A shift could have drastic consequences.
A new study suggests that the recent change in the fast-moving, narrow air current known as the jet stream is causing longer lasting, more severe weather patterns over North America and Europe. The findings were presented at the annual meeting of the American Association for the Advancement of Science in Chicago.
According to Jennifer Francis, a professor at Rutger University’s Institute of Marine and Coastal Sciences, the observed change in the jet stream could be a result of increased warming of the Arctic, which has seen temperatures rise as much as three times faster than the rest of planet.
The study shows that the jet stream has been taking a slower, more circuitous route over the northern latitudes. This means weather events last for more prolonged periods than in the past.
“This does seem to suggest that weather patterns are changing and people are noticing that the weather in their area is not what it used to be,” Francis said.
A strong jet stream tends to take a fast, straight path but a weak one meanders, remaining in one spot for long periods. And, Francis says, the warming of the Arctic is to blame.
The jet stream is greatly influenced by temperatures in the Arctic because its strength “is directly proportional to the difference in temperature between the poles and the tropics,” Francis explained. “As the Arctic is experiencing warming at faster rates than the tropics, that difference is getting smaller, so the jet stream is weakening along with it.”
That means that weather patterns will get stuck over a location, resulting in long periods of sun, rain, and snow. It also means cold weather will be driven further south and warm weather further north. Alaska and Scandinavia, for example, are experiencing unusually warm weather this winter.
Francis says it’s too soon to know whether recent weather patterns are the result of manmade climate change or due simply to natural variations.
“The Arctic has been warming rapidly only for the past 15 years,” Francis said, adding that as scientists collect more data she expects they’ll begin to see the effect of climate change. She presented her study at a session on Arctic change along with Mark Serreze, the director of the U.S. National Snow and Ice Data Center in Colorado.
“Fundamentally, the strong warming that might drive this is tied in with the loss of sea-ice cover that we’re seeing, because the sea-ice cover acts as this lid that separates the ocean from a colder atmosphere,” Serreze explained. “If we remove that lid, we pump all this heat up into the atmosphere.”