Climate: Arctic sea ice now in ‘uncharted territory’

Arctic sea ice extent for September 16, 2012 was 3.41 million square kilometers (1.32 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Graphic courtesy NSIDC.

Low point reached Sept. 16; 293,000 square miles less ice than previous record in 2007

By Summit Voice

FRISCO — More than 4.5 million square miles of Arctic sea ice has melted away in the past six months, with the overall extent dipping 18 percent below the previous record low, set in 2007.

The ice appears to have reached its minimum on Sept. 16, according to the National Snow and Ice Data Center, and will grow once again for the next six months as long, cold nights prevail above the Arctic Circle.

The record ice loss came despite the fact that the region didn’t see extreme warmth. Temperatures were above-average, but colder than in 2007, when the previous record low ice extent was reached.

The six lowest seasonal minimum ice extents in the satellite record have all occurred in the last six years, 2007 to 2012.

“We are now in uncharted territory,” NSIDC Director Mark Serreze said in a release. “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.”

Ice researchers said many climate models still have not been able to capture the unexpectedly rapid rate of sea ice decline, leaving open the question of how soon the Arctic may be ice-free in the summer.

This year’s minimum follows a record-breaking summer of low sea ice extents in the Arctic. Sea ice extent fell to 4.10 million square kilometers (1.58 million square miles) on August 26, breaking the lowest extent on record set on September 18, 2007 of 4.17 million square kilometers (1.61 million square miles).

On September 4, it fell below 4.00 million square kilometers (1.54 million square miles), another first in the 33-year satellite record.

“The strong late season decline is indicative of how thin the ice cover is,” said NSIDC scientist Walt Meier. “Ice has to be quite thin to continue melting away as the sun goes down and fall approaches.”

NSIDC scientists have observed fundamental changes in the Arctic’s sea ice cover. The Arctic used to be dominated by multiyear ice, or ice that survived through several years. Lately, the Arctic is increasingly characterized by seasonal ice cover and large areas are now prone to completely melt away in summer.

The loss of thicker multi-year ice resulted in an unexpected late-season decline.

“The later minimum date is somewhat surprising because we expected that the late melt in the Chukchi and East Siberian seas would result in cool surface waters that would quickly refreeze once the atmosphere cooled,” Meier said. “However, ice loss continued north of the Kara and Laptev seas, opening up a gap in the ice cover that reduced extent.”

The dramatic loss of sea ice is considered to be a significant climate indicator. This year’s minimum is about 47 percent lower than the 1979 to 2000 average. As the ice disappears, the entire Arctic region warms up.

“This will gradually affect climate in the areas where we live,” said NSIDC researcher Ted Scambos. “We have a less polar pole–and so there will be more variations and extremes.”

Research from recent years suggests that warming in the Arctic has fundamentally changed the pressure gradient between the high- and mid-latitude regions, slowing the jet stream and resulting in the amplification of high pressure ridges and low pressure troughs that subsquently affect the march of weather systems across the northern hemisphere.

“Recent climate models suggest that ice-free conditions may happen before 2050, said NSIDC scientist Julienne Stroeve.

“While lots of people talk about opening of the Northwest Passage through the Canadian Arctic islands and the Northern Sea Route along the Russian coast, twenty years from now from now in August you might be able to take a ship right across the Arctic Ocean,” Serreze said.


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