The Arctic ice cap is close to its record lowest level with a fortnight remaining until the end of the melt season.
Scientists in the US said the loss of ice in the Arctic this summer was likely to be greater than in 2007, when the previous record was set.
Five years ago, the ice crap shrank by more than 1.5 million square miles but with two weeks of the summer season still to go, this year is likely to see a significant loss.
"The numbers are coming in and we are looking at them with a sense of amazement," said Mark Serreze, director of the National Snow and Ice Data Center at the University of Colorado.
"If the melt were to just suddenly stop today, we would be at the third lowest in the satellite record. We've still got another two weeks of melt to go, so I think we're very likely to set a new record."
An Arctic cyclone earlier this month was said to be a contributory factor to the decline but Mr Serreze said the lack of extraordinary weather influences made the melt more remarkable.
He added it was possible that the rapid melt had played a part in severe storms in the US in recent years as it changed the nature of the planet's temperature gradients.
"The ice now is so thin in the spring just because of the general pattern of warming that large parts of the pack ice just can't survive the summer melt season anymore," he said.
As more of the ice cap thaws, Arctic-bordering countries including Russia, Canada, Denmark, Norway and the US were expected to start considering the ocean for trade.
The first ship from China - the Xuelong, or Snow Dragon - recently sailed from the Pacific to the Atlantic through the Arctic Ocean, cutting the distance by more than 40 percent.
Egill Thor Nielsson, an Icelandic scientist who participated in the expedition, said he predicted China would be increasingly interested in the route as it was relatively easy to sail.