The Arctic ice cap is on track to completely disappear within 100 years, US scientists have warned.
This year saw the warmest Arctic summer in 400 years. A joint study by the National Snow and Ice Data Centre (NSIDC) and NASA reveals that the polar ice pack has shrunk by 30 per cent since 1978 and that melting is speeding up.
NSIDC scientist Mark Serreze said: "The year 2005 puts an exclamation point on the pattern of Arctic warming we've seen in recent years.
"The sea ice cover seems to be rapidly changing and the best explanation for this is rising temperatures." The study said the Arctic may be caught in a vicious loop caused by global warming.
As sea ice melts there is less to reflect the sun's radiation back into space. Dark, ice-free seas absorb more of the sun's heat and warm the planet. Experts fear that the downward trend is reaching a tipping point from which the ice will not recover.
By the end of the century, and possibly much earlier, the region is likely to be ice-free through the summer months - pushing temperatures not seen there for around a million years.
Ted Scambos, NSIDC lead scientist, warned: "Feedbacks in the system are starting to take hold." Experts said that even if ice retreats significantly one summer, it makes a comeback the following winter when temperatures fall well below freezing.
But last winter ice levels did not fully build back up, leaving it even more susceptible to warmer summer temperatures. This year is expected to see the lowest amount of ice cover in more than a century.
Whole villages are said to be falling into the sea, forcing people to relocate. The decline will also have a huge impact on Arctic animals. Polar bears spend summer on land using stored fat until they can return to the ice, but as it disappears they will starve.