New Delhi:
The hole in earth's protective Ozone layer shrank to the smallest it's been since 1988 due to higher temperatures over Antarctica in 2017, according to the study done by NASA scientists.
According to NASA, the ozone hole reached its peak on September 11 which covered almost an area about two and a half times the size of the United States.
Now, NOAA ground and balloon-based measurements also revealed the latest amount of ozone depletion above the continent since 1988. In a bid to monitor the growth and recovery of the ozone hole every year, NOAA and NASA collaborated.
“The Antarctic ozone hole was exceptionally weak this year,” said Paul A. Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland. “This is what we would expect to see given the weather conditions in the Antarctic stratosphere.”
NASA scientists revealed that an unstable and warmer Antartic vortex leads to the smaller ozone hole in 2017. This helped minimize polar stratospheric cloud formation in the lower stratosphere.
The formation and persistence of these clouds are important first steps leading to the chlorine- and bromine-catalyzed reactions that destroy ozone, scientists said.these recent Antartic conditions resemble those found in the Arctic, where ozone depletion is much less severe.
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The ozone hole reaches to peak in September or October as the Ozone depletion occurs in cold temperature.The growth of the ozone hole was limited by warmer stratospheric temperatures in 2016.
Last year, the ozone hole reached a maximum 8.9 million square miles, 2 million square miles less than in 2015. The average area of these daily ozone hole maximums observed since 1991 has been roughly 10 million square miles.
Scientists also revealed that there is not a signal sign of rapid healing, the smaller ozone hole extent in 2016 and 2017 is due to natural variability.
Thirty years ago, the international community signed the Montreal Protocol on Substances that Deplete the Ozone Layer and began regulating ozone-depleting compounds. The ozone hole over Antarctica is expected to gradually become less severe as chlorofluorocarbons—chlorine-containing synthetic compounds once frequently used as refrigerants – continue to decline. Scientists expect the Antarctic ozone hole to recover back to 1980 levels around 2070.
"In the past, we've always seen ozone at some stratospheric altitudes go to zero by the end of September," said Bryan Johnson, NOAA atmospheric chemist. "This year our balloon measurements showed the ozone loss rate stalled by the middle of September and ozone levels never reached zero."
