And a researcher at the U.S.-based National Snow and Ice Data Center said that open water at the top of the globe may already be affecting weather in more southern reaches of North America.
"It's not like Las Vegas," said Walter Meier, who cautioned that the link is still poorly understood. "What happens in the Arctic doesn't stay in the Arctic."
On Thursday, the center said the amount of ice in the North is almost at the all-time low of 2007 and could drop further in coming weeks. That assessment came days after German researchers concluded ice cover is already less than it was four years ago, which was the lowest since satellite monitoring began in 1979.
There is now about one-third less ice in the Arctic than the 1979-2000 average.
Northern sea ice is considered a leading indicator of climate change.
Although the data center suggests the ice level could still drop below the all-time low, this year's result is more worrisome because it happened in a summer that didn't have the same kind of unusual weather as in 2007.
Meier said that year was marked by remarkably sunny skies and winds that tended to bunch the ice together. This year had none of those special conditions.
"(This year) has more to do the changing long-term climate of the Arctic rather than just a single one-year extreme event," said James Overland, an oceanographer with the National Oceanic and Atmospheric Administration.
Although satellite data only exists for the last 32 years, there's ample other evidence that the extent of modern sea ice is at historic lows, Meir said.
"We haven't seen ice cover this low probably for the last several thousand years."
Much has been made of the possibility of faster shipping routes and greater access to resources in an increasingly ice-free Arctic, but Overland said there are also implications for weather in the rest of North America that are starting to emerge.
"There is some evidence that warming in the Arctic will bring cooling to some of the weather further south," he said. "In some way, it looks like the Arctic is interacting more with storm tracks at mid-latitudes."
Air warms up more over dark open water than it does over white, reflective sea ice and some scientists believe that the warmer air is starting to disrupt wind patterns that normally keep Arctic air bottled up in the North. Overland theorizes that disruption may have helped create the cold, snowy winters of 2008 and 2009 in Eastern Canada, as well as the cold weather along the U.S. east coast in 2009 and 2010.
"We're not sure about this," said Overland. "It's very controversial."
Although the linkage remains a mystery, some impacts are likely, he said.
"If we're absorbing a whole lot more solar energy in the Arctic that we used to reflect, there ought to be some large-scale climate change. This is the big question."
Meier said the weather impacts of an ice-free Arctic -- now expected as early as 2030 -- are an increasingly urgent research topic.Suggest a correction