The polar jet steam is a high-velocity air current that is connected to the Northern Hemisphere as it circulates for about 15 kilometers above our heads like an ethereal zigzag crown on the planet.
This belt of strong winds separates the cold air from the North Pole from the warm air in the South, and is responsible for transporting weather from west to east across the United States, over the Atlantic Ocean, and into Europe.
This controls the humidity and warmth of these areas.
But according to a recent study published in PANS on September 21, the polar jet stream is shifting northward due to rising global temperatures, because the delicate balance between warm and cold air that keeps the stream in place is being disturbed.
The study found that if greenhouse gas emissions continue unabated, the polar jet stream will deviate from its normal range by 2060.
“It may be that the beginning of the northward migration of the jet stream has already begun,” Matthew Osman, a researcher at the University of Arizona's Climate Systems Center and co-author of the study, told Business Insider. ".
According to Othman, this would wreak havoc on the weather in the northern hemisphere, bringing more extreme events such as droughts and heat waves to southern Europe and the eastern United States, and more rain and flooding in northern parts of Europe and Scandinavia.
Ice crater on top of the Greenland ice sheet, where most of the core samples for the study came from (Yurik Alert)
migratory jet stream
The North Atlantic Jet Stream exists and is kept in place thanks to the clash between warm air heading north from the tropics and cold air in the Arctic.
Once these air masses meet, they are moving east at 161 kilometers per hour, propelled by the Earth's rotation.
But rising air temperatures are spoiling this flow. The North Pole is warming on average twice as fast as the rest of the planet, so warm air travels farther north before it finds cooler air, causing the location of the jet stream to migrate toward higher latitudes.
Othman points out that the jet stream is volatile, and that its location is constantly changing with the fluctuation of the temperature difference that it causes, but the study he conducted focused on the long time period, as it examined the location of the stream over the past 1250 years.
By drilling deep into Greenland's ice sheet, researchers have reconstructed the jet stream's turbulent past and found that climate-induced disruptions are likely to have severe weather-related consequences for communities on both sides of the Atlantic.
Then, using climate models, the team simulated where the jet stream might move over the next four decades if greenhouse gas emissions continued at their current rates.
The results showed that the current movement of the current portends the overrun of anything previous, and is expected to deviate significantly from the norm, with potentially serious consequences.
“By pushing the jet stream beyond its already large natural range, we could expose ourselves to increased climate risks in the future,” Othman says.
Thin clouds with orthogonal bands along a jet stream over Canada (Yurik Alert)
droughts and floods
Osman's study suggests that jet stream migration will likely cause the US East Coast to warm faster than it actually is.
North America and Europe will see more droughts and heat waves.
"Europe, which is at the lower end of the jet stream, will feel these effects more acutely," Osman says.
In particular, semi-arid regions of southern Europe could become drier, and parts of northern Europe that already have a wetter and milder climate, such as Scandinavia, could become wetter.
The extra precipitation will lead to more floods like the one that plagued Europe in the summer of 2021.
dangerous polar vortices
Changes in the jet stream can affect polar eddies as well, and some scientists believe that warming will make the jet stream more wavy than it already is.
The jet stream's path is sinuous and sinuous because not all warm air moves north at the same rate, and not all polar air travels south uniformly, and hence there are many waves in the jet stream's range.
But a study published last month in the journal Science suggests that melting sea ice in the Arctic could increase the density and size of these drifting bulges.
Researcher Matthew Osman installing an ice drill barrel in Greenland (Yurik Alert)
When this sea ice melts, more heat and moisture is transferred from the Earth's surface into the atmosphere.
This is like rock being thrown into a pool of atmosphere, causing strong ripples over the North Pole to distort the jet stream.
This creates vibrations that push the unusually cool air toward the equator.
Thus, a more fluctuating jet stream increases the chances of severe winter storms and cold waves in the United States.
Examples of this harsh winter weather include the polar vortex that struck the United States in 2019, and the winter storm that left millions of Texans without electricity in February 2021.
“If the jet stream ripples further in the future, it could mean that extreme events like the polar vortex could become more frequent,” Othman says.