2003 ANTARCTIC OZONE 'HOLE' NEAR
Oct. 7, 2003 — This year's Antarctic ozone "hole" is the second largest ever observed, according to NOAA scientists. The size of the ozone depletion region shows an increase in its total size from last year, further indicating that the relatively smaller hole of 2002 was mostly a quirk of meteorological conditions over Antarctica. The difference is directly attributed to year-to-year temperature variations across the Antarctic continent, not an increase in the amount of ozone-depleting compounds in the atmosphere. (Click NOAA satellite image for larger view of Antarctic ozone hole taken Oct. 5, 2003. Click here for latest look at ozone hole. Please credit “NOAA.”)
"We expect to see year-to-year variations in the size of the ozone hole because stratospheric temperatures can vary from year to year. In colder years, the same amount of ozone-depleting compounds can destroy more ozone, in comparison to warmer years," said Daniel L. Albritton, director of the NOAA Aeronomy Laboratory in Boulder, Colo.
The Antarctic ozone "hole" is defined as thinning of the springtime ozone layer to levels significantly below those seen prior to 1979. Extreme cold in the upper atmosphere is one key factor that affects the amount of ozone loss caused by ozone-depleting compounds. Year-to-year changes in the size and amount of depletion in the vertical column of the ozone hole are dominated by the year-to-year variations in temperature in this part of the atmosphere.
Chlorine- and bromine-containing compounds from human activity are the primary cause of ozone depletion. The 1987 United Nations Montreal Protocol and its subsequent amendments sharply curtailed the use of chlorine-containing chlorofluorcarbons (CFCs) and bromine-containing halons. Because of the protocol, the amounts of these ozone-depleting substances have begun to decline in the lower atmosphere and to level off in the stratosphere, where the ozone layer resides.
international protocols have greatly reduced the production and release
of ozone depleting chemicals, they will remain active in the stratosphere
for several decades," said James Laver, director of the NOAA
Climate Prediction Center. "With the protective atmospheric layer
so compromised, greater amounts of ultraviolet radiation may be allowed
to reach the surface and potentially increase certain health risks."
NOAA provides predictions of expected levels of ultraviolet radiation
in support of the Environmental Protection Agency's Sunwise program.
Ozone measured by a balloon instrument on Sept. 26 showed nearly complete ozone destruction in the 9-13 mile altitude layer. Total column ozone indicated a 60 per cent drop from early August measurements.
"This year, ozone depletion over the South Pole, from 7-to-14 miles above Antarctica, has shown large losses, similar to losses seen in the 1990s," said Bryan Johnson of the NOAA Climate Monitoring and Diagnostics Laboratory.
Ozone blocks harmful ultraviolet "B" rays. Prolonged over-exposure to ultraviolet radiation has been linked to skin cancer in humans and other adverse biological effects on plants and animals. The dramatic ozone "hole" exists only over Antarctica, but currently, the ozone layer over the United States is depleted by about 6 percent.
Temperature over the Antarctic affects the formation of polar stratospheric clouds, which accelerate the destruction of stratospheric ozone by human-produced chlorine and bromine compounds. The Antarctic ozone hole is still expected to recover in about 50 years, when the atmospheric amounts of reactive chlorine and bromine return to their pre-ozone-hole levels.
size of the ozone depletion region in 2003 is a stark contrast from 2002.
The reduced size in 2002 was attributed to warmer-than-normal stratospheric
temperatures and temperature patterns above Antarctica. The size of this
year's Antarctic ozone hole reached 10.9 million square miles on Sept.
11, 2003, smaller than Sept. 10, 2000, the largest ever recorded when
it covered 11.5 million square miles. Last year the ozone hole was smaller,
covering 8.1 million square miles.