Robust Asymmetry of the Future Arctic Polar Vortex Is Driven by Tropical Pacific Warming

The future stratosphere is globally dominated by a strong radiative cooling due to the increase in greenhouse gases. However, we find that over North America, the Arctic stratospheric cooling is suppressed or rather warming occurs, whereas over Eurasia stratospheric cooling is most pronounced, leading to an asymmetric polar vortex, based on 21st century climate model simulations. There are many causes that drive polar vortex variability, which make future projections highly uncertain. Our model simulations demonstrate that tropical warming induces the asymmetric polar vortex. The eastern equatorial Pacific warming causes eastward-shifted teleconnection with a deepened Aleutian low, which strengthens the polar vortex over Eurasia and weakens over North America by enhancing the vertical wave propagation into the stratosphere. The asymmetric polar vortex is projected to markedly develop in the 2030s, and so could affect winter surface climate over mid- to high-latitudes of Eurasia in the near future.

Automated summary

The future stratosphere is globally dominated by strong radiative cooling due to an increase in greenhouse gases. However, differences in stratospheric cooling over North America and Eurasia, driven by factors such as tropical warming and eastern equatorial Pacific warming, may lead to an asymmetric polar vortex. The asymmetric polar vortex is projected to significantly develop in the 2030s, potentially impacting the winter surface climate over mid- to high-latitudes of Eurasia in the near future.