Melting Arctic ice altering mid-latitude weather patterns
By Bob Berwyn
SUMMIT COUNTY — If it feels like the weather has been stuck in a rut, that may not be too far from the truth. The jet stream is slowing down and meandering farther north and south, with more blocking patterns setting up across the northern hemisphere.
That leads to more extreme weather, both on the wet and dry side of the scale, said Rutgers University research professor Dr. Jennifer Francis, speaking at last week’s Glen Gerberg Weather and Climate Summit in Breckenridge.
Francis has been studying the connection between vanishing Arctic sea ice and weather in the mid-latitudes of the northern hemisphere, and evidence is piling up that the intense warming at high latitudes has serious implications for North America, Europe and Asia.
Francis sprinkled her scientific talk to broadcast meteorologists with climate change warnings, pointing out the need to make drastic cuts in greenhouse gas emissions.
“The amount of ice loss this summer is just such a stunning example of climate change. This is a real problem, a big problem, it’s happening now, not generations from now and we need to do something about it,” she said, going to recite a litany of extreme weather events in recent years, from floods in Venice and China to extreme winter weather in Europe and last summer’s record-setting heatwave in the U.S.
“We’re just now starting to make the connection between weather and climate … But I think we can all agree that the last few years, Mother Nature in the last several years has dished up an incredible smorgasbord of extreme weather,” she said.
As a result of recent events, Francis said she’s noticed a change in the tone of the conversation about climate and weather. People aren’t shying away from making the connection anymore.
“The high northern latitudes is where the warming is happening the fastest … And we’re starting to see the impacts,” she said. “The high latitudes are going to get even wetter, dry areas are going to get even drier. There are going to be more precipitation extremes in both directions … “We have changed the deck of cards that we are playing with in terms of the climate system … When you take out some of the low cards, you have a much better chance of getting high cards,” she said.
Francis then zeroed in on the Arctic, where temperatures have warmed twice as fast as rest of northern hemisphere, with the greatest warming trends in the winter and fall. The greatest temperature anomalies are at the surface, but extend all the way through the troposphere.
“The last time the Arctic was this warm was 125,000 years ago, and sea level was six to eight meters higher than now … This is really bad news,” she said. “The volume of ice 80 percent less than just a few years ago,and what’s left is broken, thin, rotten slushy,” she said.
The current increases in atmospheric CO2 concentrations are happening so quickly that Earth’s temperatures are still lagging way behind.
“There’s no reason think it won’t keep getting warmer … Going back about 450,000 years into the past, the relationship between CO2 and and temperatuers is very clear. CO2 is at levels not seen for 650,000 years, we have a long way to go to catch up,” Francis said.
As the Arctic ice melts, the sun’s heat is absorbed by the sea instead of being reflected back into space.
“That’s hat’s what creating Arctic amplification … If you warm the Arctic more than the mid-latitude, it’s weakening the gradient, and that’s what drives the jet stream, and it’s weakening. It started to drop off when the sea ice started to disappear. When the jet stream is weak and sluggish it meanders more. The large -scale waves tend to not move very fast,” she said.
“We tend to see cut-off lows and blocking highs. What we’ve seen is that the maximum latitudes, the peaks of ridges migrating northward, especially since sea ice really started to disappear in early 90s, particularly in the North Atlantic, with more ridging around Greenland … The storm track in the Pacific is moving northward,” she said explaining that that movement is also linked with increased ridging.
Francis said many of the recent weather extremes seen around the world match up with the changing jet stream patterns, including record snowfall last winter in Alaska and a spring heatwave in the U.S. that shattered many March temperature records.
She ended her presentation by advocating for better communication.
“The word is not getting to the people who need to hear it and operate on that information,” she said. “There have been organizations out there who have deliberately tried to cover up the evidence of climate change. A lot of money has been spent on trying to confuse the issue.
“If there’s any doubt, people would rather hear the story that’s not so discouraging. But people are starting to see the evidence with their own eyes, they’re realizing the disinformation that they’ve been served is wrong,” she concluded.