Understanding coastal erosion in Alaska Alaska Center for Climate Assessment and Policy Statewide Teleconference October 9, 2007. David E. Atkinson International Arctic Research Center / Atmospheric Science Program University of Alaska Fairbanks
Coastal erosion: Significant, immediate/near-term threat for many Alaska (and Arctic) communities Several AK villages are in need of emergency intervention Shishmaref Newtok Kivalina Many more are threatened US Army Corps of Engineers reports Baseline Technical Erosion report (2006) Information Paper (July 2007) US General Accounting Office (GAO 2003)
Coastal erosion (Shishmaref October 2004) Photo: Tony Weyiouanna Sr.
Coastal erosion (Shishmaref October 2005) Photo: Ned Rozell
Photos: Tony Weyiouanna Sr. Shishmaref bluff retreat severe erosion caused by
waves Teller, AK
and flooding (inundation storm and tsunami) Teller, AK
and flooding (inundation storm and tsunami) Teller, AK
Both of these are responses of the water to being "forced" by a "driver" > Unlike the south, this response is altered by ice > Ice greatly complicates study and understanding > Also must consider the sea depth near the shore > shallow shelf vs. deep water > Erosion response also dependent on the coast > type of sediment (rocks or loose) > ice in the ground > shore facing (cliff/no cliff) > stabilizing vegetation
Waves Waves caused by wind drag transfer of wind energy to water > Stronger wind = more energy = higher waves > Also stable winds (persistent) > And long fetches of open water > Combination gives very large waves
How do waves erode? Kinetic energy just like a car crash
How do waves erode? Kinetic energy just like a car crash Do the math! Two cubic yards of water 6 feet wide, 3 feet high, 3 feet deep = two tons a mid-size car hitting at 31 miles per hour one every 10 seconds! - of course water is not rigid but there is still a lot of force recall standing in the surf
What happens to all this energy as waves near the coast? Why aren t they hammering all coasts into oblivion?
What happens to all this energy as waves near the coast? Why aren t they hammering all coasts into oblivion? > Wave energy is dissipated as they move up the beach slope
Foreshorten and break as approach shallows Shallow slope provides for energy dissipation = weak waves at the beach and no heavy impact (recall Teller photo) Steeper shoreface = less energy dissipation = stronger waves at the beach
Surges Persistent wind (direction, speed maintained) near the coast can lead to surges > Short-term increases in water level (several hours) cause > flooding (inundation) > allow waves to attack higher up on bluff > arguably the most damaging coastal impact of a storm
And Nome (Oct. 2004)
Nome, AK during the storm
Nome, AK Front Street (where the Iditarod finishes)
Return to ICE Said that ice complicates things how for the marine side?
Add sea ice waves are reduced
Ice frozen into the ground at the coast - "land fast" or "shore fast" ice - armors and protects the coast against waves - And thus: Trends of later freezeup and earlier melt expose the coast to greater potential damage
If sea ice is not land fast the wind can move ice ashore as an "ice push" an "ivu"
Barrow ivu 2006 Photo of Anne Jensen taken by Alice Brower.
Taken by me in Gambell, May 2006
Ice on the terrestrial side Permafrost permanently frozen ground > Very strong when frozen > Very weak when melted mud, essentially
Permafrost can be melted > By the relatively warm water > By warm temperatures/solar radiation
Permafrost coasts Cliff notching and slope slump failure High wave energy + positive surge S. Solomon, Cdn Beaufort S. Solomon, Cdn Beaufort Thermal stress on ice bodies Arctic Coastal Dynamics 5 th Annual meeting Montréal, Canada Block failure S. Solomon, Cdn Beaufort A. Mahoney, US Beaufort V. Rachold, East Siberian V. Rachold, Laptev
In fact for arctic coasts Trying to calculate rates of erosion using only wave energy will not give you the whole story
Responses - storms research - coastal dynamics research - partnerships with NOAA and EPA - partnerships with educational outreach
Nome storm counts
Compilation: Brown, Jordan and Graves
Responses: projects I have underway NOAA Cooperative Institute for Arctic Research (NOAA-CIFAR office, UAF) Pacific Region Integrated Data Enterprise (2 projects) 1. With James Partain of NOAA s National Weather Service (Anchorage) directly improve NOAA s coastal forecast ability 2. With John Marra/Eileen Shea of NOAA s Pacific Services Center (Honolulu) develop climatology products tailored to end-users NOAA Oceanic and Atmospheric Research (NOAA OAR) Social Vulnerability to Climate Change in Alaska Coastal Communities Large, interdisciplinary project Anthropology, Marine Ecology, Weather Modeling, Climate research Work directly with communities to identify specific problematic weather types and trends EPA Office of Research and Development (EPA ORD and Region 10) Improved Inundation-Hazard Warning Capacity in the Arctic Coastal Zone With John Lyon and Jackie Poston parntership with NOAA to support development of detailed wave modeling for AK
Responses data gathering for wind analysis (partner with a UAF Geophysical Institute education project)
Take home points: Reduction of sea ice is a major problem for erosion In the Arctic erosion must be considered in terms of wave energies and temperature (melt) permafrost issues Surges must be factored in flooding/inundation events worsen wave erosion
Thank you questions?