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2018 Arctic sea ice melt season just got a big headstart

  • This Spring, Arctic sea ice extent nearly achieved a new record low for May, but instead came in at second place at 12.2 million square kilometers (4.7 million square miles). That’s 310,000 square kilometers (120,000 square miles) greater than the all time May record set in 2016.
  • While scientists and the media have focused in the past mostly on the September sea ice extent minimum, four years in a row of record winter Arctic heatwaves, along with a better understanding of ice melt mechanisms, has resulted in researchers putting much more attention on Spring events as the annual melt season gets underway.
  • It is now understood that shrinking Arctic sea ice extent is having a significant influence on the global climate system, but extent isn’t all researchers are watching. They are becoming more and more concerned about the quality of the sea ice at the start of each melt season – thickness, as well as the disappearance of large amounts of multiyear ice.
  • Thinner, more fractured ice, and more numerous Spring melt ponds make the Arctic ice more vulnerable to summer heatwaves and a warmer Arctic Ocean. As with May, June 2018 has so far seen rapid ice melt, with extent lagging only slightly behind the record set in June 2016. That doesn’t bode well for the September sea ice extent minimum.
Arctic sea ice in eastern Greenland. What happens in the Arctic doesn’t stay in the Arctic. Scientists theorize that large-scale ice loss up north may be altering, and sometimes stalling, the jet stream, which can result in drought or severe storms hovering over one locale for lengthy periods of time. Image by mariusz kluzniak, Flickr.

Close, but no cigar. That assessment, though unscientific, well describes May 2018 sea ice extent in the Arctic Ocean – a month some polar experts thought could be one for the record books.

At the month’s mid-point, freakishly warm weather brewed above the northern ocean. But in the end, May 2018 staggered over the finish line in second place, and far from a photo finish at 12.2 million square kilometers (4.7 million square miles). That’s 310,000 square kilometers (120,000 square miles) greater than the all time May record set in 2016.

Yet the fact that so much debate swirled around May this year is news enough, as it’s often a month overlooked by the sea ice community and by the media, with May falling between March’s winter maximum sea ice extent and September’s summer minimum. But attention is shifting as global warming escalates.

“Now, what’s happening in winter and spring is starting to become very, very interesting,” says Mark Serreze, director of the National Snow and Ice Data Center which tracks and analyzes sea ice. September, he says, is no longer the only hot topic: “We’re seeing these big heatwaves over the North Pole in the middle of winter. Wow. That’s not supposed to happen and yet [it has] the last four winters.”

Arctic sea ice extent for May 2018 was 12.2 million square kilometers (4.7 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Image and data courtesy of National Snow and Ice Data Center.

These recent winter headstarts, along with a growing understanding of how the melt season operates, means that the months of March, April, and May (which qualify as the start of the melt season), are no longer being pushed to the sidelines, but are being seen as increasingly important in forecasting how things could shake out come September.

And clearly, summer ice loss matters in a big way. Scientists monitor Arctic sea ice melt not only because it’s a key local and regional climate indicator, but because less sea ice and more open water in summer appears to impact the entire global climate system. Ice loss could even be destablizing the planetary climate by causing jet stream blocking (acting like a traffic jam in the sky, according to new findings), which can result in extreme weather around the globe.

It’s likely that the Arctic Ocean could regularly experience near ice-free summers within the next few decades. So scientists are keen to document when exactly that tipping point will occur, as well as the conditions leading to it.

Pack ice after sunset in East Greenland near Kulusuk. Predicting the Arctic September minimum in advance remains beyond science’s predictive capabilities. However, signs so far this year indicate the possibility for a new record low ice extent, beating 2012. Image by Markus Trienke, Flickr.

The heatwaves that have come to define the new-normal Arctic winters have often been “corrected” by cooler temperatures in May and June, which return the polar region to near-average temperatures. But May 2018 offered no such reprieve. Throughout the month, temperatures over the Arctic Ocean remained warmer than average, with the last week spiking to 0.85 degrees Celsius (1.5 degrees Fahrenheit) above average. In Svalbard, an Arctic Circle archipelago north of Norway, the average May temperature was six degrees Celsius (10.8 degrees Fahrenheit) above average, and by month’s end, the north and west coasts of Svalbard were largely ice-free.

Also by the beginning of May, the Bering Sea had melted out (a record for that date which stunned scientists). And in the Chukchi sea, off the coast of Alaska, the leading ice edge is far behind where it should be. Arctic ice watchers are concerned, too, after one of the most intense Arctic cyclones on record swept through the Kara Sea in early June, where warm atmospheric temperatures are driving rapid melt as we approach the Summer Solstice.

But according to Serreze, extent isn’t all that we should be worried about. More and more, scientists are zeroing in on the March maximum and asking not only “How much ice have we got?” but “How thin is that ice?”

As Mongabay reported last fall, scientists are increasingly concerned about the quality of the sea ice at the start of each melt season – thickness, not just extent. The Arctic Ocean used to have substantially more thick, multi-year ice. But now, even if the ice is wide-reaching, it’s thinner and often newer, only having formed one or two years ago. Last July, for example, the average sea ice thickness in the Arctic was equivalent to the lowest on record.

This large melt pond sitting atop Arctic sea ice was seen from an Operation IceBridge flight over the Beaufort Sea on July 14, 2016. Each melt pond acts like a lens, focusing the Sun’s intensifying 24-7 heat on the ice below. like Image courtesy of NASA.

“The Arctic Ocean in March of this year had a whole lot of thin first-year ice, and not a lot of thicker ice,” reveals Serreze. “That’s important because it’s saying that the melt season already underway is starting off on a bad footing.” When ice is thin, less energy from the ocean and heat from the overlying atmosphere are needed to melt it, “which leads to a lot of open water in September.”

The National Snow and Ice Data Center is already reporting considerable fracturing of multiyear ice floes this Spring too, in the Beaufort Sea off Alaska. Open water around these large ice floes accelerates their melt via the absorption of solar energy, and some of these floes appear to already be partially covered by melt ponds. Each of these melt ponds acts like a magnifying glass, intensifying the 24-7 Arctic summer sunlight as it beats down on the vulnerable sea ice.

Melt ponds, and thin and fractured ice, aren’t the only melt factors involved, but they can set us up for a very bad fall. Ultimately, though, forecasting the September minimum is even harder than betting on the winning horse in the Triple Crown. The state of ice in the Arctic always comes down to weather, which scientists can’t yet predict past seven to 10 days.

Sea Ice Index data. The graph above shows Arctic sea ice extent as of June 17, 2018, along with the daily ice extent data for 2016 (which set an ice melt record for that day), and 2012 (which set an annual record for low minimum extent). As of June 17, 2018, the sea ice extent was barely 227,000 square kilomters above the 2016 record. (2018 is shown in orange, 2016 in red, and 2012 in dotted brown. The 1981 to 2010 median is shown as a dark gray line. The gray areas around the median line represent the interquartile and interdecile ranges of the data.) Image and data courtesy of the National Snow and Ice Data Center.

That being said, the ice prognosis for June isn’t looking good so far. The first week of June, a critical time during melt season, saw temperatures roughly 1 degree Celsius (1.8 degrees Fahrenheit) higher than normal across the Arctic, extending May’s hot streak. But still lying ahead are swirling high and low pressure systems, periods of sun and cloud, heatwaves and cold waves, and maybe summer cyclones. So where the ice will be by September remains to be seen.

“We’re set up for a world of hurt this summer because we’ve got all this thin ice, but we still won’t know what is going to happen,” concludes Serreze.

As of June 17, Arctic sea extent was only a perilous 227,000 square kilometers (87,645 square miles) greater than the all-time record low for that same day, set in 2016. Close, but once again, no cigar.

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