SCISAT: Ozone Research

Update on Canada’s Ozone Layer

Arctic Ozone Loss

The Atmospheric Chemistry Experiment (ACE) on the new Canadian science satellite (SCISAT) will take measurements of Canada’s ozone layer with a particular focus on the Arctic. Scientists are concerned about ozone depletion in the Canadian Arctic, where significant ozone losses of up to 45% have been observed during the late 1990s.

A recent Environment Canada report*, which reviews the recent findings of Canadian ozone scientists, states that serious thinning of the Arctic ozone layer could become more frequent over the next 10 to 20 years despite international action taken to reduce ozone destroying chemicals. Preliminary studies indicate that climate change may be altering the Arctic atmosphere making it more susceptible to ozone loss. Ozone-depleting industrial chemicals, however, are still considered the major cause of ozone thinning.

Increased ozone depletion in the Arctic could be damaging to sensitive northern life forms. Ozone thinning over the Arctic could also reduce ozone levels over southern Canada as ozone is redistributed to compensate for losses in the far north.

Over the next 10 to 20 years, Arctic ozone depletion could even become as frequent and possibly as severe as that over the Antarctic. The ozone hole in the Antarctic has grown in extent every year since 1979 and has now reached record proportions. It covered nearly 25 million km² with depletions of up to 70%. In the Arctic, however, weather conditions are more variable than those over the Antarctic, and the ozone layer is not expected to develop a large stationery "hole" each spring.

Other Recent Findings

• Ozone thinning is continuing over the rest of Canada, where ozone values have decreased by an average of about 6% since the late 1970s, with greater losses of about 8 to 10% in the springtime.
• Ozone depletion is not fully understood. Only about half of the observed ozone loss in the atmosphere can be definitely attributed to known ozone-depleting industrial chemicals; other factors, such as climate change may be also contributing to ozone depletion. Due to these uncertainties, changes in the ozone layer must be carefully tracked to determine the effectiveness of actions taken to reduce ozone-depleting substances. The new Canadian science satellite will contribute by taking measurements of the ozone layer from space.
• As a result of the thinning ozone layer, sunburn-inducing UV rays have increased by an average of about 7% in Canada, with levels increasing to 10 to 12% in the springtime. These increased UV levels, which are expected to remain higher than normal for the next 30-40 years, will affect human health, crops, forests and marine and freshwater ecosystems.

Verifying the Satellite’s Arctic Measurements

In 1987, Canada became the first country in the world to focus on the Arctic ozone layer, following the discovery of the ozone hole over the Antarctica. Ozone thinning in the Arctic is greatest during the winter months, when research must be carried out in 24-hour darkness and in temperatures which regularly drop to -40°C. To assist scientists working in this harsh northern environment, Environment Canada built a scientific ozone laboratory at Eureka, on Ellesmere Island, a remote weather station less than 1,000 km from the north pole. Opened in 1993, the observatory has enabled researchers to carry out intensive studies of the Arctic ozone layer and has now become a centre for international research.

As the new Canadian science satellite passes overhead, Environment Canada scientists will take measurements of the upper atmosphere from the Eureka Observatory. They will record ozone levels, as well as other chemicals and the occurrence of polar stratospheric clouds, a form of high level ice clouds which speed up the process of ozone depletion. These measurements will be later compared to data taken by the satellite, to verify the accuracy of the space observations.

Canadian Ozone Research

Canada has made a major contribution to global ozone science, both by monitoring ozone levels, and by conducting research into the causes and impacts of ozone depletion. Canadian research into the ozone layer began in the 1930s and was strengthened in the 1980s when decreases in ozone levels were first observed.

In 1993, Environment Canada scientists completed the first long-term study conclusively showing that the thinning of the stratospheric ozone layer has led to an increase in ultraviolet levels at the earth’s surface. As well, Environment Canada scientists developed the Brewer Ozone Spectrophotometer, a state-of-the-art scientific instrument. Recognized as the world’s most accurate ozone-measuring instrument, it is now in use in more than 35 countries.

Environment Canada operates a network of cross-country monitoring stations which has kept continuous watch on Canada’s ozone layer for more than three decades. The early records, which were taken before any major human influence on the ozone layer, are vital to understanding the changes that are occurring today.

Canadian scientists use a variety of techniques to keep tabs on the ozone layer, including high-altitude research balloons, satellite measurements and ground-based instruments. Two Canadian astronauts, Marc Garneau and Steve MacLean, have even used Canadian instruments to take readings of the ozone layer from inside the space shuttle.

Why is the ozone layer not recovering?

Considerable action has already been taken to reduce the industrial chemicals that are depleting the ozone layer. Canada played a key role in the development of the Montreal Protocol, the international agreement to protect the ozone layer signed in 1987. The build up of the most significant CFCs in the lower atmosphere has now been slowed, and in some cases, even reversed. For example, one of the key chemicals (CFC-11) is now decreasing. However, large concentrations of ozone depleting substances still remain in the atmosphere and are expected to persist for many years to come.

If all countries comply with the terms of the Montreal Protocol, scientists eventually expect to see improvements in the ozone layer, and a recovery should occur around the year 2050. However, scientists are uncertain how the rising levels of greenhouse gases and other pollutants may affect ozone loss, particularly in the Arctic. Ozone depletion over the Earth’s poles may well get worse before it gets better.

For further information, please contact:

David Wardle
Environment Canada
Telephone: (416) 739-4632

*The report, titled Arctic Ozone - the Sensitivity of the Ozone Layer to Chemical Depletion and Climate Change, is posted at http://www.ec.gc.ca/ozone/en/index.cfm. It is also available at Environment Canada’s Inquiry Centre, at 1-800-668-6767