domingo, 8 de diciembre de 2013

Arctic ozone loss..

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Arctic ozone loss
NASA study leads the unprecedented loss of Arctic ozone:

A NASA-led study documented an unprecedented decline of the ozone layer above the Arctic winter and last spring caused by an unusually prolonged period of extremely low temperatures in the stratosphere.The study, published online Sunday, October 2, in the journal Nature, believe the amount of ozone destroyed in the Arctic in 2011 was comparable to that in a few years in Antarctica, where an ozone "hole" formed every spring since mid-1980. The stratospheric ozone layer, which extends from about 10 to 20 miles (15 to 35 km) above the surface, protects life on Earth from ultraviolet rays.

The Antarctic ozone hole is formed when extremely cold conditions, common in the stratosphere of the Antarctic winter, trigger reactions that convert chlorine into the atmosphere from human produced chemicals in ways that destroy ozone. The same ozone loss processes occur each winter in the Arctic. However, the warmer stratospheric conditions generally do not limit the area affected and the period of time during which chemical reactions occur, resulting in much less ozone loss in most years in the Arctic than the Antarctic.

To investigate Arctic ozone loss in 2011, scientists from 19 institutions in nine countries (U.S., Germany, Holland, Canada, Russia, Finland, Denmark, Japan and Spain) analyzed a comprehensive set of measures. These included daily global observations of trace gases and clouds of NASA's Aura and CALIPSO spacecraft; ozone measured by instrumented balloons, meteorological data and atmospheric models. Scientists have discovered that at some altitudes, the Arctic cold spell lasted more than 30 days longer in 2011 than in any previously studied Arctic winter, leading to unprecedented ozone loss. More studies are needed to determine what factors caused the cold period
"Day-to-day temperatures in the Arctic winter 2010-11 did not reach values ​​lower than in previous winters in the Arctic," said lead author Gloria Manney of NASA's Jet Propulsion Laboratory in Pasadena, California, New Mexico and Institute of Mining and Technology in Socorro. "The difference is that previous winters the temperatures were low enough to produce ozone destroying forms of chlorine for a much longer time. This implies that if the Arctic stratospheric winter temperatures drop slightly in the future, for example, as a result of climate change, then severe Arctic ozone loss can occur more often. "The 2011 Arctic ozone loss occurred over an area considerably smaller than the ozone hole in Antarctica. This is because the Arctic polar vortex, a persistent large-scale cyclone in which the loss of ozone occurs, was about 40 percent lower than a typical Antarctic vortex. Although smaller and more ephemeral than their counterparts in Antarctica, the Arctic polar vortex is more mobile, often moving on the densely populated north. Decreases in overhead ozone lead to increased surface ultraviolet radiation, which are known to have adverse effects on humans and other life forms.Although the total amount of ozone in the Arctic was far more than twice that normally found in an Antarctic spring, the amount destroyed was comparable to that in some of the Antarctic ozone hole above. This is because ozone levels at the beginning of the Arctic winter are typically much larger than those at the beginning of the Antarctic winter.Manney said that without the 1989 Montreal Protocol, an international treaty limiting the production of ozone-depleting substances, chlorine levels so high that it would be an Arctic ozone hole would form each spring. The long-lived chemicals in the atmosphere of ozone depletion in the atmosphere already means that the Antarctic ozone hole, and the possibility of severe Arctic ozone loss in the future, will continue for decades."Our ability to quantify the loss of polar ozone and associated processes will be reduced in the future, when NASA's Aura and CALIPSO spacecraft, whose trace gas cloud and measures were essential to this study, reaching the end of their operational lives," said Manney. "It is imperative that this capability is maintained if we are to reliably predict future ozone loss in a changing climate."

By Alan BuisJet Propulsion Laboratory



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