British explorers walking to to the North Pole on a mission to gauge how fast Arctic ice sheets are melting say they are surprised by how little permanent ice they have found so far.

The three adventurers set off in early March on a 620-mile (1,000 km) trek from Canada's Arctic to the North Pole. The team was set down in an area where scientists had been sure there would be permanent multiyear ice.

But so far, the average depth of the ice has been just under 1.8 meters (6 feet), indicating they are finding predominantly new first year ice that is likely to melt in summer months.

"To discover that there's virtually no multiyear ice in this part of the (Arctic) is a real surprise to me," the team quoted lead explorer Pen Hadow as saying this week.

The team said the findings pointed to an ever-smaller summer ice covering around the Pole this year.

One top polar expert said last month the Arctic is warming so quickly that the summer sea ice cover could vanish as early as 2013, decades earlier than some had predicted.

The Arctic is warming at twice the rate of the rest of the world and the sea ice cover shrank to a record low in 2007 before growing slightly in 2008.

Scientists link Arctic warming to the greenhouse gas emissions blamed for global warming.

Hadow and his two companions have also discovered that the snow cover on top of the ice is thinner than they had expected, said Chip Cunliffe, the team's head of operations.

"What we were looking at was potentially that we would start in an area of multiyear ice and then move over into first year ice as they headed north," he told Reuters in a phone interview on Friday.

"The average thickness ... is obviously telling us that it's more likely to be first year ice than anything else."

Summer ice tends to be concentrated around the North Pole while much of the thicker multiyear ice is clumped around the islands of Canada's Arctic archipelago.

"What we are finding is that amount of multiyear ice around the archipelago is probably thinner than might have been expected," said Cunliffe. He declined to say what he thought might have caused this, saying he would let the team's scientists analyze the data.

The team spends four hours a day drilling into the ice to take measurements. Hadow has a manual drill that can go down 5.2 meters and so far has hit ice that deep just four times.

"If we'd had more multiyear ice there it's more likely that he would have got (that deep) on more than just four occasions," Cunliffe said.

The team had planned to use an experimental portable radar set to measure the ice more accurately but had to resort to the drill after the intense cold knocked out the radar.

The three explorers, who have covered about 380 km so far, are due to be picked up in late May.

The main sponsor for the three million pound ($5.4 million) expedition is British insurer Catlin

($1=0.56 pounds)

Reuters