October 25, 2012
Ozone Hole In The Antarctic Is Second Smallest In 20 Years
[ Watch the Video: 2012 Ozone Hole Max ]
April Flowers for redOrbit.com - Your Universe Online
According to data from NASA and National Oceanic and Atmospheric Administration (NOAA) satellites, the average area covered by the Antarctic ozone hole this year was the second smallest in the last 20 years, which scientists attribute to warmer temperatures in the Antarctic lower stratosphere.
The ozone reached its maximum size for the 2012 season on September 22. On this date, it covered 8.2 million square miles, which is about the size of the United States, Canada and Mexico combined. Average size for the ozone hole in 2012 was 6.9 million square miles. The largest ozone hole on record, at 11.5 million square miles, was recorded on September 6, 2000.
"The ozone hole mainly is caused by chlorine from human-produced chemicals, and these chlorine levels are still sizable in the Antarctic stratosphere," said 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 like an invisible layer of sunscreen for the entire planet, acting as a shield against ultraviolet radiation, which can cause skin cancer and DNA-mutations. NASA and NOAA keep a close eye on the ozone layer's health with satellite data, ground-based measurements and balloon-borne instruments under the mandate of the Clean Air Act.
Scientists first noticed the ozone hole phenomenon in the early 1980s. Newman said that the Arctic ozone layer would not return to its pre 1980s state until approximately 2065 because of the long lifetimes of ozone-depleting substances in the atmosphere. Overall, the ozone layer is no longer declining as concentrations of ozone-depleting substances decrease, mostly because of an international agreement regulating the production of certain chemicals.
“It happened to be a bit warmer this year high in the atmosphere above Antarctica, and that meant we didn´t see quite as much ozone depletion as we saw last year, when it was colder,” said Jim Butler with NOAA´s Earth System Research Laboratory in Boulder, Colo.
2012 also saw a change in the ozone layer over the Antarctic, with the minimum value of the total ozone being the second highest level in two decades. Total ozone is measured in Dobson units (DU). On October 1, the DU reached 124. Ground based measurements taken by NOAA at the South Pole recorded 136 DU on October 5. In comparison, when the ozone hole is not present, the total ozone typically ranges from 240 — 500 DU.
This is the first year that ozone hole growth has been observed by an ozone-monitoring instrument on the Suomi National Polar-orbiting Partnership (NPP) satellite. The instrument, called the Ozone Mapping Profiler Suite (OMPS), is based on previous instruments such as the Total Ozone Mapping Spectrometer (TOMS) and the Solar Backscatter Ultraviolet instrument (SBUV/2). Satellites have been recording ozone data since the early 1970s.
Scientists hope that OMPS will help them understand ozone destruction in the middle and upper stratosphere with its Nadir Profiler, in addition to observing the annual formation and extent of the ozone hole. OMPS's Limb Profiler will measure ozone variations in the lower stratosphere.
"OMPS Limb looks sideways, and it can measure ozone as a function of height," said Pawan K. Bhartia, a NASA atmospheric physicist and OMPS Limb instrument lead. "This OMPS instrument allows us to more closely see the vertical development of Antarctic ozone depletion in the lower stratosphere where the ozone hole occurs."