NASA leads study of unprecedented Arctic ozone loss

NASA: A NASA-led study has documented an unprecedented depletion of Earth's protective ozone layer above the Arctic last winter and spring caused by an unusually prolonged period of extremely low temperatures in the stratosphere.

The study, published online Sunday, Oct. 2, in the journal Nature, finds the amount of ozone destroyed in the Arctic in 2011 was comparable to that seen in some years in the Antarctic, where an ozone "hole" has formed each spring since the mid-1980s. The stratospheric ozone layer, extending from about 10 to 20 miles (15 to 35 kilometers) above the surface, protects life on Earth from the sun's harmful ultraviolet rays.

The Antarctic ozone hole forms when extremely cold conditions, common in the winter Antarctic stratosphere, trigger reactions that convert atmospheric chlorine from human-produced chemicals into forms that destroy ozone. The same ozone-loss processes occur each winter in the Arctic. However, the generally warmer stratospheric conditions there limit the area affected and the time frame during which the chemical reactions occur, resulting in far less ozone loss in most years in the Arctic than in the Antarctic.

..."Day-to-day temperatures in the 2010-11 Arctic winter did not reach lower values than in previous cold Arctic winters," said lead author Gloria Manney of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the New Mexico Institute of Mining and Technology in Socorro. "The difference from previous winters is that temperatures were low enough to produce ozone-destroying forms of chlorine for a much longer time. This implies that if winter Arctic stratospheric temperatures drop just slightly in the future, for example as a result of climate change, then severe Arctic ozone loss may occur more frequently."...

Left: Ozone in Earth's stratosphere at an altitude of approximately 12 miles (20 kilometers) in mid-March 2011, near the peak of the 2011 Arctic ozone loss. Right: chlorine monoxide – the primary agent of chemical ozone destruction in the cold polar lower stratosphere – for the same day and altitude. Image credit: NASA/JPL-Caltech