Developing a model to assess the erosion of permafrost coastlines in Northern Canada

Most Northern communities in Canada are located in coastal areas, which provide critical access to shipping lanes, traditional hunting grounds and important cultural ecosystem services. With climate change, the Arctic has been particularly dynamic due to rapid warming and associated glacier retreat and seasonal sea ice reduction. This has led to an increasing risk of flooding and erosion in coastal communities, as more open water results in higher waves and storm surges. These stresses have contributed to the rapid retreat of the coastlines in many areas, with the average retreat in the Arctic around 0.5 m per year. This retreat has a significant impact on communities as it threatens infrastructure, cultural sites, and freshwater resources, with cascading impacts such as releasing pollutants and stored carbon back into the environment.Unlike for temperate and tropical coastlines, the erosion of permafrost coastlines is due to both thermal and mechanical stresses acting on the coast through a process known as ThermoMechanical Erosion (TME). Erosion can occur when water accesses new areas of the coast ' for example, during a large surge event. The warmer, saline water induces thermal and saline gradients, which can initiate permafrost thaw. Thawed permafrost soils have greatly reduced soil strength and can therefore be easily eroded and transported through the mechanical action of waves and currents. At coastal bluffs, this process forms a thermomechanical niche, eventually leading to block failure that exposes more material to erosive stresses. As most models used for examining coastal processes were developed for southern shorelines, the unique processes driving erosion in the North are not well captured, creating critical gaps in both knowledge and engineering tools. The primary objective of the proposed project is the development of a model to investigate and predict TME along permafrost coastlines. The proposed project aims to take a bottom-up approach to model development, starting with the fundamental processes of TME and building in complexity at later iterations. Based upon previous empirical observations of TME, a numerical model will be developed that links mechanical processes with coupled density-dependent water flow, solute (salt) transport, and heat transfer with salinity-dependent freeze-thaw. The model will be validated using a set of physical modelling experiments to investigate the erosion of frozen soil samples exposed to wave action. The soil sample will be placed in an environmental containment unit to limit thermal processes to the seaside face of the sample. The idealized experimental setup will enable the model to be evaluated against specific thermomechanical processes. A field campaign will also be performed to help identify key limitations of the numerical model and physical model experiments. The project will train at least four HQP (one research intern, two Masters and one PhD) jointly supervised between INRS and Dalhousie University. This project will provide an important starting point for the development of a model that can aid communities in assessing the risk of coastal retreat as well as the design of infrastructure along Canadian permafrost coastline.