Large ozone holes have reappeared over Antarctica

A study conducted by researchers at the University of Otago has revealed disturbing trends in ozone holes over Antarctica.

According to the study, the ozone hole has been alarmingly large and persistent over the past few years, contrary to public perception.

Large ozone holes

“The past three years (2020–2022) have witnessed the re-emergence of large, long-lived ozone holes over Antarctica,” wrote the researchers.

“Understanding ozone variability remains of high importance due to the major role Antarctic stratospheric ozone plays in climate variability across the Southern Hemisphere.” 

Focus of the study 

The study authors noted that climate change has already incited new sources of ozone depletion, and the atmospheric abundance of several chlorofluorocarbons has recently been on the rise.

“In this work, we take a comprehensive look at the monthly and daily ozone changes at different altitudes and latitudes within the Antarctic ozone hole.”

Significant discoveries

Hannah Kessenich, the lead author and a PhD candidate in the Department of Physics, said the team found there is much less ozone in the center of the ozone hole compared to 19 years ago.

“This means that the hole is not only larger in area, but also deeper throughout most of spring,” said Kessenich. “We made connections between this drop in ozone and changes in the air that is arriving into the polar vortex above Antarctica. This reveals the recent, large ozone holes may not be caused just by CFCs.”

Delayed recovery of ozone holes

“Taking ozone modulating factors into account, the 2022 Scientific Assessment of Ozone Depletion concluded that the Antarctic ozone hole should be on track to recover by 2065,” wrote the researchers.

“Latest results, however, indicate that recovery may be delayed due to previously unaccounted for chlorine release from wildfire aerosols and anthropogenic emissions.”

Unresolved issue

The Montreal Protocol, which was finalized in 1987, is a global agreement to protect the ozone layer by phasing out the production and consumption of ozone-depleting substances such as chlorofluorocarbons (CFCs).

“Most major communications about the ozone layer over the last few years have given the public the impression that the ‘ozone issue’ has been solved,” said Kessenich.

“While the Montreal Protocol has vastly improved our situation with CFCs destroying ozone, the hole has been amongst the largest on record over the past three years, and in two of the five years prior to that.”

“Our analysis ended with data from 2022, but as of today the 2023 ozone hole has already surpassed the size of the three years prior – late last month it was over 26 million km2, nearly twice the area of Antarctica.”

Study implications

Kessenich emphasized the importance of understanding ozone variability. “We all know about the recent wildfires and cyclones in Australia and New Zealand and the Antarctic ozone hole is part of this picture.”

“While separate from the impact of greenhouse gases on climate, the ozone hole interacts with the delicate balance in the atmosphere. Because ozone usually absorbs UV light, a hole in the ozone layer can not only cause extreme UV levels on the surface of Antarctica, but it can also drastically impact where heat is stored in the atmosphere.”

“Downstream effects include changes to the Southern Hemisphere’s wind patterns and surface climate, which can impact us locally,” said Kessenich.

More about ozone holes

As discussed above, the term “ozone hole” refers to a significant depletion of the ozone layer in Earth’s stratosphere. This layer, rich in ozone (O₃) molecules, plays a crucial role in shielding the planet from the Sun’s harmful ultraviolet (UV) radiation.

An “ozone hole” is a region where the concentration of ozone is drastically lower than the surrounding areas.

Causes of ozone depletion

Chlorofluorocarbons (CFCs): The primary cause of ozone depletion is human-made chemicals known as chlorofluorocarbons (CFCs). These compounds, once widely used in refrigerators, air conditioners, and aerosol sprays, release chlorine and bromine upon exposure to UV light. These elements are highly effective at breaking down ozone molecules, leading to the thinning of the ozone layer.

Other Contributing Factors: Other contributors to ozone depletion include other halogenated ozone-depleting substances like halons, carbon tetrachloride, and methyl chloroform. Natural phenomena such as volcanic eruptions can also temporarily enhance ozone depletion by increasing the stratospheric particle load, which facilitates the destruction of ozone.

Effects of ozone depletion

Increased UV Radiation: With less ozone in the stratosphere, more UV radiation reaches the Earth’s surface. This increase in UV exposure can lead to higher rates of skin cancer, cataracts, and other health issues in humans. It also negatively impacts marine ecosystems, particularly affecting plankton, and can harm terrestrial plant life.

Climate Impacts: Ozone depletion also contributes to climate change, as substances that destroy ozone are often potent greenhouse gases. However, the relationship between ozone depletion and global warming is complex, as the two phenomena impact different layers of the Earth’s atmosphere.

Recovery efforts

The Montreal Protocol: A significant step in addressing the issue was the adoption of the Montreal Protocol in 1987. This international treaty was designed to phase out the production and use of CFCs and other ozone-depleting substances. Amendments and adjustments to the protocol have further strengthened its effectiveness.

Signs of Recovery: Thanks to global efforts under the Montreal Protocol, the ozone layer is showing signs of recovery. Scientists predict that with continued adherence to the treaty, the ozone layer could return to its pre-1980 levels by the middle of the 21st century.

In summary, ozone holes are a clear example of the impact human activities can have on our planet. The success story of the Montreal Protocol demonstrates that global cooperation and proactive measures can lead to the restoration and preservation of crucial environmental resources. Continued vigilance and adherence to environmental protocols are essential to ensure the full recovery of the ozone layer.

The study is published in the journal Nature Communications.

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