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TitleLong-term ice-rich permafrost coast sensitivity to air temperatures and storm influence: lessons from Pullen Island, Northwest Territories, Canada
AuthorBerry, H B; Whalen, DORCID logo; Lim, M
SourceArctic Science vol. 7, issue 4, 2021 p. 723-745, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200675
PublisherCanadian Science Publishing
File formatpdf; html
ProvinceNorthwest Territories
AreaPullen Island; Canada
Lat/Long WENS-138.3333 -131.3333 70.1667 68.2500
SubjectsScience and Technology; general geology; coastal erosion; permafrost; Climate change; Arctic
Illustrationslocation maps; satellite images; charts; diagrams; photographs
ProgramClimate Change Geoscience Coastal Infrastructure
Released2021 01 29
AbstractThe potential effects of climate change on the length of the open-water season, storm activity, and annual permafrost thaw have raised concerns over the future of the Beaufort Sea permafrost coasts, which already have some of the highest erosion rates in the Arctic. The research examines a marked acceleration in cliff retreat rate in the outer Mackenzie Delta (Pullen Island) over a 71-year period based on aerial photogrammetry and historic imagery. Block collapse from notch development in sub-vertical cliffs and slumping from sprawling thaw complexes are the two predominant failure mechanisms governing coastal erosion in this region. Using a combination of aerial imagery and ground survey data we show mean erosion rates increased from 0 + 4.8 m/a in 1947 to 12 + 0.3 m/a in 2018. The rate of cliff line retreat also became more varied through time. The erosion responses are positively correlated with summer air temperature; this relationship has a stronger correlation coefficient in areas where slumping is the dominant erosive mechanism compared to areas where block failure is dominant (r2 = 0.08), and compared to the mean rate for the entire study area (r2 = 0.34). Similarly, there is a significant positive correlation between storm duration and the rate of retreat, which is stronger in areas where the dominant mechanism is block failure compared to areas where slumping is dominant.. These data indicate that storm duration has the greatest impact on these ice-rich permafrost coasts and most acutely on areas undergoing block failures, whilst air temperature has a greater impact on slump-dominated areas than elsewhere along the coast. The increase in heterogeneity of the cliff retreat rate is likely a result of different magnitudes of response to the increase in summer air temperatures and storm duration depending on erosive mechanism, and on the morphological differences such as cliff height and ground ice occurrence, which prescribe the occurrence of retrogressive thaw slumps.

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