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Antarctic ozone hole splits in two

By Richard Stenger (CNN)

Satellite view of Antarctic ozone hole, dark blue, splitting in late September
Satellite view of Antarctic ozone hole, dark blue, splitting in late September

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A graphic animation of the splitting of the Arctic ozone hole (September 30)
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(CNN) -- Like a giant amoeba in the sky, the ozone hole above Antarctica has divided into two parts, which have spread away from the southernmost continent.

The surprising development is the first of its kind since NASA and other U.S. agencies began monitoring the ozone hole, a seasonal vortex high in the atmosphere, more than two decades ago.

Ozone is part of the stratosphere, which stretches from six to 30 miles above the Earth's surface. Ozone shields the planet from dangerous ultraviolet solar rays, which can cause skin cancer. In fact, without the ozone layer, life as we know it could not exist.

Recent satellite images reveal that the ozone hole had shrunk considerably compared with the previous two years. Scientists caution that the data are insufficient to conclude that the fragile ozone layer is on the mend.

"This is the first time we've seen the polar vortex split in September," said Craig Long, a meteorologist with the National Oceanic and Atmospheric Administration (NOAA).

Exceptionally strong weather disturbances this autumn in the Southern Hemisphere stratosphere spawned the ozone hole division, Long said.

Moreover, the hole had dwindled in size before the split because of unusually warm temperatures in the atmosphere, according to NASA ozone scientist Paul Newman.

Since the 1970s, satellite, balloon and ground-based instruments have observed a temporary ozone hole open up over Antarctica for several months during the winter and spring in the Southern Hemisphere.

Certain chlorine and bromine chemical compounds used in everything from aerosol cans to air conditioning are considered the culprit. The industrial pollutants, phased out by the Montreal Protocols by the mid-1990s, are known to persist high in the atmosphere where they can repeatedly break down ozone molecules.

Between 1996 and 2001, the ozone hole reached more than 9 million square miles (24 million square km). The 2000 hole was the largest ever recorded at about 11 million square miles (28 million square km), roughly three times the size of the United States.

Preliminary estimates from early September 2002 suggest that the seasonal hole had dwindled to about 6 million square miles (15 million square km), according to NASA.

The air over the South Pole usually becomes coolest in August and September. The frigid weather is associated with the formation of thin clouds, where the floating industrial chemicals eat up the fragile ozone molecules.

By October, the atmospheric region warms up and the hole begins to disappear.

The 2002 development could be an aberration caused by weather patterns and does not necessarily reflect a long-term trend, NOAA and NASA scientists said.

"While chlorine and bromine chemicals cause the ozone hole, temperature is also a key factor in ozone loss," Newman said.



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