(CNN) -- The North Pole may be briefly ice-free by September as global warming melts away Arctic sea ice, according to scientists from the National Snow and Ice Data Center in Boulder, Colorado.

"We kind of have an informal betting pool going around in our center and that betting pool is 'does the North Pole melt out this summer?' and it may well," said the center's senior research scientist, Mark Serreze.

It's a 50-50 bet that the thin Arctic sea ice, which was frozen in autumn, will completely melt away at the geographic North Pole, Serreze said.

The ice retreated to a record level in September when the Northwest Passage, the sea route through the Arctic Ocean, opened briefly for the first time in recorded history.

"What we've seen through the past few decades is the Arctic sea ice cover is becoming thinner and thinner as the system warms up," Serreze said.

Specific weather patterns will determine whether the North Pole's ice cover melts completely this summer, he said.

"Last year, we had sort of a perfect weather pattern to get rid of ice to open up that Northwest Passage," Serreze said. "This year, a different pattern can set up. so maybe we'll preserve some ice there. We're in a wait-and-see mode right now. We'll see what happens."

The brief lack of ice at the top of the globe will not bring any immediate consequences, he said.

"From the viewpoint of the science, the North Pole is just another point in the globe, but it does have this symbolic meaning," Serreze said. "There's supposed to be ice at the North Pole. The fact that we may not have any by the end of this summer could be quite a symbolic change."

Serreze said it's "just another indicator of the disappearing Arctic sea ice cover" but that it is happening so soon is "just astounding to me."

"Five years ago, to think that we'd even be talking about the possibility of the North Pole melting out in the summer, I would have never thought it," he said.

The melting, however, has been long seen as inevitable, he said.

"If you talked to me or other scientists just a few years ago, we were saying that we might lose all or most of the summer sea ice cover by anywhere from 2050 to 2100," Serreze said. "Then, recently, we kind of revised those estimates, maybe as early as 2030. Now, there's people out there saying it might be even before that. So, things are happening pretty quick up there."

Serreze said those who suggest that the Arctic meltdown is just part of a historic cycle are wrong.

"It's not cyclical at this point. I think we understand the physics behind this pretty well," he said. "We've known for at least 30 years, from our earliest climate models, that it's the Arctic where we'd see the first signs of global warming.

"It's a situation where we hate to say we told you so, but we told you so," he said.

Serreze said the Arctic sea ice will not be the same for decades.

"If we had a few cold years in a row, we could put sort of a temporary damper on it, but I think at this point going to an ice-free Arctic Ocean is inevitable," he said. "I don't think we can stop that now."

Reduced greenhouse gas emissions could "cool things down a bit," he said.

"It would recover fairly quickly, but it's just not going to happen for a while," he said. "I think we're committed at this point."

There are some positive aspects to the ice melting, he said. Ships could use the Northwest Passage to save time and energy by no longer having to travel through the Panama Canal or around Cape Horn.

"There's also, or course, oil at the bottom of the Arctic Ocean," he said. "Now, the irony of that is kind of clear, but the fact that we are opening up the Arctic Ocean does make it more accessible."

The U.S. National Snow and Ice Data Center Web site, NSIDC.org, publishes a near-real-time image of the Arctic sea ice cover.

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