Evidence for gas hydrate occurrences in the Canadian Arctic Beaufort Sea within permafrost-associated shelf and deep-water marine environments

Riedel, Michael; Brent, T A; Taylor, Gary G.; Taylor, Alan E.; Hong, Jong Kuk; Jin, Young Keun; Dallimore, S. R.

doi:10.1016/j.marpetgeo.2016.12.027

Cited by 24 publications

(39 citation statements)

References 48 publications

(77 reference statements)

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“…Methods based on electrical properties of frozen vs. unfrozen ground were shown to be applicable in shallow coastal water, but results of these surveys require thorough validation by observational data [22,95]. Recently reported results [68] presented evidence for widespread occurrence of gas hydrates across water depths of 60-100 m on the shelf of the Canadian Beaufort Sea using 3D and 2D multichannel seismic data. However, any interpretation of data obtained using any methods should be validated by recovered sediment core analysis; this implies that widespread scientific drilling is required over the entire Arctic shelf, not only in the ESAS, in order to recover a sufficient number of sediment cores representative of different types of sediments and geological Some experimental work has been performed to investigate subsea permafrost physics, establishing the basis for improved modeling of subsea permafrost and associated processes.…”

Section: Discussion and Outlookmentioning

confidence: 99%

“…These studies showed that self-preservation in porous hydrates depends on host sediment properties, hydrate structure and saturation, salt and ice content of pore water, etc. [67,68]. Stability of these hydrates in the ESAS is determined by the dynamics of coupled pressure/temperature (P/T) conditions, which change drastically during the repeated freeze-thaw cycles experienced by a permafrost-hydrates system in glacial-interglacial epochs.…”

Section: Mechanism Of Arctic Hydrate Originationmentioning

confidence: 99%

“…A change in the thermal regime of a permafrost-hydrate system after its submergence would lead to partial thawing of permafrost, causing destabilization of intra-permafrost hydrates; this would be manifested as patchy (mosaic, spotty) gas releases over the destabilized areas [5,14,15,21,68]. The fraction of intra-permafrost hydrates was suggested to not only survive the thawing cycle due to the self-preservation phenomenon, but also to become denser and more saturated owing to recrystallization caused by repeated freeze-thaw cycles [69].…”

Section: Mechanism Of Arctic Hydrate Originationmentioning

confidence: 99%

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Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf

2019

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This paper summarizes current understanding of the processes that determine the dynamics of the subsea permafrost-hydrate system existing in the largest, shallowest shelf in the Arctic Ocean; the East Siberian Arctic Shelf (ESAS). We review key environmental factors and mechanisms that determine formation, current dynamics, and thermal state of subsea permafrost, mechanisms of its destabilization, and rates of its thawing; a full section of this paper is devoted to this topic. Another important question regards the possible existence of permafrost-related hydrates at shallow ground depth and in the shallow shelf environment. We review the history of and earlier insights about the topic followed by an extensive review of experimental work to establish the physics of shallow Arctic hydrates. We also provide a principal (simplified) scheme explaining the normal and altered dynamics of the permafrost-hydrate system as glacial-interglacial climate epochs alternate. We also review specific features of methane releases determined by the current state of the subsea-permafrost system and possible future dynamics. This review presents methane results obtained in the ESAS during two periods: 1994-2000 and 2003-2017. A final section is devoted to discussing future work that is required to achieve an improved understanding of the subject.Significant reserves of CH 4 are held in the Arctic seabed [10], but the release of CH 4 to the overlying ocean and, subsequently, to the atmosphere has been believed to be restricted by impermeable subsea permafrost, which has sealed the upper sediment layers for thousands of years [11]. In the regions where permafrost exists, hydrate-bearing sediment deposits can reach a thickness of 400 to 800 m [12,13]. Shallow hydrate deposits are predicted to occupy~57% (1.25 × 10 6 km 2 ) of the East Siberian Arctic Shelf (ESAS) seabed [14]. It has been suggested that destabilization of shelf Arctic hydrates could lead to large-scale enhancement of aqueous CH 4 , but this process was hypothesized to be negligible on a decadal-century time scale [15].Consequently, the continental shelf of the Arctic Ocean (AO) has not been considered as a possible source of CH 4 to the atmosphere until very recently [16][17][18].The key area of the AO for atmospheric venting of CH 4 is the East Siberian Arctic Shelf (ESAS). The ESAS covers greater than two million square kilometers (equal to the areas of Germany, France, Great Britain, Italy, and Japan combined). This vast yet shallow region has recently been shown to be a significant modern source of atmospheric CH 4 , contributing annually no less than terrestrial Arctic ecosystems [19,20]; but unlike terrestrial ecosystems, the ESAS emits CH 4 year-round due to its partial openness during the winter when terrestrial ecosystems are dormant [21]. Emissions are determined by and dependent on the current thermal state of the subsea permafrost and environmental factors controlling permafrost dynamics [21,22]. Releases could potentially increase by 3-5 orders of magnitude,...

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Section: Discussion and Outlookmentioning

confidence: 99%

Section: Mechanism Of Arctic Hydrate Originationmentioning

confidence: 99%

Section: Mechanism Of Arctic Hydrate Originationmentioning

confidence: 99%

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Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf

2019

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“…Ice-bonded permafrost and gas hydrate are found mainly in the Iperk sequence (Blasco et al, 1990;Hu et al, 2013). Gas hydrates are associated with thick permafrost, occurring to depths exceeding 1,200 m below seafloor (mbsf), deeper than the base of the relict permafrost Judge & Majorowicz, 1992;Riedel et al, 2017;Weaver & Stewart, 1982). The top of the gas hydrates zone presently partially overlaps with ice-bonded and ice-bearing sediments (Judge et al, 1987;Osadetz & Chen, 2010).…”

Section: Shelf Permafrost and Gas Hydratesmentioning

confidence: 99%

Freshwater Seepage Into Sediments of the Shelf, Shelf Edge, and Continental Slope of the Canadian Beaufort Sea

Gwiazda

Paull

Dallimore

et al. 2018

Geochem Geophys Geosyst

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Long‐term warming of the continental shelf of the Canadian Beaufort Sea caused by the transgression associated with the last deglaciation may be causing decomposition of relict offshore subsea permafrost and gas hydrates. To evaluate this possibility, pore waters from 118 sediment cores up to 7.3‐m long were taken on the shelf and slope and analyzed for chloride concentrations and δ180 and δD composition. We observed downcore decreases in pore waters Cl− concentration in sediments from all sites from the inner shelf (<20‐m water depth), from the shelf edge, from the outer slope (down to 1,000‐m water depths), and from localized shelf features such as midshelf pingo‐like features and inner shelf pockmarks. In contrast, pore water freshening is absent from all investigated cores of the Mackenzie Trough. Downcore pore waters Cl− concentration decreases indicate regional widespread freshwater seepage. Extrapolations to zero Cl− of pore water Cl− versus δ180 regression lines indicate that freshwaters in these environments carry different isotope signatures and thus are sourced from different reservoirs. These isotopic signatures indicate that freshening of shelf sediments pore waters is a result of downward infiltration of Mackenzie River water, freshening of shelf edge sediments is due to relict submarine permafrost degradation or gas hydrate decomposition under the shelf, and freshening of slope sediments is consistent with regional groundwater flow and submarine groundwater discharge as far as 150 km from shore. These results confirm ongoing decomposition of offshore permafrost and suggest extensive current groundwater discharge far from the coast.

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“…Chinese and international researchers have used it to conduct a number of related studies. Many geophysical and electromagnetic logging technologies were investigated for gas hydrate mineral deposits in the Mackenzie Delta in Canada and Alaska North Slope in the USA [3][4] . The Geological Survey of China has carried out geophysical exploration works and effectiveness experiments in the Muli area of Qilian Mountain, such as audio-frequency magnetotellurics, low frequency ground penetrating radar (GPR), surface nuclear magnetic resonance (NMR) method, and electromagnetic well logging technique [5] .However, after drilling, it is found that many identification marks are not completely related to natural gas hydrate deposits.…”

Section: Introductionmentioning

confidence: 99%

Physical Experiment Research on Dielectric Properties of Hydrate-bearing Sediment in Sandstone Reservoir

Du¹,

Bai²,

Zhang³

et al. 2019

E3S Web Conf.

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Dielectric constants can be used to detect hydrates in permafrost regions. Therefore, this study investigated the relationships between the dielectric constant characteristics of sandstone reservoir hydrate and the hydrate saturation degree through physical simulation experiments, as well as the granularity of the surrounding rock. Methane and tetrahydrofuran (THF) hydrates with quartz sands were prepared, and their dielectric constants were analyzed. With different granularities of quartz sands, the dielectric constants of two different methane hydrate sediments decreased with increasing saturation degrees. At a given saturation degree, the dielectric constant of methane hydrate sediments with small granularity was larger than that with medium granularity, a result attributed to the unreacted water in the larger pores of the latter. In addition, the dielectric constant of methane hydrate sediments was larger than that of THF hydrates, which was also attributed to gas-phase factors and the presence of unreacted water. At a given granularity and saturation, the dielectric constants of both the THF and methane hydrates decreased with increasing saturation degrees. We conclude that at low temperature and under normal pressure, THF hydrates cannot be used as a substitute for methane hydrates in laboratory experiments investigating geophysical phenomena.

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Evidence for gas hydrate occurrences in the Canadian Arctic Beaufort Sea within permafrost-associated shelf and deep-water marine environments

Cited by 24 publications

References 48 publications

Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf

Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf

Freshwater Seepage Into Sediments of the Shelf, Shelf Edge, and Continental Slope of the Canadian Beaufort Sea

Physical Experiment Research on Dielectric Properties of Hydrate-bearing Sediment in Sandstone Reservoir

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