Atmosphere Daily Earth Science Repost

Polar Vortex: Cold weather meets global warming

A record-breaking cold snap brings misery to the mid-continent USA. This is a headline we see more often. Changes in the Arctic, driven by global warming, are linked to an increased frequency of these cold-weather incursions from Canada.  Research points to Arctic warming as the enabler for these frigid blasts of air. But the key to understanding how warming in the Arctic leads to freezing in the midcontinental USA is the polar vortex.

Low-pressure cyclone systems in the northern hemisphere, like the polar vortex, cause air to flow counter-clockwise around the system’s center. Think of hurricanes, which are large low-pressure vortexes. So in the northern hemisphere, their winds flow counter-clockwise around the eye of the storm. Because the polar vortex is a cyclone it flows counter-clockwise with its center near the north pole.

The polar vortex extends into the stratosphere some 30 miles above the earth’s surface. Its winds blow year-round, but are strongest in the winter. The lower the pressure in the center of the vortex, the stronger it is. 

The jet stream

The outside edge of the polar vortex is the jet stream. This river of air forms in the upper troposphere a few miles above the earth’s surface and then circles the outer edge of the polar vortex flowing from west to east at speeds that often exceed 100 mph. So the jet stream is why a round trip flight can be shorter timewise on the west-to-east leg. Airplane ground speed is faster traveling with the jet stream winds rather than flying against them.

When the vortex is strong, the winds flow fast, and the system maintains a more circular shape. A strong vortex keeps the cold air trapped above the Arctic. However, if the vortex weakens, it causes the jet stream to slow down, and the slower moving jet stream is more prone to develop waves or lobes that carry blasts of polar air farther southward.

Temperature is important

Temperature is one of the drivers of the polar vortex, making global warming an essential factor. The strength of the polar vortex is related to temperature differences between the system’s center, and the warmer air in the mid-latitudes. A warmer Arctic decreases the temperature differential and thus weakens the polar vortex. The weaker vortex also weakens the jet stream, causing it to meander, creating lobes that pour freezing air into the midcontinent USA.

This is how warming in the Arctic can create colder weather systems in other places on the planet.


Arctic Warming (Source: ArcheanWeb) –

A hot earth analog (Source: ArcheanWeb) –  


Climate Change, Frigid Temperatures and the Polar Vortex: 3 Things to Know –

CarbonBrief Q&A: How is Arctic warming linked to the ‘polar vortex’ and otherextreme weather?

Here’s The Real Connection Between The Brutal Polar Vortex And Global Warming –

Understanding the polar vortex process –

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.