Pole's ozone hole: who NOZE?

Pole's ozone hole: Who NOZE?

"We suspect that a chemical process is fundamentally responsible for the formation of the [Antarctic ozone] hole,' said atmospheric chemist Susan Solomon at an Oct. 20 press conference beamed to Washington, D.C., from McMurdo Station in Antarctica. Solomon is the leader of the National Ozone Expedition (NOZE), which went to Antarctica in August to study the stratospheric ozone hole that has worsened each Antarctic spring during the last decade (SN: 3/1/86, p.133).

NOZE researchers have not determined how the hole is created. But Solomon says they have "strong evidence' against two proposed theories that don't lean primarily on chemistry: a dynamic model involving the upward movement of ozone-poor air from the troposphere into the stratosphere, and the "old-nitrogen' theory, which holds that the highly active sun during the last solar cycle generated large levels of ozone-destroying nitric oxide (SN: 10/11/86, p.239).

Several scientists involved with these two theories dispute the NOZE conclusion. Mark Schoeberl at NASA Goddard Space Flight Center in Greenbelt, Md., sayd that NOZE evidence, based on only one station at the edge of the hole, cannot be used to dismiss dynamic vertical motion. Adds Richard Stolarski, also at Goddard, "I don't believe the dynamic theories are dead.'

Part of the evidence against the odd-nitrogen idea, developed by Linwood B. Callis at NASA Langley Research Center in Hampton, Va., is that Antarctic nitrogen dioxide levels during the expedition have been low--the lowest ever observed in the world. Callis says low levels are to be expected, since solar activity is on the wane. "Their suggestion that the solar cycle is not playing a role in this thing is wrong,' he says. "And even if it is not wrong, it's certainly premature.'

NOZE measurements of 15 kinds of atmospheric molecules should help scientists establish whether the hole is a result of natural processes or of human activities such as the emission of chlorofluorocarbons (CFCs). Some researchers have worried that the chlorine in CFCs, which are used in car air conditioners and many industrial practices, is destroying the ozone layer. The NOZE evidence for chlorine theories is not overwhelming: While the observed nitrogen dioxide concentrations are consistent with chlorine models, chlorine monoxide levels are lower than some theories predict. Solomon, however, says this finding doesn't exonerate chlorine.

Whatever the hole's cause, Solomon says it is more complex than anyone had imagined and "may well be something not yet though of.'