| Title | Submarine permafrost dynamics along the Arctic shelf edge |
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| Author | Paull, C K; Dallimore, S ; Jin, Y K; Caress, D W; Lundsten, E M; Anderson, K; Gwiazda, R; Riedel, M; Melling, H; Duchesne, M J; King, E L |
| Source | American Geophysical Union, Fall Meeting 2019, abstracts; EP11B-01, 2019 p. 1  Open Access |
| Links | Online - En ligne
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| Image |  |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20200368 |
| Publisher | American Geophysical Union |
| Meeting | American Geophysical Union Fall Meeting 2019; San Francisco, CA; US; December 9-13, 2019 |
| Document | Web site |
| Lang. | English |
| Media | on-line; digital |
| File format | html; pdf |
| Province | Northwest Territories; Northern offshore region |
| NTS | 107; 117 |
| Area | Beaufort Sea; Tuktoyaktuk Peninsula |
| Lat/Long WENS | -140.0000 -130.0000 72.0000 68.0000 |
| Subjects | marine geology; surficial geology/geomorphology; sedimentology; geochemistry; Nature and Environment; Science and Technology; permafrost; ground ice; continental margins; continental shelf; continental
slope; marine sediments; marine sediment cores; sedimentary structures; thermal analyses; thermal regimes; pore water samples; sea water geochemistry; seabottom salinities; seabottom temperatures; periglacial features; pingos; geophysical surveys;
bathymetry; seafloor topography; methane; sulphates; carbonates; gas seeps; salinity; cumulative effects; Phanerozoic; Cenozoic; Quaternary |
| Program | Public Safety Geoscience Assessing landslides and marine geohazards |
| Released | 2019 12 01 |
| Abstract | Exploration in the Canadian Beaufort Sea, offshore of the Tuktoyaktuk Peninsula, has revealed a remarkable a zone of rugose morphology at the shelf edge and upper slope. This morphology is especially
common in 100 to 200 m water depths where seafloor features include topographic mounds, pockmarks, slope parallel ridges, and slide scars. This area occurs at the seaward edge of a sub-sea ~600 m thick relict permafrost zone and geothermal modelling
suggests that the lower 100 m of the permafrost zone has decomposed during the Holocene. Sediment cores show escaping brackish waters with pore water chloride content indicating widespread down core freshening, especially near the shelf edge on the
upper slope. Bottom waters corresponding with this band have a mean annual temperature of less than -1.4°C, cold enough to freeze escaping brackish pore waters. Positive relief mound features are up to 10 m high circular to oval shaped and ~50 m in
diameter, occurring at a density of ~6 per km2. Pore and lense ice has been observed in sediment cores and we interpret these features as offshore pingos. Intermixed are circular topographic depressions up to 20 m deep. Detailed investigations
utilizing a mapping Autonomous Underwater Vehicle (AUV) to provide 1-m grid bathymetric and Chirp profiles, and Remotely Operated Vehicle observations, were made to provide insights as to the origin and age of these features. AUV surveys of one 8 km2
area first conducted in 2013 were repeated in 2017. Repeat mapping shows significant changes within this 4-year period. Multiple circular or elongated depressions have developed which are up to 10 m deep and 100 m long. A corresponding volume of
newly accreted material around the depressions equal to the missing volume was not detected. No evidence for high methane concentrations were found within this survey area as pore waters sulfate gradients indicate the sulfate-methane transition zone
is >8 m below seafloor in most sediment cores and no chemosynthetic seep fauna or authigenic carbonates were seen. We attribute the concentrated band of features to be related to the on-going degradation of relict permafrost, the expulsion of
brackish waters, and formation of ground ice within the near seafloor sediments. These observations have significant geohazard implications, which may be characteristic of Arctic settings. |
| Summary | (Plain Language Summary, not published)
The paper presents a geologic model to account for disturbed sea floor terrain at the transition between the Beaufort shelf and upper slope. The research
was carried out as part of the ESS Beaufort Sea geohazards activity within the ESS Public Safety Geoscience program. The research pertains mostly to advancing understanding of the geologic environment and within this context the unique sediment
properties that influence some marine geohazards such as sea floor settlement, heave and downslope movements. |
| GEOSCAN ID | 327138 |
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