An enormous iceberg the size of central London is causing alarm among scientists, who predict that it could be on the move in a matter of months, posing a potential threat to shipping and oil rigs in Arctic waters.
The two-million-ton, 25-square-mile block of ice is part of the Ayles ice shelf. Its existence only recently came to light thanks to satellite images from Nasa. Lying 30 miles off Canada's Ellesmere Island, it will be on the move in the summer, as temperatures rise and break up the surrounding pack ice.
"The potential issue here is that the ice island could go into the oil rigs in the Beaufort Sea," said Dr Luke Copland, a specialist in ice masses based at the University of Ottawa. "This hasn't happened in the past, but it could happen."
The ice could move several hundred miles over the summer, taking it closer to busy shipping routes for oil and gas. "If it ever came on a collision course with an oil rig, it is unlikely that we would be able to do much to stop it," said Dr Copland. "Maybe you would have to consider aerial bombardment to break it up, or use lots of tugs to try and move it, but it would be a lot of ice to move."
Tugs are already on permanent standby along Canada's coastline to lasso stray icebergs and tow them away from busy shipping routes, but researchers say controlling the main mass, dubbed "ice island", would be a completely different proposition.
Scientists blame global warming. "This is the most dramatic climate-related event we've seen in recent times in the high Arctic," said Professor Warwick Vincent of Laval University in Quebec. "We think it was associated with record warm temperatures and record minimum sea ice. Of course these days, every year sets a new record. The ice island has already moved 50km [30 miles] to the west, and could eventually end up in shipping and oil-exploration areas."
Scientists in Canada and the US have stepped up their monitoring of the ice as they attempt to predict where and when it is likely to go next. A team of researchers will visit the ice island in March, before it starts to move in the summer. It is thought most likely to follow a clockwise current in the Arctic Ocean, known as the Beaufort Gyre, that could see it reach the eastern coast of Greenland in 10 years. The warmer waters of the Atlantic would prevent it from travelling further south.
Climate change is altering the region's landscape. The Ayles ice shelf, thought to be 4,000 years old, was one of just six remaining on Ellesmere Island, Canada's most northern landmass. The ice shelves there have shrunk by up to 90 per cent in the past century - a loss of 3,500 square miles of ice, along with an unknown number of life forms.
Experts now claim the next 10 years could see massive changes in sea ice in the region. Researchers from the Canadian Ice Service have already seen average temperatures for the past few months 7C higher than they would normally expect.
"There is a lot more fracturing of the sea ice than we'd normally see at this time of year," said Dr Copland. "When you look at Arctic sea ice, it has been reducing dramatically over the past 30 years and it is hard to explain why that would happen without invoking climate warming."