NASA and NOAA Announce Ozone Hole Is a Double Record Breaker
23.10.2006 - Other
Scientists from the US's National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Administration (NOAA) report that this year's ozone hole in the polar region of the Southern Hemisphere has broken records for both area and depth.
"From September 21 to 30, the average area of the ozone hole was the largest ever observed, at 27.5 million square kilometres," said Paul Newman, atmospheric scientist at NASA's Goddard Space Flight Center (Greenbelt, Maryland).
The Ozone Monitoring Instrument on NASA's Aura satellite measures the total amount of ozone from the ground to the upper atmosphere over the entire Antarctic continent. Scientists from NOAA's Earth System Research Laboratory (Boulder, Colorado) use balloon-borne instruments to measure ozone directly over the South Pole.
Dobson units (DU) are a measure of ozone amounts above a fixed point in the atmosphere. By Oct. 9, the total column ozone had plunged to 93 DU from approximately 300 DU in mid-July. More importantly, nearly all of the ozone in the layer of stratosphere between 13 and 20 kilometres above the Earth's surface had been destroyed. In this critical layer, the instrument measured a record low of only 1.2 DU., having rapidly plunged from an average non-hole reading of 125 DU in July and August. The temperature readings from NOAA satellites and balloons during late-September 2006 showed the lower stratosphere at the rim of Antarctica was approximately 12.7 degrees Celsius colder than average, increasing the size of this year's ozone hole by 3.1 to 3.88 million square kilometres.
The ozone layer acts to protect life on Earth by blocking harmful ultraviolet rays from the sun. "We now have the largest ozone hole on record," said Craig Long of NOAA's National Centers for Environmental Protection (NCEP). As the sun rises higher in the sky during October and November, this unusually large and persistent area may allow much more ultraviolet light than usual to reach Earth's surface in the southern latitudes.
As a result of the Montreal Protocol and its amendments, the concentrations of ozone-depleting substances are decreasing in the atmosphere and the ozone hole is estimated to decrease in area very slowly each year over the next 5-10 years. This slow decrease is masked by large year-to-year variations caused by Antarctic stratosphere weather fluctuations.
