Tuesday, March 15, 2011

Huge ozone hole spreads over Arctic, scientists say

Extremely cold temperatures in the upper atmosphere over the Arctic have triggered a "massive" loss of ozone in just the past few weeks, a situation that could create the most severe ozone hole yet observed in the Far North, according to Europe’s leading Arctic research group.
An international network of more than 30 ozone measuring stations have tracked this sudden reduction in the concentrations of the trace gas that protects life on Earth from dangerous solar radiation, according to a release from the Alfred Wegener Institute.
"Our measurements show that at the relevant altitudes about half of the ozone that was present above the Arctic has been destroyed over the past weeks," said AWI atmospheric researcher Markus Rex. "Since the conditions leading to this unusually rapid ozone depletion continue to prevail, we expect further depletion to occur."
The depletion in the Arctic could migrate southward on air currents, Rex said, and ultimately lead to reduced protection against ultraviolet radiation in more populated areas of Alaska, Canada and Europe later in the season.
"Special attention should thus be devoted to sufficient UV protection in spring this year," Rex said.
Ozone or O3 is a naturally occurring gas molecule comprised of three oxygen atoms -- the oxygen that we breathe is O2. When present at sufficient concentrations in the upper atmosphere six to 31 miles high, ozone helps block dangerous ultraviolet radiation from reaching the Earth’s surface.
Scientists say the overall level of ozone has plunged over recent decades, mostly due to the release of chlorofluorocarbons by humans, and this loss could lead to health problems, especially increases in certain kinds of skin cancers. Under the international Montreal Protocol Treaty, substances that deplete the ozone are being phased out, with full recovery of the ozone layer possible by 2050.
In the meantime, dramatic plunges in ozone concentrations can develop in the polar springs over Antarctica and the Arctic Ocean, mainly due by extreme cold in the stratosphere. This winter, parts of this layer in the Arctic has chilled to more than Minus 100 degrees Fahrenheit. The so-called "ozone hole" over Antarctica often gets big press coverage and attention from policy makers, while the Arctic version is less well known.
Increased concentration of human-produced greenhouse gases in the air ends up chilling the stratosphere by slowing the loss of heat into space, making climate change a critical factor in the ozone drama. 
"For several years climate scientists have pointed to a connection between ozone loss and climate change, and particularly to the fact that in the Arctic stratosphere where the ozone layer is, the coldest winters seem to have been getting colder and are leading to larger ozone losses," wrote the staff of the blog Science 2.0 about this situation.
That warmer temperatures at the surface can cause extreme cold aloft is no paradox, Rex explained.
"To put it in a simplified manner, increasing greenhouse gas concentrations retain the Earth's thermal radiation at lower layers of the atmosphere, thus heating up these layers," he said. "Less of the heat radiation reaches the stratosphere, intensifying the cooling effect there."
Scientists haven't worked out all the details yet and don't fully understand how ozone interacts with climate change. A 3.5 million euro ozone investigation involving 16 research institutions from eight European countries is now underway.
The ozone layer will continue to recover, Rex said, despite this winter's record loss in the Arctic. But countries must continue to eliminate the damaging chemicals.
"By virtue of the long-term effect of the Montreal Protocol, significant ozone destruction will no longer occur during the second half of this century," Rex said.

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