Levels of protective ozone over the Arctic fell dramatically this spring and last, a trend scientists fear might be linked to the greenhouse effect. If it continues over the next few decades, they say it could threaten the health of humans and wildlife over the United States and throughout the Northern Hemisphere.
Scientists are divided over whether the drop is severe enough to constitute an ozone hole like the one identified over Antarctica in 1985. But they agree the trend is worrisome, in part because they don’t know why it’s happening.
“There is no question that this is reason for concern,” said Joe Waters, an atmospheric chemist with the Jet Propulsion Laboratory in Pasadena and principal author of a report in the latest issue of Geophysical Research Letters. “We need over the next decade or two to watch the situation very, very closely.”
The depletion over the Arctic is still not as widespread or as deep as it is over the Antarctic, scientists said in a series of reports over the last two months.
But it could potentially affect many more people. The region around the Antarctic is mostly ocean, although ozone-poor air does spread into Australia, New Zealand and the southern tip of South America; in contrast, the Arctic depletion affects Europe, North America and Asia.
The roughly circular area where the depletion takes place is not fixed in place, but can meander and dip as far as the Great Lakes and the Mediterranean Sea.
Ozone, a compound that consists of three oxygen atoms bound together, is the chief component of smog. But it also forms a protective layer high in the atmosphere, screening out ultraviolet radiation from the sun that would otherwise harm wildlife, disrupt ecosystems and give people skin cancer.
Levels of ozone over the Arctic have been dropping for the past few decades, bottoming out each spring and gradually returning to more normal levels each summer. But the destruction of the ozone layer above the Arctic accelerated sharply this spring and last, plunging to the lowest levels ever recorded there, the researchers said.
By March, the average ozone concentration over the entire region was 21 percent lower than it had been two decades ago, and it fell to 40 percent lower than normal in a small area near the North Pole.