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Sea ice in the Arctic Ocean has reached its minimum size following the summer melting season, and coverage is not as low as it has been in recent years, scientists said on Wednesday.
The National Snow and Ice Data Center at the University of Colorado estimated that the minimum level was most likely reached Thursday, and estimated the total size of ice this year to be 1.82 million square miles, or 4.72 million square kilometers.
This is the 12th lowest total since satellite detection in the Arctic began in 1979, and about 25 percent higher than last year.
The center’s director, Mark Serreze, described this year as a “delay” for Arctic sea ice as colder and stormy conditions lead to less melting. In particular, a persistent zone of colder, low-pressure air over the Beaufort Sea in northern Alaska has slowed the rate of melting there.
The aggregate is a reminder that climate is naturally variable and that variability can sometimes outweigh the effects of climate change. But the overall downward trend of Arctic sea ice continues as the region warms twice as fast as other parts of the world. The minimum record was set in 2012, and this year’s results are about 40 percent higher than that.
But this year’s total is still about 600,000 square miles below the average minimum between 1981 and 2010. And the minimums for the last 15 years, including this year, are the 15th lowest since 1979.
What’s more, the relatively high minimum appears to have been achieved at the expense of thicker, multi-year ice that remains near its lowest totals in satellite records.
There are two elements of natural variability that can affect sea ice, said Robbie Mallett, a sea ice researcher at University College London, who is not affiliated with the National Snow and Ice Data Centre.
One is temperature. But another said, “it’s how the ice is set up each winter to melt.”
Mr Mallett said last winter, winds drove much thicker, old ice from the north of Greenland to the west, into Beaufort and the neighboring sea, the Chukchi. This summer, the thicker ice has thinned, but most of it has not completely melted.
“We filled the Beaufort Sea and the Chukchi Sea with this durable, perennial ice and it pushed it all the way,” he said. “And that was a positive result.”
But the thinning or complete melting of thicker Arctic sea ice (it’s now about a quarter of what it was forty years ago) is troubling.
The thinner the sea ice, the more sunlight passes into the water below, which can affect marine ecosystems and generate even more warmth as more of the solar energy is absorbed and re-radiated as heat.
And because the thinner first-year ice is, the more prone to complete melting replaces older ice, making the region more susceptible to melting overall. Many scientists expect the Arctic to become ice-free during the summer months in a decade or two.
“I suspect we will see perhaps not a record low thickness, but a low average thickness for the entire Arctic Ocean,” said Mr Mallett, when the thickness of sea ice was measured this winter by satellite-borne radar.
“There’s definitely more than one diagnosis for the health of the Arctic,” he said. “The coverage is just one, but thickness and age are also on the decline.”
Mr Mallett, who monitors sea ice coverage closely, said he expects this year’s total to be “slightly higher” than long-year, as perennial ice flows into the Beaufort and Chukchi seas, among other factors. The futures may suggest a bearish trend. “But it turned out to be much higher,” he said.
The westward blowing of ancient ice from northern Greenland last winter could be a continuation of a disturbing pattern noticed in 2020.
The region is normally filled with such permanent, perennial ice that it is known as “”.last ice fieldEven if the ice disappeared completely during the Arctic summers, it was thought that enough ice would remain to serve as a sanctuary for polar bears and other ice-dependent wildlife.
But last year, a German icebreaker on a one-year expedition encountered little thick ice while traveling through the area. And one study suggested that variable wind patternsCombined with the warming-induced thinning and melting of the ice, it had caused much of the thicker ice to be blown out of the area.
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