The sea ice in the Arctic has shrunk to its lowest extent measured since satellites began collecting data in the region in the late 1970s, according to the National Snow and Ice Data Center at the University of Colorado.
A storm that blew through the Arctic in early August dealt a blow to the already-fragile and diminished sea ice in the region, speeding the pace of melting. Satellite images taken Sunday and returned to Boulder on Monday morning showed that this year's ice cover broke the low-ice record set in 2007 -- and the sea ice is expected to continue dwindling into mid- or, possibly, late September.
Boulder scientists recognized as early as June that the sea ice was melting quickly and could meet or exceed the losses in 2007, but the storm sealed the deal, breaking up the ice into smaller chunks that melt more easily than a contiguous block of ice.
"The ice cover was already quite thin and ready to melt out before the storm hit," said Walt Meier, a scientist at the National Snow and Ice Data Center.
In prior decades, when a larger percentage of Arctic sea ice was made up of thicker multi-year ice -- which survives through one summer to the next -- instead of thinner ice that forms over a single winter, storms like the one that roiled across the Arctic earlier this month had a lesser impact, Meier said.
"The ice cover was much thicker and more resilient -- it could kind of take a punch," Meier said.
The amount of sea ice that melts each summer varies annually, depending on the coldness of the winter, the warmth of the summer and wind conditions, among other variables. But over the last decade and a half, the overall sea ice minimums -- which usually occur in mid- to late September before the temperature drops and ice begins to reform -- have continued to trend downward.
"The record of Arctic sea ice has definitely had a lot of interannual variability (since the late 1970s)," said Claire Parkinson, a climatologist at NASA's Goddard Space Flight Center in Maryland. "By the late 1990s, it was quite clear that the trend was strongly downward, in terms of satellite data. ... It was also becoming clear from submarine data that the ice was also thinning."
In 2007, the amount of sea ice at the end of the summer dropped off precipitously, setting the previous record low before bouncing back up again in 2008.
"That was a gigantic decrease from previous years," Parkinson said. "All of us that had been working on sea ice studies for a long time were just stunned by what a decrease that was."
The last six years, from 2007 through today, have seen the lowest extent of sea ice in the satellite record, and 2011 now trails 2012 and 2007 for the third-lowest extent on record.
The loss of summer sea ice may have impacts beyond the Arctic. While ice reflects up to 80 percent of the sunlight back to space, keeping the Earth cooler, open water absorbs much of the sun's rays, causing the ocean to heat up. Meier and his colleagues say the current trend in diminished summer sea ice could mean that the Arctic will be ice-free in the summers within the next several decades.
Now, the total amount of sea ice still left in the Arctic is just 1.58 million square miles, compared to 1.61 million square miles at the end of the 2007 season. But that area could continue to shrink in the coming weeks.
"We have exceeded the 2007 ice minimum already, and it's still in August," said Joey Comiso, senior scientist at Goddard. "Normally, the minimum is reached around the middle of September."
When asked whether he could estimate exactly how much further the sea ice would decline, Meier said that's difficult to say.
"We're in undiscovered territory," he said. "We haven't been here before -- that makes it fairly difficult."
Contact Camera Staff Writer Laura Snider at 303-473-1327 or email@example.com.