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Climate change threatens the arctic ozone layer



Climate change is not only causing increasing warming of the Earth, it is also obviously causing increased depletion of the ozone layer over the Arctic. This despite the global ban on the use of chlorofluorocarbons (CFCs) since 1987, according to an analysis of data measured in the Arctic during the one-year expedition of the German research vessel Polarstern from 2019 to 2020. “Nos. measurements show that the chemical loss of ozone over the Arctic last spring was greater than ever before, ”says expedition leader Markus Rex of the Alfred Wegener Institute (AWI) in Bremerhaven and leader of the MOSAiC expedition. At an altitude where the ozone concentration is highest, around 95 percent of the triatomic oxygen molecules had been destroyed. The thick ozone layer, which absorbs high-level ultraviolet radiation. energy and protects life on Earth, had thus been reduced by more than half. A full analysis of the data has now revealed that this development is also the result of the high levels of carbon dioxide in the atmosphere. tight e heats the lower layers of the air, the atmosphere cools even more at an altitude of 15 to 50 kilometers.

Low temperatures release chlorine and bromine

Temperatures in the North Polar region naturally drop particularly sharply during the winter months, when the Arctic Polar Vortex, an area of ​​stable low pressure in the stratosphere, determines weather conditions. If temperatures drop sufficiently, chlorine and bromine, which had reached the upper layers of the air with CFCs and are bound there to harmless substances, are released and destroy ozone. This effect is sometimes stronger, sometimes weaker, depending on the winter. However, current analyzes show a significant trend towards lower and lower temperatures in the arctic stratosphere during the winter months. This has been correlated with the increase in greenhouse gas emissions, particularly carbon dioxide, over the past decades. An increasing loss of ozone to the upper atmosphere is the result, according to researchers at Rex.

So far, it has been disputed that winters in the Arctic are getting colder and colder, which could accelerate the depletion of the ozone layer. The measurements of the MOSAiC expedition now clearly prove this. Computer calculations show that recurrent ozone depletion could continue until the end of the century if CO? emissions are not significantly reduced. Climate change is also affecting dominant wind systems due to the decrease in temperature differences between the tropics and the Arctic as the Earth warms. The researchers speculate that this also helps lower temperatures in the polar vortex. As the polar vortex also drifts towards Europe on numerous occasions – like this spring – a depleting ozone layer could also affect our latitudes. Higher UV radiation could lead to more sunburns and increase the risk of skin cancer, according to AWI researchers. The Polarstern spent a year in the Arctic sea ice. Frozen in a pack ice, it drifts towards the North Pole.

Image of Jeyaratnam Caniceus