Dynagas Ltd via EPA In this 2012 file photo, the liquefied natural gas carrier OB River moves through ice in the Arctic. A new study says melting ice there will open more routes to shipping.

By the middle of this century, thanks to climate change, anyone with a light icebreaker can spend their Septembers going anywhere they want in the Arctic Ocean, including straight over the North Pole, according to a new study.

Ordinary vessels, which account for more than 99 percent of shipping traffic, could easily navigate the Northern Sea Route along the Russian coastline and, in some years, even find a route through the fabled Northwest Passage.

"That’s kind of crazy and, frankly, a little bit worrisome," Laurence C. Smith, a geographer and sea ice expert at the University of California, Los Angeles, told NBC News. "It is not like these will be open blue seas and safe or open year round."

Nevertheless, the temptation is likely to prove irresistible to some shipping companies and adventurous tourists, which opens up new concerns about search and rescue infrastructure, the environmental impact from increased shipping traffic and the potential for oil spills, among other issues.

Smith and graduate student Scott Stephenson used the output of climate models to chart the fastest, most efficient, and realistic routes through the Arctic for different classes of ships that will become possible as more sea ice disappears each summer.

Proceedings of the National Academy of Sciences The fastest navigation routes for ships seeking to cross the Arctic Ocean by mid-century include the Northwest Passage (on the left) and over the North Pole (center), in addition to the Northern Sea Route (on the right).

New shipping routes through the Arctic can shave weeks off voyages between Europe and Asia and are often discussed as an upside to global warming. Most of the attention has focused on the Northern Sea Route, which is controlled by the Russians and requires expensive sea escorts to use.

The new findings, published today in the Proceedings of the National Academy of Sciences, indicate shipping companies willing to invest in light icebreaker technology, known as Polar Class 6 vessels, can avoid those fees by going over the North Pole or through the Northwest Passage.

Regular ships, too, will be able to navigate at least some of these routes unescorted. And, "it doesn’t matter whether we get serious about curbing the growth of greenhouse gas emissions or not," Smith said. "Either way, the result is the same. The ice will thin sufficiently."

But just because the routes are opening up, doesn’t necessarily mean shipping companies will race to take advantage, according to Lawson Brigham, a professor of geography and Arctic policy at the University of Alaska, Fairbanks.

He said the most likely users of the expanded shipping access are bulk cargo carriers hauling commodities such as oil and gas and hard minerals including nickel and zinc — the type of ships already plying the Russian coastline.

"It is the connection of natural resources to global markets that today and in the future is driving (Arctic) marine traffic," Brigham, who chaired the Arctic Marine Shipping Assessment for the Arctic Council, told NBC News.

Container ships of the sort that haul flat-screen TVs, iPhones, and IKEA furniture from factories in China to the U.S. and Europe are less likely to ply the new routes given the vagaries of ice and weather, which can wreak havoc on travel times for ships that must meet tight delivery schedules.

"It is possible" container ships would take the Northern Sea Route, Brigham said, "but the economics haven’t been worked out yet."

In addition to the economics of shipping, there are a host of development and political considerations the opening of these routes bring to the fore, according to Smith.

To start, there’s little infrastructure in place for search and rescue in the Arctic. Then there’re issues about whether the Northwest Passage is an international strait, as the U.S. maintains, or falls under Canada’s sovereignty as an internal domestic waterway.

"At the moment, the U.S. and Canada have a tacit agree-to-disagree policy on this because it doesn’t matter," Smith said. "But it could. The study suggests this needs to be resolved."

What’s more, the U.S. has yet to ratify the United Nations Convention on the Law of the Sea, a treaty that establishes international laws to govern the maritime rights of countries. If signed, the U.S. could claim sovereignty over some of the newly opened shipping lanes.

As these issues are sorted out – and Brigham said this study should help apply pressure to do so – increased access to shipping will almost certainly increase natural resource extraction in the Arctic.

"Whether the open access and greater shipping is a benefit to the world is an open book," he said. "We are going to produce even more oil and gas and carry it to the world and just enhance the (greenhouse gas) emissions. But the coastal states, all of us, want to develop our oil and gas."

John Roach is a contributing writer to NBC News. To learn more about him, check out his website.