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Ozone loss over Antarctic at record levels
03/Oct/2006: The European Space Agency (ESA) has said that the ozone loss over the Antarctic is at record levels, this year. Ozone, an allotrope of oxygen found in the Earth’s atmosphere, protects the world from the harmful ultraviolet radiations of the sun.
Measurements made by the ESA’s Envisat Satellite showed that 40 million tons of ozone was lost over the Antarctic in October, breaking the earlier record set in 2000 when 39 million tons of ozone was lost to ozone-depleting compounds.
Ozone loss is calculated by measuring the area and depth of the ozone-hole in the middle and lower stratosphere, about 15 miles above the Earth’s surface. The ozone-hole measured 10.81 million square miles this year, as large as in 2000 and its depth is 100 Dobson units (one Dobson unit is equivalent to a 10 micrometer thick layer of ozone, under standard temperature and pressure). Dobson units are usually used to express the ozone amounts in the atmosphere. This year’s measurement (Dobson units) is as high as the record levels set in 1990.
Ozone layer filters shorter wavelengths (less than 320nm) of ultraviolet radiations from the sun, which are capable of harming most of the life forms down under. Man-made compounds like Chlorofluorocarbons (CFC’s), commonly known as freons, deplete the ozone layer by destroying the ozone molecules in a catalytic cycle. The chemical reaction which depletes the ozone layer, reaches its peak with colder high altitude temperatures in the southern hemisphere winter, from late August to October.
Claus Zehner, an atmospheric engineer at ESA, said that depletion of ozone requires very low temperatures in the stratosphere coupled with sunlight. He added that this year’s extreme loss of the ozone can be attributed to the temperatures over the Antarctic, which are at record lows since 1979. The World Meteorological Organization (WMO) recently gave a notice that the seasonal ozone-hole in 2006 was heading for a record.
K Siva
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