Scientists from the University of Colorado, Boulder, and the United States Geological Survey have provided Dot Earth with a closeup view of the remarkable rate of erosion along parts of Alaska’s thawing Arctic Ocean coast. The video clip below is one month of crumbling, from late June through late July this year, at a point east of Barrow, the northernmost community in the United States. It’s clear that simple thawing is much more of an influence than wave action at this spot.

Several influences are speeding the land loss, according to Cameron Wobus, a visiting postdoctoral fellow at the university’s Cooperative Institute for Research in Environmental Sciences. He answers a few questions below:



Q. Any idea how this rate of land loss compares to the long-term trend?

A. There are only a couple of studies documenting long-term trends in coastal erosion rates in this chunk of Arctic. Both of them suggest that rates have been increasing in recent decades. Mars and Housenecht at U.S.G.S. in a 2007 Geology paper looked at Landsat imagery that suggested that erosion rates between 1985-2005 were about twice the rates documented between 1955-1985; more recently Ben Jones at U.S.G.S. has suggested in a paper in review that rates over just the past decade are faster and more uniform than historical rates. But certainly the 20+ meters/year we’ve seen over the past couple years cannot have been sustained too far into the past.



Q. What are biggest contributors?

A. We’re still in the midst of quantifying the relative roles of thermal vs. mechanical (i.e., wave) energy in driving that you’ve now seen, it’s clear that simple melting away at the base of the bluffs followed by topple-failure is a major contributor. But in imagery we’ve obtained for the latter part of the summer, it’s also clear that episodic storm events can do a lot of damage, as well. We were stymied this summer in our attempts to deploy wave sensors offshore to document the wave energy inputs because (ironically) the sea ice along the northern N.P.R.A. coastline actually hung around long enough that we couldn’t get out in our Zodiac to deploy them.



Q. Are other areas GAINING land through sediment accretion? (That silt has to go somewhere…)

A. I should emphasize that we’ve so far been focusing only on this ice-rich, silty section of coastline. In this particular environment, it doesn’t look like there are strong negative feedbacks on erosion rates because the material appears to be simply too fine-grained and ice-rich to be redeposited locally and form barriers, bars, etc. However, there is some indication from previous work that there are parts of the Beaufort coast where more sandy material is being redeposited by long-shore currents. Next summer we plan to focus our field work on a more sandy section of coastline to try to understand the dynamics there.