‘Triple whammy’ takes toll on Arctic erosion

Coastal erosion is a growing problem related to AGW you don’t hear much about.  Erosion, and habitat and property loss, is related to sea level rise, but can be compounded by other things such as changes in storm intensity and frequency and by fetch and exposure duration, which in the Arctic is increasing due to sea ice loss.

U. COLORADO—The combined effect of declining sea ice, warming seawater, and increased wave activity is causing the northern coastline of Alaska to erode by up to one-third the length of a football field each year.

Robert Anderson, associate professor of geological sciences at the University of Colorado at Boulder, says the conditions have led to the steady retreat of 30 to 45 feet a year of the 12-foot-high bluffs.

The bluffs are actually frozen blocks of silt and peat containing 50 to 80 percent ice—which are toppled into the Beaufort Sea during the summer months by a combination of large waves pounding the shoreline and warm seawater melting the base of the bluffs.

Once the blocks have fallen, the coastal seawater melts them in a matter of days, sweeping the silty material out to sea.

The problem is caused by several factors, including increased erosion along the Alaskan coastline due to longer ice-free summer conditions and warmer seawater bathing the coast, Anderson says.

The third potential factor is that 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.

“What we are seeing now is a triple whammy effect,” Anderson says.

“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.

Read the full story on Futurity here