I was a member of a team researching the ozone hole over Antarctica. Atmospheric components involved in the chemical destruction of ozone absorb and emit infrared radiation. They can be studied using remote sensing instruments (Michelson interferometers) that detect infrared wavelengths. Remote sensing is the use of electromagnetic radiation to collect information about an area without actually visiting it.

Ozone is a form of oxygen that contains three atoms per molecule. It occurs naturally in the stratosphere, the part of the atmosphere between 10 and 50 kilometers (6 and 31 miles) above Earth's surface. Ozone occurs in a layer in the stratosphere, where it absorbs ultraviolet radiation from the sun. Ultraviolet radiation that reaches the Earth's surface can cause skin cancer and can damage plants. Over the past several decades an annual "hole" in the ozone layer has developed over Antarctica each spring. Sunlight is absent from polar regions during the long, dark winter. Return of solar radiation provides the energy to drive chemical reactions involving man-made chemicals such as CFC's (ChloroFluoroCarbons). These chemicals accumulate in the polar stratosphere during the winter. In the presence of sunlight they destroy ozone. The end result is to convert three-atom oxygen molecules (ozone) into molecules containing only two atoms of oxygen. This form of oxygen (which we breathe) is ineffective in absorbing ultraviolet radiation.

The Michelson interferometers used in this study are being operated at two Antarctic sites. They can measure many industrial compounds involved in ozone destruction, such as chlorine and bromine compounds (including CFC's) as well as nitrogen oxides. CFC's are employed in refrigeration systems and aerosols, among other uses. Nitrogen oxides produced by combustion and are emitted by aircraft. The presence of these components in the atmosphere will be measured throughout the year, and special attention will be paid to the conditions leading up to the development of the annual ozone hole.

The interferometer at McMurdo Station measures infrared absorption of solar radiation in the atmosphere. It can make measurements only when sunlight reaches the Antarctic region, so it does not collect data during the long, dark winter. The interferometer at the South Pole measures infrared emissions, so it can collect data throughout the year. Even though the infrared absorption interferometer only works when the sun is above the horizon, it is used because it is a more sensitive instrument.

Some decrease in ozone levels has been observed at lower latitudes, where most of us humans live. Decreases in atmospheric ozone result in increased amounts of harmful ultraviolet radiation reaching the surface of the Earth. Remote sensing by satellites is being used to monitor global ozone levels.

Summer living quarters for visiting scientists at Amundsen-Scott Station. Photograph courtesy of Erik R. Venteris, The Ohio State University.

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