The North Pole has become an island for the first time in human history as climate change has made it possible to circumnavigate the Arctic ice cap.
The historic development was revealed by satellite images taken last week showing that both the north-west and north-east passages have been opened by melting ice.
Prof Mark Serreze, a sea ice specialist at the National Snow and Ice Data Centre (NSIDC) in the US said the images suggested the Arctic may have entered a "death spiral" caused by global warming.
Shipping companies are already planning to exploit the first simultaneous opening of the routes since the beginning of the last Ice Age 125,000 years ago. The Beluga Group in Germany says it will send the first ship through the north-east passage, around Russia, next year, cutting 4,000 miles off the voyage from Germany to Japan.
Meanwhile, Stephen Harper, Canada's Prime Minister, has announced that ships entering the north-west passage should first report to his government. The routes have previously opened at different times, with the western route opening last year, and the eastern route opening in 2005.
The satellite images gathered by Nasa show that the north-west passage opened last weekend and the final blockage on the east side of the ice cap, an area of sea ice stretching to Siberia, dissolved a few days later.
Last year the extent of sea ice in the Arctic reached a record low that could be surpassed in the next few weeks, with some scientists warning that the ice cap could soon vanish altogether during summer.
Four weeks ago tourists had to be evacuated from a park on Baffin Island because of flooding caused by melting glaciers, and polar bears have been spotted off Alaska trying to swim hundreds of miles to the retreating ice cap.
Measurements on August 26 showed an ice cap of just over two million square miles, confirming the second biggest ice cap melt since records began. News of the opening of the passages emerged as the British explorer and adventurer Lewis Gordon Pugh began a kayak expedition to the North Pole aimed at drawing attention to the dramatic impact of melting polar ice.
"I want to bring home to world leaders, on this expedition, the reality of what is now happening here in the Arctic," said the 38-year-old environmentalist in his blog.
"The rate of change is clearly faster than nearly all the models predict, which has huge implications for climate change and how to tackle it."
Meanwhile Prof James Lovelock, of the University of Oxford, has claimed "planet-scale engineering of the climate" may have to be attempted to counter global warming.