Sea ice cover in the Arctic shrank to one of its smallest extents on record this week, bringing forward the days of an entirely ice-free Arctic during the summer.
The annual sea ice minimum of 5,099m sq km reached on 13 September was not as extreme as last year, when the collapse of sea ice cover broke all previous records.
But it was still the sixth lowest Arctic sea ice minimum on record, and well below the average set over the past 30 years of satellite records. This suggests the Arctic will be entirely ice-free in the summer months within the next few decades, scientists said.
The annual sea ice minimum, based on a five-day average, is expected to be officially declared by the National Snow and Ice Data Centre in Boulder, Colorado within the next few days.
“It certainly is continuing the long-term decline,” said Julienne Stroeve, a scientist at the National Snow and Ice Data Centre. “We are looking at long-term changes and there are going to be bumps and wiggles along the long-term declining trend, but all the climate models are showing that we are eventually going to lose all of that summer sea ice.”
Thickly packed sea ice in the Arctic from a photo taken in 1949. One day thick, stable sea ice in the Arctic may be a thing of the past. Photo by: Rear Admiral Harley D. Nygren.
Overall, the Arctic has lost about 40% of its sea ice cover since 1980. Most scientists believe the Arctic could be entirely ice-free in the summer by the middle of the century—if not sooner.
The most dramatic changes have occurred in the past decade. The seven summers with the lowest minimum sea ice extents have all occurred in the past seven years.
The loss of sea ice cover is a leading indicator of climate change, and will be a key part of the findings released next week by the United Nations’ climate science panel, the IPCC.
The loss of Arctic sea ice has also emerged as a driver of extreme weather events in Europe.
The extent of Arctic sea ice cover has generally decreased in all regions since satellite records began in the late 1970s. The Arctic continues to warm at about twice the rate of lower latitudes.
This year’s minimum was reached despite cooler temperatures in some areas, which slowed melting, Stroeve said. Air temperatures in the central Arctic were 1-4C colder than they were for the last six years.
“We had a pretty cold summer in general for the time period we’re looking at and yet the sea ice cover didn’t recover to the extent that we had in the 1970s and 1980s,” she said.
Rapid warming last year reduced the area of frozen ocean water in the Arctic to less than 3.5m sq km last year.
This year’s low, of about 5.099m sq km, was more in line with the summer of 2009, Stroeve said.
After reaching 5.099m sq km on 13 September, the summer sea ice extent rose to 5.104m sq km on 14 September and 5.105m sq km on 15 September before falling back to 5.103m sq km on 16 September.
Arctic sea ice volume (not extent) from 1979 to Spring 2013. Note: the graph does not show this year’s low.
But the decline of the surface area of frozen water in the Arctic tells only part of the story of ice loss, scientists said.
Ice in the Arctic has also been thinning over the years—which makes it more vulnerable to melting in the summer.
Scientists now believe it is the combination of reduction in thickness and surface area that is hastening the advent of an ice-free Arctic in the summer months.
Observations from the Cryosat mission released last week by the European Space Agency showed the volume of sea ice in the Arctic falling to a new low over the last winter.
Last March and April—typically the time of year when the ice floes are at their thickest—there was just 15,000 cubic km of ice. There would have been 30,000 cubic km, or twice that volume, at the height of winter 30 years ago, scientists said.
“There is very little thick multi-year ice left covering these great areas. It is really thin so if you get a little weather the next year, it’s all gone,” said Andreas Münchow, a scientist at the University of Delaware who studies the Arctic.
The loss of the thicker, multi-year ice was also one reason for the larger year-to-year changes in Arctic ice cover, Münchow said.
But the overall direction of sea ice cover in the Arctic was clear, he added. “We really are heading towards an ice-free Arctic in the summer. It just takes a freak event eventually, in the next five or 10 or even 20 years, and the next year there will be a huge Arctic cover. But it is all going to be thin on top, and the long-term trend is that the ice is disappearing in the summer in the Arctic,” he said.
Original story: Suzanne Goldenberg. Arctic sea ice shrinks to sixth-lowest extent on record. The Guardian – September 18th, 2013
(09/19/2012) Some twenty days after breaking the record for the lowest sea ice extent, the Arctic sea ice has hit a new rock bottom and finally begun its seasonal recovery. In the end, the Arctic sea ice extent fell to just 3.4 million square kilometers (1.32 million square miles) when only a few months ago scientists were wondering if it would break the 4 million square kilometers. The speed of the sea ice decline due to climate change has outpaced all the computer models, overrun all expert predictions, and shocked even the gloomiest scientists.
(08/20/2013) As sea ice levels continue to decline in the northern hemisphere, scientists are observing an unsettling trend in harp seal young mortalities regardless of juvenile fitness. While a recent study found that in harp seal breeding regions ice cover decreased by up to 6% a decade from 1979 on, a follow-up study in PLoS ONE compared the rate of harp seal strandings to total ice cover from 1992 to 2010.
(07/30/2013) Rapid thawing of the Arctic could trigger a catastrophic “economic timebomb” which would cost trillions of dollars and undermine the global financial system, say a group of economists and polar scientists. Governments and industry have expected the widespread warming of the Arctic region in the past 20 years to be an economic boon, allowing the exploitation of new gas and oilfields and enabling shipping to travel faster between Europe and Asia.
(05/08/2013) Weather patterns around the globe are getting weirder and weirder: heat waves and record snow storms in Spring, blasts of Arctic air followed by sudden summer, record deluges and then drought.
(04/17/2013) Four young explorers including American actor Ezra Miller have planted a flag on the seabed at the north pole and demanded the region is declared a global sanctuary. The expedition, organized by Greenpeace, saw the flag lowered in a time capsule that contained the signatures of nearly 3 million people who are calling for a ban on exploitation in the region.
(03/26/2013) Climate scientists have linked the massive snowstorms and bitter spring weather now being experienced across Britain and large parts of Europe and North America to the dramatic loss of Arctic sea ice.
(03/05/2013) Rapidly melting sea ice in the Arctic due to global warming will open new shipping lanes that will speed transit between northern Asia, Europe, Canada and Alaska but unleash new safety, environmental and legal issues, according to scientists writing in this week’s issue of the Proceedings of the National Academy of Sciences.
(02/18/2013) Few places are changing as rapidly as the Arctic due to global warming. Last year, scientists were stunned when the Arctic’s seasonal ice extent fell to record low that was 18 percent below the previous one set in 2007. But new research in Geophysical Research Letters finds that the volume of ice is melting away just as quickly: satellite and ocean-based measurement have found that Arctic sea ice has fallen by 36 percent in Autumn since 2003. In winter, the ice volume has dropped 9 percent.