Changes in the Arctic climate contribute to more frequent violations of polar vortices, favorable for extreme winter weather in the northern hemisphere, similar to the one that was observed in 2020-2021 in the United States and Europe. To this conclusion, scientists of the University of Massachusetts in Lowell (USA) and the Jewish University in Jerusalem (Israel), who published the results of the study in the SCIENCE journal.
satellite data show that stratospheric polar vortices throughout the observation time after 1979 increasingly take an elongated, and not more typical circular view. Scientists have demonstrated the connection of tensile vortices with harsh winter weather in the United States. According to the results of numerical modeling, changes in the Arctic, including accelerated warming, melting of sea ice and an increase in the amount of snowfall in Siberia, turned out to be favorable for stretching the polar vortex, followed by extreme winter weather in North America to the east of the Rockies.
Over the past three decades, the Arctic has experienced the strongest climate change from all regions on Earth, which includes a rapid increase in temperature, melting of sea ice, a decrease in spring snow cover and an increase in autumn snow cover.
Most theories about the connection between the enhancement of warming in the Arctic and winter weather in medium latitudes argue that it is carried out either through a wavy inkjet stream or through sudden stratospheric warming, which are the largest type of polar vortex violations. However, a new study provides convincing evidence that the strongest communication between the weather in the Arctic and average latitudes, at least in the United States, can be carried out through weaker “stretched” polar vortex breaks.
Extreme Winter weather phenomena occur when the high pressure wave between Northern Europe and the Urals and the low pressure region over Eastern Asia are strengthened. The reason for this strengthening may be changes in the Arctic during the autumn season, in particular, the melting of sea ice in the Barents-Kara seas and stronger snowfall in Siberia. The excess energy of the Eurasian wave is reflected from the polar vortex and is absorbed by a similar north-American wave with high pressure over the Alaska and the northern part of the Pacific Ocean and low pressure over the eastern part of North America, causing rapid strengthening and increasing the likelihood of extreme weather.