E-Thesis 301 views 128 downloads
Integrated Geophysical Investigations of a Methane Releasing Pingo in a Changing Permafrost Environment, Svalbard / CRAIG HAMMOCK
Swansea University Author: CRAIG HAMMOCK
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Copyright: The Author, Craig P. Hammock, 2023. Distributed under the terms of a Creative Commons Attribution 4.0 License (CC BY 4.0).
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DOI (Published version): 10.23889/SUthesis.63653
Abstract
Open-system pingos form a fluid-flow conduit through continuous permafrost that enables the release of methane; a potent greenhouse gas. However, the factors that impact the formation and structure of open-system pingos remains poorly understood, and the parallels that these terrestrial landforms ha...
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Swansea, Wales, UK
2023
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Kulessa, Bernd; Hubbard, Alun; Hodson, Andrew J.; Hiemstra, John F. and Thompson, Sarah S. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa63653 |
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| Abstract: |
Open-system pingos form a fluid-flow conduit through continuous permafrost that enables the release of methane; a potent greenhouse gas. However, the factors that impact the formation and structure of open-system pingos remains poorly understood, and the parallels that these terrestrial landforms have with methane emitting submarine forms is uncertain. In this thesis, a series of geophysical investigations are conducted on Lagoon Pingo, Svalbard: a coastal open-system pingo that emits locally significant quantities of methane. In investigations into pingo structure through electrical resistivity tomography, resistivities imply that Lagoon Pingo is dominated by segregation ice, thereby highlight the impact of frost-susceptible, fine-grained sediments on pingo formation. Seismic investigations outline the depth of these sediments locally (~68 m), and indicate an uncertainty surrounding the flow path of local groundwaters. Constraining the groundwater dynamics through self-potential investigations, elevated magnitudes in potential measurements on the northern side of the pingo are interpreted as groundwaters flowing beneath the pingo complex from an alluvial fan on the northern side of Lagoon Pingo. Transient electromagnetics, when combined with seismic velocities within a four-phase model, identify a heterogeneous layer containing alluvial fan deposits beneath the open-system pingo. The integrated geophysical observations highlight the role that alluvial fans can have in pingo growth, by providing a hydraulically conductive medium through poorly permeable sediments characteristic of Holocene marine environments. This can act as a confined aquifer, explaining the artesian conditions at Lagoon Pingo. This also provides sedimentological circumstances that were favourable for previous pockmark formation, and may explain how a spring has persisted through Holocene sedimentation. These integrated geophysical investigations therefore highlight the role that alluvial fans have in pingo formation, and indicate how open-system pingos may evolve from submarine seeps and pockmarks. |
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| Keywords: |
Pingo, permafrost, geophysics, methane release |
| College: |
Faculty of Science and Engineering |