But the dwindling sea ice may actually interfere with that effort. Shell's bid to drill this year had to be halted due to the dangers of drifting ice. In fact, the reduction in sea ice actually makes the Arctic Ocean more hazardous for oil exploration, not less, thanks to massive chunks floating free and much more speedily than in the past. "Overall, sea ice is becoming much more mobile," Barber says. On the other hand, shipping across the Arctic Ocean has become viable for the first time—and weak or rotten ice, as it is called, suggests a path across the topmost part of the planet is already open for at least a short period of time. "We have already reached that point," Barber argues, based on three decades of field experiments on the ice.
The warmer Arctic waters and land have also begun to release methane, a short-lived but potent greenhouse gas that is also the primary hydrocarbon in natural gas fuel. The Arctic Ocean alone contains more methane than the rest of the world's oceans combined—though when and even if such a thawing would contribute a massive methane release remains a "known unknown" in the words of former Defense Secretary Donald Rumsfeld and oceanographer Wieslaw Maslowski of the Naval Postgraduate School in Monterey. "If we release that methane, we will amplify global warming by an unknown amount," Maslowski says. "We have no idea."
On a larger scale, the biggest impact may be the changes in the Arctic's ability to function as a cooling system for the global ocean. Both the Pacific and Atlantic now have warmer waters from the top to the bottom, based on measurements from computerized floats. The Arctic has been functioning as a global air conditioner, losing roughly 350 watts of heat per square meter of open ocean to the atmosphere during the fall storm season as well as the early part of the winter. A warmer Arctic may not be able to shed those greater amounts of heat.
That inability, in turn, will affect the temperature differences between the northern polar region and areas further south. In the atmosphere, it is that temperature gradient that creates and sustains the jet stream—a band of high winds at altitude flowing from west to east that typically steers weather systems in the Northern Hemisphere. "The jet stream becomes more kinked," NSIDC's Meier notes, which allows cold air to spill further south or warm air to penetrate further north.
The loss of this temperature gradient may also stall weather patterns within the jet stream, allowing particular weather systems to park for a while in one place. That may, in turn, create stronger heat waves and droughts or precipitation. "If it's a rain pattern that gets stuck in place, you get flooding that becomes a problem," Meier says.
Understanding these so-called "teleconnections" is an urgent area of scientific rsearch, given the potential impacts on farming and other vital pursuits. "Our society depends on stable agriculture," Barber notes. It is also likely to be the one that people notice. As climate scientists Jennifer Francis of Rutgers University and Stephen Vavrus of the University of Wisconsin–Madison wrote in a paper laying out how Arctic warming might stall weather patterns via the jet stream: "Gradual warming of the globe may not be noticed by most, but everyone—either directly or indirectly—will be affected to some degree by changes in the frequency and intensity of extreme weather events as greenhouse gases continue to accumulate in the atmosphere."