WASHINGTON — An already relentless melting of the Arctic greatly accelerated this summer, a warning sign that some scientists worry could mean global warming has passed an ominous tipping point. One even speculated that summer sea ice would be gone in five years.
Greenland’s ice sheet melted nearly 19 billion tons more than the previous high mark, and the volume of Arctic sea ice at summer’s end was half what it was just four years earlier, according to new NASA satellite data.
“The Arctic is screaming,” said Mark Serreze, senior scientist at the government’s snow and ice data center in Boulder, Colo.
Just last year, two top scientists projected that Arctic sea ice was melting so rapidly that it could disappear entirely by the summer of 2040.
This week, after reviewing his own new data, NASA climate scientist Jay Zwally said the Arctic Ocean could be nearly ice-free in 2012, “much faster than previous predictions.”
“The Arctic is often cited as the canary in the coal mine for climate warming,” said Zwally. “Now as a sign of climate warming, the canary has died. It is time to start getting out of the coal mines.”
It is the burning of coal, oil and other fossil fuels that produces carbon dioxide and other gases that scientists say leads to global warming.
What happens in the Arctic has implications for the rest of the world. Faster melting there means eventual sea level rise and more immediate changes in winter weather because of less sea ice.
In the United States, a weakened Arctic blast moving south to collide with moist air from the Gulf of Mexico can mean less rain and snow in some areas, including the drought-stricken Southeast, said Michael MacCracken, a former federal climate scientist who now heads the nonprofit Climate Institute. Some regions would likely get extra rain or snow.
More than 18 scientists said they were surprised by the level of ice melt this year.
“I don’t pay much attention to one year … but this year the change is so big, particularly in the Arctic sea ice, that you’ve got to stop and say, ‘What is going on here?’ You can’t look away from what’s happening here,” said Waleed Abdalati, NASA’s chief of cyrospheric sciences. “This is going to be a watershed year.”
Shattered records
Records were shattered this year for Arctic melt in the following ways:
552 billion tons of ice melted this summer from the Greenland ice sheet, according to preliminary satellite data to be released by NASA today. That’s 15 percent more than the annual average summer melt, beating 2005’s record.
A record amount of surface ice was lost over Greenland this year, 12 percent more than the previous worst year, 2005, according to data the University of Colorado released Monday. That’s nearly quadruple the amount that melted just 15 years ago.
The surface area of summer sea ice floating in the Arctic Ocean this summer was nearly 23 percent below the previous record. The dwindling sea ice already has affected wildlife, with 6,000 walruses coming ashore in northwest Alaska in October for the first time in recorded history. Another first: the Northwest Passage was open to navigation.
NASA data shows the remaining Arctic sea ice to be unusually thin, another record. Scientists calculate that the overall volume of ice is half of 2004’s total.
Surface temperatures in the Arctic Ocean this summer were the highest in 77 years of record-keeping, with some places 8 degrees Fahrenheit above normal, according to research to be released today by University of Washington’s Michael Steele.
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