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TitlePermafrost coast sensitivity to air temperature and storm influence on Pullen Island, N.W.T.
AuthorBay, B H; Whalen, D; Lim, M
SourceArcticNet, ASM2019 Annual Science Meeting: abstracts/ArcticNet, ASM2019 Réunion scientifique annuelle : abstracts/ArcticNet, ASM2019 Annual Science Meeting: abstracts; 2019 p. 154 (Open Access)
LinksOnline - En ligne (complete volume - volume complet, PDF, 2.80 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20200480
MeetingASM2019 - ArcticNet Annual Science Meetin; Halifax, NS; CA; December 2-5, 2019
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaPullen Island; Beaufort Sea; Mackenzie Delta
Lat/Long WENS-135.0000 -134.0000 69.8333 69.6667
Subjectssurficial geology/geomorphology; environmental geology; geophysics; Nature and Environment; Science and Technology; permafrost; ground ice; coastal environment; coastal erosion; storms; temperature; climate effects; landslides; slope failures; slumps; remote sensing; field work; permafrost thaw; climate change; airborne platforms
Released2019 12 01
AbstractThe ice-rich cliffs along the Canadian Beaufort Sea are subject to the rapid erosion characteristic of permafrost coasts. The Mackenzie Delta region experiences, on average, 1 m/yr coastal erosion, with rates in excess of 20 m/yr reported at some sites. Thaw-related erosion presents a unique problem to investigating the effects of changing weather trends on coastal dynamics; warming temperatures not only affect erosion indirectly by increasing energy to storms, but also have a direct influence on thaw rates. Two predominant failure mechanisms are identified for this study. Failure of intact frozen blocks, attributed to undercutting from wave action, is a dramatic and episodic process, characteristic of the permafrost cliffs along the Beaufort Sea coast. Slumping, a gravity driven movement of active layer sediments with the potential to form sprawling thaw complexes through rapid, retrogressive headwall retreat, is also present throughout the Mackenzie Delta region. Pullen Island, one of the outer islands of the Mackenzie Delta, exhibits both block failure and slumping along fairly constrained cliff sections, allowing the investigation of relationships between weather trends and erosion rates with regard to specific failure mechanisms. We use aerial imagery and ground survey data to show that mean erosion rates increased progressively from 0 + 4.8 m/a in 1947 to 12 + 0.3 m/a in 2018, accompanied by an increase in the variability of erosion rate across the study area. The increased heterogeneity of the cliff retreat rate is likely a result of different magnitudes of response to changing weather trends depending on erosive mechanism, and thus the morphological differences (such as cliff height and ground ice occurrence) which prescribe the mechanism. When compared to the summer air temperature and storm records, it was found that a correlation exists between mean erosion rate and both temperature and storm duration. However, when the study area is sub-divided based on erosive mechanism, the correlation with summer air temperature was stronger in areas where slumping was dominant than in block failure areas. Similarly, the correlation with storm duration was stronger in areas where block failure was the dominant mechanism compared to slumping areas. 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. Coastal sites are typically assessed based on mean retreat rates for the entire surveyed section. Areas chosen for study because of a single erosive mechanism of interest are likely to show a fairly uniform change in erosion rate. However, the presence of multiple erosion mechanisms, with mixed response to the changing climate, can complicate projections of future coastal change. Based on observations at Pullen Island, we can expect coastal erosion rates across the Beaufort Sea area to increase and diversify in response to the current and projected climate trends.