NASA has recorded an unprecedented decrease in Earth’s protective ozone layer over the Arctic this past winter and spring, caused by an unusually long period of extremely low temperatures in the stratosphere.
The study, published in the online edition of the journalNature, reveals thatthe amount of ozone destroyed in the Arctic in 2011 is comparable to that observed in some years in Antarctica, where a hole in the ozone layer has been forming every spring since the mid-1980s. The ozone layer of the stratosphere, which extends 15 to 35 kilometers above the earth’s surface, protects life on the planet from harmful ultraviolet rays from the sun.
TheAntarctic ozone hole formswhen theextreme cold conditions, very common in the stratosphere during the Antarctic winter, trigger reactions that convert atmospheric chlorine into ozone-depleting forms. The same processes of ozone layer loss occur every winter in the Arctic. However, generally warmer stratospheric conditions so far limited the affected area and the time period during which chemical reactions could take place, resulting in much less ozone loss than in Antarctica.
Arctic ozone hole
To investigatewhy the ozone loss in the Arctic in 2011 has been greater,Scientists from 19 institutions in nine countries (the United States, Germany, the Netherlands, Canada, Russia, Finland, Denmark, Japan and Spain) have analyzed daily global observations of gases and clouds made from the NASA Aura and CALIPSO satellites, as well as those obtained by balloons, meteorological data and atmospheric models. In this way they have verified thatat certain altitudes the cold spell in the Arctic lasted more than 30 days longer in 2011 than in any previous Arctic winter examined. More studies are needed to determine the factors that made the cold spell last so long.
According to Gloria Manney, a researcher at NASA’s Jet Propulsion Laboratory and lead author of this research, without the 1989 Montreal Protocol – an international treaty that limits the production of ozone-depleting substances – chlorine levels They would already be so high that an ozone hole would form every spring in the Arctic. The long lifespan of ozone-depleting chemicals already accumulating in the atmosphere means that Antarctica’s ozone holes, and the potential for future severe loss of the Arctic ozone layer, will continue for decades. .
