Ozone hole over Arctic worst in history
Intense cold in the upper atmosphere of the Arctic last winter activated ozone-depleting chemicals and produced the first significant ozone hole ever recorded over the high northern regions.
A NASA-led study has documented an unprecedented depletion of Earth’s protective ozone layer above the Arctic last winter and spring caused by an unusually prolonged period of extremely low temperatures in the stratosphere, NASA reports.
The amount of ozone destroyed in the Arctic was comparable to that seen in some years in the Antarctic, where an ozone “hole” has formed each spring since the mid 1980s.
- Day-to-day temperatures in the 2010-11 Arctic winter did not reach lower values than in previous cold Arctic winters, said Gloria Manney from NASA. - The difference from previous winters is that temperatures were low enough to produce ozone-destroying forms of chlorine for a much longer time. This implies that if winter Arctic stratospheric temperatures drop just slightly in the future, for example as a result of climate change, then severe Arctic ozone loss may occur more frequently, she added.
Last winter was extremely cold in the Barents Region. The Finnish town of Rovaniemi, for example, had 100 days of sub-zero temperatures, as BarentsObserver reported.
To investigate the 2011 Arctic ozone loss, scientists from 19 institutions in nine countries analyzed a comprehensive set of measurements. The scientists found that at some altitudes, the cold period in the Arctic lasted more than 30 days longer in 2011 than in any previously studied Arctic winter, leading to the unprecedented ozone loss. Further studies are needed to determine what factors caused the cold period to last so long.
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