Global warming: Arctic sea ice hits record low

The blue line shows this year’s Arctic sea ice decline. Graph courtesy NSIDC.

With three more weeks of melting, this year’s decline likely to far exceed previous record

By Summit Voice

SUMMIT COUNTY — The ice trackers at the National Snow and Ice Data Center said today (Aug. 27) that Arctic Sea Ice appears to have dropped below the record low set in 2007 with a few more weeks left in the melt season.

Arctic sea ice coverage fell to 1.58 million square miles on Aug. 26, about 27,000 square miles below the Sept. 18, 2007 minimum. Forecasters expect the ice pack to shrink more before the melting season ends in late September.

Including this year, the six lowest ice extents in the satellite record have occurred in the last six years (2007 to 2012).

Sea ice melting was on an equal pace with 2007 throughout much of July. In early August, the rate increased dramatically, then slowed again, to about 29,000 square miles (about the size of South Carolina) per day, which is still faster than the average melt rate of about 15,000 square miles per day for this time of year.

“It’s a little surprising to see the 2012 Arctic sea ice extent in August dip below the record low 2007 sea ice extent in September,” said NSID researcher Walt Meier. “It’s likely we are going to surpass the record decline by a fair amount this year by the time all is said and done.”

On Sept. 18, 2007, the September minimum extent of Arctic sea ice shattered all satellite records, reaching a five-day running average of 1.61 million square miles, or 4.17 million square kilometers. Compared to the long-term minimum average from 1979 to 2000, the 2007 minimum extent was lower by about a million square miles — an area about the same as Alaska and Texas combined, or 10 United Kingdoms.

The decline seen in in recent years is well outside the range of natural climate variability, said Meier. Most scientists believe the shrinking Arctic sea ice is tied to warming temperatures caused by an increase in human-produced greenhouse gases pumped into Earth’s atmosphere.

CU-Boulder researchers say the old, thick multi-year ice that used to dominate the Arctic region has been replaced by young, thin ice that has survived only one or two melt seasons — ice which now makes up about 80 percent of the ice cover. Since 1979, the September Arctic sea ice extent has declined by 12 percent per decade.

The record-breaking Arctic sea ice extent in 2012 moves the 2011 sea ice extent minimum from the second to the third lowest spot on record, behind 2007. Meier and his CU-Boulder colleagues say they believe the Arctic may be ice-free in the summers within the next several decades.

“The years from 2007 to 2012 are the six lowest years in terms of Arctic sea ice extent in the satellite record,” said Meier. “In the big picture, 2012 is just another year in the sequence of declining sea ice. We have been seeing a trend toward decreasing minimum Arctic sea ice extents for the past 34 years, and there’s no reason to believe this trend will change.”

Scientists say Arctic sea ice is important because it keeps the polar region cold and helps moderate global climate — some have dubbed it “Earth’s air conditioner.” While the bright surface of Arctic sea ice reflects up to 80 percent of the sunlight back to space, the increasing amounts of open ocean there — which absorb about 90 percent of the sunlight striking the Arctic — have created a positive feedback effect, causing the ocean to heat up and contribute to increased sea ice melt.


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