April 5, 2011
Record Loss Of Ozone Layer Over Arctic
In the spring of 2011, the ozone layer that protects us from harmful levels of ultraviolet rays has shown a record loss in the Arctic region, according to the U.N. weather agency.
The continued presence of ozone-depleting substances in the atmosphere coupled with a very cold winter in the stratosphere is to blame.Although an international agreement from 1987 called the Montreal Protocol has successfully reduced the production and consumption of these ozone destroying chemicals, the long atmospheric lifetimes of these compounds remain in the air for several decades.
Refrigerators, spray cans and fire extinguishers used to contain ozone depleting substances such as chlorofluorocarbons (CFCs) and halons. However, these substances have been phased out under the Montreal Protocol.
"The Arctic stratosphere continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities," said WMO Secretary-General Michel Jarraud.
Observations from the ground, satellites and balloons reveal a loss of about 40% over the Arctic region that started from the beginning of winter into late March. Over an entire winter, the highest ozone loss previously recorded was 30%.
Due to extreme cold and low temperatures in the Antarctica stratosphere, the ozone hole there is an annual occurrence.
On the other hand, the Arctic weather conditions are much more varied from year to year, with temperatures much warmer than Antarctica.
Therefore, some winters in the Arctic experience no loss of ozone layer, while other winters that last beyond the polar night can occasionally lead to substantial ozone loss, reports the agency.
"The degree of ozone loss experienced in any particular winter depends on the meteorological conditions. The 2011 ozone loss shows that we have to remain vigilant and keep a close eye on the situation in the Arctic in the coming years," Jarraud said.
This year, although the Arctic experienced a warmer than normal winter on the ground, the air was colder than normal at the stratosphere level, where the depletion occurs.
The result of the loss is unprecedented but according to the agency and scientists, it is not unexpected.
"Stratospheric ozone depletion occurs over the polar regions when temperatures drop below -78°C. At such low temperatures clouds form in the stratosphere. Chemical reactions that convert innocuous reservoir gases (e.g. hydrochloric acid) into active ozone depleting gases take place on the clouds particles. The result is rapid destruction of ozone if sunlight is present," the agency says.
According to the WMO/UNEP Scientific Assessment of Ozone Depletion, the ozone layer that is outside the polar regions is projected to recover to its pre-1980 levels somewhere around 2030-2040, thanks in part to the international agreement.
The ozone layer over Antarctica is expected to recover around 2045 to 2060, whereas the Arctic ozone should recover one to two decades earlier.
In the meantime, the public is advised to stay informed with national UV forecasts.
"WMO's Global Atmosphere Watch Network has many stations in the Arctic and helps us to obtain an early warning in case of low ozone and intense UV radiation."
The agency warns that "as the solar elevation at noon increases over the next weeks, regions affected by the ozone depletion will experience higher than normal UV radiation."
UV-B rays are known to be linked to skin cancer, cataracts and can cause damage to the human immune system.
On the Net:
- World Meteorological Organization
- Images of total ozone column and vertical ozone profiles around the pole on March 30, developed by Finnish Meteorological Institute using satellite and ground based data, can be found at http://www.ava.fmi.fi/~jtammine/gomos_video.gif
- The 2010 WMO/UNEP Scientific Assessment on Ozone Depletion is available at http://www.esrl.noaa.gov/csd/assessments/ozone/ with more details about the current state of the ozone layer and projections for the future.