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The Ozone Hole over Antarctica

A large depletion of the ozone layer (an "ozone hole") has appeared over Antarctica in the past few years, especially during the Austral spring months September and October. This depletion is caused by the chemical decomposition of ozone, a process that is augmented by the low temperatures (below -80°C) in the stratosphere during the winter months. During this period the air over Antarctica is isolated from the milder air at lower latitudes.

Extremely low temperatures over Antarctica lead to the condensation of water and nitric acid to form "polar stratospheric clouds" (PSCs). Through chemical reactions on the surface of the cloud particles large quantities of chlorine and bromine, derived from CFCs and other industrially produced gases, are liberated. As the ultraviolet light increases during the spring months there is an increased depletion of ozone.



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