Arctic News: Jet Stream

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Deformation of the Jet Stream

As the temperature rises, the Jet Stream is getting increasingly deformed in a number of ways:

• Emissions by people heat up the air and oceans and make winds stronger, as discussed in an earlier post. This is illustrated by above image showing high temperature anomalies at the sea surface of the North Pacific on March 30, 2022 10 UTC, with the Jet Stream (at 250 hPa) reaching speeds as high as 323 km/h or 201 mph (green circle).

• Another mechanism affecting the Jet Stream is that, as oceans heat up, the temperature difference between land and oceans can widen and this can cause the Jet Stream to divert from the path it used to follow, as discussed in an earlier post.

On the image on the right shows the Jet Stream on February 3, 2021, initially running over the West Pacific at speeds as high as 387 km/h or 241 mph (green circle) and moving within a narrow and straight band.

The Jet Stream is then confronted with much different conditions over North America that make the Jet Stream branch out widely (white arrows), with one branch moving north and going circular over the Arctic Ocean, while at the other end a branch can be seen dipping below the Equator.

[ Temperature rise in the Arctic ]

.• The Arctic gets hit hard by temperature rises, as illustrated by the image on the right, created with a NASA image that shows the highest temperature anomalies (of up to 4.1°C versus 1951-1980) over the Arctic Ocean, in particular during El Niño periods. This narrows the temperature difference between the North Pole and the Equator, slowing down the Jet Stream; this can prolong and amplify extreme weather events on the Northern Hemisphere.

Jet Stream goes vertical and circular

In extreme cases, the Jet Stream can go vertical and circular.

The above image shows the Jet Stream forming Omega patterns on the Northern Hemisphere, going circular over the Arctic Ocean and crossing the Equator.

The image on the right shows a sea surface temperature anomaly of 9.7°C (from 1981-2011) in the North Pacific, with the Jet Stream forming many circular patterns on July 25, 2021. The image also shows high sea surface temperature anomalies in the Arctic Ocean.

The image below shows how the Jet Stream on May 20, 2023, is stretched out from pole to pole, and is crossing the Equator at several places, where it is reaching speeds as high as 101 km/h or 63 mph (at the green circle).

The image at the top further illustrates this, showing the Jet Stream (on March 30, 2022) stretched out vertically, roughly along the International Date Line, 180° longitude, moving north from approximately latitude 20°S, close to Fiji, and crossing the Equator, pushed by circular wind patterns.

[ World climate zones ]

Further north on the image at the top, the Jet Stream can be seen moving over the Arctic Ocean, roughly along 180° longitude, splitting in two at the North Pole, and then recombining again and moving roughly along the prime meridian, 0° longitude, down to Greenwich, England. A circular wind pattern is formed in the Jet Stream over the Beaufort Sea.

How it used to be

Polar Jet Stream and Subtropical Jet Stream - NOAA image

World climate zones used to be kept well apart by a stable Jet Stream.

The Jet Stream used to circumnavigate the globe in narrow and straight bands, following a predominantly east-west path in line with its strength and with the deflection caused at specific latitudes by the Coriolis force.

Polar Jet Stream (blue) and Subtropical
Jet Stream (red) - NOAA image

On the Northern Hemisphere, the coldest point used to be the North Pole, so wind used to flow from the tropics to the North Pole. This and the deflection due to the Coriolis force results in two Jet Streams forming, circumnavigating the globe in what used to be narrow and straight bands, i.e. the Polar Jet Stream at 60° North and the Subtropical Jet Stream at about 30°, both on the Northern and Southern Hemisphere, resulting in a total of four Jet Streams.

For many years, Jennifer Francis et al. has been warning that deformation of the Jet Sytream will cause more extreme weather in mid latitudes. Over the years, Arctic-News has described this in a number of posts, such as Deformation of the Jet Stream and Opening the Doorways to Doom, as one of the feedbacks (#10) of accelerated Arctic warming.

Deformed Jet Stream causes havoc on the Northern Hemisphere

As a result of deformation of the Jet Stream, extreme weather events are striking with ever greater frequency and intensity. The Northern Hemisphere has been particularly hit by stronger heatwaves, forest fires, storms and flooding.

The image below, from NOAA, shows that in 2020, in the U.S. alone, a record number of 22 weather and climate disaster events took place that each caused damage of more than 1 billion dollar.

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In 2021, the cost of such events had risen to a record 5-year average of nearly $148.4 billion/year.

For more, see the Extreme Weather page.

Heat domes over the United States

As the image below shows, temperatures are forecast to be as high as 110.4°F or 43.6°C on July 27, 2021, at 23:00 UTC (in South Dakota at green circle).

The image below shows how temperatures rise due to deformation of the Jet Stream.

The image below shows the Jet Stream and the Misery Index (indicating the 'feels like' temperature).

The image below shows the global picture, the Jet Streams and the Misery Index.

The image below shows the global picture, with the Jet Streams forming 'Omega Patterns'.

Further events and developments

Changes to the Jet Stream are part of developments associated with demise of the snow and ice cover in the Arctic that could jointly push up the temperature rise by as much 1.6°C and that could, in combination with further events and developments, result in a temperature rise by 2026 of as much as 18.43°C above pre-industrial, as illustrated by the image below.