Atmospheric ozone measurements taken since early January at 30 stations across the High North suggest that the Arctic is heading towards unprecedented ozone depletion this spring.

Ozone loss resulting from chemical reactions involving chlorofluorocarbons (CFCs) is normally less severe in the Arctic stratosphere than over colder Antarctica, where full-fledged ozone holes have occurred each year in the last couple of decades. The reactions that eat away ozone molecules take place at the surface of polar stratospheric clouds which can only form when temperature drops below -78 degrees Celsius.

During the unusually cold Arctic winter in 2005 more than half of the ozone molecules in the atmosphere were destroyed.

But this winter has been even colder, raising fears that the depletion of the already thin Arctic ozone layer will continue for another two or three weeks.

“We’re on the verge of an Arctic ozone hole,” says Markus Rex, an ozone researcher at the Alfred Wegener Institute of Polar and Marine Research in Potsdam Germany.

The position of the polar vortex on March, 14th, 2011. Air masses exposed to ozone loss are coloured in red.

The polar vortex with reduced ozone concentrations is projected to shift towards Eastern Russia early next week. The image shows the expected position for March, 20th, 2011.

If ozone-depleted air drifts southwards it could significantly increase ultraviolet radiation – which causes sunburn and skin cancer – in populated areas in Europe, North America and Asia in early spring. People should use sufficient UV protection early in the year, says Rex.

The polar vortex, an extended low pressure system that isolates the Arctic from warmer air masses farther south, has been particularly stable this winter, which seems to have caused the low temperatures and massive ozone loss in recent weeks. Scientists believe that conditions that favour Arctic ozone loss will become more frequent in the future as a result of rising greenhouse gas concentrations which have a cooling effect in the stratosphere.

The 1987 Montreal Protocol banned the production of CFCs. But scientists fear it will take at least another couple of decades before the ozone layers in the Arctic and Antarctica show real signs of recovery.

Maps: European Center for Mediumrange Weatherforecast, AWI.