Large Fractures Spotted in Vulnerable Arctic Sea Ice

Following more than two decades of Arctic sea ice thinning and melting, an unusual event just weeks before the start of the spring melt season is providing visual proof of how vulnerable the ice pack really is.

Animation of the ice fracture using satellite AVHRR data.

Credit: Arctic Sea Ice blog via NSIDC.

During the end of February and continuing into early March, large fractures in the sea ice were observed off the north coast of Alaska and Canada, from near Ellesmere Island in the Canadian Arctic to Barrow, Ala., the northernmost city in the U.S.

The rapid climate change in the Arctic and sharp decline of sea ice has been attributed to manmade global warming, along with natural climate variability, and projections show the region becoming seasonally sea ice free by midcentury.

According to the National Snow and Ice Data Center (NSIDC) in Boulder, Colo., this fracturing event appears to be related to a storm that passed over the North Pole on Feb. 8, 2013, creating strong off-shore ice motion. The event is unusual but not unheard of, as similar patterns were seen in early 2011 and 2008. However, the NSIDC said the fracturing this time is more extensive.

The spread of the ice fractures can be seen in a video animation from satellite imagery, provided by the NSIDC.

The NSIDC said the fracturing is likely a sign of the prevalence of young and thin sea ice, which can be disturbed more easily by weather patterns and ocean currents, and also melts more easily when exposed to warm air and ocean temperatures during the melt season. As Arctic sea ice extent has plummeted since 1979, down to a record low in September 2012, first-year ice has become much more common across the Arctic, as thick, multiyear ice has declined.

“The large area of fractured ice is located in predominantly first-year ice, which is thinner and easier to fracture than thick, multiyear ice,” the NSIDC said on its website.

Arctic sea ice extent as of March 12, 2013, along with daily ice extent data for 2012, the record low year. 2013 is shown in blue, and 2012 in green. The gray area around the average line shows the two standard deviation range of the data.

Click on the image for a larger version. Credit: NSIDC.

Writing on his Arctic Sea Ice blog, the blogger known as Neven wrote of the fracturing event: “This, of course, is a very bad prelude to the melting season, even if there are a couple of weeks left for the ice to thicken. Those huge cracks will freeze over, but the ice will be very brittle and the first to go, probably creating open spaces between multi-year ice floes where the Sun will shine and quickly heat things up.”

Average sea ice extent for February 2013 was 378,000 square miles below the 1979 to 2000 average for the month, and was the seventh-lowest February extent in the satellite record. However, the Arctic gained a larger amount of sea ice during the month than average, even though it still wound up with less ice overall compared to normal.

According to the NSIDC, through 2013, February sea ice extent has declined at a rate of 2.9 percent per decade compared to the long-term average. This represents an overall reduction of more than 606,000 square miles from 1979 to 2013, which is equivalent to more than twice the area of the state of Texas.



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