The North Atlantic jet stream has a profound influence on the northern hemisphere’s weather. A new analysis indicates that climate change could spark some worrying changes to this system of strong winds within the next few decades, bringing with it some drastic weather-related changes for both sides of the Atlantic.
The recent study was published last month in the journal Proceedings of the National Academy of Sciences.
The North Atlantic jet stream is a ribbon of fast-flowing air currents that snakes across the Atlantic Ocean between North America and western Europe. It’s the production of the pressure gradient created by the wall of warm air in the south coming from the tropics and another wall of cold air from the polar regions. Not only does this band of winds influence the time it takes for an airplane to hop across the pond, but it also has an impact on weather in Western Europe. While it can bring warmer water, it can also help to drive the stereotypical wet and windy UK weather seen in the winter months.
Natural changes to the jet stream account for 10 and 50 percent of the variation in annual rainfall and temperature in both eastern North America and western Europe. As the climate crisis continues to deepen, we can expect to see some significant shakeups to the North Atlantic jet stream that will trigger some major changes to the weather.
To understand the future of the jet stream, researchers from the University of Arizona Climate Systems Center looked to the past. They examined how the jet stream varied over the past 1,250 years using a cutting-edge analysis of glacial ice core samples from nearly 50 sites spanning the Greenland ice sheet. This helped them reconstruct changes to the North Atlantic jet stream as far back to the 8th century CE – around about the time Vikings started to make their presence known in the world. This gave the researchers some insight into the jet stream's natural variability and how it's influenced by wider changes.
Their works suggest that the position of the jet stream could migrate significantly outside of the range of natural variability by as early as the year 2060 if greenhouse gas emissions remain uncontrolled. This is because 21st-century warming scenarios are likely to push the jet stream northwards, causing significant deviations from the norm.
"Such variations have huge implications on the types of weather that people might experience at a given place," Matthew Osman, lead study author from the University of Arizona Climate Systems Center, said in a statement. "For example, when the jet stream is situated farther south, the normally dry Iberian Peninsula tends to experience milder, moister conditions. But, as the jet stream migrates northward, much of that moisture also moves away from Iberia towards already-wet regions of Scandinavia. A poleward-shifted jet stream in the future thus might have similar, but more permanent, consequences."
Osman notes that we are already starting to feel the tremors of these changes. Over the past summer alone, the unprecedented events in the Pacific Northwest and the floods in Europe were strongly influenced by the jet stream. Some of these short-term events could be within the natural range of variability – extreme weather events over the past millennia, such as numerous famines in western Europe, can be attributed to changes to the jet stream – but the next 40 years could see the situation become pushed beyond the “normal zone” if the climate crisis remains unaddressed
"Our results serve as a warning: Although pushing the jet stream beyond its natural range would be problematic, its ultimate trajectory is still largely in our control," Osman concluded.
