Ozone Hole Hasn't Begun to Heal Yet, Studies Show

More than 20 years after the Montreal Protocol introduced limits to the emission of ozone-depleting substances, the hole in the ozone layer has yet to heal.

This was the conclusion brought forth by NASA scientists in two new studies Wednesday at the annual meeting of the American Geophysical Union in San Francisco.

According to the researchers, a deeper look at the inner workings of the hole that forms each year over Antarctica revealed that while the hole has stopped growing in size, it has yet to begin to patch itself together again. Any noticeable changes, they said, can be traced back to temperature and winds.

"Ozone holes with smaller areas and a larger total amount of ozone are not necessarily evidence of recovery attributable to the expected chlorine decline," said Susan Strahan of NASA's Goddard Space Flight Center in Greenbelt, Md. "That assumption is like trying to understand what's wrong with your car's engine without lifting the hood."

Along with her colleague Natalya Kramaorva, also from Goddard, the two used satellite data to peer inside the cavity.

Kramarova focused on the 2012 ozone hole, relying on information gathered by the NASA-NOAA Suomi National Polar-orbiting Partnership satellite in order to determine what was behind the hole's small size that year. Converting the data into a map, the researcher discovered a far more complex scenario than she anticipated. 

During October, greater amounts of ozone at upper altitudes, carried in by wind, were found hanging out above the ozone destruction in the lower stratosphere.

The findings indicate "that the classic metrics based on the total ozone values have limitations - they don't tell us the whole story," Kramarova said, noting that levels of harmful substances were high that year. 

Strahan, meanwhile, used data from the NASA Aura satellite to track levels of nitrous oxide, which is inversely related to the amount of ozone-depleting chlorine. She was surprised to find that 2006 and 2011 contained different amounts of chlorine in spite of equally severe holes.

By simulating the atmosphere's chemistry and winds, Strahan found that 2011 saw less ozone destruction than 2006 due to winds transporting less ozone to the Antarctic that year, meaning there was less ozone to lose.  

Based on their findings, the researchers concluded that the primary reason behind the decline in the ozone's hole will be meteorolgically based, rather than chemically based, until after the mid-2030s when chlorine levels in the lower stratosphere have declined below early-1990s levels.