Mechanisms, volumetric assessment, and prognosis for rapid coastal erosion of Tuktoyaktuk Island, an important natural barrier for the harbour and community

The coastline of the Inuvialuit Settlement Region (ISR) in the Mackenzie–Beaufort region of the western Canadian Arctic is characterised by rapid erosion of ice-bonded sediments with abundant excess ground ice, resulting in widespread thermal and mechanical process interactions in the shore zone. Coastal communities within the ISR are acutely aware of the rapidly eroding coastline and its impacts on infrastructure, subsistence activities, cultural or ancestral sites, and natural habitats. Tuktoyaktuk Island is a large natural barrier protecting the harbour and surrounding community from exposure to waves. It is threatened by coastal erosion, a better understanding of which will inform adaptation strategies. Using historical and recent aerial imagery, high-resolution digital elevation models, cliff geomorphology, stratigraphy, and sedimentology, including ground-ice content, this study documents erosional processes, recession rates, volume losses, and sediment delivery since 1947 and projected into the future. Erosion along the northwest-facing (exposed) cliff, primarily by thermo-abrasional undercutting and block failure, has accelerated since 2000 to a mean of 1.80 ± 0.02 m/year, a 22% increase over the previous 15 years and 14% faster than 1947–2000. Lower recession rates on the harbour side of the island increased more than two-fold. Projection of future shoreline vectors by extrapolation, using the post-2000 accelerated coastal recession rates at 284 transects, points to breaching of this vital natural harbour barrier by 2044, after which rapid realignment is expected to occur as the new inlet evolves. Further acceleration of rates, as seems highly likely, brings the breaching date closer.