PARIS – Arctic ice has shrunk to the lowest level on record, new satellite images show, raising the possibility that the Northwest Passage that eluded famous explorers will become an open shipping lane.

The European Space Agency said nearly 200 satellite photos this month taken together showed an ice-free passage along northern Canada, Alaska and Greenland, and ice retreating to its lowest level since such images were first taken in 1978.

The waters are exposing unexplored resources, and vessels could trim thousands of miles from Europe to Asia by bypassing the Panama Canal. The seasonal ebb and flow of ice levels has already opened up a slim summer window for ships.

An officials of the Danish National Space Center, Leif Toudal Pedersen, said that Arctic ice has shrunk to some 1 million square miles. The previous low was 1.5 million square miles, in 2005.

“The strong reduction in just one year certainly raises flags that the ice (in summer) may disappear much sooner than expected,” Mr. Pedersen said in an ESA statement posted on its Web site Friday.

Mr. Pedersen said the extreme retreat this year suggested the passage could fully open sooner than expected — but ESA did not say when that might be. Efforts to contact ESA officials in Paris and Noordwik, the Netherlands, were unsuccessful yesterday.

A U.N. panel on climate change has predicted that polar regions could be virtually free of ice by the summer of 2070 because of rising temperatures and sea ice decline, ESA noted.

Russia, Norway, Denmark, Canada and the United States are among countries in a race to secure rights to the Arctic that heated up last month when Russia sent two small submarines to plant its national flag under the North Pole. An American study has suggested as much as 25 percent of the world’s undiscovered oil and gas could be hidden in the area.

Environmentalists fear increased maritime traffic and efforts to tap natural resources in the area could one day lead to oil spills and harm regional wildlife.

Until now, the passage has been expected to remain closed even during reduced ice cover by multiyear ice pack — sea ice that remains through one or more summers, ESA said.

A Researcher at Norway’s Fridtjof Nansen Institute, which works on Arctic environmental and political issues, Claes Ragner, said for now, the new opening has only symbolic meaning for the future of sea transport.

“Routes between Scandinavia and Japan could be almost halved, and a stable and reliable route would mean a lot to certain regions,” he said by phone.

But even if the passage is opening up and polar ice continues to melt, it will take years for such routes to be regular, he said.

“It won’t be ice-free all year around and it won’t be a stable route all year,” Mr. Ragner said. “The greatest wish for sea transportation is streamlined and stable routes.”

“Shorter transport routes means less pollution if you can ship products from A to B on the shortest route,” he said, “but the fact that the polar ice is melting away is not good for the world in that we’re losing the Arctic and the animal life there.”

The opening observed this week was not the most direct waterway, ESA said. That would be through northern Canada along the coast of Siberia, which remains partially blocked.

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