Arctic ozone reaches record high in positive step for climate

Modeling representation of Arctic ozone hole recovery in 2024. Credit: Michala Garrison, NASA Earth Observatory.
The Earth’s ozone hole in polar regions, where stratospheric ozone levels have been significantly reduced, has been featured frequently in climate change news in recent decades. Anthropogenic chlorofluorocarbons (CFCs) are the main culprit and are emitted by household products such as refrigerators, air conditioners, and spray can refrigerants. Because the ozone hole has a lifespan of several decades in the atmosphere, limiting its use was, and remains, paramount to its recovery.
Policies to combat ozone depletion, such as the Montreal Protocol, a 1987 international agreement, halt the production and consumption of ozone-depleting substances in order to repair the Arctic and Antarctic ozone holes by 2045 and 2066, respectively. It is intended to. Therefore, since the beginning of 2000, levels of inorganic chlorine and bromine, which deplete the ozone layer in the Arctic stratosphere, have decreased, albeit rather slowly.
Amid these gloomy predictions, a study published in Geophysical Research Letters suggests a brighter future ahead. Paul Newman, Ph.D., a principal investigator geoscientist at NASA’s Goddard Space Flight Center, and his colleagues predict that March 2024 will be the year for record Arctic ozone concentrations since the 1970s, after a period of overall increase in the winter of 2023-2024. It was identified as the highest month of the year.
Above-average ozone levels continued into September 2024. This is important because previously, the combination of large, cold, rotating, low-pressure weather systems known as polar vortices and high CFC levels in the spring have been linked to ozone depletion.
The research team highlights the importance of this study as preliminary evidence that CFC levels are now decreasing to allow the ozone layer to begin a long-term recovery. Dr Newman said: “Ozone is the earth’s natural sunscreen. Increased ozone is good for the environment and is encouraging news that the global Montreal Protocol agreement is producing positive results, so it’s a positive story. ”
To explore this change, Dr. Newman and his colleagues looked at meteorological data and satellite backscattered ultraviolet data to measure total column ozone (the total amount of ozone from the Earth’s surface to the top of a particular atmospheric column) since 1979.
The March 2024 ozone average peaked at 477 Dobson Units (DU), which is 6 DU higher than the previous record in March 1979 and 60 DU higher than the average for the study period (1979-2023). In the Arctic, record levels of daily sunshine reached about half of the month, reaching a maximum of 499 DU on March 20th.


Stratospheric ozone levels for the winter of 2023-2024 compared to the climatological average over the 1979-2024 study period. Credit: Michala Garrison, NASA Earth Observatory.
They found that the lowest part of the stratosphere (10-20 kilometers above the Earth’s surface) experienced record high temperatures for 23 days out of the month, combined with rising ozone levels due to warm weather systems rising from the lower troposphere into the stratosphere. I discovered that it was.
This is in contrast to known extreme ozone depletion events in 1997, 2011, and 2020, which occurred during periods of prolonged polar vortices.
The causative mechanism for these extreme temperatures and ozone levels in March 2024 is believed to be due to enhanced winter eddy heat fluxes due to atmospheric Rossby waves. These waves travel into the stratosphere, causing downward motion in the polar regions and increasing polar temperatures.
This wave also slows the polar night jet stream (polar vortex) in the stratosphere around the North Pole, allowing air from mid-latitudes to collect at the poles and bringing more ozone into the region than normal.
“Arctic ozone is controlled by direct ozone depletion and ozone transport by chlorine and bromine compounds,” Dr. Newman explains.
“In the former scenario, temperatures were too high to cause much depletion. In the latter, waves propagating from the troposphere to the stratosphere move ozone to the North Pole, warming the polar regions and slowing the polar vortex. El Niño events and Siberian snow cover have been investigated as controlling processes for ozone transport, but do not seem to have a significant impact.
“The stronger-than-usual transport appears to have been caused by random weather years in which Rossby waves propagate significantly into the stratosphere. Perhaps lower levels of oxygen-depleting substances and higher levels of carbon dioxide cause arctic ozone to It may have helped push it even further to record levels. “
Given that carbon dioxide levels are still predicted to increase in the coming years, Dr Newman said it was “likely” that we would see more of these record ozone events in the future.
“Climate change is thought to be affecting the strength and stability of the stratospheric polar vortex. For example, changes in surface temperature and pressure due to reduced sea ice may increase the occurrence of Rossby waves. “This could result in a weaker and more unstable polar vortex.”
“Additionally, global ozone is expected to increase gradually due to the Montreal Protocol. The combination of these two factors will create favorable conditions for higher polar ozone values.”
Although the North and South Poles generally respond similarly to the effects of Rossby waves, the waves in the North Pole are much stronger, resulting in higher ozone levels than in the Southern Hemisphere, where the ozone hole is more pronounced.
“The Arctic has a stronger source of Rossby waves that propagates upward into the stratosphere (quantified by a stronger eddy heat flux). Therefore, the Arctic is warmer, has weaker eddies, and has much more ozone. Yes, because Antarctica is so cold that deep ozone holes occur every year when eddies that can contain reactive chlorine occur.
Using this insight, a combined chemistry and climate model predicts that Arctic ozone will increase by 10 to 30 DU from 2000 to 2025 due to a decrease in ozone-depleting substances in the atmosphere and an increase in greenhouse gas levels. I’m predicting.
Furthermore, if we calculate the midday clear sky ultraviolet (UV) index based on this data, Arctic ozone levels in 2024 will screen out more UV rays compared to the average for the study period from 1979 to 2023. This results in a 5% decrease in UV index. .
After all, restoring ozone is paramount to protecting life on Earth. Otherwise, increased UV radiation coming from space could have significant effects, including reduced plant growth (affecting the “lungs of the Earth” and agricultural food supplies) and disruption of the oceanic food chain. There is a gender. By affecting growth and primary production, it increases the incidence of skin cancer and immunodeficiency diseases in humans.
There is now hope that these ozone holes will one day be cured.
Further information: Paul A. Newman et al, “March 2024 Arctic ozone-wide record high”, Geophysical Research Letters (2024). DOI: 10.1029/2024GL110924
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