Protective ozone layer hits record low

A team of scientists has been monitoring the destruction of the ozone layer above the Arctic from a research station in Eureka on Ellesmere Island. (FILE PHOTO)

MARGARET MUNRO
Postmedia News

The ozone layer shielding the planet from ultraviolet rays has deteriorated to unprecedented lows over the Arctic, the World Meteorological Organization said April 12.

Much of the destruction occurred over northern Canada last month and the depleted air mass has now shifted to Europe, but could swing back during the next few weeks, said scientists.

“It was over Canada, and now it’s rotated round and peaked over Scandinavia,” said atmospheric scientist James Drummond at Dalhousie University, whose team has been monitoring the destruction from a research station in Eureka on Ellesmere Island.

Measurements from the ground, atmospheric balloons and satellites show that the Arctic region lost about 40 per cent of its ozone layer from the beginning of the winter to late March. The WMO said the highest loss previously recorded was about 30 per cent over the entire winter.

David Tarasick, whose team at Environment Canada launches several ozone measuring balloons a week as part of the international monitoring program, said some station readings have been “nearly 50 per cent below normal.”

The scientists said the intriguing and worrying phenomenon may be linked to rising carbon dioxide levels in the global atmosphere — but it does not, at this stage, pose a serious hazard.

“It is certainly an indicator that the atmosphere up there is still very active and we need to keep a very close eye on it,” Drummond said in an interview with Postmedia News Tuesday. “But I would not say it is a matter for alarm at the moment.”

Tarasick agreed, saying the sun is so low in the sky that only low levels of ultraviolet light can get through to hit the ground. But he said the “record” springtime depletion could result a one to two per cent increase in UV levels this summer.

The protective ozone is located in the stratosphere, which starts about 10 kilometres above the ground. The ozone molecules absorb ultraviolet light and help shield people, plants and ecosystems from harmful solar radiation that has been linked to skin cancer, cataracts and crop damage.

In winter, an atmospheric vortex forms in the stratosphere over the High Arctic. This “chemical cauldron” is relatively isolated, has no sun on it and radiates heat into space, making the temperature drop, said Drummond.

Then, when the sun returns in the spring, he said, the sunlight combines with the frigid temperatures to trigger reactions that destroy ozone molecules. The colder the temperature in the “cauldron,” the more the ozone is destroyed.

“This year we’ve had an unusually strong vortex and (an) usually stable one that has allowed the cold temperatures to develop that leads to the ozone depletion,” said Drummond.

The record destruction has occurred despite an international agreement that has cut production of ozone-destroying compounds produced by industry. Some scientists have suggested the new culprit is carbon dioxide, which is being pumped into the atmosphere through the burning of fossil fuels.

Carbon dioxide has been linked to record warming seen at ground level in the Arctic in the last decade, creating what Drummond described as “a blanket” that warms the lower atmosphere. “But in the upper atmosphere, more carbon dioxide actually radiates more energy into space, so you get cooling in the upper atmosphere,” he said. Colder temperatures enhance ozone depletion.

World Meteorological Organization Secretary-General Michel Jarraud said in a statement Tuesday that “the 2011 ozone loss shows that we have to remain vigilant and keep a close eye on the situation in the Arctic in the coming years.”

Drummond agreed. “One of the things that this illustrates very clearly is that you’ve got to go and do the measurements every year,” said Drummond, who is fighting to keep Canada’s northernmost environmental research laboratory in Eureka, known as PEARL, alive. A team at PEARL measured the ozone destruction in early March, ground-truthing data collected by a Canadian science satellite that flew overhead.

The station has no assured funding from year to year, putting such work in limbo.

“Canada has no real program for supporting observatories of this nature,” said Drummond, noting that European countries have made such work a priority. “We need to sort out how we fund science-in-the-public interest in Canada.”

The scientists said the huge air mass with depleted ozone will dissipate in coming weeks, as the winds shift and air — and ozone — from lower latitude mix with the stratosphere over the Arctic.