4.22.16
Megan Gannon
Sea ice photographed in the central Arctic Ocean during summer 2015, when Arctic sea ice was exceptionally thin, according to satellite data. Credit: Alfred-Wegener-Institut/ Stefan Hendricks
Recent and current conditions in the Arctic suggest that by the end of this summer, the region’s sea ice could shrink to—or even below—the record low observed in 2012, scientists announced at the 2016 European Geosciences Union (EGU) meeting in Vienna, Austria, on Thursday.
At a press conference, the researchers discussed signs of impending ice loss that they had noticed while reviewing ice thickness maps from the past several years from the CryoSat-2 satellite.
“What was striking to us is that the ice thickness distribution in this spring, or at the end of winter, is very similar to 2012, which was the previous record minimum,” said sea ice physicist Marcel Nicolaus of the Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany. The sea ice at that time extended over just 3.41 million square kilometers—roughly half the average annual minimum ice coverage between 1981 and 2010.
Multiple Factors Signal Sea Ice Shortage
In this latest evaluation and projection for 2016, the research team factored in the recent history of Arctic warming and regional ice loss and growth. The scientists also considered ice thickness measurements from 2015 and 2016 and expected ocean currents and winds.
A snow buoy erected on Arctic sea ice near the coast of Alaska. Credit: Alfred-Wegener-Institut/ Stefan Hendricks
In addition, measurements from a set of seven “snow buoys” contributed to the outlook. The researchers had affixed those sensor towers—which track snow thickness and air temperatures and pressures directly on the sea ice—to ice floes last fall.
Nicolaus and his colleagues developed the concept for using buoys to measure snow depth; they passed this concept to a Canadian company from which they now buy the devices. Each snow buoy consists of a base unit that’s drilled into ice with a 1.5-meter mast topped by a rack of four sonic ranging sensors that autonomously transmit their data via Iridium satellites. Nicolaus said his colleagues joked that the buoy looks somewhat like a rack for hanging clothing.
Balmy Winter Slowed Ice Growth
The potential replay of 2012 or worse stems in large measure from the exceptional warmth of the 2015–2016 winter, the researchers noted. Readings from the group’s snow buoys in February showed that the central Arctic temperature in that month surpassed the average by up to 8°C, the team reported. Nonetheless, the extreme winter warmth didn’t make ice melt away. “According to our buoy data from the spring, the warm winter air was not sufficient to melt the layer of snow covering the sea ice, let alone the ice itself,” Nicolaus said.
“Only over the last decade has it became more and more obvious how important the snow cover is for sea ice,” he told Eos. For instance, snow’s high albedo and other physical properties, such as its ability to provide thermal insulation, can affect the way that sea ice forms and melts.
High 2015–2016 winter temperatures instead significantly slowed the usual seasonal thickening of sea ice, the scientists explained to reporters. Ice extending from the land in areas north of Alaska, for instance, has attained just two thirds of its usual thickness, currently measuring just a meter thick rather than 1.5 meters.
Prediction Challenge
Ice researchers have observed an overall decline in Arctic sea ice abundance ever since satellite records for such data became available in the 1970s. But year-to-year predictions for sea ice decline are difficult to make because the internal variability of sea ice thickness is quite large, said Alexandra Jahn, a climate scientist at the University of Colorado Boulder, who was not involved in the projections. Jahn compared the sea ice prediction challenge to making an accurate forecast today of the weather for this coming Christmas. “We have that inherent uncertainty in the system,” she told reporters.
Weather Matters Most
Ultimately, the amount of sea ice present when its extent bottoms out at summer’s end depends disproportionately on the patterns of wind and of air and water temperatures in the months just before the minimum is reached, Nicolaus and his colleagues explained. “The Transpolar Drift Stream, a well-known [ocean] current in the Arctic Ocean, will be carrying the majority of the thick, perennial ice currently located off the northern coasts of Greenland and Canada through the Fram Strait to the North Atlantic. These thick floes will then be followed by thin ice,” said sea ice physicist Stefan Hendricks, also of AWI. “If weather conditions turn out to be unfavorable, we might even be facing a new record low.”
Julienne Stroeve, a senior research scientist with the U.S. National Snow and Ice Data Center (NSIDC) in Boulder, Colo., who wasn’t involved in the AWI analysis, agreed. “We are preconditioned for a big melt year if the weather patterns favor melt,” Stroeve told Eos. “Unfortunately, we cannot predict the weather, so it remains to be seen. However, if we have a relatively warm summer and a circulation pattern that promotes more ice flow out of Fram Strait, we certainly could be looking at a new record low this summer.”
Ice-Free Arctic?
Other sea ice research presented at the EGU meeting took a look further ahead to times when the Arctic could see up to seven ice-free months each year if greenhouse gas emissions are not cut.
One effect of that diminished ice cover could be bigger waves in Arctic seas, according to Mikhail Dobrynin, an oceanographer at Universität Hamburg’s Center for Earth System Research and Sustainability in Germany. Dobrynin presented a new model for wave patterns in the Arctic based on projections of wind and ice conditions.
His simulation showed that with less ice and longer reaches of open water, winds can build waves to greater size and strength. In turn, those more powerful waves could break up the sea ice faster and further erode already fragile coastal areas in the region.
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