High overall rates of permafrost cliff retreat, coupled with spatial variability, have been accompanied by increased uncertainty over future landscape dynamics. We map long‐term (>80 years) retreat of the shoreline and photogrammetrically analyze historic aerial imagery to quantify the processes at a permafrost coast site with massive ground ice. Retreat rates have been relatively constant, but topographic changes show that subsidence is a potentially critical but often ignored component of coastal sensitivity, exceeding landward recession by over three times during the last 24 years. We calibrate novel passive seismic surveys along clear and variable exposures of massive ground ice and then spatially map key subsurface layers. Combining decadal patterns of volumetric change with new ground ice variation maps enables past trends to be interpreted, future volumetric geomorphic behavior to be better constrained, and improves the assessment of permafrost coast sensitivity and the release of carbon‐bearing material.

Permafrost coasts are extensive in scale and complex in nature, resulting in particular challenges for understanding how they respond to both long-term shifts in climate and short-term extreme weather events. Taking examples from the Canadian Beaufort Sea coastline characterized by extensive areas of massive ground ice within slump and block failure complexes, we conduct a quantitative analysis of the practical performance of helicopter-based photogrammetry. The results demonstrate that large scale (>1 km 2) surface models can be achieved at comparable accuracy to standard unmanned aerial vehicle surveys, but 36 times faster. Large scale models have greater potential for progressive alignment and contrast issues and so breaking down image sequences into coherent chunks has been found the most effective technique for accurate landscape reconstructions. The approach has subsequently been applied in a responsive acquisition immediately before and after a large storm event and during conditions (wind gusts >50 km h −1) that would have prohibited unmanned aerial vehicle data acquisition. Trading lower resolution surface models for large scale coverage and more effective responsive monitoring, the helicopter-based data have been applied to assess storm driven-change across the exposed outer islands of the Mackenzie Delta area for the first time. These data show that the main storm impacts were concentrated on exposed North orientated permafrost cliff sections (particularly low cliffs, >20 m in height) where cliff recession was 43% of annual rates and in places up to 29% of the annual site-wide erosion volume was recorded in this single event. In contrast, the thaw-slump complexes remained relatively unaffected, debris flow fans were generally more resistant to storm erosion than the icerich cliffs, perhaps due to the relatively low amounts of precipitation that occurred. Therefore, the variability of permafrost coast erosion rates is controlled by interactions between both the forcing conditions and local response mechanisms. Helicopter-based photogrammetric surveys have the potential to effectively analyze these controls with greater spatial and temporal consistency across more representative scales and resolutions than has previously been achieved, improving the capacity to adequately constrain and ultimately project future Arctic coast sensitivity.

The coastline of the Inuvialuit Settlement Region (ISR) in the Mackenzie –Beaufort region of the western Canadian Arctic is characterized 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 1.8 ± 0.02 m/yr, a 22% increase over the previous 15 years and 17% 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.