A large gas tanker ship is set to sail across the arctic from Europe to Japan, now possible with changing climate conditions, officials said.

The Ob River, a large tanker carrying liquefied natural gas, left Norway Nov. 7 and has sailed north of Russia on its way to Japan, using an arctic route that will take 20 days off the regular journey and have it arrive in Japan in early December, the BBC reported Sunday.

The retreating ice is opening up new sea routes from the Atlantic to the Pacific: the Northwest Passage above Canada and the Northeast Passage north of Russia.

A Russian nuclear-powered icebreaker has been accompanying the OB River for much of its voyage, the first attempted arctic crossing for a tanker ship of its type.

The decision to use the northern route was prompted by the recent scientific record on melting in the arctic, the ship's owners said.

"We have studied lots of observation data -- there is an observable trend that the ice conditions are becoming more and more favorable for transiting this route," Tony Lauritzen, commercial director of the Greek company Dynagas, said. "You are able to reach a highly profitable market by saving 40 percent of the distance, that's 40 percent less fuel used as well."

"It's an extraordinarily interesting adventure," he said. "The people on board have been seeing polar bears on the route. We've had the plans for a long time and everything has gone well."

The giant Russian Gazprom energy company has chartered the Ob River for the voyage.