Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Geography & Environmental Studies

Faculty/School

Faculty of Science

First Advisor

Prof. Dr. Philip Marsh

Advisor Role

Supervisor

Second Advisor

Dr. Elizabeth Priebe

Advisor Role

Supervisor

Abstract

The growing interest in Arctic regions will likely increase the use of nuclear energy in the Arctic. While this energy source has a high potential to improve economic opportunities in the Arctic, it also increases the release of radioactive material (radionuclides). Radionuclides are already found in the Arctic and are traced back to natural as well as anthropogenic sources. Water is one of the dominant transport vectors for solutes such as radionuclides or other contaminants. Therefore, improving our understanding of Arctic hydrology is important for assessing future environmental risks such as the release of radionuclides. Topographic and microtopographic features are a fundamental constraint for hydrology. This thesis investigates two dominant landscape features of the Arctic: mineral earth hummocks and ice-wedge polygons (IWPs), which both play an important role in the Arctic hydrological cycle. It is unclear whether the mobility of radionuclides will increase with a warming Arctic and thawing permafrost (ground that remains at or below 0°C for two consecutive years). This study seeks to build the foundation for such research by deepening our understanding of the distribution of mineral earth hummocks and the heterogeneity of bulk volumetric soil water content and frost table depth on IWPs.

IWPs are dominant features of Arctic lowland permafrost landscapes that are usually easily detectable, for example, from standard satellite imagery. They clearly influence local hydrology, and their ground structure is spatially heterogeneous. This makes it challenging to characterize the dynamics of their active layer (the part of the ground that freezes and thaws throughout the year) using traditional methods. Therefore, this thesis investigates the spatial variation of frost table depth and bulk volumetric soil water content across an IWP site near the Laurier Trail Valley Creek Research Station (TVC-RS) in the western Canadian Arctic. In the study, 500 MHz ground penetrating radar (GPR) surveys and frost table probing were combined to conduct a high-resolution study across ten transects. The results were used to interpolate the active layer depth and estimate the bulk volumetric soil water content by parameterizing the relative electric permittivity retrieved from the GPR survey. The results showed extreme spatial variability, with frost table depths varying by up to 0.8 m and bulk volumetric soil water content by more than 70% within a few meters. Additionally, it was found that the center of the IWP, which shows less evidence of subsidence compared to the surrounding area, had a deeper thaw front while being relatively dry. The GPR data were also used to estimate the widths of ice wedges, which range between 0.5 m to 1 m. The findings for the center of the study site imply that the site offers a good opportunity to study the degradation processes of IWPs in great detail. The ongoing monitoring efforts of the study site should be extended and re-evaluated on the basis of these findings.


Mineral earth hummocks are widespread in Arctic regions. They are usually found in groups and act as barriers in hydrological processes by increasing surface roughness. Therefore, they play an important role in solute transport processes such as radionuclide mobility, contaminant transport, and carbon cycling. Despite their importance, it is challenging to map mineral earth hummocks. This is due to the fact that their surface area is often similar to the resolution of existing light detection and ranging (LiDAR)-derived digital terrain models (DTMs). DTMs from other sources with higher resolution are often limited by overlying vegetation, which reduces their applicability given ongoing shrubification in the Arctic . Existing LiDAR-derived DTMs are often not published at the highest resolution available from the raw data. It is possible that the raw data could provide DTMs of approximately 0.5 m, which would be near the minimal resolution needed to resolve mineral earth hummocks. Here, the feasibility of using a 0.5 m resolution LiDAR-derived DTM to detect and map mineral earth hummocks in the western Canadian Arctic is evaluated. Because of the similarity between DTM resolution and hummock size, an analytical error propagation analysis was conducted to ensure that identified features represent geomorphic signals and not noise or interpolation artifacts. The mapping algorithm was validated against a ground-based frost table probing dataset and GPR surveys. The comparison revealed a ’slight to fair’ statistical agreement with ground data (with Cohen’s Kappa values ranging between 0.11 and 0.40), showing that the 0.5 m resolution represents the minimum resolution needed for hummock mapping. However, the spatial distribution of identified hummocks appears to align with expectations. Additionally, the vegetation cover of identified hummocks was analyzed using a random forest vegetation classification, showing that identified hummocks were mostly covered by shrubs (52.6%). This shows that LiDAR-based approaches for hummock mapping are necessary, as shrubs cover a large number of hummocks. Finally, it can be said that higher resolutions (e.g., 0.3 m) should be used to map individual features. However, a resolution like 0.5 m could be sufficient if only the spatial distribution of hummocks is required, for example, for modeling solute transport processes.

Overall, this thesis improves our understanding of the variation in frost table depth for IWPs similar to that of the study site. Additionally, it opens new research questions on the effects of soil moisture (bulk volumetric soil water content) on the degradation of IWPs. The presented hummock mapping algorithm should be adjusted further, as better ground validation is needed to improve its mapping capabilities. However, it already provides insight into possible mineral earth hummock hotspots, addressing a current bottleneck in remote sensing.

Convocation Year

2026

Convocation Season

Fall

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