Ozone layer loss worst on record

Press, 2 October 1987, Page 4

Ozone layer loss worst on record

By

NIGEL MALTHUS

The annual spring depletion of the ozone layer over the Antarctic is, this year, the worst on record.

Average ozone levels recorded last month were -15 per cent below the previous September low, recorded in 1985, said a National Aeronautics and Space Administration scientist, Dr Jim Margitan, in Christchurch yesterday. He was releasing preliminary findings from an unprecedented series of flights into the “ozone hole” by two N.A.S.A. aircraft flying out of southern Chile. An ER2, a civilian variant of the high altitude U2 spy/pinne, made 12 sorties the hole, at up £

68,000 feet It carried 14 experiments gathering air samples or directly measuring concentrations of various chemicals in the atmosphere.

A modified DCB carried seven experiments, mostly remote sensing devices measuring concentrations at a distance from the aircraft using sunlight moonlight or laser reflections. It flew 13 flights, at a lower altitude, but its longer range allowed it to fly from the base at Punta Arenas, Chile, to the South Pole and return.

The DCB’s final flight took it across Antarctica to Christchurch. It will fly home to California today, collecting further reference data from a “normal” atmosphere. Dr Margitan said that the data from the expert-

ment would have to be further analysed, and backed up with further laboratory work. Some data would change as the instruments were recalibrated.

The results would be formally published next year, but on preliminary results, the team was now sure that the ozone hole was caused by both chemical and dynamic (weather pattern) factors.

“It is a lot more complex than we thought," he said.

Ozone is a relatively rare form of oxygen, comprising three atoms of oxygen in each molecule, instead of oxygen’s two. It is important because of its ability to filter out the sun’s ultraviolet radiation.

Ozone measurements taken above

Antarctica since 1957. Since 1975, marked depletion, of up to 50 per cent, has been noted each spring. Although there is still more ozone in the depleted area than naturally occurs over the equator, scientists are concerned because a widespread loss of ozone would result in increased skin cancer in humans and unknown changes in animal and plant life.

Attention has focused on chlorofluorocarbons (CFCs), a family of chemicals used as spray can propellants, refrigerants, and in other industrial uses. Their release into the atmosphere is thought to cause chemical changes which destroy the ozone.

Antarctica applets to

be susceptible to abnormal chemistry because of its unique “vortex” — a weather pattern in which the air receives very little influx from warmer latitudes. Another theory suggests that the hole is caused by purely dynamic changes — unusual air flows displacing the ozone layer. Both theories are now thought to be true. Dr Margitan said that the experiment confirmed that the chemistry was “highly perturbed.” On September 5, however, the experiment observed a patch where ozone levels fell dramatically within 24 hours. “We cannot conceive of any chemical process which can do that in such a short time,” he said. That event may be seen

as evidence of the dynamic model, said Dr Margitan, but it was not known where the lowozone air had come from and whether it was naturally occurring. It was a “complex interplay” of the two mechanisms, he said.

The N.A.S.A. scientists say it is premature for them to speculate on the global implications of the Antarctic ozone hole.

An international environmental pact aimed at limiting CFC use was signed by a number of countries, including New Zealand, at Montreal two weeks ago. N.A.S.A. say its final results, and the results of further experiments, will serve as input to a review of the Montreal Protocol, scheduled fQELI99O. ] _ _