The Ozone hole: Why over Antarctica?
When the topic of the ozone layer arises, many people immediately think of the hole over Antarctica, but few know why the hole is actually there. In 1985, British scientists discovered this hole. A special condition exists in Antarctica that accelerates the depletion of the ozone layer. Every Arctic winter, a polar vortex forms over Antarctica. A polar vortex is “a swirling mass of very cold, stagnant air surrounded by strong westerly winds” (Roan, 126). Since there is an absence of sun during Arctic winters, the air becomes incredibly cold and the formation of ice clouds occurs. When the sun returns in the spring, the light shining on the nitrogen oxide filled ice particles activates the formation of chlorine. This excess of ozone destroying chlorine rapidly accelerates the depletion of the ozone layer. Finally, when the polar vortex breaks up, the rapid dissolution decreases. It is evident that the effects of the polar vortex are dramatic. “For about two month every southern spring, the total ozone declines by about 60% over most of Antarctica. In the core of the ozone hole, more than 75% of the ozone is lost and at some altitudes, the ozone virtually disappeared in October, 1993” (Nilsson, 19). The average size of the ozone hole is larger than most continents, including South America, Europe, Australia, and Antarctica, and the maximum size of the ozone hole in 1996 was larger than North America (See Figure 5). Finally, one must note that the “hole” over Antarctica is truly a “hole” only in the Antarctic spring, when the depletion is extremely severe due to the vortex.