13 March 2013


Credit: NASA/Goddard
What made the ozone hole such a beast (20% below late winter average) in 2011? NASA says:
  1. Extreme cold temperatures
  2. Man-made chemicals 
  3. A stagnant atmosphere
Chlorine in the Arctic stratosphere was the ultimate culprit, abetted by unusually and persistently cold temps, plus uncommon atmospheric conditions that blocked wind-driven transport of ozone from the tropics to the Arctic.

"You can safely say that 2011 was very atypical: In over 30 years of satellite records, we hadn't seen any time where it was this cold for this long," says Susan E. Strahan, atmospheric scientist at NASA Goddard Space Flight Center and lead author of the new paper in the Journal of Geophysical Research-Atmospheres. "Arctic ozone levels were possibly the lowest ever recorded." 

The NASA/Goddard animation shows the dynamics of ozone from January 1 to March 23 in 2010 and 2011.

Strahan doesn't think there'll be a repeat anytime soon: "It was meteorologically a very unusual year, and similar conditions might not happen again for 30 years. [Plus] chlorine levels are going down in the atmosphere because we've stopped producing a lot of CFCs as a result of the Montreal Protocol. If 30 years from now we had the same meteorological conditions again, there would actually be less chlorine in the atmosphere, so the ozone depletion probably wouldn't be as severe."

But can we really be so confident about the unlikelihood of a repeat forecast, since so much of what's happening in the Arctic now is anomalous?
Post a Comment