Profile

Tabatha Rahman
Ph.D. student
Department of geography
Laval University
tabatha.rahman.1@ulaval.ca

Supervised by:

Pascale Roy-Léveillée (Regular member)

Research project description

Ground-ice formation, distribution and impacts on landscape evolution in the Hudson Bay Lowlands, northern Manitoba

Introduction: The Hudson Bay Lowlands (HBL) host Canada’s southernmost continuous permafrost, and are vulnerable to permafrost thaw and ground-ice melt associated with rapid climate warming. Permafrost terrain is susceptible to collapse upon thawing because when frozen, it can hold more water in the form of ice than what the soil pore-space can hold once thawed. Satellite imagery and preliminary field data south of Churchill in the HBL suggest that this region is rich in ground ice, specifically wedge ice and segregated ice. However, the Ground Ice Map of Canada (O’Neill et al., 2019), which used a paleogeographic reconstruction approach to predict ground ice potential across northern Canada, indicates scarce or non-existent ice wedges in Northern Manitoba. Permafrost and ground ice research in the HBL remain scarce, which reduces northern communities’ abilities to anticipate and mitigate risks associated with ground thaw, such as ground instability and infrastructure damage. Objectives: This research investigates the distribution and evolution of permafrost and ground ice in the continuous permafrost zone of the HBL, with a focus on the distribution, morphology, and development of a specific form of ground ice called ice wedges. The specific objectives of this project are to 1) assess the distribution of ground ice and its volume in different landscapes of the HBL, 2) elucidate the environmental conditions that favored ice-wedge growth in the HBL after the Tyrrell Sea retreated and uncovered the ground, and 3) develop a conceptual model of permafrost and ground-ice formation and degradation using existing spatial models of permafrost sustainability and response to climatic change. Study sites: Research will be conducted along a 165 km transect from Churchill to Herchmer, MB, along the Hudson Bay Railway. This North-South transect spans the continuous permafrost zone of the HBL, and reaches the southern limit of continuous permafrost near Herchmer. Study sites: with different ground-ice conditions will be selected based on remote sensing and in-situ observations, including palsas, peat plateaus and sites with extensive ice-wedge polygon networks that appear intact (potentially active) or that show signs of degradation and surface collapse. Material and methods: To assess the distribution and current state of permafrost and ground ice, a combination of satellite imagery, drone imagery, geophysical methods, and drilling for permafrost core extraction will be used. Ground temperature sensors will be installed at the ground surface and at the top of permafrost to record soil temperatures. To elucidate processes of permafrost and wedge-ice growth in the HBL, radiocarbon dating of dissolved organic carbon in ground ice will be used to establish ice growth timing. Geochemical concentrations and stable water isotope analyses will be used to determine the source of ice water. To develop a conceptual model of permafrost and ground-ice formation and degradation, projected rates of permafrost thaw will be combined with the assessment of ground ice distribution from  objective 1) with existing models of anticipated permafrost degradation in the HBL (e.g., NEST, previously applied in Wapusk, MB) (Zhang et al., 2012). References: O'Neill, H. B., Wolfe, S. A., & Duchesne, C. (2019). New ground ice maps for Canada using a paleogeographic modelling approach. The Cryosphere, 13(3), 753-773. doi: 10.5194/tc-13-753-2019 Zhang, Y., Li, J., Wang, X., Chen, W., Sladen, W., Dyke, L., . . . Burn, C. R. (2012). Modelling and mapping permafrost at high spatial resolution in Wapusk National Park, Hudson Bay Lowlands. Canadian Journal of Earth Sciences, 49(8), 925-937. doi: 10.1139/e2012-031

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