Why does the ozone hole occur over Antarctica?
Human emissions of CFCs occur mainly in the Northern Hemisphere. Gases such as CFCs which are insoluble in water and relatively unreactive are mixed within a year or two throughout the lower 10 kilometres of the atmosphere (the troposphere). The CFCs then rise from the lower atmosphere into the stratosphere, mainly in the tropics. Winds then move this air poleward – both North and South – from the tropics. The meteorologies of the two polar regions are very different. The South Pole is part of a very large land mass that is completely surrounded by ocean. These conditions produce a very cold stratosphere which leads to the formation of clouds. The clouds that form lead to chemical changes that promote rapid ozone depletion. The North Pole lacks the land/ocean symmetry of the South Pole. As a consequence the stratospheric air is much warmer and fewer clouds form. Therefore the ozone depletion in the Arctic is very much less than in the Antarctic.
