The new study provides insights into how the position and intensity of jet streams in the North Atlantic have changed over the last 1,250 years. The findings show that by 2060, jet stream locations could move out of the range of natural variability under unabated greenhouse gas emissions, creating dramatic weather for societies on both sides of the Atlantic. It suggests that it may have relevant consequences.
The study, led by Postdoctoral Fellow Matthew Othman, Center for Climate Systems, University of Arizona, Minutes of the National Academy of Sciences, Also PNAS..
Familiar to air travelers flying between North America and Europe, the North Atlantic jet stream is a westerly ribbon that orbits the Arctic. These high-altitude winds, often referred to as “polar jets,” affect the weather and climate in eastern North America and western Europe, accounting for 10% to 50% of annual precipitation and temperature fluctuations in both regions. .. However, little is known about how jet streams have changed in the past or in the future.
The Ottoman research team collected ice core samples from nearly 50 sites across the Greenland ice sheet and reconstructed wind changes throughout the North Atlantic dating back to the 8th century. Reconstruction suggests that so far natural variability has masked the effects of anthropogenic warming on mid-latitude atmospheric dynamics over years and longer timescales.
“In most parts of the globe, direct climate observations usually should not exceed decades,” Othman said. “Therefore, we are not sure how or why the jet stream changes over the long term. Abnormal fluctuations in the jet stream can have serious social consequences such as floods and droughts. We know that, we can now start using the past as a kind of prologue when thinking about the future, such as its impact on weather patterns. “
This study reveals that while natural variability largely controls the location of the North Atlantic jet stream, continuous warming can cause significant deviations from standards. In particular, model projections predict that the North Atlantic jet stream will move north under a 21st century warming scenario. Due to such a transition, jet streams can vary significantly within decades.
The polar jet stream blows fastest near the typical cruising altitude of an airplane, but the wind band actually extends all the way to the ground. Othman explained that although less strong, it is often referred to as a storm truck near the ground. Storm tracks affect the weather and climate throughout Greenland, affecting changes in precipitation and temperature on the island. By analyzing the year-to-year fluctuations in snowfall accumulated in Greenland’s ice cores and the chemical composition of the water molecules that make up those annual snow layers, researchers can see how jet streams flow. I was able to extract clues about centuries ago.
“These layers also tell us how much precipitation has decreased in a particular year, and the temperature at which Airmass was exposed,” Othman said.
Meteorological events such as this summer’s heat waves in the northwestern Pacific and floods in Europe are recent examples of how jet streams affect. Weather pattern According to Othman, it is based on its strength and location in the short term. But socially significant changes also occur on longer time scales. Reconstructing the jet stream past reveals that in a few years it will be far north, and in a few years it could be more than 10 degrees further south.
“Such changes have a significant impact on the types of weather people may experience in a particular location,” Ottoman said. “For example, if the jet stream is located further south, the normally dry Iberian Peninsula tends to experience calm and moist conditions, but as the jet stream moves north, much of its moisture. Moves from Iberia to already moist areas. Scandinavia. Therefore, in the future, polar-shifted jet streams may have similar, but more lasting consequences. “
The team was able to adapt specific and geographical changes in wind speed to past weather-related disasters. For example, during the famine that struck the Iberian Peninsula in 1374, the jet stream was unusually far north. Similarly, the two famines that occurred in the British Isles and Ireland in 1728 and 1740 coincided with the years when the wind blew nearly half as strong as normal, dramatically lowering temperatures and reducing precipitation. .. The latter of these events is estimated to have killed nearly 500,000 people in 1740.
Ottoman and his co-authors predict that future changes in the North Atlantic jet stream will also have dramatic impacts on daily weather and ecosystems, with the trickle-down effect affecting the country’s economy and society. increase.
“Our results act as a warning. Pushing the jet stream beyond its natural range is problematic, but its final trajectory is still largely under our control,” he said. Told.
Forecast of North Atlantic Jet Stream in the context of the last 1,250 years, PNAS (2021). DOI: 10.1073 / pnas.2104105118 , www.pnas.org/content/118/38/e2104105118
University of Arizona
Quote: Jet stream changes were obtained from https://phys.org/news/2021-09-jet-stream-amplify-weather-extremes.html on September 13, 2021 in the 2060s (September 2021). 13th) may amplify extreme weather
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Changes in jet stream could amplify extreme weather events by the 2060s
Source link Changes in jet stream could amplify extreme weather events by the 2060s