Investigating the Geothermal Energy Potential and Permafrost Structure in Nunavut with Magnetotelluric Data
Bibliographic record
Abstract
To reduce reliance on fossil fuels, Canada is investigating the development of alternative energy systems that have lower carbon emissions than those currently in use. This is particularly important for communities in the Canadian Arctic, where the vast majority of electricity and heat is currently generated by burning fossil fuels. Geothermal energy systems have the potential to provide an alternate source of heat in this region, and their feasibility in remote Northern settlements is being investigated. Knowledge of subsurface rock type and groundwater conditions is an essential part of exploration for geothermal energy. In summer 2023 a group from the University of Alberta collected magnetotelluric (MT) data at two communities in Nunavut to investigate the subsurface conditions. The MT method can determine the subsurface electrical resistivity to depths of several kilometers. Resistivity is a parameter that is sensitive to the temperature and porosity of the subsurface, and to the quantity and salinity of groundwater. At Cambridge Bay, MT data was collected at 26 stations in July 2023 in an east-west array that covered an area of 17 x 8 km. At Resolute Bay, 33 stations were recorded in August 2023 in a region that was 8 x 5 km. Data from an additional 11 stations were previously recorded at Resolute Bay in 2022. The time series data were processed to give frequency domain data in the frequency band 500 – 0.001 Hz. The data were then used to generate models of subsurface resistivity using a combination of 1-D and 3-D inversion methods. Interpretation of the resistivity used knowledge of subsurface temperatures and experiments on frozen / unfrozen sedimentary rocks that contained saline ground water. At Cambridge Bay the resistivity model was characterized by two layers: (1) a 100 m thick surficial layer that has a low-resistivity due to the presence of limestone saturated with partially frozen saline pore water and (2) a deeper high-resistivity layer interpreted as limestone containing low salinity pore water. Knowledge of the geothermal gradient suggests that the upper part of this surface layer was frozen and the lower part unfrozen. At Resolute Bay, the resistivity model was characterized by three layers: (1) a high-resistivity limestone layer containing partially frozen saline pore water (2) a low-resistivity layer containing unfrozen saline pore fluids, and (3) a deeper high-resistivity layer containing low salinity pore water. Porosity estimates of the subsurface below Cambridge Bay were low, indicating poor natural reservoir potential, whereas the subsurface below Resolute Bay may have greater porosity. These results also indicate that the geothermal gradients at both communities are relatively low, suggesting that direct use geothermal installations are more feasible at each location, and engineered geothermal systems (EGS) may be required to produce the reservoir characteristics required for geothermal use. The low resistivity of the 100 m thick surface layer at Cambridge Bay may have originated in the diffusion of seawater from the surface when the land surface was submerged after the retreat of the Laurentide Ice sheet. Simple 1-D diffusion modelling is consistent with the timescales and layer thickness of approximately 100 m.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".