The Antarctic ozone hole was smaller this year than in all but one of the last 20 years, according to observations taken by NASA and NOAA satellites. The reduced ozone hole has been attributed by researchers to the warmer temperatures that have been observed in the lower stratosphere over Antarctica.
“The ozone hole reached its maximum size Sept. 22, covering 8.2 million square miles, or the area of the United States, Canada and Mexico combined. The average size of the 2012 ozone hole was 6.9 million square miles. The Sept. 6, 2000 ozone hole was the largest on record at 11.5 million square miles.”
“The ozone hole mainly is caused by chlorine from human-produced chemicals, and these chlorine levels are still sizable in the Antarctic stratosphere,” said NASA atmospheric scientist Paul Newman of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Natural fluctuations in weather patterns resulted in warmer stratospheric temperatures this year. These temperatures led to a smaller ozone hole.”
The ozone layer is essentially a large atmospheric ‘shield’ that stops ultraviolet radiation from reaching the ground. The ozone hole first appeared in the early 1980’s, after decades of the use of ozone-depleting chemicals. The ozone layer over Antarctica isn’t expected to return to its early 1980’s state until around 2065. Even though the involved chemicals have long been phased out, those chemicals possess long lifetimes, taking a long-time to degrade. The phase-out of ozone-depleting chemicals occurred in the early 90’s thanks to an international policy agreement.
“This year also marked a change in the concentration of ozone over the Antarctic. The minimum value of total ozone in the ozone hole was the second highest level in two decades. Total ozone, measured in Dobson units reached 124 DU on Oct. 1. NOAA ground-based measurements at the South Pole recorded 136 DU on Oct. 5. When the ozone hole is not present, total ozone typically ranges from 240-500 DU.”
“This is the first year growth of the ozone hole has been observed by an ozone-monitoring instrument on the Suomi National Polar-orbiting Partnership satellite. The instrument, called the Ozone Mapping Profiler Suite, is based on previous instruments, such as the Total Ozone Mapping Spectrometer and the Solar Backscatter Ultraviolet instrument. OMPS continues a satellite record dating back to the early 1970s.”
Source and Images: NASA/Goddard Space Flight Center