Arctic ozone hole affects our weather

Since 2010, the Arctic ozone layer has shrunk three times dramatically: in 2011, 2016 and 2020, when as much as 95 percent of the core ozone was depleted. According to a study by Marina Friedel from ETH Zurich and her colleagues in Nature Geoscience, this ozone hole appears to be affecting the weather over Central Europe. The team had observed that in the same years that the shrinkage was particularly pronounced, there were also strong weather anomalies in northern and central Europe and in Siberia. Around the North Pole, on the other hand, it was wetter than the long-term average.

It was initially unclear to the working group whether one triggers the other or whether both have a common cause: for example the dynamic variability of the lower stratosphere. Both would then be a symptom of this atmospheric change. Friedel and co therefore simulated ozone depletion in two different climate models, which has so far mostly not been done because the additional consideration of stratospheric ozone would cost too much computing capacity.

However, their calculations then clearly showed that the two weather anomalies considered in 2011 and 2020 were largely due to the respective ozone holes over the Arctic. The simulations therefore corresponded closely with the observation data from the two years and with eight other such events from the last 40 years, which were used for comparison purposes. However, if the working group switched off the ozone destruction in the models, they could not reproduce the observations.

The phenomenon begins with ozone depletion in the stratosphere: it starts when the temperatures in the Arctic are very low. “The ozone is only destroyed when it is cold enough and the polar vortex in the stratosphere around 30 to 50 kilometers above the ground is strong,” says Friedel.

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