Global warming has forced two teenage adventurers off their skis and into frozen Arctic waters within miles of the North Pole.

James Hooper and Rob Gauntlett have set off on a 22,000 mile, 180-degree journey across the earth from pole to pole.

The intrepid pair, both 19, of Christ's Hospital School in Horsham, have been walking alone through the frozen tundra of the Arctic in temperatures of -30 degrees Centigrade.

Yet within four days and 30 miles of the pole they found the ice was melting, forcing them to swim.

The teenagers had to don immersion suits to cross one stretch of open water, dragging their sleds of gear behind them on ropes.

In video footage now showing on www.theargus.co.uk, Rob, whose parents live in Petworth, said: "We've just come across water, which is absolutely unheard of at this time of year but we've come well prepared.

"I'm just going to have to jump in this and hopefully make my way across. It could be full of walruses, seals or even polar bears so we do have to be careful."

After successfully negotiating the frozen water in their plastic jackets, James said: "The ice here is very unstable - a consequence of global warming. The local hunters have told us it is the worst it has ever been."

James and Rob became the youngest Britons ever to reach the summit of Mount Everest in May 2006.

Now they hope to become the first to travel from the North to South Pole using only human and natural power - walking, cycling, skiing and sailing.

The teenagers, who first met at the boarding school when they were 11, said the adventure is as much about environmental awareness as believing "you really can do anything if you put your mind to it".

They have so far covered about 150 miles, with days spent locked in their tents due to the impenetrable weather.

After a week the sleds they had been using to carry their equipment began splitting.

James, originally from Somerset, said: "We've encountered some very rocky and rough terrain which hasn't wholly agreed with our sleds. As such we've had to bodge a few repairs."

Their tent has since been battered and broken by howling winds as they try to sleep.

Rob said: "It's taken us a long time to get our hands warm and prepare to put up the tent because it's so desperately cold.

"Even the moisture around my eye lashes has frozen. It's very uncomfortable."

The pair have since recuperated at an Inuit hunters' settlement and are now travelling to Thule airbase in Greenland, 930 miles south of the North Pole which was built as a US listening post during the Cold War.

But Jon Winchester, the assistant expedition manager, said they were all shocked by the environmental damage witnessed at the geo-magnetic tip of the globe.

He said: "The conditions up there have been changing so fast its a real problem especially for the people living there.

"The guys are well though, all in one piece, and with only a few broken tent poles and a battered sled so far."

The Argus website is featuring regular video updates of the boys' adventures. For more information visit www.180degrees.co.uk.