The Antarctic ozone hole, which yawns wide every Southern Hemisphere spring, reached its annual peak on Sept. 12, becoming the ninth largest ozone hole on record.
According to data obtained by NASA and the National Oceanic and AtmosphericAdministration (NOAA), the ozone hole stretched to 10.05 million square miles.
Above the South Pole, the ozone hole reached its deepest point of the season on Oct. 9, tying this year for the 10th lowest in this 26-year record.
NASA and NOAA use balloon-borne instruments, ground-based instruments and satellites to monitor the annual Antarctic ozone hole, global levels of ozone in the stratosphere and the manmade chemicals that contribute to ozone depletion.
“The colder than average temperatures in the stratosphere this year caused a larger than average ozone hole,” said Paul Newman, chief scientist for atmospheres at NASA’s Goddard Space Flight Centre in Greenbelt, Md.
“Even though it was relatively large, the area of this year’s ozone hole was within the range we’d expect given the levels of manmade ozone-depleting chemicals that continue to persist in the atmosphere,” he noted.
James Butler, director of NOAA””s Global Monitoring Division in Boulder, Colo said, “The manmade chemicals known to destroy ozone are slowly declining because of international action, but there are still large amounts of these chemicals doing damage.”
NASA currently measures ozone in the stratosphere with the Dutch-Finnish Ozone Monitoring Instrument, or OMI, on board the Aura satellite.
The instrument measured the 2011 ozone hole at its deepest at 95 Dobson units on Oct. 8 this year.
This differs slightly from NOAA””s balloon-borne ozone observations from the South Pole (102 Dobson units) because OMI measures ozone across the entire Antarctic region.
NOAA has been tracking ozone depletion around the globe, including the South Pole, from several perspectives.
NOAA also tracks ozone with ground-based instruments and from space.
