Based on the study of Greenland ice cores, scientists have reconstructed the history of changes in the high-altitude atmospheric jet stream in the North Atlantic over the past 1250 years, and also made a forecast for the future. The modeling results showed that at the current rate of global climate change, by the 2060s, the North Atlantic atmospheric current may go beyond the range of natural variability, which will lead to a sharp increase in the number of catastrophic natural phenomena - droughts, fires, hurricanes and floods. The research results are published in the journal Proceedings of the National Academy of Sciences.
The North Atlantic high-altitude jet stream is a circumpolar belt of high-altitude westerly winds of a wavy shape. It is familiar to pilots flying between Europe and North America. The position and intensity of this atmospheric flow largely determines the main weather parameters - temperature and amount of precipitation - on both coasts of the North Atlantic. However, until now little was known about how this atmospheric current, most important for the Northern Hemisphere, changed in the past.
American researchers led by Matthew Osman of the University of Arizona's Climate Systems Center decided to fill this gap. They used cores from more than 50 wells drilled in the Greenland ice sheet as a source of paleoclimatic information. From the thickness of the ice layers and their composition, scientists determined the amount of precipitation, surface temperature, direction of winds and the number of storm events for each year up to the eighth century.
"For most places on Earth, direct observations of climate usually span no more than a few decades," Osman said in a press release from the University of Arizona. What we really knew was that the unusual fluctuations in the jet stream have serious social consequences such as floods and droughts due to its effect on the weather."
Reconstruction of the previous jet stream showed that in some years it moved far to the north, and a few years later it could have gone more than 10 degrees to the south, but so far the atmospheric flow has been within the framework of natural variability. At the next stage of the study, the authors constructed a forecast of the dynamics of changes in the North Atlantic Current.
"In terms of thinking about the future, we can now use information about the past as a kind of prologue," Osman says.
The authors conclude that, in accordance with global warming scenarios, the North Atlantic Current will continue to migrate to the north, and over the next four decades, its location may change so much that the high-altitude atmospheric flow will go beyond its usual boundaries.
“Such deviations are of great importance for the weather. For example, when the jet stream goes further south, the usually dry Iberian Peninsula experiences milder and wetter conditions. And when the jet stream migrates north, most of this moisture moves to already wet areas. Scandinavia. A stronger displacement of the jet stream in the future may have similar, but more serious consequences, "- explains the scientist.
Extreme weather events in recent years, such as this summer's heatwaves in the Pacific Northwest and floods in Europe, are recent examples of how air currents affect weather patterns based on intensity and location, the authors say.