ARCTIC ice has shrunk to the lowest level ever recorded, according to satellite data from the past week that shows a massive melt is still under way.
The ice cap had contracted to just over four million square kilometres, about 77,000 square kilometres smaller than the previous record low in 2007, data from the International Arctic Research Centre and the Japan Aerospace Exploration Agency indicates.
With two or three weeks of warm temperatures yet to come, the area covered by ice may fall yet further, to below four million square kilometres.
It means that, unless the pole grows dramatically cooler, the Arctic ice cap is very likely to vanish entirely during summer by the middle of this century.
''This is significant, because the trend is strongly down and it is consistent with the polar amplification effect,'' said Will Steffen, the executive director of the Australian
National University's Climate Change Institute.
''Polar amplification is where the Arctic is experiencing about double the temperature rise of the global average.
''Because as the ice melts it uncovers darker water beneath, which traps more heat - it creates feedback.
''We can expect to see an ice-free Arctic at about the middle of this century.'' The last time the Arctic ice cap vanished is thought to have been about 130,000 years ago.
Back then, average global temperatures were about 1.5 degrees Celsius above the average for pre-industrial times.
Today, the temperature has already risen a degree above the pre-industrial average, driven mainly by human greenhouse gas emissions, with about half a degree of further warming already ''locked in'' by levels of emissions.
''I'm not that interested in the breaking of records in itself, because the key thing is the downward movement over the last 30 or 40 years of data,'' Professor Steffen said.
His colleague at Australia's Climate Commission, Macquarie University's Lesley Hughes, agreed.
''This is consistent with the trend we've been seeing up until now, and it seems to be accelerating, which is very concerning,'' Professor Hughes said.
The record low appears to have been accelerated by unusual polar weather, including storms which can break up ice, as well as well above-average heat.
The US National Snow and Ice Data Centre, which keeps separate satellite records of the extent of sea ice, is expected to publish further results over the next week to confirm record-breaking low.