The Northwest Passage - without ice

A Canadian police patrol boat has completed a voyage through the fabled Northwest Passage without encountering any pack ice.

It opens up the possibility of commercial shipping using a route which would shorten the journey between Europe and Asia by about eight-thousand kilometres (5,000 miles).

It's hubris to think human influence is going to melt the Pole

Jim Delgado, expedition leader

Most of the passage along the coast of Alaska and Canada lies north of the Arctic Circle and scientists say that the absence of ice may be further evidence of global warming.

But conservationists are concerned that commercial exploitation could irreversibly damage the pristine environment, particularly if the route is used by oil tankers.

The Canadian patrol boat the St Roch II - renamed after an earlier Canadian expedition in 1944 - made the journey in nine weeks, less than half the time expected.

The long quest

In contrast, the first successful attempt at the passage by Norwegian Roald Amundsen in 1906 took three years, with two winters being spent stuck fast in the ice.

The search for an ice-free route linking the Atlantic and the Pacific has been the goal of sailors for more than 400 years.

Hundreds died in the quest for a shorter passage between Europe and the Far East.

Scientists who have been monitoring the Arctic icecap say it is melting more and more each summer and its size has been reduced by 6% since 1980.

Scientific surveys of the Arctic by British and American submarines show that the thickness of the ice has been reduced by nearly half in the past 50 years.

Last month it was revealed that a large area of water had opened up at the North Pole.

In parts of the Arctic, researchers have found, temperatures have risen significantly in a very short time.

Parts of Alaska and northern Eurasia, for example, have warmed by nearly six degrees Celsius (11 degrees Fahrenheit) in the winter months since the early 1970s.

But the leader of the St Roch II expedition, Jim Delgado, warned that the North has not yet been tamed.

"The fangs grow back," he said on the team's website. "It's hubris to think human influence is going to melt the Pole."