 | Antarctic ozone hole monitored
~ NOAA
Nov. 19, 2009 - NOAA researchers report that the Antarctic ozone hole, which fluctuates in later winter and spring in the southern hemisphere, reached its peak in late September. The report was released Tuesday.
|
| iceberg in Antarctica | |
| |
THE hole is measured as a circumference and from recent measurements in late September, it covered 9.2 million square miles, a little smaller than the North American continent. The size of this hole represents the 10th largest hole since satellite measurements began in 1979.
Ozone over the South Pole Station, Antarctica, also reached its thinnest point of the year on Sept. 26. Measured in Dobson Units (DU) that indicate the amount of ozone in a vertical column of air, the 2009 low level - 98 DU - is the seventh smallest since 1986. The record low of 89 DU was recorded on Oct. 6, 1993.
According to NOAA, the atmospheric ozone layer protects the Earth from harmful ultraviolet radiation. However, it has been damaged by human-produced compounds known as chlorofluorocarbons, or CFCs, which release ozone-destroying bromine and chlorine into the atmosphere. International agreements have strictly limited the use of CFCs since the early 1990s. Extreme cold, ice cloud formation in the stratosphere, and a pattern of rapidly circulating air, called the polar vortex, make the ozone layer over Antarctica much more vulnerable to CFC-destruction than anywhere else.
“The Montreal Protocol has been effective in reducing emissions of long-lived CFC gases, but high enough concentrations remain in the atmosphere to lead to significant ozone destruction in polar regions,” Bryan Johnson, NOAA official, said. “Monitoring ozone over Antarctica provides the essential yardstick to see whether we are on the predicted track for recovery based on the current rate of declining CFCs.”
Although CFCs are slowly decreasing in the atmosphere, scientists project that the ozone hole will not fully recover before 2060.
