Beaufort offshore permafrost and gas hydrates – Climate change impact on Arctic transgressed continental shelves
Final Report Abstract
To date, submarine permafrost is still underexplored. In the context of climate change, submarine permafrost needs to be better understood in order to estimate its contribution to the global carbon-climate feedback. Through collaboration with the Geological Survey of Canada (GSC) and the Korea Polar Research Institute (KOPRI) we were able to access high-resolution multichannel seismic (MCS) data on the Canadian Beaufort Shelf. Using the MCS data, our study demonstrates that marine MCS data are a suitable and comprehensive tool for investigating submarine permafrost and permafrost-associated gas hydrates in a challenging shallow-water shelf setting. In a first study, we processed existing data from previous expeditions to the Canadian Beaufort Sea with the aim to delineate submarine ice-bearing permafrost and associated gas hydrate occurrences by seismic reflection imaging techniques. Direct and indirect reflection seismic indicators for ice-bearing permafrost and gas hydrates were identified and further used in a subsequent study to model the regional occurrences for the thermal base of permafrost, a boundary that is not necessarily visible in seismic data due to the lack of a sufficiently sharp impedance contrast. The outcome of our work indicates that the thermal base of permafrost still extends close to the shelf edge at ~100 m water depth. Although such regional extent was previously proposed by numerical modelling, analyses of existing borehole data suggested a thermal permafrost boundary that has retreated significantly landward from the shelf edge. The results of our new study suggest a refined picture of the outer thermal permafrost extent and indicate that since the onset of the Holocene marine transgression the submarine permafrost at the Beaufort Shelf is less degraded than previously assumed. When linking permafrost to future global climate change scenarios, a critical piece of information in predicting future melting processes is the actual ice-content in the subsurface. Ice-content within the subsurface is related to seismic velocity. Thus, estimating seismic velocity may allow remotely mapping ice-content. Using the diving-wavetomography technique high-resolution insight into the structure of the ice-bonded permafrost realm was gained. We applied this technique to the existing seismic data and were able to produce an unprecedented high-resolution image of the seismic velocity structure within the upper-most 200 m below seafloor, allowing the interpretation of the extent of ice-bearing permafrost. Yet, the analyses did also indicate the presence of an anisotropic nature of the velocity structure, thus making a direct prediction of actual ice-content from seismic velocity more complex than previously hoped. Future analyses, ground-truthing and incorporation of other remote-sensing techniques (e.g. electromagnetic imaging) are required to advance the quantification of the ice-content in the sediments of the Canadian Beaufort shelf.
Publications
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Identifying submarine permafrost and gas hydrates on the continental Beaufort Shelf, Canadian Arctic; CAGE International Conference on ‘Methane in a changing Arctic’, Tromso, Norway, September 2022
Grob, H.; Riedel, M.; Duchesne, M. J.; Krastel, S.; Bustamante, J.; Fabien-Ouellet, G.; Klaeschen, D.; Preine, J.; Jin, Y. K. & Hong, J. K.
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Reflection seismic indicators for submarine permafrost and gas hydrate distributions on the Canadian Arctic Beaufort Shelf; Conference of the Deutsche Geophysikalische Gesellschaft (DGG), Kiel, Germany, March 2021
Grob, H.; Riedel, M.; Krastel, S.; Bustamante, J.; Duchesne, M. J.; Fabien-Ouellet, G.; Jin, Y. K. & Hong, J. K.
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Using different seismic approaches to detect submarine permafrost and gas hydrates on the continental Beaufort shelf of the Canadian Arctic.
Grob, Henrik; Riedel, Michael; Duchesne, Mathieu J.; Krastel, Sebastian; Bustamante, Restrepo Jefferson; Fabien-Ouellet, Gabriel; Kläschen, Dirk; Preine, Jonas; Jin, Young Keun & Hong, Jong Kuk
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Identifying submarine permafrost and gas hydrates in the Canadian Beaufort Sea with 2D multichannel seismic data; AGU Fall Meeting, San Francisco, USA, December 2023
Grob, H.; Riedel, M.; Duchesne, M. J.; Krastel, S.; Bustamante, J.; Fabien-Ouellet, G.; Klaeschen, D.; Jin, Y. K. & Hong, J. K.
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Revealing the Extent of Submarine Permafrost and Gas Hydrates in the Canadian Arctic Beaufort Sea Using Seismic Reflection Indicators. Geochemistry, Geophysics, Geosystems, 24(5).
Grob, H.; Riedel, M.; Duchesne, M. J.; Krastel, S.; Bustamante, J.; Fabien‐Ouellet, G.; Jin, Y. K. & Hong, J. K.
