Scientists with the American Geophysical Union say the oldest and thickest Arctic sea ice is now disappearing at twice the pace of ice in the rest of the Arctic Ocean.
Their research, released on Tuesday, Nov. 12, in AGU’s journal Geophysical Research Letters, notes that ice in the Arctic Ocean north of Greenland is more mobile than previously thought, and as a result ice mass in the area is declining twice as fast as ice in the rest of the Arctic.
This Last Ice Area offers a sanctuary for wildlife relying on sea ice for survival, where they can retreat to in a warming world. Understanding how this area changes throughout the year could help determine areas best suited as refuges for wildlife dependent on sea ice, authors of the study said. The study presents context for policymakers to consider when they establish protected areas in the Arctic, said Kent Moore an atmospheric physicist at the University of Toronto in Canada, who is the lead author of the study.
The study was also reported by EurekAlert, the online publication of the American Association for the Advancement of Science.
Arctic warming has already created an environment which leads to younger sea ice. Now climate models predict Arctic summers will soon be ice free, maybe as early as 2030, so that less than 386,000 square miles of summer sea ice will blanket the entire Arctic Ocean.
As thin, young ice melts in future summers, only a 1,240-mile arc of ice will remain, stretching from the western Canadian Arctic Archipelago to Greenland’s northern coast, the study said. In this area, which experts call the Last Ice Area, sea ice is over five years old and can measure over 13 feet thick, compared to most ice covering the Arctic, which is just one to four years old, according to the National Snow and Ice Data Center at the University of Colorado at Boulder Cooperative Institute for Research in Environmental Sciences.
“We can’t treat the Last Ice Area as a monolithic area of ice which is going to last a long time,” said Moore. “There’s actually lots of regional variability.”
According to the study this Last Ice Area is dynamic, encompassing two sub-regions where ice thickness fluctuates by four feet from year to year. Ice is becoming thinner in two distinct subregions, which are losing 1.3 feet of ice thickness per decade, amounting to a five-foot loss of ice since the late 1970s.
What makes this Last Ice Area home to the oldest and thickest ice is ocean currents and atmospheric winds that carry patches of floating ice in a circular pattern. When these blocks of ice smash into each other, they pile up along the northern edges of Greenland and Canada.
Moore and his colleagues decided to track changes in the Last Ice Area to learn more about how this ice moves and melts during the year. Their study revealed two regions with distinct seasonal and inter-annual fluctuations, one to the east and one to the west.
In both areas sea ice was thinner and covered less area in summer months and early fall than in the Arctic winter, although ice thickness in the western sector tended to hit its minimum earlier in the season, while ice thickness in the eastern portion appeared to be more stable.
Western ice, hard hit by winds blowing clockwise, has begun moving faster, which could be the result of thinning ice, the report said.
Moore concludes that loss of ice in the Last Ice Area is likely the result of ice movement out of the region, particularly in the west. If sea ice thins and moves faster, pieces at the margins will flow first into the open ocean, followed by larger pieces from the center, like a big traffic jam, the study said.