| September 25, 2003 2003 Ozone 'Hole' Approaches, But Falls Short Of Record This year's Antarctic ozone hole is the second largest ever observed, according to scientists from NASA, the National Oceanic and Atmospheric Administration (NOAA), and the Naval Research Laboratory. The Antarctic ozone hole is defined as thinning of the ozone layer over the continent to levels significantly below pre-1979 levels. Ozone blocks harmful ultraviolet "B" rays. Loss of stratospheric ozone has been linked to skin cancer in humans and other adverse biological effects on plants and animals. The size of this year's hole reached 10.9 million square miles on September 11, 2003. It was slightly larger than the North American continent, but smaller than the largest hole ever recorded, on September 10, 2000, when it covered 11.5 million square miles. Last year the ozone hole was smaller, covering 8.1 million square miles. NASA's Earth Probe Total Ozone Mapping Spectrometer and the NOAA-16 Solar Backscatter Ultraviolet instrument provided ozone measurements from space. These data were coupled with data collected by NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL) from balloon-borne instruments, which measure the ozone hole's vertical structure. NASA's own scientist Paul Newman said, "While chlorine and bromine chemicals cause the ozone hole, extremely cold temperatures, especially near the edge of Antarctica, are also key factors in ozone loss." Given the leveling or slowly declining atmospheric abundance of ozone-destroying gases, the year-to-year changes in the size and depth of the ozone hole are dominated by the year-to-year variations in temperature in this part of the atmosphere. The fact this year's ozone loss is much greater than last year's reflects the very different meteorological conditions between these two years. NASA scientist Rich McPeters said ozone observations showed the total amount of ozone from surface to space was 106 Dobson Units (DU) on September 14, 2003, the minimum value reached this year. "Dobson units" measure the "thickness" of protective ozone in the stratosphere. They range from 100 DU to 500 DU, which translate to about 1 millimeter (1/25 inch) to 5 millimeters (1/5 inch) of ozone in a layer. Bryan Johnson of CMDL said the ozone depletion region, from 7-to-14 miles above the Earth, has large losses, similar to losses seen in the 1990s. If the stratospheric temperature remains cold over the pole, then we should see complete ozone loss in the 9-13 mile layer, with total column ozone reaching 100 DU by early October. The Montreal Protocol and its amendments banned chlorine-containing chlorofluorocarbons (CFCs) and bromine-containing halons in 1995, because of their destructive effect on the ozone. However, CFCs and halons are extremely long-lived and still linger at high concentrations in the atmosphere. However, the atmospheric abundances of ozone destroying chemicals are beginning to decline. As a result, the Antarctic ozone hole should disappear in about 50 years. NASA's Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather, and natural hazards using the unique vantage point of space. For more information and images on the Internet, visit:
http://www.gsfc.nasa.gov/topstory/2003/0925ozonehole.html NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of our nation's coastal and marine resources. To learn more about NOAA, visit:
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Contacts:
Elvia H. Thompson
Headquarters, Washington
(Phone: 202/358-1696)
Carmeyia Gillis
NOAA Climate Prediction Center, Camp Springs, Md.
(Phone: 301/763-8000, ext. 7163)
Dick Thompson
Naval Research Laboratory, Washington
(Phone: 202/767-1936) | |
2003 Antarctic Ozone 'Hole'
By mid-September 2003, the ozone thinning already extended over 28.2 million square kilometers (10.9 million square miles). The maximum area in 2000 reached 29.2 million square kilometers, the largest on record. Since winter temperatures dipped lower than usual, driving the chemical reactions that deplete ozone, this year's 'hole' (dark blue) was very large. The thinnest point so far this year is 106 Dobson Units (a layer about 1.06 millimeters at sea-level pressure), 40% as thick as normal levels. This series shows the daily extent of the ozone 'hole,' regions. Data come from NASA's Total Ozone Mapping Spectrometer (TOMS) on the Earth Probe satellite, from Aug. 1-Sept. 23, 2003.
High-Resolution Image  
Calm Cool Skies Spell Losses
This year, colder temperatures and calmer winds allowed chemical reactions that break down ozone to occur at about the same rates as the past few years. However, last year's unusually moderate Antarctic temperatures and highly variable upper atmospheric winds kept the ozone 'hole' relatively small, about 40% smaller in area than the record sizes seen in 2000, 2001, and this year. In 2002, the 'hole' also split into two parts for the first time since 1979, also due to unusual weather patterns. These comparisons pit the near-record size of this year's 'hole' against a) the small area of last year's hole and b) the split shape from last year. Data from TOMS-EP. 
Nearing the Road to Recovery
Last year's unusual reduction in ozone losses proved just that — unusual. The ozone hole grew larger throughout the late 1980's and early 1990's, as shown in this time series of maximum areas from 1979 to 2002 (excluding 1995). This year the hole reached nearly the same size as 2000 and 2001, larger than the North American continent. While the manufacture and use of chlorofluorocarbons and halons (CFCs) that contribute to yearly ozone destruction have decreased, the chemicals will linger in the upper atmosphere for decades before the ozone layer will consistently recover.   
Arctic Losses Closer to Home
While the Antarctic regularly experiences ozone losses, warmer temperatures in the Arctic prevent such massive losses from occurring as often near the North Pole. However, when large Arctic ozone losses occur, the depletion can threaten populated areas with harmful doses of ultraviolet rays. Here we show the winters of 1997, 2000, and 2003, particularly severe losses stretching over populated areas such as Northern Europe. Data from TOMS-EP. 
New Satellite to See Ozone
NASA's soon-to-be-launched Aura satellite will see ozone in both the upper and lower atmosphere for the first time. Current missions examine ozone in an isolated part of the atmosphere, but Aura will track ozone and other gas transport between the lower and upper atmosphere. This information is extremely important to understanding the long-term health of the upper atmosphere. Aura's new sensors will give scientists a more complete three-dimensional picture of atmospheric ozone distribution. |
