Why does ozone depletion happen at the poles

Another pollutant we have added to the upper atmosphere that affects ozone are nitrogen oxides from air plane exhaust. So, above and beyond, the seasonal variations in ozone that are more pronounced at the poles, why do the enhanced ozone holes due to human activities occur over the poles? The air masses above the poles become isolated from the rest of the atmosphere during their winter and early spring seasons due to a phenomenon known as the "polar vortex".

In simplest terms, this vortex is a spinning, funnel shaped region of the atmosphere that forms in late fall and early winter over a pole, allowing chemical reactions in the enclosed air mass to be enhanced due to the lack of mixing with other, lower latitude, air masses. The effect of the pollutants we have added to the atmosphere are thus enhanced in these isolated regions of the atmosphere.

The Antarctic vortex over the South Pole is more effective at isolating this region of the atmosphere during the austral winter than is the corresponding arctic vortex. A second feature of the polar stratosphere that is unique and probably aids the polar ozone depletion is polar stratospheric clouds. These very high altitude clouds are composed of ice crystals, sometimes greatly enriched in nitrogen oxide specis "NO x " that can enhance the ozone degredation reactions discussed above.

These ice particles can react with various forms of Chlorine in the atmosphere and accumulate the molecule ClONO 2 , which is a source of ozone depleting Cl radicals. Once spring time comes, this ClONO 2 decomposes and allows ozone degredation reactions can occur. Where is the ozone hole and how fast is it expanding?

What scititst usually mean when they speak of the "ozone hole" is an area over the south pole where lower than normal levels of ozone have been detected. This symmetry is reflected in the meteorological conditions that allow the formation in winter of a very cold region in the stratosphere over the Antarctic continent, isolated by a band of strong winds circulating around the edge of that region. The very low stratospheric temperatures lead to the formation of clouds polar stratospheric clouds that are responsible for chemical changes that promote production of chemically active chlorine and bromine.

This chlorine and bromine activation then leads to rapid ozone loss when sunlight returns to Antarctica in September and October of each year, which then results in the Antarctic ozone hole. As the figure below depicts, the magnitude of the ozone loss has generally grown through the s as the amount of human-produced ozone-depleting compounds has grown in the atmosphere.

The lowest ozone values over the Arctic are less severe than the hole that forms every year over Antarctica. The Weather Guys. Skip to content. Home About Listen Live! Search for:. Create your free account or Sign in to continue. See Subscription Options. Fall Flash Sale. Get smart. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Create Account See Subscription Options.

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