Thermal and Mechanical Modeling of Coastal Erosion Processes on Tuktoyaktuk Island, Northwest Territories
Date
2021-09-16
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Abstract
Arctic coasts are particularly vulnerable to rapid and extreme erosion due to the presence of ice-rich permafrost sediment, with erosion rates varying anywhere from 1 to 20 m/yr in the region. Erosion is limited to the open-water season such that the factors controlling rates of erosion are warmer air temperatures and storm surges impacting the sensitive ice-rich permafrost coastal bluffs. Erosional processes in the Arctic are unique and consist of coupled thermal and mechanical mechanisms. The coastal community of Tuktoyaktuk, Northwest Territories, located along the Beaufort Sea coast in the western Canadian Arctic, has been dealing with the consequences of coastal erosion for many decades and will likely face displacement due to accelerating rates of erosion. In this study, a process-based thermal-mechanical erosion numerical model was developed for Tuktoyaktuk Island, which currently shelters the harbour and eastern shores of the community from wave impact, to investigate erosional processes commonly impacting ice-rich permafrost coasts including thermal denudation of the cliff face, and thermal abrasion and formation of thermoerosional niche at the base of the cliff under a storm surge to understand the impact of permafrost sediment properties on rates of erosion. It was found that erosion rates vary significantly between stratigraphic units, where sandy silt sediments have higher rates than ice rich clayey silt layers due to latent heat effects, and therefore should be considered on a site-specific scale for engineering purposes rather than the traditional cliff edge retreat method. The increased granularity improved our understanding of erosion rates on Tuktoyaktuk Island thus enabling future detailed consideration of mitigation strategies. It was concluded that massive block failure due to the formation of a thermoerosional niche under a storm surge is presently unlikely to occur on the island. For block failure to occur, either a storm of extreme duration or storm surge level is required. Lastly, it is expected that erosion rates will increase under climate-driven change such that the drivers of accelerated erosion are relative sea level rise, decrease in sea ice extent, and increase in surface air temperatures.
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Arctic, Permafrost, Coastal Erosion, Numerical Modeling
Citation
Ouellette, D. S. (2021). Thermal and Mechanical Modeling of Coastal Erosion Processes on Tuktoyaktuk Island, Northwest Territories (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.