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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, leadi...

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Bibliographic Details
Published in:Geophysical research letters 2021-06, Vol.48 (11), p.n/a
Main Authors: Matsumura, Shinji, Yamazaki, Koji, Horinouchi, Takeshi
Format: Article
Language:English
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Summary: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. Plain Language Summary Recent cold extremes in northern mid‐latitudes have seriously damaged economic and societal activities. It has been suggested that during the past three decades the Arctic stratospheric polar vortex has slightly shifted away from North America toward Eurasia associated with Arctic sea ice loss, favoring the cold extremes. Our study shows that in a few decades, such extreme weather events might further increase or intensify due to the enhancement of the polar vortex asymmetry between North America and Eurasia. We found that the asymmetric polar vortex significantly develops in the 2030s and is robust throughout the late 21st century. The asymmetric polar vortex is caused by tropical ocean warming. These findings provide a new insight into Arctic climate changes and would help advance our understanding of ongoing mid‐latitude climate change. Key Points The Arctic stratospheric cooling in the future is most pronounced over Eurasia, whereas over North America stratospheric warming occurs Tropical Pacific warming takes the place of Arctic sea ice loss as the dominating forcing of the polar vortex The asymmetric polar vortex could act to increase the cold extreme events over mid‐ to high‐latitudes of Eurasia in the near future
ISSN:0094-8276
1944-8007
DOI:10.1029/2021GL093440