Coastal Erosion Responses for Alaska - the National Sea Grant ...

Coastal Erosion Responses for Alaska: Workshop Proceedings 25
Alaska Sea Grant College Program • AK-SG-06-03, 2006
Ice, Wind, Waves, and Storminess
Trends along the Alaska Coast
David E. Atkinson
International Arctic Research Center/Department of Atmospheric Sciences,
University of Alaska Fairbanks, Fairbanks, Alaska
Introduction
Alaska has emerged as the canary in the mine for manifestation of climate
change. We are not discussing hypothetical situations but instead are dealing
with emerging, serious problems on a variety of fronts. The coastal zone
has been among the hardest hit. This paper briefly reviews trends in major
environmental forcing parameters that affect the coast, and focuses on likely
trajectories for these trends, so that state planners and agencies have a better
idea where to commit resources.
Sea ice
Sea ice is one of the most important moderating/driving agents in the arctic
coastal zone. Its effects are manifested in a variety of ways: land-fast ice significantly
dampens wave energy incident upon the coast. Open water distance to
the ice edge controls wind fetch which in turn governs wave and surge height.
Ice floes driven ashore by the wind can exert significant geomorphological
impact at the local scale. Sea ice trends of interest to coastal managers center
around the first two factors. In general, trends over the last two decades have
been toward later land-fast ice formation and greater open water distances.
There are three important factors to bear in mind, however, when working
with sea ice trends and projections. The first is that there are long-term, multidecadal
cycles in sea ice occurrence that are imperfectly understood at the
present time. Some researchers feel that, despite the recent trend, there will
be a return to heavier ice conditions, such as were observed along the north
shore in the mid-late 1970s. Second is the inherent year-to-year variability in
sea ice cover. This stems from a broader issue, that trends in natural phenomena
are rarely the smoothed, gradual slope that statistical assessments reduce
them to, but instead represent averages that in some cases encompass significant
swings about the average point. Computer model simulations of arctic