet B rays are short, high-energy light waves known to cause skin cancer.

"The shorter the wavelength, the more energy. Since UVBs carry more energy (than UVAs) they penetrate deeper into the skin, damaging DNA," said Deshler. "When many DNA cells are destroyed, the chances of not repairing them properly increases and this can lead to cancer."

The short and fast invisible rays also dive deep into the Southern Ocean, leaving marine organisms unprotected from the sun's power. This effects one of the world's most productive marine ecosystems by damaging microscopic algae called phytoplankton that form the foundation of the Antarctic food chain.

"When ice starts to break up at the end of the polar night, marine organisms are exposed to elevated UV levels under the ozone hole. It is extremely complex to quantify the effects of increased UV on ecosystems, and this topic is therefore still the focus of ongoing research," said Bernhard. "However, without the upper layer ozone there would be no life on Earth."