Seismic and electrical geophysical characterization of an incipient coastal open-system pingo:Lagoon Pingo, Svalbard

• Main Authors: Hammock, C. P. (Craig P.), Kulessa, B. (Bernd), Hiemstra, J. F. (John F.), Hodson, A. J. (Andrew J.), Hubbard, A. (Alun)
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2022
• Subjects: electrical resistivity tomography; methane release; open-system pingo; permafrost; seismic reflection; seismic refraction; Adventdalen; Svalbard; Ice; open system Pingo
• Online Access: http://urn.fi/urn:nbn:fi-fe2022092760263

Abstract Whilst there has been a recent appreciation for the role of open-system pingos in providing a fluid-flow conduit through continuous permafrost that enables methane release, the formation and internal structure of these ubiquitous permafrost-diagnostic landforms remains unclear. Here, we combine active-source seismic measurements with electrical resistivity tomography to investigate the structural and subsurface characteristics of an incipient open-system pingo actively emitting methane within the glacio-isostatically uplifting fjord valley of Adventdalen, Svalbard. Wavefront inversion of seismic refractions delineate a spatially heterogeneous active layer, whilst deeper reflections identify the lithological boundaries between marine sediments and underlying shales at ∼68 m depth (p-wave velocity of ∼1,790 ms−1). Low geometric mean inverted resistivities of 40–150 Ωm highlight the dominance of saline permafrost, whilst elevated resistivities (∼2 kΩm) occur close to the groundwater spring and in heaved areas around the pingo. Based on our results, we speculate that segregation ice dominates the pingo structure, given the absence of a notable resistivity contrast characteristic of injection ice that is typically expected within early open-system pingo formation, and provides the most plausible geomorphic agent within the local fine-grained sedimentology. Our results thereby indicate that sediment grain size and moisture availability can provide important controls on pingo formation. This study shows that open-system pingos in coastal, saline permafrost environments may form differently, with implications for localized permafrost structure, its permeability to underlying gas reservoirs and consequent methane release.