New research shows that extremely cold temperatures have stripped the Arctic atmosphere of most of its protective ozone. An Arctic ozone hole could be formed for the first time and the effects could be felt as far south as New York.
Yesterday, National Geographic reported a "continuing high-altitude freeze over the Arctic may have already reduced the ozone to half its normal concentrations."
The extremely low Arctic temperatures have enabled polar stratospheric clouds (PSCs) to last longer, leading to record ozone loss. NASA explains the process on its website:
These high altitude clouds [PSCs] that form only at very low temperatures help destroy ozone in two ways—they provide a surface which converts benign forms of chlorine into forms that lead to ozone destruction, and they remove nitrogen compounds that moderate the destructive impact of chlorine. In recent years the atmosphere above the Arctic has been colder than usual, and polar stratospheric clouds have lasted into the spring. As a result, ozone levels have been decreasing.
Photo: Ross J. Salawitch, University of Maryland
Polar stratospheric cloud – the link between ozone depletion and climate change
In a media release, research leader Dr Markus Rex of the German Alfred Wegener Institute for Polar and Marine Research, said that the ozone levels could drop further. “Since the conditions leading to this unusually rapid ozone depletion continue to prevail, we expect further depletion to occur," he said.
Dr Rex has analysed the data from 30 international ozone-monitoring stations throughout the Arctic and his results show Arctic ozone loss this winter is greater than ever before. "We may even get the first Arctic ozone hole ... which would be a dramatic development—one which would make it into coming history books," he said in the National Geographic report.
The position of the polar vortex on March, 14th, 2011. Air masses exposed to ozone loss are coloured in red.
Dr Rex does not believe the extreme cold is coincidental and thinks that global warming is a factor. He says greenhouse gases trap heat in the lower levels of the atmosphere while the higher levels tend to be colder, reports National Geographic. "This is the continuation of a long-term tendency that the cold Arctic winters have become colder," Dr Rex said.
The ozone layer is about 12 miles (20 kilometers) above Earth and prevents most harmful UVB wavelengths (280–315 nm) of ultraviolet light from passing through the Earth's atmosphere.
Experts are warning an Arctic ozone hole could mean major changes to the environment and an increased skin cancer risk similar to the affects that resulted from the Antarctic ozone hole . National Geographic reports:
Marko Herrmann, Alfred Wegener Institute
Weekly launch of an ozone sonde from the AWIPEV research base. In winter, two ozone sondes are launched weekly.
Any spike in UV radiation can impact both the Arctic ecosystem and human health, research leader Rex noted. For instance, more sunlight can slow the growth of certain species of ocean algae that provide food for larger organisms—and whose absence can have reverberations up the food chain.
More worrisome, Dr Rex said, is that ozone-depleted air can catch a ride south to more highly populated areas with the Arctic polar vortex. Low-ozone air is often pushed southward to 40 or 45 degrees latitude by natural atmospheric disturbances, Dr Rex said.
A low-ozone air mass's southern "excursions" can take it as far as northern Italy in Europe or New York or San Francisco in the United States, he said.
Despite the record depletion in the Arctic ozone, Dr Rex is confident that, in the long term, the ozone layer is still on the predicted road to recovery. “By virtue of the long-term effect of the Montreal Protocol, significant ozone destruction will no longer occur during the second half of this century,” explains Dr Rex.
The Montreal Protocol is an international treaty adopted in 1987 to protect the ozone layer by phasing out the production of numerous substances, such as chlorofluorocarbons, believed to be responsible for ozone depletion.
Dr Rex's view is supported by a 2010 assessment of ozone levels sponsored by the UN Environment Program. This comprehensive assessment found that global ozone levels are at a turnaround point and that a return to pre-1980 levels of ozone is expected in the second half of this century.
So, it seems in the short-term, those in the Northern Hemisphere would be wise to reach for their hats and sunscreen when they go out in the midday sun.