NEW data collected by the Catlin Arctic Survey, led by the Dartmoor explorer Pen Hadow, provides more evidence that the Arctic Ocean sea ice is thinning.

Measurements of ice thickness collected by his team earlier this year, supports the emerging view that the ocean will be largely ice-free during summer within a decade.

The data, collected by manual drilling and observations on a 450-kilometre route across the northern part of the Beaufort Sea, suggests the survey area is comprised almost exclusively of first-year ice.

This is significant because the region has traditionally contained older, thicker multi-year ice. The average thickness of the ice-floes measured 1.8 metres, a depth considered too thin to survive next summer's ice melt.

These findings have been analysed by the Polar Ocean Physics Group at the University of Cambridge, led by Professor Peter Wadhams, one of the world's leading experts on sea ice cover in the North Pole region.

'With a larger part of the region now first year ice, it is clearly more vulnerable,' said Professor Wadhams. 'The area is now more likely to become open water each summer, bringing forward the potential date when the summer sea ice will be completely gone.'

He now estimates that the Arctic will be ice-free in summer within about 20 years, with much of the decrease happening within ten years.

'That means you'll be able to treat the Arctic as if it were essentially an open sea in the summer and have transport across the Arctic Ocean.'

According to scientists who have studied the data, the technique used by the explorers to take measurements on the surface of the ice has the potential to help ice modellers to refine predictions about the future survival or decline of the ice.

Expedition leader Mr Hadow said: 'This is the kind of scientific work we always wanted to support by getting to places in the Arctic which are otherwise nearly impossible to reach for research purposes. It's what modern exploration should be doing. Our on-the-ice techniques are helping scientists to understand better what is going on in this fragile ecosystem.'

Reduced ice cover will lead to more greenhouse gases being released from the vast store of carbon currently in the frozen Arctic region. The loss of more sea ice will accelerate melting of the Greenland Ice Sheet, speeding global sea level rises, in turn causing more flooding which could potentially affect one-quarter of the world's population.