However, this essential atmospheric shield now faces an unexpected challenge. The 2019/20 Australian wildfires led researchers to observe a dramatic rise in stratospheric aerosols, tiny particles that can affect climate, health, and atmospheric chemistry.
Smoke-charged Vortex Transports Aerosol Up to 35 Kilometers
Using new satellite data and numerical modeling, the research team discovered the impact of wildfires through a novel phenomenon: 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, one of the corresponding authors of the study. "This process led to at least a doubling of the aerosol burden in the southern hemisphere's middle stratosphere. Once reaching such high altitudes, these aerosols initiated a series of chemical reactions at their surface that impacted ozone concentrations."
The international team found that wildfire-induced aerosols facilitated heterogeneous chemical reactions in the stratosphere, paradoxically causing both ozone depletion and increase at different atmospheric layers.
While the lower stratosphere experienced significant ozone depletion, the study shows that the increase in smoke aerosol particles in the middle stratosphere enhances the heterogeneous uptake and hydrolysis of N2O5. This leads to a decrease in reactive nitrogen gases, like NOx, and an increase in ozone. In Southern Mid-Latitudes, this complex interplay buffered approximately 40% (up to 70%) of the ozone depletion observed in the lower stratosphere in the months following the mega-bushfire events.
The Importance of These Findings
"Our study uncovers an unexpected and crucial mechanism by which the 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, which allows 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 role of the ozone layer in filtering UV radiation is crucial for protecting all 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 delicate atmospheric layer. With the increasing frequency and intensity of wildfires due to 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
Forest and Wild Fires - News, Science and Technology
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