Washington: A portion of the northern Alaska coastline is eroding by a maximum of 45 feet annually, thanks to the combined effect of declining sea ice, warming sea water and increased wave activity, says a new study.
The conditions have caused the steady retreat of 30 to 45 feet a year of the 12-foot-high bluffs - frozen blocks of silt and peat containing 50 to 80 percent ice, said Robert Anderson, Colorado University-Boulder (CU-B) associate professor and study co-author.
"What we are seeing now is a triple whammy effect," said Anderson. "Since the summer Arctic sea ice cover continues to decline and Arctic air and sea temperatures continue to rise, we really don`t see any prospect for this process ending."
The longer the sea ice is detached from the coastline, the further out to sea the sea-ice edge will be. This open-ocean distance between the sea ice and the shore, known as the "fetch," increases both the energy of waves crashing into the coast and the height to which warm seawater can come into contact with the frozen bluffs, said Anderson.
"One of the concerns we have is that some larger ponds and lakes located slightly further inland may begin draining into the sea as the shoreline continues to recede," said Anderson.
Arctic sea ice during the annual September minimum is now declining at a rate of 11.2 percent per decade, said the CU-B study.
Only 19 percent of the ice cover was more than two years old -- the least ever recorded in the satellite record and far below the 1981-2000 summer average of 48 percent.
Anderson, along with Cameron Wobus of Stratus Consulting and Irina Overeem of CU`s Institute of Arctic and Alpine Research (INSTAAR) presented results from components of their study at the annual meeting of the American Geophysical Union in San Francisco Dec 14 - 18.