Even after a frigid winter, Arctic sea ice is still really low

Large parts of the U.S. experienced a pretty wimpy winter this year, thanks to cold air staying parked over the Arctic.

This made for a relatively frigid winter season in the high north, which is good for making sea ice. Although Arctic sea ice this season reached its biggest extent since 2013, it's still significantly lower than it was four decades ago. The Arctic is the fastest-warming region on Earth, and though there will always be fluctuating winters, sea ice is in a deep decline.

"While this year's maximum sea ice extent was a bump up from the last few years, it is still well below average and far from conditions in the 1980s and 1990s," said Zack Labe, a climate scientist and Ph.D. candidate at the University of California, Irvine.

"The bottom line is that the Arctic is still trending over the long term toward less extensive ice cover throughout the year, but with year to year variations," agreed Walt Meier, a senior research scientist at the National Snow and Ice Data Center.

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Officially, after a pretty cold Arctic winter, the maximum, or largest, amount of sea ice was the eleventh lowest in 42 years of satellite record-keeping, which was the highest in eight years. "It doesn’t in any way indicate a rebound, but rather year-to-year variations, which we expect to see," said Meier.

The colder winter was largely caused by a well-known fluctuating weather pattern, called the Arctic Oscillation. This year, zones of high pressure below the Arctic kept the cooler Arctic air, and the infamous polar vortex, locked in place. That meant an increase in sea ice. But nothing extreme.

It's dark in the high north over winter, but overall, the Arctic suffers from a vicious sun-related cycle that decimates its ice. It's called the albedo effect, wherein bright white sea ice melts (often due to warmer air temperatures). This leaves large swathes of dark ocean exposed to absorb more heat from the sun, which warms the ocean and in turn melts more ice. It's a relentless feedback loop of melting.

By the end of summer, this leaves sea ice profoundly melted before each winter begins.

"The 13 lowest [sea ice] extents in the satellite era have all occurred in the last 13 years," the National Snow and Ice Data Center said last year.

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On top of the Arctic's relentless warming trend, fluctuating weather will always play a role in shaping the extent and volume of sea ice. Sometimes this will lead to bumps in sea ice, and sometimes dips.

"Changes in daily weather conditions play a major role in the evolution of Arctic sea ice," said Labe.

For example, storms and winds have decimated sea ice in the Bering Sea over the last week. This rapidly dropped Arctic sea ice to its fourth-lowest levels, for this time of year, on record.

But the big picture remains clear. The climate situation remains unchanged. Earth is relentlessly warming — 19 of the last 20 years are the warmest on record — and the Arctic is dramatically changing.

"The basic story is the same, but this year represents a bit of an upward 'bump' on the overall downward trend," said Meier.