Abstract
Scientific knowledge and engineering tools for predicting coastal erosion are largely confined to temperate climate zones that are dominated by non-cohesive sediments. The pattern of erosion exhibited by the ice-bonded permafrost bluffs in Arctic Alaska, however, is not well explained by these tools. Investigation of the oceanographic, thermal, and mechanical processes that are relevant to permafrost bluff failure along Arctic coastlines is needed. We conducted physics-based numerical simulations of mechanical response that focus on the impact of geometric and material variability on permafrost bluff stress states for a coastal setting in Arctic Alaska that is prone to toppling mode block failure. Our three-dimensional geomechanical boundary-value problems output static realizations of compressive and tensile stresses. We use these results to quantify variability in the loci of potential instability. We observe that niche dimension affects the location and magnitude of the simulated maximum tensile stress more strongly than the bluff height, ice wedge polygon size, ice wedge geometry, bulk density, Young’s Modulus, and Poisson’s Ratio. Our simulations indicate that variations in niche dimension can produce radically different potential failure areas and that even relatively shallow vertical cracks can concentrate displacement within ice-bonded permafrost bluffs. These findings suggest that stability assessment approaches, for which the geometry of the failure plane is delineated a priori, may not be ideal for coastlines similar to our study area and could hamper predictions of erosion rates and nearshore sediment/biogeochemical loading.
Highlights
Permafrost coastlines account for one-third of the global coastline (Lantuit et al, 2012)
The value of the work we present here lies in its ability to (1) improve process-based understanding of coastal permafrost bluff failure characteristics and (2) provide a foundation for more complex simulation scenarios geared toward resolving long-term erosion rates from an eventbased perspective
We simulated the impacts of variability in coastal permafrost bluff geometry and material properties on stress states leading up to block failure using continuum mechanics theory with static simulations of 3D elastic finite deformation
Summary
Permafrost coastlines account for one-third of the global coastline (Lantuit et al, 2012). Declining sea ice in the Arctic Ocean has increased the length of the open-water season, exposing permafrost coastlines to more frequent and intense forms of wave energy and storm surge (Maslanik et al, 2007; Serreze et al, 2007; Overeem et al, 2011; Simmonds and Rudeva, 2012; Stammerjohn et al, 2012; Vermaire et al, 2013; Barnhart et al, 2014a). Much of Arctic Alaska is inaccessible by all-season roads; people and infrastructure are concentrated near the coastline. Coastal erosion in Arctic Alaska is projected to increase the cost of maintaining infrastructure (e.g., roads and pipelines) by billions of dollars in the coming decades (Larsen et al, 2008). The financial impact of enhanced coastal erosion will likely be further exacerbated by emerging geopolitical pressures, including the discovery of natural resources (e.g., hydrocarbons and minerals) and the opening of new shipping routes and the construction of support facilities in the Arctic (Clement et al, 2013)
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