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Van Tuyl Lecture: Matt Thomas, USGS
September 26, 2019 @ 4:00 pm - 5:00 pm
Matt Thomas, United States Geological Survey
Berthoud 241, 4-5PM
The Arctic Coastal Erosion Problem
Abstract: The Arctic coastline spans ~45,000 km (28,000 miles) across six nations, including the United States. Declining sea ice in the Arctic Ocean has increased the length of the open-water season, exposing the coasts to more frequent and intense forms of wave energy and storm surge. As a result, rates of coastal erosion in the Alaskan Arctic have doubled since the middle of the 20th century, and are now among the highest in the world. Much of the Alaskan Arctic is inaccessible by all-season roads; therefore, people and infrastructure are concentrated near the coast. Native coastal villages in Alaska are now more frequently affected by erosion, with some facing relocation. Active U.S. Department of Defense sites, including long-range Arctic coastal radars dedicated to maintaining national sovereignty in the air, need to be fortified due to higher-than-expected rates of bluff retreat. Overall, the price to develop new public or private coastal infrastructure in the Arctic is projected to increase dramatically. Scientific knowledge and engineering tools to plan for coastal erosion are largely confined to geographic regions with temperate climates dominated by non-cohesive sediments. The character of erosion exhibited by the cohesive, permafrost-laden bluffs in the high latitudes of the Alaskan Arctic, however, is not well-explained by these tools. Therefore, investigation of the oceanographic and thermo-mechanical processes that are relevant to permafrost bluff failure along Arctic coastlines is needed. This presentation will introduce the Arctic Coastal Erosion (ACE) Model, an approach that aims to sequentially couple numerical simulations of (i) circum-Arctic wave conditions, (ii) nearshore circulation, and (iii) coastal bluff failure. The bluff failure model includes the solution of a geomechanical boundary-value problem that produces three-dimensional fields of stress and displacement. Preliminary simulations focusing on coastal permafrost bluff stress states for an Alaskan site that is prone to toppling-mode landslide movement will be discussed.