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Antarctic Ozone Hole Expected To Last Longer This Year
Washington - Oct 17, 2001 The Antarctic ozone hole has formed again this year, as expected, but it hasn't matched the records set last year. "It reached a maximum size of just over 26 million square kilometres in mid-September, and it still occupies more than 20 million square kilometres", said Dr Stephen Wood, a NIWA scientist currently at Scott Base, New Zealand's Antarctic research station. "Last year the hole reached 30 million square kilometres in area, and the minimum ozone reading was 126 Dobson Units at Scott Base, whereas this year's minimum was 132 Units." However, this year's hole looks set to stay around longer. Last year the hole formed early and broke up early. This time last year it was already 5 million square kilometres smaller than the hole is now. The ozone holes that form each springtime over Antarctica are triggered by a combination of chlorine pollutants in the atmosphere, extremely cold winter temperatures, and the return of sunlight in spring. The polar vortex, a band of strong winds that effectively keeps the atmosphere above Antarctica isolated during winter, is a key part of the recipe. Large year-to-year variations in the severity of the ozone hole can be caused by differences in the polar vortex. Last year, features of the vortex contributed to an early formation of the ozone hole and a very early break up. This year the vortex and the hole appear to be much more stable and circular, which suggests that the hole will probably last longer -- into November and possibly even into December. "The longer the ozone hole persists, the more likely it is that ozone- depleted air from the dispersing hole will reach New Zealand when the sun is high in the sky, increasing the risk of occurrence of periods with high ultraviolet radiation", said Dr Wood. Despite the record ozone loss over Antarctica in 2000, the impact on New Zealand was less severe than in 1998, because last year the hole broke up at the end of November. In 1998, the hole broke up around Christmas, when the sun is highest in the sky and UV penetration is greatest and large numbers of New Zealanders are enjoying the outdoors. NIWA actively monitors UV levels and provides regular public updates. As well as the short-term impact of high UV radiation for a few days, there is another part to this Antarctic ozone hole phenomenon. "When the ozone hole breaks up, it reduces ozone levels throughout the Southern Hemisphere. This dilution accounts for about half of the 15% increase in peak summertime UV levels that have occurred in the last 20 years over New Zealand." The Antarctic ozone holes will be with us for several decades to come. If current models are correct, the ozone holes are now at their most severe. Climate change could delay the recovery in ozone levels by some years. Measures to reduce the levels of chlorine pollutants are starting to take effect, but it could be 50 years before ozone levels are restored. Related Links National Institute of Water & Atmospheric Research EO Data and Images at Earth Observatory SpaceDaily Search SpaceDaily Subscribe To SpaceDaily Express
2001 Ozone Hole About The Same Size As Past Three Years
Washington - Oct 17, 2001Satellite data show the area of this year's Antarctic ozone hole peaked at about 26 million square kilometers -- roughly the size of North America -- making the hole similar in size to those of the past three years, according to scientists from NASA and the National Oceanic and Atmospheric Administration (NOAA). Researchers have observed a leveling-off of the hole size and predict a slow recovery. |
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