Please note that it is incorrect to say that Ozone Hole is actually a Hole. It is a vast region of the upper atmosphere where there is less Ozone than elsewhere. Second, it is also incorrect to say that Ozone Hole is only on Antarctica. The Ozone depletion has been seen everywhere beyond tropics and there is a severe depletion in the Polar Regions due to some reasons which are explained here. The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent (since about 1975) ozone levels have dropped to as low as 33% of their pre- 1975 values. The ozone hole occurs during the Antarctic spring, from September to early December; as strong westerly winds start to circulate around the continent and create an atmospheric container. In this container over 50% of the lower stratospheric ozone is destroyed.Announcement of polar ozone depletion over Antarctica in March 1985 prompted scientific initiatives to discover the ozone depletion processes, along with calls to freeze or diminish production of chlorinated fluorocarbons.A complex scenario of atmospheric dynamics, solar radiation, and chemical reactions was found to explain the anomalously low levels of ozone during the polar springtime. Recent expeditions to the arctic regions show that similar processes can occur in the northern hemisphere, but o a somewhat lesser degree due to warmer temperatures and erratic dynamics patterns. However, this ozone layer has been destroyed by chlorofluorocarbons and other factors, creating an ozone hole nearly twice the size of Antarctica in 1998.Every summer (December to January) the hole repairs itself when stratospheric temperatures rise and the air above Antarctica mixes with the rest of the world’s atmosphere. This cycle of ozone hole formation and reparation is repeated every year. The ozone hole over Antarctica has been forming every year since the early 1970s. In recent years the hole has become both larger and deeper, in the sense that more and more ozone is being destroyed.Every March to April during the Northern Hemisphere springtime similar, but less pronounced ozone hole forms above the Arctic. The natural circulation of wind – the polar vortex – which isolates Antarctica from the rest of the world during the Southern Hemisphere winter and early spring, contributing to the ozone loss there, is much less developed in the Northern Hemisphere above the Arctic.In addition, stratospheric temperatures at Arctic, are not as low as in the Antarctic, and consequently the loss of ozone is not as severe. However, the formation of even a moderate ozone hole above the Arctic region can give cause for considerable concern due to the greater populations in the higher latitudes of the Northern Hemisphere. Many were worried that ozone holes might start to appear over other areas of the globe but to date the only other significant, localized depletion is much smaller ozone dimple, observed during the arctic spring over the North Pole.The Antarctic hole is a warning that if conditions become more Antarctic, i.e. cooler stratospheric temperatures, more stratospheric clouds, more active chlorine; and then ozone will decrease at a much greater pace.Some of the more popular scenario of global warming predict that these changes could occur in larger portions of the statrasphere. When the Antarctic ozone hole does break-up, the ozone-depleted air tends to drift out into nearby areas. Decreases in the ozone’s level of up to 10% have been reported in new Zealand in the month following the break-up of the Antarctica ozone hole.
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