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Earthworks & Systems

Over Antarctica, the Ozone Hole May Be Shrinking
but It Will Take a While for the Earth's Ozone Layer to Return to Normal

October 22, 2001

Nearly three times the size of the United States, the ozone hole over Antarctica (above in blue) appears to be shrinking or at least stabilizing, according to scientists. Reduction of human emissions which destroy ozone in the atmosphere has contributed to this reduction. But the ozone layer may take 50 years or more to return to normal. (Image: NASA)
Having reached nearly three times the size of the United States, the ozone hole over Antarctica appears to be slowing down, possibly reversing its growth rate, according to scientists at New Zealand's National Institute of Water and Atmospheric Research (NIWAR). The hole in the ozone layer, a region of the Earth's stratosphere that contains relatively high levels of the toxic gas and is about 12-30 miles high, forms each year during the Antarctic spring. Last September, the ozone hole reached its maximum size of about 10 million squaremiles, down by about 1.6 million square miles from its peak size in September 2000.

While the ozone hole appears to be stabilizing or even shrinking, it also appears to be staying around longer, according to NIWAR. And this extends the additional risks of ultraviolet radiation to plants and animals on the Earth's surface. Even though the peak size of the ozone hole was less this year than last year's peak, it is about 3.1 million miles larger than it was this time last year. But it may be December before it breaks up again.

How the Ozone Hole Forms

Ozone is simply a molecule that consists of three atoms of oxygen (O3), and is produced when normal oxygen molecules (O2) are bombarded by great amounts of ultraviolet radiation from the sun. As a result, the ozone layer is formed in the stratosphere because it is closer to the sun than the lower layers of the atmosphere. The ozone layer essentially forms a blanket around the earth to filter out harmful ultraviolet radiation and prevent it from reaching the surface. However, scientists estimate that holes have been occurring in this protective ozone layer since the early 1980s.

In Antarctica, winter begins to arrive in March. With the onset of winter, the atmosphere cools and high-altitude winds begin blowing around Antarctica to create a circular wall that prevents air from the north latitudes (latitudes north of Antarctica) from mixing with the southern air. As a result, clouds form in the stratosphere that include both ozone and substances ? from human emissions on the surface ? that can destroy ozone.

As the southern spring arrives, the sun's energy begins to warm up the atmosphere. This causes the chemical reactions between the ozone-destroying matter and ozone, and the hole in the ozone layer begins to form. Essentially, the clouds serve to change chemicals derived from the human emissions into chemicals that destroy ozone.

When the Antarctic summer arrives, the high-altitude winds forming the circular pattern around Antarctica begin to break up, and the ozone rich air from the north flows back across the Antarctic region to replenish the depleted ozone layer. Thus, the hole usually disappears in November or December.

 CFCs are non-toxic, non-flammable chemicals that consist of atoms of chlorine, carbon and fluorine. When radiation hits a CFC molecule, chlorine breaks off and attacks and destroys ozone. (Image: NASA)
Chlorofluorocarbons (CFCs), the best known commercial brand of which is called Freon, are the primary human emissions that causes ozone depletion. These substances are usually found in aerosols and coolants used in refrigerators, freezers and automobile radiators. In the mid-1970s, scientists discovered that CFCs were a primary cause of ozone depletion. This was confirmed a few years later by satellite. CFCs are moved by air currents where they end up in the ozone layer of the atmosphere.

Effects of the Ozone Hole on the Surface

Full, unhindered ultraviolet radiation, primarily from the type of ultraviolet radiation called UV-B, can destroy animal tissue. Sunburn is the most visible and well-known results of over-exposure to ultraviolet radiation. Exposure is also closely linked to skin cancer, cataracts, and serious weakening of the immune system. Certain amphibian species can also decline due to over-exposure of UV-B. Over time, exposure to ultraviolet radiation discolors human skin and can result in severe wrinkling and liver spots.

Ultraviolet radiation from ozone depletion may be the cause of decline in amphibian populations of the Western United States, according to the US Geological Survey (USGS). The regions where these disappearances have occurred are relatively pristine and the amphibians were previously abundant. Above, scientists are shown measuring the ultraviolet radiation in the affected habitat of amphibians. (Photo: USGS)
Plants can also suffer from over exposure to ultraviolet radiation. UV-B can damage and kill plants by interfering with photosynthesis, cause mutation of important growth cells, and interfere with respiration or the plants' ability to absorb carbon dioxide and produce oxygen.

While the ozone hole is, fortunately, located over a sparsely populated region, it poses its greatest threat to New Zealanders and other adjacent temperate areas when it begins to break up in the height of the southern summer. Fragments of the ozone-depleted air will move over New Zealand and other areas during this time when the sun's energy reaches its maximum impact on the southern hemisphere.

UV Benefits

Over-exposure to ultraviolet radiation, like over exposure to most things, is what is harmful to plants and animals. Even with a full, healthy ozone layer, some ultraviolet radiation will make it through. In humans, ultraviolet radiation helps humans produce Vitamin D which is essential to the growth of healthy bones, among other aids. Brief exposure to the sun can supply 100 percent of the body's vitamin D needs. Ultraviolet radiation can also aid in the treatment of chronic skin diseases, such as psoriasis and alopecia areata and resulting hair loss.

Scientists and medical doctors also create their own form of ultraviolet radiation for positive uses in medicine and industry. UV radiation is artificially made by passing an electric current through a gas or vapor, such as mercury vapor. These rays are used for such things as killing bacteria and viruses.

Existence of Other Ozone Holes & Outlook

(Image: EPA)

While the ozone hole over Antarctica was the first to be detected, very large ozone losses have been observed in the Arctic since 1997. Scientists reported the first one, about the size of Texas, in March 1997 (source: Arctic Science Journeys, Radio Script, 1997). Some of the ozone holes detected have lasted only a few weeks and some only a few days.

Although ozone-depleting gases have ceased to grow in the atmosphere, most researchers say it could be 30-50 years before normal ozone levels are restored. Since the signing of the Montreal Protocol in 1987, and with international cooperation, the worst of the ozone-depleting compounds and CFCs dropped dramatically in the 1990s. In 1977, the Environmental Protection Agency (EPA) and Food and Drug Administration (FDA) banned the use of CFCs in the production of most aerosol cans in the United States

While ozone-depleting gases are no longer increasing in the atmosphere, the damage is being maintained by a feedback mechanism. According to a report filed by BBC News, the ¦general decrease of ozone in the lower stratosphere and the global increase in greenhouse gases² are contributing to the extended periods of time in which the ozone holes occur. And, there are natural occurrences that also contribute to ozone depletion, such as sulfuric acid droplets that make their way from volcanic eruptions to the ozone layer.

But the good news is, there has been worldwide cooperation in reducing emissions that contribute to ozone loss and the outlook in the long-term is good.

– Eric McLamb

Important Ecology Tip

Ultraviolet radiation will always make it through even the healthiest ozone layer and can have severe impact on humans, animals and plants if over-exposed. Sunburn is the most common effect of exposure to UV radiation, but skin cancer, cataracts and other diseases can also result. So always ... always ... protect yourself and your animals from the sun by using protective clothing, using UV-rated sunglasses or sunscreen when outdoors. The sunscreen you use should be at least SPF (Sun Protection Factor) 30 or higher. You can be seriously affected by UV radiation even on a cloudy day. And remember, that beautiful, golden brown tan you get today can very well turn into very rough, wrinkled and spotted skin as you get older!


Did you know...?

  • The ozone hole is not really a complete hole in the ozone layer, but rather a thinning of the ozone in the stratosphere.

  • The Antarctic ozone hole has reached as far as the Falkland Islands and the tip of South America, where people were warned to protect themselves against the sun; however, in Antarctica, mainly researchers are affected because the continent is relatively uninhabited by people.

  • Comparatively, there is not much ozone in the atmosphere. Ozone makes up only .0001 percent of all atmospheric gases.