Hole in ozone forms above Arctic

Updated October 14, 2011 11:25:00

Photo: Researchers measured an 80 per cent drop in ozone levels over the Arctic.

Related Story: Scientists say ozone layer depletion has stopped

Map: Norway

A hole five times the size of California formed in the ozone layer above the Arctic in the 2010-11 northern winter, with scientists saying it was the largest on record.

Scientists say the hole is a sign that chlorofluorocarbons (CFCs) are still damaging the stratosphere, even though their production stopped 15 years ago.
A similar hole has formed above the Antarctic every southern winter since the 1980s.
This year, for the first time on record, an ozone hole of similar scale formed above the Arctic.
Senior researcher at NASA's Jet Propulsion Laboratory Gloria Manney has been monitoring the phenomenon.
"We started seeing in this past winter in the Arctic in February and March, that the ozone in the stratosphere was decreasing much more rapidly than it typically does," she said.

Audio: First hole forms in Arctic ozone layer (AM)

Levels of ozone over the polar regions drop every winter as the intense cold turns man-made chemical emissions in the stratosphere into a type of chlorine which destroys ozone.
The Arctic is not as cold as the Antarctic, and it does not usually get cold enough there for the ozone layer to develop as large a hole.
But Ms Manney said the last northern winter was abnormally cold.
"Usually in the Arctic in the northern hemisphere there is only just a little bit of ozone loss, because it isn't that cold for that long," she said.
"This year it was cold for longer than usual and so the chlorine was in forms that could destroy ozone, and so much more ozone was destroyed than in previous winters that we've observed."
The production of ozone-destroying chlorofluorocarbons was phased out by 1996, but a senior research scientist with the Australian Antarctic Division, Dr Andrew Klekociuk, says it will take decades for CFCs to disappear entirely from the stratosphere.
"They take 20 or 30 years to break down and we're still seeing, I guess, the delayed effects of the controls on those gases," he said.
The researchers measured an 80 per cent drop in ozone levels over the Arctic, leading to a hole which grew as big as five times the size of California.
That is smaller than this year's Antarctic hole, but Dr Klekociuk says it is likely the hole will increase harmful UV radiation in the northern hemisphere.
"Those low ozone levels combined with sunlight produce more UV potentially at the earth's surface," he said.
"We are yet to see the results in from UV measurements in the Arctic but one would expect there to be elevated ultraviolet levels for that particular winter and early spring period."
The results of the research, led by Gloria Manney, have been published in the journal Nature.
Editor's note (October 12, 2011): The original version of this story incorrectly suggested it was the first time a hole had formed in the ozone layer above the Arctic. This is not correct; it is the first time a hole on the scale of those regularly detected in the Antarctic has been recorded over the Arctic. The story has been changed to reflect this.

Source: http://www.abc.net.au/news/2011-10-03/hole-in-ozone-forms-above-arctic/3206356