Jet stream seen as one culprit in Alberta floods and upside-down weather

EDMONTON - It's a long way from the Arctic Ocean to southern Alberta, but scientists are increasingly intrigued by theories that link disappearing sea ice to off-the-hook weather such as last week's flooding.

Many are coming to believe there's a common thread between not enough ice on the ocean and too much water in the rivers — a high-altitude, high-speed torrent of air called the jet stream.

"There's been a lot interest in the jet stream in the last two or three years," said Dave Phillips, an Environment Canada climatologist.

The jet stream usually rushes rapidly from west to east in a mostly straight direction, more or less around the Canada-U.S. border. But lately it's been wobbling and weaving like a drunken driver, causing havoc as it goes.

The jet stream gets its energy from the temperature difference between the frigid Arctic and the milder south. The greater the difference, the straighter and more powerful the stream.

Other influences, such as continents and oceans, deflect that steady Vancouver-to-Halifax flow.

But Arctic sea ice has been collapsing for the last several years. The Arctic Ocean itself is also growing slightly warmer.

It's not much, but the temperature gradient between the Arctic and equator has weakened. The jet stream is about 14 per cent slower in the fall now than in the 1990s, according to a recent study by Jennifer Francis of Rutgers University in New Jersey.

The continental and oceanic influences are now relatively stronger, causing the jet stream to undulate more north and south.

"What we're seeing now is more of the dipping and the diving, looking more like a roller coaster than a ribbon," said Phillips.

"When that happens, it tends to kind of slow down. It doesn't move as energetically as it did and so therefore the weather can back up."

Instead of what Phillips describes as typically Canadian "hit-and-run" weather, systems can hang around for days. And when those systems are wet, there's a risk of flooding.

"What we seem to be developing, and there are some papers that are discussing this, is that the jet stream seems to be locking into these patterns longer," said climatologist James Byrne at Alberta's University of Lethbridge.

The theory could help explain anomalous seasons such as the warm winter of 2011-12 on the Prairies.

Last May, the weather was upside-down. Early California wildfires fuelled by heat contrasted with more than a foot of snow in Minnesota. Seattle was the hottest spot in the United States one day, while Maine and Edmonton were warmer than Miami and Phoenix.

Phillips points out that last year there were more tornadoes in Saskatchewan than in Oklahoma.

Not all scientists make those connections. They see the randomness of weather or long-term cycles at work.

Many others are taking a wait-and-see approach about this latest theory. It's far from a scientific consensus, but it is something that is being studied more often and getting a lot of scientific buzz.

"There's going to be a lot more to it that just a wobbly jet stream," said Byrne.

But he called the theory a potentially powerful way to explain how climatic changes show up as weather.

"There's controls on how the jet stream behaved historically," he said.

"Weaken one set of those controls, we're going to get some changes on how the jet stream behaves. It's probably demonstrating it quite well now."

Stay tuned, said Phillips.

"(The theory's) exciting. It seems plausible."

With the overwhelming majority of scientists agreeing that human-caused global warming is fact, Phillips said the new frontier in research is linking climate change and weather.

"Now what seems to be the focus is, 'Is this having an effect on weather?'" he said.

"This is the move in the science of climatology, to connect it with extreme weather, as opposed to going back and saying, 'Gee, is the weather really warmer?'"

— With files from The Associated Press