The Arctic ice cap will disappear completely in summer months within 20 to 30 years, a polar research team said as they presented findings from an expedition led by adventurer Pen Hadow.
It is likely to be largely ice-free during the warmer months within a decade, the experts added.
Veteran polar explorer Hadow and two other Britons went out on the Arctic ice cap for 73 days during the northern spring, taking more than 6,000 measurements and observations of the sea ice, AFP reports.
Peter Wadhams, professor of ocean physics at the University of Cambridge, said much of the melting will take place within a decade, although the winter ice will stay for hundreds of years.
The changes will mean the top of the Earth will appear blue rather than white when photographed from space and ships will have a new sea route north of Russia.
Scientists say evidence of melting Arctic ice is one of the clearest signs of global warming and it should send a warning to world leaders meeting in Copenhagen in December for U.N. talks on a new climate treaty.
"The data supports the new consensus view -- based on seasonal variation of ice extent and thickness, changes in temperatures, winds and especially ice composition -- that the Arctic will be ice-free in summer within about 20 years," Wadhams said in a statement. "Much of the decrease will be happening within 10 years."
Ed Miliband, the Energy and Climate Change Secretary, said the findings set out the "stark realities of a rapidly changing climate" and "illustrated the risk of an ice free summer in the Arctic in the not-too-distant future".
"This further strengthens the case for an ambitious global deal in Copenhagen in December which the UK is fully committed to achieving," he said.
Dr Martin Sommerkorn, from the WWF International Arctic Programme, warned there was "no time to lose".
"Countries must see these results and think there is no alternative.
"We must deal with the problem and make investments. Humankind and our way of life is at stake," SKY News informs.
On the second day of the St. Petersburg International Economic Forum, a plenary meeting was held, in which Russian President Vladimir Putin, French President Emmanuel Macron, Japanese Prime Minister Shinzo Abe, Chinese Vice President Wang Qishan and IMF head Christine Lagarde took part