The measurements of NASA's Aura satellite showed a decrease in the amount of chlorine in the Antarctic ozone hole between 2005 and 2016, indicating a reduction in depletion of the ozone layer
Credit: NASA's Katy Mersmann / Goddard Space Flight Center
Efforts to heal the hole in the Earth's ozone layer over the Antarctica seems to be paying off, according to a new study of its kind that looked directly at the chemicals that destroy ozone in the atmosphere.
The Earth's ozone layer protects the planet's surface from some of the most damaging rays of the sun that can cause cancer and cataracts in humans, and damage plant life, according to NASA. In the mid-1980s, researchers identified a massive hole in the ozone layer over Antarctica and determined that it had been caused to a large extent by chemicals produced by humans called chlorofluorocarbons (CFCs).
Previous satellite observations have observed changes in the size of the ozone hole, noting that it can grow and shrink from one year to the next. But the new study is the first to directly measure changes in the amount of chlorine, the main CFC byproduct responsible for ozone depletion, in the atmosphere over Antarctica, according to a NASA statement. The study showed a 20 percent decrease in ozone depletion due to chlorine between 2005 and 2016. [Earth’s Atmosphere: Composition, Climate & Weather]
The new study analyzed the ozone data collected between 2005 and 2016 by the Microwave Limb Sounder (MLS) instrument aboard the Aura satellite. The instrument can not directly detect chlorine atoms, but detects hydrochloric acid, which is formed when chlorine atoms react with methane, and then bind with hydrogen. When Antarctica is bathed in sunlight in the Southern Hemisphere summer, CFCs decompose and produce chlorine, which then separates the ozone atoms. But during the winter months (early July to mid-September), chlorine tends to bind to methane "once all of the ozone has been destroyed" in its surroundings, according to the statement.
"By mid-October, all chlorine compounds are conveniently converted into a gas, so when measuring hydrochloric acid, we have a good measure of total chlorine," said study lead author Susan Strahan, atmospheric scientist of the Goddard of NASA. Space Flight Center in Greenbelt, Maryland, said in the statement.
The MLS instrument observed the ozone hole daily during the southern hemisphere winter.
"During this period, Antarctic temperatures are always very low, so the rate of ozone destruction depends mainly on the amount of chlorine there is," Strahan said. "This is when we want to measure ozone loss."
Because previous studies were based on measurements of the physical size of the ozone hole, the authors of the new study say their research is the first to directly demonstrate that ozone depletion is decreasing. as a direct result of a decrease in the presence of chlorine from CFC, according to the statement. The 20 percent reduction in depletion is "very similar to what our model predicts we should see for this amount of chlorine decrease," Strahan said.
"This gives us confidence that the decrease in depletion of the ozone layer until mid-September that the MLS data show is due to the decrease in chlorine levels from CFCs," he said. "But we still do not see a clear decrease in the size of the ozone hole because it is mainly controlled by the temperature after mid-September, which varies greatly from one year to the next."
The study was published on January 4 in the journal Geophysical Research Letters.