Arctic sea ice at record low level
The amount of sea ice in the Arctic has fallen to the lowest level on record, a confirmation of the drastic warming in the region and a likely harbinger of larger changes to come.
Satellites tracking the extent of the sea ice found over the weekend that it covered about 1.58 million square miles, or less than 30 per cent of the Arctic Ocean's surface, scientists said.
That is only slightly below the previous record low, set in 2007, but with weeks still to go in the summer melting season, it is clear that the record will be beaten by a wide margin.
The National Snow and Ice Data Centre, a government-sponsored research agency in Boulder, Colorado, announced the findings last night in collaboration with Nasa.
The amount of sea ice in summer has declined more than 40 per cent since satellite tracking began in the late 1970s, a trend that most scientists believe is primarily a consequence of human activity.
"It's hard even for people like me to believe, to see that climate change is actually doing what our worst fears dictated," said Jennifer A Francis, a Rutgers University scientist who studies the effect of sea ice on weather patterns.
"It's starting to give me chills, to tell you the truth."
Scientific forecasts based on computer modelling have long suggested that a time will come when the Arctic will be completely free of ice in the summer, perhaps by the middle of the century.
This year's prodigious melting is lending credibility to more pessimistic analyses that it may come much sooner, perhaps by the end of the decade.
"It's an example of how uncertainty is not our friend when it comes to climate-change risk," said Michael E Mann, a climate scientist at Pennsylvania State University.
"In this case, the models were almost certainly too conservative in the changes they were projecting, probably because of important missing physics."
Experts say that a large storm in the Arctic this summer may have contributed to setting the record. But it would not have happened, they say, if the ice had not been steadily contracting for the past several decades.
The pace of that decline seems to be accelerating.
But scientists are somewhat cautious in their predictions, given that sea ice is prone to natural variability.
They have only a 33-year record of careful satellite observations, and before that, only sketchy data from maps and other historical sources.
By itself, the melting of sea ice does not raise global sea levels, because the floating ice is already displacing its weight in seawater. But the sharp warming that is causing the sea ice to melt also threatens land ice, notably the Greenland ice sheet, which is melting at what appears to be an accelerating pace, and melting land ice does raise sea levels.