"This glacier is dying," guide Eirik Karlsen said on a visit to a tunnel through the ice left by last summer's melt water cascading through the heart of the fast-retreating 3 km (2 mile) long glacier above the village of Longyearbyen.

The tunnel, big enough to walk along with ice stalactites hanging from the roof, snakes its way 15 metres below the surface of the Longyearbyen Glacier and shows that huge volumes of water flowed down towards the valley in 2006.

"In the end, the roof here will collapse," Karlsen told a group of visitors. "Hopefully not today." He said it was hard to blame the melt squarely on global warming. The glacier only formed 2,000 years ago when snowfall patterns changed.

Many residents say bone-chilling temperatures, blizzards and storms always vary drastically from year to year around the world's most northerly village, with or without global warming.

Still, UN climate experts says the Arctic is heating up faster than the rest of the planet because of global warming, threatening human livelihoods and species such as polar bears that depend on sea ice for hunting seals.

They say dark sea water and land, once exposed, soaks up more heat than ice and snow. Glaciers are in retreat in many parts of the world, from the Alps to the Himalayas, and could push up sea levels in coming decades and centuries.

WARMER

"In winters it hasn't been so cold recently," said Andreas Umbreit, who has lived in Svalbard for 21 years, adding that the lowest temperature in the past winter had been about -25 degrees Celsius (-13 degrees Fahrenheit), against a more normal -30.

"The water in the Longyearbyen fjord has no ice, just as last year," he said. Other years, he said, the fjord was frozen in late April. But he said that the climate always varied.

Snow buntings, which arrive from Siberia at the end of the winter, turned up about a week earlier than normal. Little auks also migrated to the islands early, residents say.

People have been little affected by the melt. The main business is a coal mine and food is imported from the Norwegian mainland to the south. Buildings are already built on high stilts to protect against any thaw of permafrost.

The Norwegian Polar Institute says that a melt of glaciers in western Svalbard, such as Longyearbyen glacier, has clearly accelerated in recent years. Others have held their ground.

"Smaller sea ice means problems for polar bears and seals which depend on the ice for their hunts," said Miriam Geitz of the WWF environmental group.

Two climate activists studying the region stripped off to swimming costumes and sat on the ice by the fjord to highlight risks of climate change.