Sea ice in the Arctic has sunk to its lowest level since satelliterecord-keeping began, fully opening the most direct route through the Northwest Passage, the European Space Agency said Friday.

Northwestpassage-ESA

The orange line on the satellite image shows the most direct route of the Northwest Passage, and the blue line shows the partially blocked Northeast Passage. Dark gray represents ice-free areas, and green is sea ice. ((European Space Agency))

The much-coveted shortcut connecting Asia to Europe through the Canadian Arctichas been historically impassable.

The European Space Agency says sea ice continues to melt year after year, but a drastic drop this year has made the direct route "fully navigable" for the first time since satelliterecords began in 1978.

"We have seen the ice-covered area drop to just around three million square kilometres," said Leif Toudal Pederson from the Danish National Space Center.

Over the past decade, he says, a drop of about 100,000 square kilometres per year is the average.

"So a drop ofone million square kilometres in just one year is extreme," said Toudal.

The ice loss has also meant the Northeast Passage, along the Siberian coast, is "only partially blocked," the space agency says.

First travelled in 1903

While usually impassable, the Northwest Passage has been open enough for some explorers to travel through, with the first to travel the entire route in 1903.

And from 1940 to 1942, an RCMP schooner navigated the passage from west to east, then back again in a show of Canadian sovereignty over the North.

As ashorter shipping route than the Panama Canal by 5,000 kilometres, the Northwest Passage is seen as the "Arctic Grail."

The promise of an openpassage has already led to international disputes.

Canada claims full rights tothe parts of thepassage running through its territory, saying it can control transit there. During the last election, Prime Minister Stephen Harper made a campaign promise to defend Canada's Arctic sovereignty.

Countriesdisputing Canada's claim argue the route should be open to all vessels.