When it comes to climate, what happens in the Arctic, scientists are fond of saying, doesn't stay in the Arctic.
And it turns out that the reverse is also true: What happens in the middle latitudes can make for changes farther north.
That's because of changes to the way water moves through the atmosphere and oceans -- even rivers -- and the transfer of heat with it, according to an emerging picture of how the climates at different latitudes interact.
The idea that the climates of the Arctic and lower latitudes are connected, once limited to scientific debate, has become increasingly mainstream. Recent research has supported the theory that Arctic warming is causing the jet stream to meander into a wavy pattern that affects weather events in temperate regions. And a study publicized earlier this year found the "chemical fingerprint" of Arctic water molecules in Northeast U.S. snowfall samples.
But just as the warming Arctic is skewing weather in latitudes far to the south, warming conditions in Earth's midlatitudes are now cited as a source of new heat coming into the Arctic.
"There is a driver that's outside the Arctic that at least gets things going," said John Walsh, chief scientist at the International Arctic Research Center at the University of Alaska Fairbanks.
While sea ice extent dwindles, allowing more ocean heat into the Arctic atmosphere and feeding the long-term cycle of melt, other forces are contributing to the warming, he said at the Arctic Science Summit Week last month at UAF.
"It's sort of a joint effort, the contribution from lower latitudes and then the Arctic amplifies what's going on," he said.
Some of the new warmth is linked to those same jet-stream changes behind the polar vortex.
The phenomenon as self-perpetuating, says Jennifer Francis of Rutgers University.
Francis and several co-authors argue in a study newly published in the Journal of Climate that those changes are accelerating warming and melt of the Greenland ice sheet. Reduced summer sea ice leaves more ocean area open, sending more moisture and warmth into the atmosphere, creating pressure systems that block the jet stream and exacerbate far north summer heat and ice sheet melting, they say.
At the same time, recent research has found, warmth from the more southern latitudes has been flowing into the north -- dramatically so this year.
The starkest example may have been the December storm that sent heat from the south to the Arctic, bringing temperatures near the North Pole almost to thaw. That event sent a pulse of warm air and water from as far south as the tropical Atlantic to the regions north of the Norwegian archipelago of Svalbard and caused sea ice there to actually thin, a notable development in the dead of winter, the National Snow and Ice Data Center reported.
That was just one of the standout events of the 2015-16 winter, which featured sparse ice in the Bering Sea, relatively warm weather throughout most of Alaska and even more dramatic warmth in northern Europe's Barents and Kara Seas, said Nicholas Bond, a University of Washington research meteorologist who serves as the Washington state climatologist.
"We're seeing lots of weird stuff in lots of places," Bond said.
Research by scientists from UAF and other institutions shows how changing ocean patterns are sending warmth north and helping create a "new Arctic." Heat from the water that warms the underside of sea ice is turning out to be a more powerful thaw force than the heat from the air above -- even as they create more spaces of open water that allow atmospheric heat in, said Igor Polyakov of the International Arctic Research Center at the University of Alaska Fairbanks.
"Recent observations based on new technologies tell us that the melt of ice is more accelerated from the bottom, not from the top. That means that openings in the ice cover produce more open water and absorb a lot of heat from (the) atmosphere. And this heat is redistributed in the upper mix layer of the ocean and delivered to the bottom of ice," Polyakov said in a news briefing at last month's science conference at UAF. "This way for ice melt is more efficient than atmospheric direct melt."
A newly published study by Polyakov and collaborating scientists identifies several sources of new heat coming into Arctic waters from points south.
Among them: The Atlantic and Pacific oceans are both warming, so currents from those oceans that normally flow into the Arctic are bringing in extra heat; the movement is especially strong on the Atlantic side. Wind and the movement of broken ice across the water are mixing up the layers in the ocean, bringing warmer water that usually remains deep up closer to the surface -- and nearer to the underside of sea ice.
More freshwater runoff into the Arctic Ocean from major rivers, especially those in Eurasia, is also bringing up temperatures in the water and speeding the ice melt, perpetuating and accelerating the cycle.
Since waters from south flow north through the Bering Strait, scientists are watching for impacts on the Arctic from a warm-up in the Bering Sea, where ice was extraordinarily low this winter, and a multiyear series of warming events in the North Pacific -- the long-stationary mass of warm water known as "the Blob" that emerged in the North Pacific in 2013, the positive and warm phase of the Pacific Decadal Oscillation and the season's extraordinarily powerful El Nino.
"The warmer the Bering Sea, the more heat is going to be transferred into the main Arctic Ocean," said Bond, who named the "Blob."
That's likely to have a pronounced effect in areas off Alaska, but whether it will be significant elsewhere is yet to be determined, Bond said. "How much it matters to the entire Arctic is the big question," he said.
The Svalbard region, where there were notably high temperatures this winter, is particularly vulnerable to the movement of heat north, because it is much more open than the narrow Bering Strait, said Rick Thoman, climate science and services manager for the National Weather Service in Alaska.
Not all the trends in the Arctic are pointing to higher temperatures.
"That's been going on for years, and now it's starting to surface," Thoman said.
New research indicates that the cold blob might be overturning Atlantic circulation patterns.
If it is, it would likely trigger still more changes in in the way water conducts warmth between the Arctic and points farther south.