Arctic sea ice has shrunk to its lowest level since records began, with Nasa warning that ice cover at the pole is "fundamentally changing."
According to scientists from Nasa and the National Snow and Ice Data Center in Boulder, Colorado, the ice cover is the smallest in the three decades since the polar cap has been monitored by satellite.
The ice is measured by a Special Sensor Microwave Imager, on a US spacecraft. The ice is currently 1.58 million square miles.
Today's ice is 27,000 square miles smaller than 2007, when 1.61 million square miles of ice were measured.
And the 2012 "melt season" could still continue for several weeks, resulting in an even larger loss of ice.
The sea ice cap naturally grows during the cold Arctic winters and shrinks when temperatures climb in the spring and summer.
But over the last three decades, satellites have observed a 13% decline per decade in the sea ice, which is measured when it is at its smallest, and the ice is steadily getting thinner.
Joey Comiso, senior research scientist at Nasa, said the results were particularly unusual, because temperatures had not been exceptionally warm.
He said: "The persistent loss of perennial ice cover - ice that survives the melt season - led to this year's record summertime retreat. Unlike 2007, temperatures were not unusually warm in the Arctic this summer."
"In 2007, it was actually much warmer. We are losing the thick component of the ice cover.
"And if you lose the thick component of the ice cover, the ice in the summer becomes very vulnerable.
NSIDC research scientist Walt Meier said: "By itself it's just a number, and occasionally records are going to get set.
"But in the context of what's happened in the last several years and throughout the satellite record, it's an indication that the Arctic sea ice cover is fundamentally changing."
Cambridge University's Professor Peter Wadhams, told BBC News: "A number of scientists who have actually been working with sea ice measurement had predicted some years ago that the retreat would accelerate and that the summer Arctic would become ice-free by 2015 or 2016.
"I was one of those scientists - and of course bore my share of ridicule for daring to make such an alarmist prediction."
Rod Downie, Polar Programme Manager for WWF-UK said the new research was concerning.
“It's likely that the loss of summer sea ice will result in dramatic changes to Arctic ecosystems, and have a profound effect on traditional lifestyles.
"Thousands of years of evolution have prepared Arctic species like the polar bear, walrus and narwhal for life on and around the sea-ice.
"But with the speed of change that we are now witnessing in the Arctic, it is uncertain whether ice-dependent species will be able to adapt fast enough.”