by According to a new study, climate change has attacked crucial Arctic sea ice thickness in two sudden big gobbles instead of constant gnawing.
Just over 15 years ago, sea ice rapidly lost more than half its thickness, becoming weaker, more prone to melt and less likely to recover, according to the study which highlights the importance of two big ‘regime shifts’ ” that changed the complexion of the Arctic.
Those big bites came in 2005 and 2007. Before that, the Arctic sea ice was older and warped in a way that made it difficult to move out of the region. This has helped the polar area act as the globe’s air conditioner even in the hottest summers. But now the ice is thinner, younger and easier to push out of the Arctic, putting that crucial cooling system at greater risk, the study’s lead author said.
Before 2007, 19 percent of sea ice in the Arctic was at least 13 feet (4 meters) thick — thicker than most elephants — but now only about 9.3 percent of the ice is at least that thick. And the age of the ice has dropped by more than a third, from an average of 4.3 years to 2.7 years, according to the study in the journal Nature on Wednesday.
He cited “the lasting impact of climate change on Arctic sea ice”.
“Ice is much more vulnerable than before because it’s thinner, it can melt easily,” said study lead author Hiroshi Sumata, a sea ice scientist at the Norwegian Polar Institute. Thicker sea ice is critical for all types of life in the Arctic, he said.
The study shows “how the Arctic sea ice environment has undergone a fundamental change,” said Walt Meier, a scientist at the National Snow and Ice Data Center, who was not part of the research. “This paper helps explain why sea ice hasn’t recovered from those big drops.”
Previous studies have focused more on the extent of Arctic sea ice, or how widespread it is, because it’s easily measured by satellites, which don’t observe volume well. But 90 percent of sea ice is eventually ejected out of the Arctic through the Fram Strait from Greenland, so Sumata has overcome the challenges of measuring from space by focusing its observations on that choke point on land.
He found that the first ice was getting younger, which made it thinner and more uniform, and easier to push out through Fram Strait. Thicker ice has all kinds of odd edges and shapes that make it more difficult to get out of the Arctic due to aerodynamics, but that’s not the case with shinier, younger ice, Sumata said.
Scientists had known before that sea ice was shrinking in size and thinning, but this “washing” is key, said Mark Serreze, director of the National Snow and Ice Data Center, who was not part of the study.
“Such washing episodes have reduced the time ice remains in the Arctic Ocean by more than a year, so there’s less time to thicken and it’s the thicker ice that resists melting,” Serreze said in an email. “But because the Arctic is rapidly warming, we’re probably past the point of hoping the Arctic Ocean can recover.”
What likely happened in 2005 and 2007 were periods of warm, large, ice-free open waters in the Arctic that exceeded periods in previous summers, Sumata said. White ice reflects the sun’s rays, but the dark ocean absorbs them and heats up — something called ice albedo feedback. This cycle of warmer water has made it more difficult for ice to form, survive and thicken, she said.
Once the ocean has built up that heat, it can’t go back easily. So bigger, hotter changes could occur in the future to make the ice thinner and weaker, but don’t count on sudden curative cooling changes, the scientists said.
Sumata and Serreze think those sudden hot jumps will happen soon and are surprised they haven’t yet. Recent projections predict that the Arctic Ocean will be ice-free in parts of the summer in 20 to 30 years.
Sea ice thickness and the general health of the Arctic are also critical for areas thousands of kilometers away not freezing, Sumata said.
“It will affect the whole Earth because the north and south pole are something like a radiator of the Earth, the air conditioning system of the Earth,” Sumata said. “And the situation we’ve observed indicates that the air conditioner is malfunctioning.”
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