A "northern sea route" along the Siberian coast would be almost 40 percent shorter than the current Europe-Asia route, which requires a lengthy detour through the Suez Canal.

"Perhaps by the mid-century, this route will be used because the other routes do have some security elements," said Lawson Brigham, the deputy director and Alaska office director of the US Arctic Research Commission.

This positive consequence of the melting ice cap contrasts starkly with otherwise dire predictions for climate change in the Arctic, as researchers warned of rising sea levels and the extinction of some species, such as polar bears which need the ice to access their prey.

Traditional shipping routes, which often require a passage through either the Suez or Panama canals, are risky. In the first three months of this year, 22 sailors were killed in acts of piracy, which are relatively common off the coast of Indonesia and the Malacca Strait, for example.

Terrorists also target the merchant navy, as illustrated by the 2002 Al-Qaeda attack on the French supertanker Limburg off the coast of Yemen, in which one crewman died and 12 others were injured.

Brigham said a trans-Arctic route could be of particular interest for transports of sensitive cargo, such as Japanese nuclear waste sent to Europe for treatment, to prevent the materials from falling into the hands of terrorists.

Ships can already sail through the Arctic Ocean about 20 or 30 days a year, but this period could be extended to up to 150 days for ships with ice-strengthened hulls around the year 2080, according to a report by an Arctic climate research team being discussed by researchers at a conference in Reykjavik.

"The question is whether this could be a year-round route," Brigham said, noting that "some small shipping companies are already making plans".

Once the Arctic ice melts, activities on the waterway will abound.

Currently the domain of icebreakers, the Arctic Ocean will in the future be increasingly open to local fishing trawlers and cruise liners for adventurous travellers, while indigenous populations will increasingly use their canoes and kayaks for transport and traditional activities such as hunting and fishing.

But before a trans-Arctic route can be a reality a number of scientific, economic and geopolitical issues need to be resolved.

In addition to questions about what the Arctic will look like in the future -- which will determine its navigability -- doubts remain about the financial profitability of a northern passage.

While two weeks could be shaved off the Osaka-Rotterdam shipping route, a route across the Arctic Ocean would most likely only be approved for vessels with ice-strengthened hulls.

That would increase ship construction and operation costs because in the winter months, these heavier and slower vessels would still have to use the traditional routes.

In addition, thorny issues of sovereignty and borders would have to be resolved given that international waters make up only a small portion of the vast Arctic Ocean.

Opposition from environmentalists would also certainly enter into the picture.

"The question is not whether an accident is going to happen but when and where," said Samantha Smith, the head of the WWF environmental organisation's Arctic programme.

"Technically we do not know how to clean an oil spill on ice," she said, stressing that "governments must set very strict environmental rules before shipping may take place in the Arctic."

Yet experts said they did not expect any extensive commercial use of the northern passage for a number of decades.

"There won't be any boom in the coming future since the ice won't significantly retreat before 30 or 40 years," Walter Parker, chairman of the Arctic Council Circumpolar Infrastructure Task Force, said.

Container ships are too big to navigate the often shallow waters off the Russian coast and oil tankers have no reason to sail that route, he said.

"Things might change dramatically if they find oil off the Russian northern coast but they have not found anything yet," he said.