Record 40% decline in Arctic ozone hole

THE protective ozone layer in the Arctic that keeps out the sun’s most damaging rays — ultraviolet radiation — has thinned about 40% this winter, a record drop, the UN weather agency has said.

It comes as scientists monitor a massive pool of fresh water in the Arctic Ocean that could spill into the Atlantic and potentially alter the ocean currents that bring Western Europe its moderate climate.

The Arctic’s damaged stratospheric ozone layer isn’t the best known “ozone hole” — that would be Antarctica’s, which forms when sunlight returns in spring there each year. But the Arctic’s situation is due to similar causes: ozone-munching compounds in air pollutants that are chemically triggered by a combination of extremely cold temperatures and sunlight.

The losses this winter in the Arctic’s fragile ozone atmospheric layer strongly exceeded the previous seasonal loss of about 30%, the UN’s World Meteorological Organisation in Geneva said.

It blamed the combination of very cold temperatures in the stratosphere, the second major layer of the Earth’s atmosphere, just above the troposphere, and ozone-eating CFCs from aerosol sprays and refrigeration.

Atmospheric scientists concerned about global warming focus on the Arctic because that is a region where the effects are expected to be felt first.

“The Arctic stratosphere continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities,” the UN weather agency’s secretary-general Michel Jarraud said.

Although the thinner ozone means more radiation can hit Earth’s surface, the ozone levels in the Arctic remain higher than in other regions.

Ozone losses occur over the polar regions when temperatures drop below -78 degrees Celsius and iridescent ice clouds form. Sunlight on icy surfaces triggers the ozone-eating reactions in chlorine and bromine that comes from air pollutants such as chlorofluorocarbons, or CFCs, once widely used as refrigerants and flame retardants in household appliances.

Meanwhile, oceanographers said the unusual pool in the Arctic has been caused by Siberian and Canadian rivers dumping more water into the Arctic, and from melting sea ice. Both are consequences of global warming.

If it flushes into the Atlantic, the infusion of fresh water could, in the worst case, change the ocean current that brings warmth from the tropics to European shores, said Laura De Steur, of the Royal Netherlands Institute for Sea Research.

Ireland’s climate, for example, benefits from the Gulf Stream, a current that arrives from the Gulf of Mexico.