Tag Archives: northern-hemisphere

Wacky jet stream to blame for wild North American weather

Wacky jet stream to blame for wild North American weather

A lot of wild weather has afflicted North America this year: deluges in Colorado and Alberta, a heatwave in Alaska, and bitter cold in Florida. But there’s a high-altitude link between each of these unusual events which itself might be tied to climate change: erratic behavior by the polar jet stream.

NOAA

This famous current of air zips eastward at high altitudes from the continent’s West, normally passing over North America somewhere near Seattle. It is one of two jet streams in the Northern Hemisphere — the other being the subtropical jet stream. Together, these powerful currents have long held weather patterns in their normal places, one year after another. But something weird is going on up there.

Vagabond Shutterbug

Storm clouds over Denver, Colo., Sept. 14.

The normally direct polar jet stream has been swinging wildly this summer, dipping north and south like the line graph on a U.S. jobs report. At times it splits in two. From Popular Mechanics:

The jet stream is a year-round feature of our atmosphere, but the double jet stream phenomenon is more common in winter. When it shows up in the summer, watch out.

“Usually at this time of year the jet stream is a single band around the Northern Hemisphere,” [Texas A&M University atmospheric science professor John] Nielsen-Gammon says. “But in the last month what we’ve seen is a smaller jet stream over the Arctic Ocean, and another jet stream in the midlatitudes.”

That article was published in June after more than 100,000 people were forced from their homes by flooding in Calgary. Media and scientific interest in the jet stream’s newfound vagaries rose again after the recent flood-inducing rainfall in Colorado. From NPR:

During the summer, the double jet stream produced a very strange temperature pattern along the Pacific coast, Nielsen-Gammon says. Down in Southern California it was unusually hot — in Death Valley the temperature reached 129 degrees. Meanwhile, up in British Columbia, it remained unseasonably cold.

Even farther north, in Anchorage, Alaska, residents experienced a relative heat wave, with a record number of 70-degree days. But even farther up in the Arctic, temperatures were relatively cold again.

The double jet stream also played a big role in the Colorado flooding this month, [Rutgers University researcher Jennifer] Francis says. High up in the atmosphere, one stream was carrying moist air from the Pacific to the Rockies. Then, lower down, an unusual eddy was pulling in more moist air from the Gulf of Mexico. Finally, an unusual bulge in the jet stream was causing all this weather to stall near Boulder.

There’s no scientific agreement right now on what role, if any, climate change is playing in the polar jet stream’s erratic behavior. But Francis points out that it is the product of vast temperature differences between the equator and the North Pole. As the globe warms, the Arctic heats at a disproportionately fast rate, and that chips away at the temperature gradient. If that turns out to be what sent the jet stream into a weird spin cycle, then the Northern Hemisphere has a lot more extreme weather coming its way.

“It could be drought. It could be heat waves. It could be flooding due to prolonged rainfall,” Francis told NPR. “All of those kinds of patterns should be becoming more likely.”

NOAAJohn Upton is a science fan and green news boffin who tweets, posts articles to Facebook, and blogs about ecology. He welcomes reader questions, tips, and incoherent rants: johnupton@gmail.com.Find this article interesting? Donate now to support our work.Read more: Climate & Energy

Source article: 

Wacky jet stream to blame for wild North American weather

Posted in alo, ALPHA, Anchor, FF, G & F, GE, LG, ONA, solar, solar panels, Uncategorized | Tagged , , , , , , , , , | Comments Off on Wacky jet stream to blame for wild North American weather

Ice, ice, maybe: Snow and ice melting at record speed

Ice, ice, maybe: Snow and ice melting at record speed

Shutterstock

Take a picture — it’ll last longer than the snow cover.

You may have noticed it’s been a hot summer so far. June temperatures were above average across the world, and both NASA and NOAA ranked the month among the top five warmest since record keeping began in the late 1800s.

Not surprisingly, snow extent in the Northern Hemisphere was at its third-lowest on record by June. But what makes the current paltry snow cover more significant is the fact that, just a few months ago, the Northern Hemisphere was unusually snowy — April 2013 had the ninth-highest snow extent since 1967. A month later, half that snow had melted away. The Washington Post reports:

“This is likely one of the most rapid shifts in near opposite extremes on record, if not the largest from April to May,” said climatologist David Robinson, who runs Rutgers University Global Snow Lab.

The snow extent shrunk from 12.4 million square miles to 6.2 million square miles in a month’s time. By June, just 2.3 million square miles of snow remained in the Northern Hemisphere (a decline of 63 percent from May), third lowest on record.

“In recent years it hasn’t seemed that unusual to have average or even above average winter snow extent rapidly diminish to below average values come spring,” Robinson said.

It’s the same story for ice. Although Arctic sea ice extent is not as low as it was in mid-July of 2012 (the year that Arctic ice dropped to its lowest level on record), over the last two weeks, the ice has melted 61 percent faster than average, with 51,000 square miles disappearing every day. The Arctic Sea Ice Blog writes that despite the slower start to this year’s ice-melting season, 2013 could still approach 2012’s record.

Meanwhile, new research from the State University of New York at Albany purports to have narrowed the window of when we can expect to see an ice-free Arctic to some time in the mid-2050s, under a high-emissions scenario (and with the way things are going, it’s hard to imagine any other scenario playing out over the next 40 years).

Mark Serreze of the National Snow and Ice Data Center thinks the ice will melt even sooner, according to NBC News:

“But I still think you are conservative here,” he [said of the SUNY-Albany study], sticking to his earlier projection of ice-free conditions by the year 2030. “Because what we’re seeing here is that the sea ice cover continues to surprise us.”

For example, he explained, there are poorly understood changes in the flow of ocean heat from the Atlantic to the Arctic, as well as evidence that the heat absorbed by the Arctic Ocean in the summer lingers around through the winter, affecting ice melt the following year.

It’s not just the amount of melting ice and snow but the speed at which they are melting that continue to increase, meaning the effects of warming snowball every year — pun intended.

Claire Thompson is an editorial assistant at Grist.

Find this article interesting? Donate now to support our work.Read more: Climate & Energy

Also in Grist

Please enable JavaScript to see recommended stories

Original link:  

Ice, ice, maybe: Snow and ice melting at record speed

Posted in Anchor, Dolphin, FF, G & F, GE, LG, ONA, PUR, The Atlantic, Uncategorized | Tagged , , , , , , , , , , | Comments Off on Ice, ice, maybe: Snow and ice melting at record speed