ARCTIC:

Ice loss in the polar north may deliver a frigid spring in the temperate zone

Ice loss in the Arctic may be fueling extreme weather like the frigid spring conditions lingering over much of the United States, scientists said yesterday.

While no one weather pattern can be tied to climate change, the ongoing chill is consistent with global warming in the sense that diminishing sea ice could be changing the jet stream, they said.

"The reduction in Arctic sea ice could be having a significant impact on weather patterns, not just in the Arctic, but throughout the middle latitudes," said Stephen Vavrus, a senior scientist at the University of Wisconsin, Madison, on a conference call organized by Climate Nexus that touched on everything from the U.S. Navy to the likelihood of an ice-free Arctic in the summer.

Vavrus' arguments came as AccuWeather released a new statement stating that the first part of April in parts of the United States will have weather patterns about a month behind schedule, with cold outbreaks possible in the southern United States.

"It appears the first half of April will be what March should have been like," AccuWeather.com said in a statement.

Eventually, spring temperatures are expected to be higher than normal (ClimateWire, March 22).

Vavrus expanded on a series of recent studies hypothesizing that ongoing losses in Arctic sea ice could make a big difference on weather patterns far away from the North Pole.

Last year, Arctic sea ice hit record lows in September.

On Monday, the National Snow and Ice Data Center reported that this year's maximum ice extent, reached on March 15, was the sixth-lowest on the satellite record. The 10 lowest maximums have occurred in the last decade, the center said.

A case of meandering Arctic air

The reason why ice loss could be causing extreme spring weather lies in "simple physics," explained Vavrus. The Arctic is warming twice as fast as the global average, creating a much weaker temperature differential than in the past with areas south.

Because temperature and pressure are tightly linked, the weakened temperature differential can in turn weaken the air flow of the jet stream over the Northern Hemisphere. The pattern also tends to create wavier air that meanders around, rather than flowing simply from West to East, he said.

The loss of sea ice amplifies the warming effect in the Arctic by allowing solar radiation to be absorbed by dark ocean waters, rather than reflected.

The "meandering" of the air means that Arctic air that used to stay more in place may be more likely to dip down in U-shaped patterns into places like the eastern United States. The weakened air flow, in addition, can cause air to linger longer and prolong prevailing weather.

"Instead of a three-day heat wave, you might get a weeklong heat wave," he said.

The unusually warm spring that occurred in parts of the United States last year is consistent with the same phenomenon, even though a cause and effect in one year cannot be proved, he said. In that case, the meandering air dipped farther west into California, which was unusually cold, said Jennifer Francis, a research professor at Rutgers University who collaborated with Vavrus on some of his research.

The other end of that dip held cold air in Canada, while the eastern United States -- where Washington, D.C.'s cherry trees bloomed early -- got unseasonably warm air brought up from Mexico, Vavrus said.

Vavrus and Francis' hypothesis builds on other studies, including one led by NOAA scientists last year documenting how changing Arctic wind patterns may spur ice loss and influence U.S. and European weather.

Vladimir Petoukhov, a professor of Earth system analysis at the Potsdam Institute in Germany, was lead author on a recent study in Proceedings of the National Academy of Sciences proposing that man-made climate change disturbs how waves of air flow around the globe.

That study pointed to Arctic warming's effects on stalling atmospheric waves, leading to a "blocking" where weather patterns stayed in place. Petoukhov has credited that blocking with recent heat waves, like one in Russia in 2010 and one in the United States in 2011, that lasted over long periods of time.

Petoukhov has also attributed sea ice loss to some of the chilly temperatures seen this spring in Europe and parts of the United States.

"There is no unique single explanation of what is happening, and even the role of this sea ice is still debatable, but my personal point of view is, of course sea ice plays an important role in what's happening now," Petoukhov said.

But Vavrus said that there needs to be additional research on the link between Arctic ice loss and non-Arctic weather. The link to meandering air out of the Arctic, in particular, is still a focus of debate, he said.

Some questions for navies

There also is an ongoing debate about when the Arctic is likely to be nearly ice-free in the summer, a situation that would raise numerous geopolitical issues for shipping near the North Pole.

The U.S. Navy is working quietly behind the scenes on multiple fronts, including the development of better Arctic maps, said Rear Adm. David Titley, a former deputy undersecretary of Commerce for operations. It also is examining how to build Arctic capability into ships that are not icebreakers, he said.

Wieslaw Maslowski, a research professor at the U.S. Naval Postgraduate School at the University of Monterey, said the projections of many climate models are too conservative, because they are not fully considering the amount of heat held in the ocean. Instead, many of the models consider that all of that heat is released in the atmosphere, when some of it may actually be accelerating ice melt, he said.

A recent study published online in Geophysical Research Letters says that some global climate models may be far too conservative and that there is a possibility of a nearly sea ice-free summer in the Arctic within the next decade.

At the same time, several scientists on the call said there is enough natural variability in the system to make it difficult to predict how quickly a nearly ice-free Arctic in the summer could occur. Some models show some stabilization of ice loss by 2040 despite the general trend, while others show something very different, they said.

What they agreed on is that a year-round ice-free Arctic, rather than just in the summer, is a long way away.

"I don't think it's going to happen in our time, our children's time or our grandchildren's time," Maslowski said.