ABSTRACT: Limits of submergence and coastal response across the Canadian Arctic.

CGRG Bibliography of Canadian Geomorphology
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Abstract

As sea-level rise accelerates over coming decades, it can be expected to overtake rates of residual isostatic uplift in some parts of the Canadian Arctic. Some communities on previously emergent or stable shorelines may begin to experience rising relative sea levels with attendant impacts of inundation, increased ?ood risk, and accelerated shoreline erosion. We report here on part of an effort to develop projections for sea-level rise and potential coastal impacts at communities and other critical sites across the Canadian Arctic from the Yukon North Slope to northern Ellesmere Island to Labrador. Studies of geomorphological evolution and short-term shoreline change have been carried out to complement geodynamic modelling efforts and a network of continuous and episodic GPS measurements. In areas marginal to former centres of ice mass and rapid postglacial uplift, GPS observations and modelling efforts are particularly challenged to de?ne slow rates of uplift <2 mm a-1, yet areas within this range may be among the most susceptible to future sea-level rise. In such situations, we may gain insight on limits of submergence from geological evidence of marine transgression, such as shoreward migration of coastal landforms, landscape inundation, ?ooded river mouths, rising beach-ridge sequences, and widespread coastal erosion. Flooded coastal basins have been mapped on southern Banks Island and the mainland coast of the Parry Peninsula and adjacent islands. Evidence of coastal submergence can also be found on the north coast of Banks Island, where ?eld work in 2009 completed a third GPS epoch at three monuments and repeat surveys of coastal landforms documented slow coastal change. Flooded river mouths south of Ulukhaktok NWT and east of Kugluktuk NU, and rapid erosion including landward migration of beaches over backshore marsh adjacent to the Coppermine Delta all point to a transition to slow submergence in this area. In eastern Nunavut, a shallow submerged delta terrace and beach trangression over supratidal marsh at Clyde River suggest a recent switch to rising relative sea level (RSL) along the eastern edge of Baf?n Island, while the heads of the fjords remain emergent. Along the north side of Lancaster Sound (southeast Devon Island), published RSL curves descend below present sea level and rising RSL is indicated by coastal features such as the transgressive gravel barrier at Dundas Harbour, which has buried part of the path to the RCMP post. Across the Sound, the large beach-ridge foreland at Cape Charles Yorke on Baf? n Island and small forelands in northern Navy Board Inlet show seaward trends of rising beach-ridge crest elevation. Near Lavoie Point at the south end of Navy Board, where a well-constrained history of isostatic uplift and emergence is available, the youngest beach ridges show a slight tendency to higher crest elevation. Slow rates of uplift through the central Northwest Passage suggest that some parts may be on the cusp of a shift to submergence, consistent with the high active beach ridges at the base of emergent beach-ridge sequences on southern Cornwallis, Grif?th, and Lowther Islands.

Bibliography of Canadian Geomorphology