2021-09-22 21:42:34 Arctic Sea Ice Hits Annual Low, but It’s Not as Low as Recent Years

Arctic Sea Ice Hits Annual Low, but It’s Not as Low as Recent Years

According to scientists, sea ice in the Arctic Ocean has reached its minimum extent following the summer melt season, and coverage is not as low as it has been in recent years.

According to the National Snow and Ice Data Center at the University of Colorado, the minimum was most likely reached on Thursday, and the total ice extent for this year is estimated to be 1.82 million square miles, or 4.72 million square kilometers.

This is the 12th-lowest total since satellite sensing of the Arctic began in 1979, and it is about 25% higher than the previous year.

The center’s director, Mark Serreze, described this year as a “reprieve” for Arctic sea ice, owing to colder and stormier conditions that resulted in less melting. A persistent zone of colder, low-pressure air over the Beaufort Sea north of Alaska, in particular, slowed the rate of melting there.

The sum reminds us that the climate is naturally variable, and that this variability can sometimes outweigh the effects of climate change. However, the overall decline in Arctic sea ice continues, as the region warms more than twice as fast as the rest of the world. The record low was set in 2012, and this year’s results are roughly 40% higher.

However, this year’s total is nearly 600,000 square miles less than the average minimum from 1981 to 2010. And, with this year included, the minimums for the last 15 years are the lowest since 1979.

Furthermore, the relatively high minimum appears to have come at the expense of thicker, multiyear ice, which continues to be near its lowest totals in the satellite record.

Natural variability could affect sea ice in two ways, according to Robbie Mallett, a sea ice researcher at University College London who is not affiliated with the National Snow and Ice Data Center.

The first is temperature. But the other was “how the ice is set up every winter to melt,” he explained.

Winds drove a lot of thicker, older ice westward from north of Greenland to the Beaufort and a neighboring sea, the Chukchi, last winter, according to Mr. Mallett. That thicker ice thinned out this summer, but most of it didn’t melt completely.

“We packed the Beaufort and Chukchi Seas with this resilient multiyear ice, and it made it to the end,” he said. “And that was a good outcome.”

However, the thinning or complete melting of thicker Arctic sea ice (which is now about one-fourth of what it was four decades ago) is concerning.

The thinner the sea ice, the more sunlight it allows through to the water below, affecting marine ecosystems and generating even more heat as more of the sun’s energy is absorbed and re-emitted as heat.

Because first-year ice is thinner and more prone to melting completely, as it replaces older ice, the region as a whole becomes more vulnerable to melting. Many scientists believe the Arctic will be ice-free in the summers within the next decade or two.

Mr. Mallett predicted that when sea-ice thickness is measured by satellite-borne radar this winter, “I suspect we’ll see a low average thickness for the entire Arctic Ocean, rather than a record-low thickness.”

“There is certainly more than one diagnostic for Arctic health,” he said. “Extent is only one factor; thickness and age are also declining.”

Mr. Mallett, who closely monitors sea-ice extent, predicted that due to the flow of multiyear ice into the Beaufort and Chukchi seas, among other factors, this year’s total would be “a little bit higher” than the long-term downward trend. “But it turned out to be a lot higher,” he explained.

Last winter’s westward blowing of older ice from north of Greenland may have been a continuation of a troubling pattern observed in 2020.

The area is normally so densely packed with long-lasting, multiyear ice that it is known as the “last ice area,” where, even as ice melts completely in Arctic summers, it is thought that enough ice will remain to provide a safe haven for polar bears and other ice-dependent wildlife.

However, a German research icebreaker on a yearlong expedition through the area last year encountered little thick ice. A study also found that variable wind patterns, combined with warming-induced ice thinning and melting, resulted in much of the thicker ice being blown out of the area.

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Arctic Sea Ice Hits Annual Low, but It’s Not as Low as Recent Years