Climate change

Arctic sea ice at lowest recorded level, US centre says

"We're in uncharted territory," US scientists warn after summer melt leads to smallest cover

PUBLISHED : Friday, 21 September, 2012, 12:00am
UPDATED : Friday, 21 September, 2012, 4:31am


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Arctic sea ice has shrunk to its smallest surface area since record-keeping began, taking the world into "uncharted territory" as climate change intensifies, US scientists warned.

Satellite images show the ice cap has melted to 3.4 million square kilometres as of Sunday, the predicted lowest point for the year. That's the smallest Arctic ice cover since record-keeping began in 1979, according to the National Snow and Ice Data Centre.

"We are now in uncharted territory," the centre's director Dr Mark Serreze said. "While we've long known that as the planet warms up, changes would be seen first and be most pronounced in the Arctic, few of us were prepared for how rapidly the changes would actually occur."

Arctic sea ice expands and contracts seasonally, with the lowest extent usually occurring in September. This year's minimum followed a season already full of records for shrinking ice. In the last two weeks, the ice cover melted by more than 518,000 sq km, a large margin for summer's end.

"The strong late season decline is indicative of how thin the ice cover is," said Dr Walt Meier, a scientist with the centre. "Ice has to be quite thin to continue melting away as the sun goes down and autumn approaches."

Scientists use Arctic sea ice extent as a gauge of the overall climate. Despite year to year fluctuations from natural weather variations, the ice cap has shown a clear trend towards shrinking over the past 30 years, according to the centre. "This year's minimum will be nearly 50 per cent lower than the 1979 to 2000 average," it said.

The centre, based in the US state of Colorado, said the Arctic was shifting in composition. Whereas most of the ice previously stayed frozen through several summers, much of it now melts and refreezes each season.

"Twenty years from now in August, you might be able to take a ship right across the Arctic Ocean," once blocked year-round by ice, said Dr Julienne Stroeve, a scientist with the centre. Models predict "ice free conditions" before 2050, she said, but the decline appeared to be happening faster than predicted.

Environmental group Greenpeace lamented the announcement, expressing hope it would trigger a sense of urgency for action to slow the trend. "In just over 30 years, we have altered the way our planet looks from space, and soon the North Pole may be completely ice free in summer," Greenpeace chief Kumi Naidoo said.

"I hope future generations will mark this day as a turning point, when a new spirit of global co-operation emerged to tackle the huge challenges we face."