Coastlines of the Findlay Island Group, Nunavut, and Mackenzie King Island, Northwest Territories: aerial video surveys and ground observations

Low-altitude aerial oblique video imagery acquired in 1986 provided the first continuous shore-zone coverage of the Findlay Island Group and the east and north coasts of Mackenzie King Island since vertical air photography in 1959-1960. The video was used to map physical shoreline characteristics and their changes since the earlier photography. Physical shore-zone characteristics and inshore sea-ice conditions were not significantly different in 1959 and 1986. Specific sites of sea-ice thrusting onshore had changed, but the landward extent of ice thrusting in 1986 did not exceed an older distinctive band of irregular, ice-pushed morphology. Along the shores investigated, the landward extent of ice-thrusting pre-dated 1959 and may be much older, marking the emerged, maximum postglacial landward extent of sea- ice impact. Eight primary shore types were identified based upon coastal processes, sediment texture and shore morphology. Two sea ice-dominated shore types - the scarred and shore ridge are unique to the northwestern Canadian Arctic Archipelago. All shores were low and consisted mainly of sand, mud, or a combination of the two. Gravel and bedrock fragments were present along some shores but did not dominate shore morphology. The distribution of shore types was closely associated with specific bedrock substrates. The present shore and adjacent backshore were dominated by sea ice and fluvial processes. Aeolian processes were locally important along some sand shores. Potential seasonal wave generation was greater along the Findlay Island Group than Mackenzie King Island. Wave generation along most shores was restricted by grounded multi-year ice or pressure ice ridges. Nevertheless, micro-tidal conditions concentrate the energy of very small waves across a narrow beach zone, enabling them to rework or cut these fine-grained shores. Wave-cut banks and minor wave-built features were developed best in small embayments and some inter-island channels where annual open water conditions were more common. Submerged river mouths and low-lying shores, some landward migrating beaches and an abundance of truncated ice-built features provide evidence for coastal submergence and marine transgression. Brief field investigations on Lougheed Island provided critical information on the development of three primary shore types during a time of substantive sea-ice cover. Issues related to shore clean-up of a potential marine oil spill are provided based on present physical attributes of each shore type. Given the low relief and backshore gradient, abundance of fine sediment, a rising relative sea level and increasing open water, dramatic changes in shore morphology and stability are anticipated in the northwest CAA in the next century. Markers were established at five sites to facilitate the measurement of future shoreline changes as environmental conditions change. Subsequent measurements of physical changes since 1986 have not been completed and are long overdue. Shoreline mapping from aerial video surveys along the shores of Mackenzie King Island would also benefit from additional ground investigations.

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