Ozone Depletion and Antarctic Weather
July 19, 2002
Scientists have been perplexed by two seemingly contradictory trends in Antarctica. While parts of the continent have warmed in recent decades, the interior has cooled.
For instance, average temperatures on the continent's western peninsula have warmed 2.5 degrees Celsius since the 1950s. Global warming has been blamed for the higher temperatures, which were dramatically illustrated by the breakup of part of the western peninsula's Larsen B ice shelf earlier this year.
Scientists with the National Oceanic and Atmospheric Administration and Colorado State University have an explanation for 90 percent of the cooling and about half of the warming.
Global warming isn't the explanation, say the scientists. Instead, both temperature trends are strongly linked to atmospheric ozone depletion.
Analyzing more than 30 years of temperature measurements from weather balloons and additional data from monitoring stations across the continent, they found that:
- An abnormally intense westerly flow of air in the lower atmosphere encircles the continent during the summer months (December and January).
- By bottling up cold air over the pole and restricting warm air to the outer ring, this vortex cools the continent's center, but warms its edges.
- The scientists say these atmospheric changes are driven by the ozone hole over Antarctica, which grows every spring.
Previous research had established that ozone losses above Antarctica -- exceeding 50 percent during October throughout the 1990s -- have cooled the atmosphere 12 miles to 31 miles above the surface by more than 6 degrees C.
The existence of the ozone hole is attributed to the presence of chlorofluorocarbons (CFCs), manmade chemicals which are being phased out worldwide. As CFC use subsides, the ozone hole will shrink and the intense westerly flow will ebb, creating more uniform Antarctic temperatures.
Source: Sarah Simpson, "A Push from Above," Scientific American, August 2002.
Browse more articles on Environment Issues