Sea ice extent in the Arctic is as low as it has ever been measured in late October, and air temperatures are record warm. Sea ice experts say it is difficult to project what the current ice depletion means for the next year, but the unmistakable long-term trend toward less ice is troubling.
“The overall trajectory is clear — sometime in the next few decades, maybe as early as 2030, we’ll wake up to a September with no Arctic sea ice,” said Mark Serreze, director of the National Snow and Ice Data Center (NSIDC), in Boulder, Colo.
The present ice levels reflect a record slow recovery after the summer minimum on Sept. 10, which tied for the second-lowest extent on record.
Shortly after the minimum, it seemed as if the ice was headed for a fast recovery. But then the ice growth abruptly slowed because of unusually warm temperatures in the Arctic.
Zachary Labe, a PhD student at the University of California at Irvine who is studying Arctic sea ice and extreme weather, tweeted that air temperatures over parts of the Arctic have been more than 18 degrees Fahrenheit warmer than normal.
Labe also implicated unusually warm sea surface temperatures in the record-slow ice recovery. “The anomalously warm sea surface temperatures are largely contributing to the currently record-breaking low sea ice and this is likely to continue to affect sea ice formation into 2017,” Labe said in an email.
Walt Meier, a research scientist at NASA’s Goddard Space Flight Center and an expert on Arctic sea ice, said the slow ice growth reflects a self-reinforcing cycle that leads to more Arctic warmth and less ice.
“Even though the sun has gone down and the atmosphere is trying to cool, the ocean still has a lot of heat,” he said. “That ocean heat is gradually being transferred to the atmosphere, which warms the atmosphere. Until the ocean reaches the freezing point, sea ice won’t form.”
Meier said, if winter temperatures are cold, the ice could “catch up to some degree” while NSIDC’s Serreze warned that if temperature remain mild, “we’ll be starting the 2017 melt season on a rather bad footing.”
Serreze’s colleague at NSIDC Julienne Strove said not only does a slower fall freeze “precondition” the ice for large summer retreats but also reduces snowfall on the ice during winter. “A thinner snowpack will melt off earlier than a thicker snowpack, which can also lead to less summer sea ice,” she said.
But a mild winter in the Arctic will not guarantee record-low ice next summer. Year-to-year weather patterns dictate how much ice melts once the warmer months arrive.
“Arguably, we were set up last spring to have a record low in September 2016, but we had a fairly cool and stormy summer, which saved us,” Serreze said.
Labe said, “We were fortunate not to see a weather pattern more conducive for greater sea ice losses during the summer given the initial conditions at the start of the melt season were significantly worse off than 2012.”
Irrespective of the whims of Arctic weather through the upcoming winter and summer, the record-low October ice extent and record slow growth are stark indicators portending the continued downward spiral of ice extent.
Labe and Meier agreed with Serreze’s prediction that, as soon as the 2030s, there could be a September minimum with no ice. But they cautioned that does not mean it will be gone forever.
“Ice behavior is pretty noisy,” Labe said. “There’s a significant component of inter-annual variability. I think it will take until the end of the century for back-to-back years of no ice.”
Meier stressed there is a good deal of uncertainty as to when that first ice-free minimum will occur. “I might lean toward 2040 plus-or-minus-10 years,” he said. He noted “ice-free” does not mean ice is gone entirely from the Arctic, but it refers to an area of less than 1 million kilometers because “ice will be clogged up in places, and it’s unrealistic to get rid of every single chunk.”
Meier said that even though many people tend to focus on the projected milestone of the first ice-free year, it’s more of a symbolic milestone because the effects of shrinking Arctic ice have already begun.