The impact of climate change on an emerging coastline affected by discontinuous permafrost: Manitounuk Strait, northern Quebec

Abstract

A comparative analysis of air photos and a field survey show that permafrost-affected sectors of the coastline along Manitounuk Strait receded at an increasing rate between 1950 and 1995. These sectors are in bays where post-glacial Tyrrell Sea clays outcrop. During the same period, sand beaches at the mouths of streams and rock and till shorelines on headlands prograded at the pace of isostatic uplift. Permafrost that had aggraded and formed lithalsas and plateaus during the 19th century (i.e., during the Little Ice Age) had expanded over the tidal marsh and had locally provoked accelerated coastal emergence as frost heaving added to post-glacial isostatic uplift. Climate warming during the 20th century, particularly during the summer months, generated a chain of impacts involving forest growth, snow cover, ground warming, and permafrost degradation. Waves and tidal currents are mainly responsible for the evacuation and transport of thermokarst-produced silts and clays from the shore into the marine basin.