False-color view of whole ozone over the Arctic pole in the course of the starting of 2020. The purple and blue colours are the place there’s the least ozone, and the yellows and reds are the place there’s extra ozone. Credit: NASA Ozone Watch
Many persons are conscious of the opening within the ozone layer over Antarctica, however what’s much less extensively identified is that the protecting ozone within the stratosphere over the Arctic is periodically destroyed as effectively, thinning the ozone layer there. This final occurred within the spring of 2020, and earlier than that, within the spring of 2011.
Climate scientists have seen climate abnormalities over the entire northern hemisphere each time the ozone layer over the north pole has been thinned out. Those spring seasons have been unusually heat and dry all through central and northern Europe, Russia, and particularly in Siberia. However, in different areas, resembling polar areas, moist circumstances prevailed. These climate anomalies have been notably pronounced in 2020. That spring in Switzerland was additionally abnormally heat and dry.
In local weather analysis, it’s a matter of debate whether or not there’s a causal relationship between stratospheric ozone destruction and the noticed climate anomalies. A job can be performed by the polar vortex within the stratosphere, which kinds in winter and decays in spring. Researchers who’ve investigated the phenomenon up to now have arrived at contradictory outcomes and completely different conclusions.
New findings are actually shining gentle on the state of affairs, because of doctoral pupil Marina Friedel and Swiss National Science Foundation Ambizione Fellow Gabriel Chiodo. Both are members of the analysis group headed by Thomas Peter, Professor of Atmospheric Chemistry at ETH Zurich, and are collaborating with Princeton University and different establishments.
A view of Earth’s ambiance from area. Credit: NASA
Simulations reveal correlation
To uncover a attainable causal relationship, the scientists ran simulations that built-in ozone depletion into two completely different local weather fashions. Most local weather fashions think about solely bodily elements, not fluctuations in stratospheric ozone ranges, partly as a result of this is able to require far more computing energy.
However, the brand new calculations make it clear: the reason for the climate anomalies noticed within the northern hemisphere in 2011 and 2020 is usually ozone depletion over the Arctic. The simulations the scientists ran with the 2 fashions largely coincided with observational information from these two years, in addition to eight different such occasions that have been used for comparability functions. But when the scientists “turned off” ozone destruction within the fashions, they might not reproduce these outcomes.
“What surprised us most from a scientific point of view is that, even though the models we were using for the simulation are utterly different, they produced similar results,” says co-author Gabriel Chiodo, SNSF Ambizione Fellow on the Institute for Atmospheric and Climate Science.
False-color view of whole ozone over the Arctic pole. The purple and blue colours are the place there’s the least ozone, and the yellows and reds are the place there’s extra ozone. Credit: NASA Ozone Watch
The mechanism explained
According to the researchers’ new understanding, the phenomenon begins with ozone depletion in the stratosphere. For ozone to be broken down there, temperatures in the Arctic must be very low. “Ozone destruction occurs only when it is cold enough and the polar vortex is strong in the stratosphere, about 30 to 50 kilometers above the ground,” Friedel points out.
Normally, ozone absorbs UV radiation emitted by the sun, thereby warming the stratosphere and helping to break down the polar vortex in spring. But if there is less ozone, the stratosphere cools and the vortex becomes stronger. “A strong polar vortex then produces the effects observed at the Earth’s surface,” Chiodo says. Ozone thus plays a major role in temperature and circulation changes around the North Pole.
Greater accuracy possible for long-term forecasts
The new findings could help climate researchers make more accurate seasonal weather and climate forecasts in the future. This allows for better prediction of heat and temperature changes, “which is important for agriculture,” Chiodo says.
Friedel adds, “It will be interesting to observe and model the future evolution of the ozone layer.” This is because ozone depletion continues, even though ozone-depleting substances such as chlorofluorocarbons (CFCs) have been banned since 1989. CFCs are very long-lived and linger in the atmosphere for 50 to 100 years; their potential to cause ozone destruction lasts for decades after they have been taken out of circulation. “Yet CFC concentrations are steadily declining, and this raises the question of how quickly the ozone layer is recovering and how this will affect the climate system,” she says.
Reference: “Springtime arctic ozone depletion forces northern hemisphere climate anomalies” 7 July 2022, Nature Geoscience.
DOI: 10.1038/s41561-022-00974-7
