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After record lows in 2012, Arctic sea ice volume is back up by 50 percent

CBC NewsEye on the Arctic
Ned Rozell photo

The volume of sea ice in the Arctic is 50 percent greater than it was last fall, satellite measurements show.

In October 2013, the European Space Agency satellite CryoSat measured 2,160 square miles (9,000 cubic kilometers) of sea ice on the Arctic Ocean, said an ESA news release Monday. At the same time of year in 2012, it measured just 1,440 square miles (6,000 cubic kilometers) -- a record low.

The satellite, launched in 2010, is designed to measure sea ice thickness across the Arctic Ocean, allowing scientists to monitor changes in volume and not just surface coverage.

Despite the short-term rebound, sea ice volumes remain low compared to historical averages, scientists say.

“It’s estimated that there was around 20,000 cubic kilometers of Arctic sea ice each October in the early 1980s, and so today’s minimum still ranks among the lowest of the past 30 years,” said Andrew Shepherd, a co-author of the study, in a statement. Shepherd, who is a researcher at University College London, was part of a team that presented the study last week at the American Geophysical Union’s annual meeting in San Francisco.

Both the surface coverage and volume of Arctic sea ice are monitored by scientists as climate indicators.

In September, the U.S. National Snow and Ice Data Center reported that Arctic ice cover at its summer minimum this year was 1.97 million square miles. That was also up 50 percent from last year’s record low, but the sixth lowest on record. The seven lowest levels have all been recorded in the last seven years.

Coverage versus volume

Scientists had noticed that generally, since CryoSat was launched in 2010, Arctic sea ice volumes haven’t varied as much from year-to-year as sea ice coverage.

Because of that, they hadn’t expected an increase in volume comparable to the increase in surface coverage, said Rachel Tilling, lead author of the new study, in a statement.

“But it has been, and the reason is related to the amount of multi-year ice in the Arctic,” added Tilling, a researcher at the U.K.’s Centre for Polar Observation and Modelling.

Multi-year ice survives more than one summer without melting and is considered an indicator of “healthy” Arctic sea ice cover, the ESA reported.

About 90 percent of the increase in sea ice volume this year is from the growth of multiyear ice, the release said, which now averages about 20 percent thicker than last year -- 30 centimeters, or 12 inches.

Last week, NOAA issued its annual Arctic report card, which found that Arctic temperatures in 2013 were cooler compared to the past six years, although they remained warm compared to the 20th century.

“The Arctic caught a break, if you will, in 2013,” said Martin Jefferies, the University of Alaska geophysicist who edited the report card, at the AGU conference. “But one year doesn’t change the long-term trend toward a warmer Arctic.”

This story is posted on Alaska Dispatch as part of Eye on the Arctic, a collaborative partnership between public and private circumpolar media organizations.