Magazine article Science News

Antarctic Ozone Hole Expands in Altitude

Magazine article Science News

Antarctic Ozone Hole Expands in Altitude

Article excerpt

Atmospheric pollution over Antarctica has pushed its assault on the ozone layer to new heights this year, causing a subtle worsening of the so-called ozone hole over the southern continent.

The zone of total ozone destruction, which had reached from 14 to 19 kilometers in altitude, crept up to 20.5 km this month, reports David Hofmann of the National Oceanic and Atmospheric Administration in Boulder, Colo. The shift may have resulted from increased chlorine- and bromine-containing pollution in the atmosphere, he says. Fluctuations in atmospheric temperatures may also have contributed to the rise.

The ozone hole develops in the extremely cold Antarctic stratosphere each August, when sunlight returns after the darkness of the polar winter. The light drives reactions in which chemical pollutants rapidly destroy ozone, usually reaching a peak during the first 2 weeks of October. During the next 2 months, the hole fills in over Antarctica, and the ozone-depleted air spreads throughout the Southern Hemisphere.

In the past, ozone at an altitude of 20 km has escaped total destruction. This year, however, balloons launched from the South Pole in early October could not detect any ozone at that altitude.

While the vertical extension of the hole was big enough to catch the attention of scientists, it had little effect on the total concentration of ozone in the sky above Antarctica, says Hofmann. The minimum value recorded this year, 112 Dobson units. matched the minimum of the last few years. …

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