Permafrost aggradation and degradation in relation to disturbance in isostatically uplifted landscapes of the Hudson Bay region

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Purpose and objectives My long-term research goal is to explain the susceptibility of permafrost terrain to thaw as well as its potential for post-disturbance recovery by examining a suite of interactions between climate, vegetation, and Quaternary history. I aim to facilitate direct application of my research results in other fields via collaborations with, for instance, experts in infrastructure design and maintenance, carbon cycling, contaminant mobilisation, and with local knowledge holders who can facilitate proactive adaptation to environmental change in their own communities. In the next five years, I propose to characterize permafrost thermal conditions and dynamics in isostatically uplifted landscapes surrounding the Hudson Bay, particularly in the Hudson Plains ecoregion, which hosts a permafrost wetland of global significance and a range of existing and planned infrastructure (e.g. Churchill Railway, roads, several communities) yet where permafrost conditions are poorly understood and largely understudied. My proposed research focuses on three themes: 1. Links between Quaternary history and permafrost conditions in a sequence of isostatically uplifted, emerged landscapes in the Hudson Plains region. We will investigate the aggradation of permafrost and ground ice in relation to post-emergence vegetation succession, with a focus on wedge ice distribution, activity, and growth rates. This will improve the model used in the latest Ground Ice Map of Canada, which includes important unresolved inaccuracies in this region. 2. Controls on terrain vulnerability to different mechanisms of permafrost degradation and associated landscape evolution pathways. In lowlands, we will elucidate controls on pond and lake expansion rates, early stabilisation, and post-drainage permafrost recovery. On hillslopes, we will investigate relations between the warming of ground temperatures, associated changes in geotechnical properties, and recent increases in mass wasting in Tyrell Sea deposits along Hudson Bay tributaries. 3. Implications of permafrost degradation patterns for biogeochemical cycling. We will investigate the impacts of permafrost degradation processes (e.g. increases in unfrozen water content near 0°C, active layer deepening and thaw subsidence, thermoerosion) on the emission of greenhouse gases from decomposing thawed organics, and on the methylation and potential mobilisation mercury towards water bodies. Anticipated impacts This project will improve understanding of landscape-scale permafrost dynamics in this crucial and understudied region of the Canadian North, elucidate controls on permafrost aggradation and degradation in lowlands near the forest-tundra transition, and advance understanding of mass-wasting in emerged permafrost landscapes. This research will provide crucial foundations to predict consequences of landscape change on ecosystems, biogeochemical feedbacks, hydrological regimes, and risks to communities and infrastructure.