Climate Change Triggered Another Year of Extremes in the Arctic
Rising global temperatures due to the burning of fossil fuels continue to transform the Arctic faster than any other region on Earth, according to a report released Tuesday by an international team of scientists.
Climate change’s impacts over the past year included all-time-high air temperatures, a record-setting low in winter sea ice, and melting across 50 percent of the surface of the Greenland ice sheet, according to the updated “Arctic Report Card,” from the United States National Oceanic and Atmospheric Administration.
Air temperatures across the Arctic were the highest seen since record keeping began in 1900, said Jacqueline Richter-Menge, a researcher with the U.S. Army Corps of Engineers, who contributed to the NOAA report. Temperatures were on average more than 2 degrees Fahrenheit higher than historic norms, with many areas seeing highs of nearly 6 degrees above average.
The year’s maximum sea ice extent occurred on Feb. 25—15 days earlier than the historic average, Richter-Menge said. At 9 million square miles, it was the lowest ice area since satellite measurements began in 1979.
As of March, about 70 percent of the ice pack was first-year ice, compared with 35 percent in 1985, while four-year-old ice dropped from 20 percent of the sea ice pack to under 5 percent, Richter-Menge said, resulting in “thinner and more vulnerable sea ice cover.”
Warm, dry conditions and below-average snow cover in central Alaska contributed to the state’s nearly record-breaking summer fire season, said Martin Jeffries, an Arctic science adviser with the U.S. Office of Naval Research. June snow cover in North America and Eurasia was the second lowest since satellite records began in 1967.
The 2015 report card highlights the effects of warming temperatures and diminishing sea ice on Pacific walruses. While many factors influence the animal’s population numbers, the Arctic’s carrying capacity for the large pinnipeds appears to be shrinking along with its ice cap, according to the report.
“The walrus population in the North Pacific is thought to have dropped by over 50 percent in last decade” as the ever more distant summer ice edge forces walruses to haul out in massive numbers along the shores of the Chukchi Sea, said Kit M. Kovacs, a biodiversity researcher with the Norwegian Polar Institute and the lead author of the walrus chapter of the report.
Female walruses and their calves would normally spend the summer on the sea ice that floats above the most abundant clam beds, the report noted. The lack of sea ice has forced walrus mothers to swim 110 miles from land to feed, which saps their energy for nursing their young. Crowding onto land has also put calves at higher risk of being trampled to death.
“The land herds we are seeing in the North Pacific are not things we’ve seen before in the lifetime of living people,” Kovacs told reporters.
The Obama administration is considering whether to extend endangered species protections to the Pacific walrus, because of the ongoing loss of the species’ sea ice habitat.
The news was cheerier for the walruses of the Svalbard archipelago, on the Atlantic side of the Arctic. A regional hunting ban since 1952 has allowed that walrus population to recover from extremely low numbers, Kovacs said, though sea ice in that part of the Arctic is also on a severe decline.
The condition of the Greenland ice sheet is among the most worrying indicators of the great Arctic thaw, because its collapse could trigger rapid sea level rise. More than half the ice sheet’s surface area was affected by melting during the summer of 2015, according to the report. “The length of the melt season was as much as 30-40 days longer than average in the western, northwestern, and northeastern regions” of the ice sheet, the scientists noted, “but close to and below average elsewhere on the ice sheet.”
Authored by 72 authors from 11 countries, the "Arctic Report Card" covers the 12 months between October 2014 and September 2015.
In addition to surface temperatures and sea ice, the report describes other impacts of climate change, including ongoing shifts in Arctic Ocean fish populations as warmer-water species move northward, changes in the base of the Arctic marine food web, shifting populations of plants growing on the Arctic tundra, and increasing flows of freshwater into the Arctic Ocean from eight major rivers.
At the recent climate change talks in Paris, nations agreed on the goal of keeping the global increase in temperature “well below 2 degrees C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees C.”
Both these targets are too high to stop or reverse the thaw of the Arctic. “If the globe goes to 2 degrees of warming, we’re looking at 4 to 5 degrees of warming in the Arctic by 2040 to 2050,” Jim Overland of NOAA told reporters during a media briefing.
But even if there is no going back to the region’s older norms for cold and ice, slashing greenhouse gas pollution is still critical to the Arctic, he said. “There’s a fairly close association between air-temperature value and the amount of sea ice we see,” Overland said. “So if we stabilize or reduce temperatures globally, that also looks like it will stabilize the Arctic climate” during the latter half of the 21st century.
The next generation will see ice-free summers, Overland said. But if the world acts on slashing greenhouse gas pollution, their children could see some of that ice return.