Akin to the ozone loss which has been much publicized over Antarctica, the Arctic saw massive ozone losses in 2011 thanks to unusually low temperatures which lingered for a longer than normal time in the stratosphere.
The amount of ozone depletion over the Arctic in 2011 was comparable to the losses seen over Antarctica which have resulted in the “ozone hole” occurring since the mid-1980s.
According to NASA’s Jet Propulsion Laboratory, which lead the study published online in the journal Nature, said that 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 process takes place in the Arctic, but generally, temperatures in the stratosphere are much warmer and therefore limit the amount of time and space in which the chemical reactions can take place. This results in the smaller losses of ozone the Arctic is better accustomed too.
“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.”
Scientists from 19 institutions across nine countries were led by NASA in analysing a large and comprehensive set of measurements which were gathered, including 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 over the Arctic the colder period lasted for more than 30 days longer in 2011 than in any winter that had been previously studied.
Manney said that without the 1989 Montreal Protocol, an international treaty limiting production of ozone-depleting substances, chlorine levels already would be so high that an Arctic ozone hole would form every spring. The long atmospheric lifetimes of ozone-depleting chemicals already in the atmosphere mean that Antarctic ozone holes, and the possibility of future severe Arctic ozone loss, will continue for decades.
“Our ability to quantify polar ozone loss and associated processes will be reduced in the future when NASA’s Aura and CALIPSO spacecraft, whose trace gas and cloud measurements were central to this study, reach the end of their operational lifetimes,” Manney said. “It is imperative that this capability be maintained if we are to reliably predict future ozone loss in a changing climate.”
Source: NASA JPL