What is a polar vortex?

The polar vortex is a large, persistent low-pressure area located above Earth's polar regions, containing extremely cold air. This cyclone stretches from the middle of the troposphere into the stratosphere. The polar-front jet stream contains the cold air within the polar vortex, separating it from the warmer air in the midlatitudes. The strength of the polar vortex fluctuates with the seasons, peaking in winter when the temperature contrast between the pole and the Equator is greatest; it may weaken or disappear in warmer months. Disruptions can occur in the vortex when Rossby waves weaken its circulation, leading to southward movement of Arctic air and causing cold-air outbreaks or cold waves.

Where do polar vortexes form on Earth?

Polar vortexes are large, low-pressure areas above the Earth's polar regions, from the middle troposphere up into the stratosphere. They contain extremely cold air, held in place by the polar-front jet stream that separates the cold polar air from the warmer air in the midlatitudes. The polar vortexes are strongest in the winter. The jet stream over the Northern Hemisphere is located above the midlatitudes, and if the circulation is strong, the polar vortex maintains a circular shape near the North Pole. The polar vortex over Antarctica is isolated by the polar-front jet stream, which circulates between 50° and 65° S over the Southern Ocean.

How does a polar vortex affect the weather?

The polar vortex is a large, persistent low-pressure area with extremely cold air, located above each of Earth’s polar regions. It extends from the middle troposphere into the stratosphere. Disruptions in the polar vortex, caused by Rossby waves, can push frigid Arctic air southward, resulting in cold-air outbreaks or cold waves that can drop air temperatures to dangerous levels over populated areas. The region of strongest winds, occurring at the juncture of the tropical and polar air masses, is called the jet stream . Because the temperature contrast between the tropics and the high latitudes is greatest in the winter, the jet stream is stronger during that season.

What causes a polar vortex to become unstable or move south?

The polar vortex, a low-pressure area with frigid air, is typically held in place by the polar-front jet stream. However, undulations in this jet stream, known as Rossby waves, can occur due to land-ocean temperature contrasts and air deflected by mountain ranges. These waves weaken the vortex, making it susceptible to warm air masses and high-pressure systems that can disrupt it. These disruptions can push frigid Arctic air southward, causing cold-air outbreaks and dangerous temperature drops in Eurasia and North America. The Antarctic polar vortex is more stable due to fewer land-ocean contrasts and mountains, which results in fewer Rossby waves.

What kinds of extreme weather events can a polar vortex cause?

The polar vortex is a persistent, large low-pressure area above Earth's polar regions, holding very cold air. Disruptions to the polar vortex can send frigid Arctic air southward, causing extreme cold-air outbreaks or cold waves that can drop temperatures to dangerous levels over populated areas. These cold waves often result in human fatalities and losses of crops and livestock. The cold air within the Antarctic polar vortex helps create nacreous clouds, which contribute to the ozone hole. The boundary between the polar air and warmer air is known as the polar front.

polar vortex

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Four circular thematic maps show Rossby wave patterns over the North Pole, each illustrating different stages of upper atmospheric airflow. The sequence moves from an uninterrupted jet stream around cold polar air, to the development and amplification of wave patterns, showing high- and low-pressure centers, warm and cold air movement, and the eventual restoration of the initial airflow after a cold air mass detaches. Labels indicate the positions of high (H) and low (L) pressure centers and sho

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Also called:: circumpolar vortex, polar low, or polar cyclone

Related Topics:: Winter; Rossby wave; Polar front jet stream; polar region; mother-of-pearl cloud

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Rossby wave patterns over the North Pole depicting the formation of an outbreak of cold air over Asia.

polar vortex

meteorology

Also known as: circumpolar vortex, circumpolar whirl, polar cyclone, polar low, polar winter vortex(Show More)

Written by

John P. Rafferty

Fact-checked by

Britannica Editors

Last updated

Sep. 21, 2026 •History

Top Questions

What is a polar vortex?
The polar vortex is a large, persistent low-pressure area located above Earth's polar regions, containing extremely cold air. This cyclone stretches from the middle of the troposphere into the stratosphere.

The polar-front jet stream contains the cold air within the polar vortex, separating it from the warmer air in the midlatitudes. The strength of the polar vortex fluctuates with the seasons, peaking in winter when the temperature contrast between the pole and the Equator is greatest; it may weaken or disappear in warmer months. Disruptions can occur in the vortex when Rossby waves weaken its circulation, leading to southward movement of Arctic air and causing cold-air outbreaks or cold waves.
2 Britannica Sources
1. atmosphere: Polar fronts and the jet stream
2. polar vortex
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Where do polar vortexes form on Earth?
Polar vortexes are large, low-pressure areas above the Earth's polar regions, from the middle troposphere up into the stratosphere. They contain extremely cold air, held in place by the polar-front jet stream that separates the cold polar air from the warmer air in the midlatitudes.

The polar vortexes are strongest in the winter. The jet stream over the Northern Hemisphere is located above the midlatitudes, and if the circulation is strong, the polar vortex maintains a circular shape near the North Pole. The polar vortex over Antarctica is isolated by the polar-front jet stream, which circulates between 50° and 65° S over the Southern Ocean.
1 Britannica Source
1. polar vortex
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does a polar vortex affect the weather?
The polar vortex is a large, persistent low-pressure area with extremely cold air, located above each of Earth’s polar regions. It extends from the middle troposphere into the stratosphere.

Disruptions in the polar vortex, caused by Rossby waves, can push frigid Arctic air southward, resulting in cold-air outbreaks or cold waves that can drop air temperatures to dangerous levels over populated areas. The region of strongest winds, occurring at the juncture of the tropical and polar air masses, is called the jet stream. Because the temperature contrast between the tropics and the high latitudes is greatest in the winter, the jet stream is stronger during that season.
2 Britannica Sources
1. atmosphere: Polar fronts and the jet stream
2. polar vortex
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What causes a polar vortex to become unstable or move south?
The polar vortex, a low-pressure area with frigid air, is typically held in place by the polar-front jet stream. However, undulations in this jet stream, known as Rossby waves, can occur due to land-ocean temperature contrasts and air deflected by mountain ranges. These waves weaken the vortex, making it susceptible to warm air masses and high-pressure systems that can disrupt it.

These disruptions can push frigid Arctic air southward, causing cold-air outbreaks and dangerous temperature drops in Eurasia and North America. The Antarctic polar vortex is more stable due to fewer land-ocean contrasts and mountains, which results in fewer Rossby waves.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What kinds of extreme weather events can a polar vortex cause?
The polar vortex is a persistent, large low-pressure area above Earth's polar regions, holding very cold air. Disruptions to the polar vortex can send frigid Arctic air southward, causing extreme cold-air outbreaks or cold waves that can drop temperatures to dangerous levels over populated areas. These cold waves often result in human fatalities and losses of crops and livestock. The cold air within the Antarctic polar vortex helps create nacreous clouds, which contribute to the ozone hole.

The boundary between the polar air and warmer air is known as the polar front.
2 Britannica Sources
1. atmosphere: Polar fronts and the jet stream
2. polar vortex
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

polar vortex, large area of persistent low pressure generally located above each of Earth’s polar regions and containing a mass of extremely cold air. The altitude of this cyclone extends from the middle of the troposphere (the lowest level of Earth’s atmosphere, which spans the region from the surface up to 10–18 km [6–11 miles] high) into the stratosphere (the atmospheric layer extending from 10–18 km to about 50 km [30 miles] high). Cold air is contained within the polar vortex by the polar-front jet stream (an eastward-moving belt of strong stratospheric winds that separates warm tropical air from cold polar air in the midlatitudes). The strength of the polar vortex varies with the season, but it is strongest during the winter season in each hemisphere, when the temperature contrast between the pole and the Equator is greatest. It may weaken or disappear entirely during the warmer months of the year.

Over the Northern Hemisphere in the winter season, the polar-front jet stream is located above the midlatitudes (areas located between 30° and 60° N), with wind speeds varying between 193 and 402 km (120 and 250 miles) per hour. If this jet stream’s circulation is strong, the polar vortex maintains a roughly circular shape with a centre at or very near to the North Pole. Undulations in the circulation of the polar-front jet stream (called Rossby waves) can result from incursions of energy generated by land-ocean contrasts in temperature and air deflected by large mountain ranges into the path of the jet stream in the stratosphere. These waves can weaken the circulation around the polar vortex and make the polar vortex more susceptible to disruptions by northward-moving warm air masses and high pressure systems. Disruptions in the polar vortex can push part of the main region of frigid Arctic air southward thousands of kilometres, which produce wide-ranging “cold-air outbreaks” or “cold waves” that can decrease air temperatures to dangerous levels over populated areas of Eurasia or North America. For example, a cold-air outbreak in early January 2014 caused surface air temperatures in the eastern United States to plunge roughly 20 °C (36 °F) below average. In addition, a cold wave that struck Europe in March 2013 caused temperatures to fall more than 10 °C (18 °F) below average in parts of Germany, Russia, and Eastern Europe. Such cold waves often result in losses of crops and livestock and even human fatalities.

The polar vortex over Antarctica and its adjacent seas is isolated from air outside the region by the polar-front jet stream in the Southern Hemisphere, which circulates between approximately 50° and 65° S over the Southern Ocean. The Antarctic polar-front jet stream is more uniform and constant than its Arctic counterpart, because Antarctica is surrounded by ocean rather than a mix of land and water. As a result, land-ocean temperature contrasts underneath the jet stream in the Antarctic are not as great as those in the Arctic. In addition, mountains capable of deflecting energy into the jet stream are fewer and distant, so the development of large Rossby waves is less frequent than in the Northern Hemisphere. As a result the Antarctic polar vortex is more resistant than the Arctic polar vortex to incursions made by outside air masses, and it tends to break up only during the onset of spring. Cold-air outbreaks, however, do occur in the Southern Hemisphere, but they are less frequent and strike heavily populated areas less frequently.

Umbrella colored like a rainbow sticking out above a sea of black umbrellas while it rains. (storm, weather)

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Cold air trapped within the Antarctic polar vortex contributes to the development of nacreous clouds (a type of polar stratospheric cloud [PSC] made up of water and nitric acid) during the winter months, which last through the whole of the polar night (the period in which Antarctica experiences several months of total darkness). PSCs convert less-reactive chlorine-containing molecules to more-reactive forms, such as molecular chlorine (Cl₂), which contribute to the ozone hole. In August and September these clouds are exposed to sunlight, which breaks chlorine molecules into single chlorine atoms that react with and destroy stratospheric ozone (O₃) molecules. Nacreous clouds may form naturally or may be associated with increased methane concentrations in the atmosphere, some of which may result from human activity.

John P. Rafferty

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