However, this vital atmospheric layer faces a new challenge. During the 2019/20 Australian wildfires, researchers noted a dramatic increase in stratospheric aerosols - tiny particles that affect climate, health, and atmospheric chemistry.
Smoke-charged vortex elevates aerosols to 35 kilometers
Using new satellite data and numerical modeling, researchers demonstrated the impact of wildfires through a phenomenon called the smoke-charged vortex (SCV).
"The SCV is a powerful, smoke-laden whirlpool that transports wildfire smoke into the middle stratosphere, reaching altitudes of up to 35 kilometers," explained Prof. Hang Su from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, a corresponding author of the study. "This process led to at least a doubling of the aerosol burden in the southern hemisphere's middle stratosphere. These aerosols initiated a series of chemical reactions at their surface that impacted ozone concentrations."
The international team found that these wildfire-induced aerosols facilitated heterogeneous chemical reactions in the stratosphere, leading to both ozone depletion and increase at different atmospheric layers.
While the lower stratosphere experienced significant ozone depletion, the study shows that the increase of smoke aerosol particles in the middle stratosphere enhances the heterogeneous uptake and hydrolysis of N2O5, reducing reactive nitrogen gases like NOx and increasing ozone. In Southern Mid-Latitudes, this interplay buffered approximately 40% (up to 70%) of the ozone depletion observed in the lower stratosphere following the mega-bushfire events.
Implications of the findings
"Our study uncovers an unexpected and crucial mechanism by which absorbing aerosols in wildfire smoke, such as black carbon, can induce and sustain enormous smoke-charged vortices spanning thousands of kilometers, fundamentally changing the stratospheric circulation. The vortices can persist for months, carrying aerosols deeply into the stratosphere and affecting the ozone layer in distinct ways at different altitudes. This highlights the need for continued vigilance and research as climate change progresses," said Prof. Yafang Cheng, another leading author from the Max Planck Institute for Chemistry.
"We've made a significant step forward in simulating the SCV as a new effective pathway for wildfires to modify stratospheric dynamics and chemistry, especially the ozone layer. I love this study because it once again demonstrates how closely different parts of the Earth system are connected. Smoke from a forest fire can significantly change the wind and circulation tens of kilometers above the ground, allowing the smoke to modify the ozone layer, influencing life on our planet," said Dr. Chaoqun Ma, the first author of the study and postdoc researcher in Cheng's team at the MPIC.
The ozone layer's role in filtering UV radiation is crucial for protecting life on Earth. The Montreal Protocol's success in reducing ozone-depleting substances was monumental. However, the new findings highlight that natural events, exacerbated by climate change, pose additional risks to this fragile atmospheric layer. With the increasing frequency and intensity of wildfires driven by global warming, the formation of SCVs and their impact on the stratosphere could become more common, threatening the ozone layer.
Research Report:Smoke-charged vortex doubles hemispheric aerosol in the middle stratosphere and buffers ozone depletion
Related Links
Max Planck Institute for Chemistry
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