NASA finds 'unprecedented' ozone loss in North Pole

A prolonged period of extremely low temperatures in the stratosphere caused an "unprecedented" depletion of the Earth's protective ozone layer above the Arctic in winter 2010 and spring 2011, according to a study led by the US National Aeronautics and Space Administration (NASA). The study, published online Oct. 2, showed the amount of ozone destroyed in the Arctic this year was comparable to that seen in some years in the Antarctic, where an ozone "hole" has formed each spring since the mid-1980s. "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, California, and the New Mexico Institute of Mining and Technology in Socorro. But she said 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," she said. Manney also said chlorine levels already would be so high that an Arctic ozone hole would form every spring, had the 1989 Montreal Protocol not been adopted. The protocol is an international treaty limiting production of ozone-depleting substances. The ozone layer protects life on Earth from the sun's harmful ultraviolet rays. An ozone hole in the Antarctic forms when extremely cold conditions trigger reactions that convert atmospheric chlorine from human-produced chemicals into forms that destroy ozone. Such ozone-loss processes occur each winter in the Arctic, but generally warmer stratospheric conditions there limit the area affected by the chemical reactions. Ozone loss The study showed the area where the 2011 Arctic ozone loss occurred was considerably smaller than that of the Antarctic ozone holes, because the Arctic polar vortex - a large-scale cyclone within which the ozone loss takes place - was about 40 percent smaller than a typical Antarctic vortex. However the Arctic polar vortex is more mobile and moves over densely populated northern regions. Although the total amount of Arctic ozone measured was much more than twice that typically seen in an Antarctic spring, the amount destroyed was comparable to that in some previous Antarctic ozone holes. This is because ozone levels at the beginning of Arctic winter are typically much greater than those at the beginning of Antarctic winter. Scientists' findings Investigating the 2011 Arctic ozone loss were scientists from 19 institutions in nine countries including the United States, Germany, The Netherlands, Canada, Russia, Finland, Denmark, Japan and Spain. Other institutions participating in the study included Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany; NASA Langley Research Center, Hampton, Va.; Royal Netherlands Meteorological Institute, De Bilt, The Netherlands; Delft University of Technology, 2600 GA Delft, The Netherlands; Science Systems and Applications, Inc., Greenbelt, Md., and Hampton, Va.; Science and Technology Corporation, Lanham, Md.; Environment Canada, Toronto, Ontario, Canada; Central Aerological Observatory, Russia; NOAA Earth System Research Laboratory, Boulder, Colo.; Arctic Research Center, Finnish Meteorological Institute, Finland; Danish Climate Center, Danish Meteorological Institute, Denmark; Eindhoven University of Technology, Eindhoven, The Netherlands; Arctic and Antarctic Research Institute, St. Petersburg, Russia; National Institute for Environmental Studies, Japan; National Institute for Aerospace Technology, Spain; and University of Toronto, Ontario, Canada. During the investigation, they analyzed a comprehensive set of measurements such as daily global observations of trace gases and clouds from NASA's Aura and CALIPSO spacecraft; ozone measured by instrumented balloons; meteorological data and atmospheric models. The scientists found that at some altitudes, the cold period in the Arctic lasted more than 30 days longer in 2011 than in any previously studied Arctic winter, leading to the unprecedented ozone loss. But further studies are needed to determine what factors caused the cold period to last so long. Maintaining capability Manny voiced concerns the ability to quantify polar ozone loss and associated processes will be reduced in the future when NASA's Aura and CALIPSO spacecraft reach the end of their operational lifetimes. The two spacecraft's trace gas and cloud measurements were central to this study. "It is imperative that this capability be maintained if we are to reliably predict future ozone loss in a changing climate," she said. — TJD, GMA News