In 2011 the Arctic's Ozone Layer Hole Grew to an Unprecedented Size


Left: Ozone in Earth's stratosphere at an altitude of approximately 12 miles (20 kilometers) in mid-March 2011, near the peak of the 2011 Arctic ozone loss. Right: chlorine monoxide - the primary agent of chemical ozone destruction in the cold polar lower stratosphere - for the same day and altitude. Image: NASA/JPL-Caltech, Public domain
Bigger Arctic Ozone Hole on Record
Antarctica has always had bigger ozone hole problems than the Arctic, but this year the ozone hole over the North Pole grew to the biggest size that scientists have ever recorded. Over the winter and spring of 2011, conditions in the upper atmosphere mixed with human-produced chlorine chemicals created a kind of "perfect storm" and for the first time the damage was comparable to the hole over Antarctica.

This chart shows the levels of ozone above the Arctic on 19 March 2010 (left) and 2011 (right), the latter showing about a 50% drop. Image credit: OMI/Aura/NASA

The study, which was published in Nature and required international cooperation, found that:

To investigate the 2011 Arctic ozone loss, scientists from 19 institutions in nine countries (United States, Germany, The Netherlands, Canada, Russia, Finland, Denmark, Japan and Spain) analyzed a comprehensive set of measurements. These included daily global observations of trace gases and clouds from NASA's Aura and CALIPSO spacecraft; ozone measured by instrumented balloons; meteorological data and atmospheric models. 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. [...]

The 2011 Arctic ozone loss occurred over an area considerably smaller than that of the Antarctic ozone holes. This is because the Arctic polar vortex, a persistent large-scale cyclone within which the ozone loss takes place, was about 40 percent smaller than a typical Antarctic vortex. While smaller and shorter-lived than its Antarctic counterpart, the Arctic polar vortex is more mobile, often moving over densely populated northern regions. Decreases in overhead ozone lead to increases in surface ultraviolet radiation, which are known to have adverse effects on humans and other life forms.

Although the total amount of Arctic ozone measured was much more than twice that typically seen in an Antarctic spring, the amount destroyed was comparable to that in some previous Antarctic ozone holes. This is because ozone levels at the beginning of Arctic winter are typically much greater than those at the beginning of Antarctic winter.(source)

Scientists added that without the 1989 Montreal Protocol, an international treaty limiting production of ozone-depleting substances, chlorine levels would be so high that an Arctic ozone hole would form every spring.

Via NASA, Guardian
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