Arctic sea ice maxes out at second-lowest level on record
Arctic sea ice expands and contracts throughout the year, reaching a peak extent sometime during March, just as the sun rises above the North Pole.
It shrinks back during the summer, on its way to an annual minimum during the month of September. As the climate warms, however, sea ice has declined, compared to past levels, during all seasons. But in recent years, climate scientists have become more concerned as they’ve seen what’s taking place during the Arctic winter, which had historically seen less of a climate change signal in the ice compared to other seasons
That’s not the case anymore. Scientists announced on Friday that sea ice reached a wintertime peak in 2018 that was only a smidgeon above 2017’s all-time record low.
This means that all four of the lowest winter sea ice maximums have taken place in the past four years, according to the National Snow and Ice Data Center (NSIDC) in Boulder, Colo.
“Winter’s really starting to get into the act now. What we’re really seeing now is that the Arctic is really getting hit both in the summer and in the winter now,” Mark Serreze, who directs the NSIDC, said in an interview.
“We’re really clearly trending toward less winter sea ice too.”
According to the NSIDC, sea ice cover across the Arctic Ocean most likely reached its maximum extent on March 17 at 5.59 million square miles. This is 448,000 square miles below the 1981 to 2010 average, and ranks just 23,200 square miles above the record low seasonal peak that occurred last year.
Scientists have tracked sea ice extent using satellites for the past 39 years, but they have other data sources that go further back in time.
A federal report published in December 2017 found that the magnitude and the pace of the 21st Century plunge in sea ice extent as well as the amount of ocean surface warming is unprecedented in at least the past 1,500 years.
The winter sea ice cover was heavily affected by regional weather patterns, as well as long-term climate change which is gradually replacing older, thicker sea ice with newer, thinner ice cover that’s more vulnerable to being flushed out of the region by storms, as well as to melting during spells of warm (well, warm for the Arctic at least) weather.
Arctic sea ice extent appeared to be headed for a record low until a major change in the weather pattern across parts of the region allowed for some ice growth prior to the seasonal peak.
Up until then, however, the Arctic winter of 2017-2018 was a wild one. There were repeated inflows of unusually mild and moisture-laden air from both the North Atlantic and North Pacific sides of the Arctic. Temperatures at times soared to 45 degrees Fahrenheit above average, even in the High Arctic. The North Pole even exceeded the freezing mark for a brief period in February.
Also in February, a weather observing station in Cape Morris Jesup, in far northern Greenland, located just about 400 miles from the North Pole, reached or exceeded the freezing mark on nine days of the month, which was unprecedented in the historical record.
On the Pacific side, there was record low sea ice in the Bering Sea, to the point where an island community known as Little Diomede was damaged by high waves during February. Typically, that island, which sits in the Bering Sea between Alaska and northeastern Russia, is insulated from storms by extensive sea ice cover.
Sea ice also ran extremely low in the Chukchi Sea to the north of Alaska, which helped lead to the warmest winter on record by far in Alaska’s Arctic communities. In Utqiaġvik, formerly known as Barrow, Alaska, the average winter temperature was a staggering 13.5 degrees Fahrenheit above average.
While the Arctic was relatively warm compared to average, huge parts of Europe and Asia were much colder than average during January, February, and March, while parts of the U.S. saw cold outbreaks and blitzes of winter storms known as nor’easters. There is some evidence connecting such “warm Arctic, cold continents” weather pattern to increased air and sea surface temperatures in the Arctic, which some researchers argue is having downstream effects far away from the Arctic Circle.
“Each year, the ice is subject to the whims of weather, but over the long-term the rising temperatures will win out,” said Walt Meier, an NSIDC scientist, via email. “With warmer temperatures and less ice there is the potential for more extreme events like those that characterized the Arctic this past winter.”
While each winter has its own quirks that lead to slightly different rankings, the overall trend in sea ice is starkly downward. Numerous studies show that the Arctic will be sea ice free during the summer months by the middle of this century.
Annual max #Arctic sea ice extent has likely passed —> 2nd lowest in the satellite record (after 2017)
While exact rankings may differ slightly between sea ice data sets, the long-term trend is clear. This plot is using JAXA’s AMSR2 satellite. pic.twitter.com/vPWJewRRDO
— Zack Labe (@ZLabe) March 22, 2018
As human-caused global warming causes the Arctic to warm at more than twice the rate of the rest of the world, a larger portion of the Arctic Ocean is opening up each warm season, which increases air temperatures, atmospheric moisture, and in turn melts more sea ice.
This feedback loop is known as Arctic Amplification, and the greatest amount of warming has been documented during the winter months, even though many people tend to focus on the annual sea ice minimum, which typically occurs in September.
During one of the warm episodes in February, a large area of open water appeared in the sea ice cover north of Greenland, which is typically where some of the oldest and thickest ice is found. This area has since refrozen, but the ice there could be more vulnerable to melting this summer, or being pushed into the North Atlantic via the Fram or Nares Straits, which can act like funnels by draining Arctic ice southward where it gradually melts.
Winter is catching up to summer
Serreze said winter sea ice extent has become a greater research interest as climate change’s fingerprint has spanned all the seasons, rather than just manifesting itself mostly in the drop in spring and summer sea ice.
Emerging research has tied rapid Arctic climate change with changes in weather patterns in the northern midlatitudes, with statistical links showing up in research studies but physical explanations for what is happening proving elusive so far.
Serreze, who has been cautious about tying Arctic warming to weather patterns occurring thousands of miles away, said his mind is changing on this issue as more studies are published and weird jet stream patterns occur more frequently.
“I would say at this point that the weight of the evidence is shifting toward a discernible Arctic influence” in midlatitude weather, Serreze said in an interview.
“In terms of the actual clear mechanism of what’s happening, I don’t think we’re there yet.”