Kiwi scientists working alongside NASA have detected alarming and unprecedented changes to the ozone layer caused by the devastating 2020 wildfires in Australia.
Smoke from the wildfires impacted the atmosphere in "a way that's never been seen before", New Zealand's National Institute of Water and Atmospheric Research (NIWA) said in a statement.
The devastating bushfires killed at least 34 people, harmed up to three billion animals and burnt about 14.3 million hectares of land.
Now scientists have detected unprecedented chemical changes in the stratosphere, roughly 16-20km above the earth's surface, which is where one-third of the world's protective ozone layer resides.
In the months following the bushfires, levels of hydrogen chloride (HCl) - a gas that can be converted into a reactive form that destroys ozone - dropped by about half and there was an increase in chlorine monoxide (ClO).
Study lead Susan Strahan, a senior research scientist at the University of Maryland Baltimore County and the NASA Goddard Flight Center, said the discovery revealed an important gap in our understanding of ozone chemistry.
"We were unable to replicate what we were seeing in any models, meaning that the reactions taking place in the stratosphere on these smoke aerosols are unknown. We don't know what they are, and we can't calculate their effects on ozone," Dr Strahan said.
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Dr Strahan said the findings are worrying because anything that messes with the chlorine family of gases - like HCl - has the potential to harm the ozone.
"Just one atom of chlorine can destroy over 100,000 ozone molecules before it is removed from the atmosphere," Dr Strahan said.
"From the observations of elevated chlorine monoxide (ClO), we think that ozone in the mid-latitudes experienced some depletion following the 2020 fires."
NIWA researcher Dan Smale said the smoke offered a great chance to study the impact of massive wildfire events on the atmosphere.
"Nothing like this has ever been seen in the [NIWA’s Atmospheric Research Station] Lauder data record before. Like volcanic eruptions, mega wildfires release millions of tons of smoke particles high into the air," Smale said.
"The Australian bushfires were the biggest and most destructive ever recorded and seem to have caused unknown reactions affecting ozone chemistry, which is both tantalising from a science point of view and worrying from an environmental point of view."
Smale said NIWA's findings identify a knowledge gap in the processes that control the ozone.
"With wildfires predicted to become more frequent and intense as the planet warms, the likelihood of ozone depletion is increased," Smale said.
"Laboratory studies on the chemical reactivity of wildfire smoke particles are urgently needed."