Subsea ice‐bearing permafrost on the <scp>U</scp>.<scp>S</scp>. <scp>B</scp>eaufort <scp>M</scp>argin: 1. Minimum seaward extent defined from multichannel seismic reflection data

Herman, Bruce M.; Hart, Patrick E.; Ruppel, Carolyn D.

doi:10.1002/2016gc006584

Cited by 37 publications

(57 citation statements)

References 46 publications

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“…For the Beaufort case, the increased salinity (i.e., more transgressive sediment in the profile) renders modeled permafrost thickness more sensitive to porosity, although varying the salinity of the transgressive sediment layers has little to no effect on the depth of the 0 °C isotherm (Table S2). The seismic and borehole permafrost delineation of Ruppel et al () matches within two EASE grid cells of the modeled ice content values for the upper sediment column, which matches the depth of investigation of seismic data evaluation in Brothers et al (). Modeled isothermal sediment temperatures out to maximally 20 km from the coastline suggest a narrow region of cryotic sediments that contain thawing ice.…”

Section: Discussionsupporting

confidence: 68%

“…Scientific studies of subsea permafrost on the eastern Siberian shelf are available (e.g., Fartyshev, ; Kassens et al, ; Kunitsky, ; Melnikov et al, ; Molochushkin, ; Schirrmeister, ; Slagoda, ; Soloviev et al, ) but describe surface sediment samples and boreholes shallower than 100 m below the sea floor. For the U.S. Beaufort shelf, Brothers et al () and Ruppel et al () collect all available seismic and borehole data to explore the distribution of permafrost.…”

Section: Discussionmentioning

confidence: 99%

“…Publicly available observational data are limited to shallow boreholes drilled from ships (Kassens et al, ; Rekant et al, ) or from the sea ice (Blasco et al, ; Dallimore, ; Winterfeld et al, ), a few deeper scientific boreholes, geophysical records from industrial boreholes in the Beaufort Sea (e.g., Hu et al, ), and geophysical records (e.g., Portnov et al, ; Rekant et al, ). Data from boreholes deep enough to penetrate permafrost in the prodeltaic region of the Mackenzie River and on the Alaskan Beaufort shelf have been published and analyzed for the depth of the base of permafrost (Brothers et al, ; Hu et al, ; Issler et al, ; Ruppel et al, ). Relating geophysical observations to permafrost depth, lithology, cryostratigraphy, or sediment temperature is not trivial.…”

Section: Introductionmentioning

confidence: 99%

“…Hu et al () examine over 250 borehole records, including over 70 offshore boreholes, and find permafrost 100 to 700 m thick north of the Mackenzie Delta and eastward. Ruppel et al () and Brothers et al () analyze available borehole and seismic data from the U.S. Beaufort Sea to provide a conservative representation of permafrost extent on the shelf: it is restricted to waters less than 20 m deep and closer than 30 km from shore.…”

Section: Introductionmentioning

confidence: 99%

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Submarine Permafrost Map in the Arctic Modeled Using 1‐D Transient Heat Flux (SuPerMAP)

et al. 2019

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Offshore permafrost plays a role in the global climate system, but observations of permafrost thickness, state, and composition are limited to specific regions. The current global permafrost map shows potential offshore permafrost distribution based on bathymetry and global sea level rise. As a first‐order estimate, we employ a heat transfer model to calculate the subsurface temperature field. Our model uses dynamic upper boundary conditions that synthesize Earth System Model air temperature, ice mass distribution and thickness, and global sea level reconstruction and applies globally distributed geothermal heat flux as a lower boundary condition. Sea level reconstruction accounts for differences between marine and terrestrial sedimentation history. Sediment composition and pore water salinity are integrated in the model. Model runs for 450 ka for cross‐shelf transects were used to initialize the model for circumarctic modeling for the past 50 ka. Preindustrial submarine permafrost (i.e., cryotic sediment), modeled at 12.5‐km spatial resolution, lies beneath almost 2.5 ×106km2 of the Arctic shelf. Our simple modeling approach results in estimates of distribution of cryotic sediment that are similar to the current global map and recent seismically delineated permafrost distributions for the Beaufort and Kara seas, suggesting that sea level is a first‐order determinant for submarine permafrost distribution. Ice content and sediment thermal conductivity are also important for determining rates of permafrost thickness change. The model provides a consistent circumarctic approach to map submarine permafrost and to estimate the dynamics of permafrost in the past.

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Section: Discussionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Submarine Permafrost Map in the Arctic Modeled Using 1‐D Transient Heat Flux (SuPerMAP)

et al. 2019

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“… Map of the Beaufort Sea margin, showing the borehole well data set (yellow circles) used for this paper. The red curves on the U.S. and Canadian Beaufort margin show the inferred extent of subsea IBPF based on velocity analyses of seismic reflection data on the U.S. margin [ Brothers et al ., ] and seismic refraction analyses on the Canadian margin [ Hunter et al ., ], respectively. The black dashed line indicates the nominal shelf‐break at 100 m water depth, which was the assumed seaward extent of subsea permafrost in the compilation of Brown et al .…”

Section: Introductionmentioning

confidence: 99%

Subsea ice‐bearing permafrost on the U.S. Beaufort Margin: 2. Borehole constraints

Ruppel

Herman²,

Hart

2016

Geochem Geophys Geosyst

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Borehole logging data from legacy wells directly constrain the contemporary distribution of subsea permafrost in the sedimentary section at discrete locations on the U.S. Beaufort Margin and complement recent regional analyses of exploration seismic data to delineate the permafrost's offshore extent. Most usable borehole data were acquired on a $500 km stretch of the margin and within 30 km of the contemporary coastline from north of Lake Teshekpuk to nearly the U.S.-Canada border. Relying primarily on deep resistivity logs that should be largely unaffected by drilling fluids and hole conditions, the analysis reveals the persistence of several hundred vertical meters of ice-bonded permafrost in nearshore wells near Prudhoe Bay and Foggy Island Bay, with less permafrost detected to the east and west. Permafrost is inferred beneath many barrier islands and in some nearshore and lagoonal (back-barrier) wells. The analysis of borehole logs confirms the offshore pattern of ice-bearing subsea permafrost distribution determined based on regional seismic analyses and reveals that ice content generally diminishes with distance from the coastline. Lacking better well distribution, it is not possible to determine the absolute seaward extent of ice-bearing permafrost, nor the distribution of permafrost beneath the present-day continental shelf at the end of the Pleistocene. However, the recovery of gas hydrate from an outer shelf well (Belcher) and previous delineation of a log signature possibly indicating gas hydrate in an inner shelf well (Hammerhead 2) imply that permafrost may once have extended across much of the shelf offshore Camden Bay.

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The interaction of climate change and methane hydrates

Ruppel

Kessler

2017

Reviews of Geophysics

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645

554

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Gas hydrate, a frozen, naturally‐occurring, and highly‐concentrated form of methane, sequesters significant carbon in the global system and is stable only over a range of low‐temperature and moderate‐pressure conditions. Gas hydrate is widespread in the sediments of marine continental margins and permafrost areas, locations where ocean and atmospheric warming may perturb the hydrate stability field and lead to release of the sequestered methane into the overlying sediments and soils. Methane and methane‐derived carbon that escape from sediments and soils and reach the atmosphere could exacerbate greenhouse warming. The synergy between warming climate and gas hydrate dissociation feeds a popular perception that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir. Appropriate evaluation of the two sides of the climate‐methane hydrate synergy requires assessing direct and indirect observational data related to gas hydrate dissociation phenomena and numerical models that track the interaction of gas hydrates/methane with the ocean and/or atmosphere. Methane hydrate is likely undergoing dissociation now on global upper continental slopes and on continental shelves that ring the Arctic Ocean. Many factors—the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea‐air interface in most cases—mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate‐derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate‐hydrate synergy in the future.

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Subsea ice‐bearing permafrost on the U.S. Beaufort Margin: 1. Minimum seaward extent defined from multichannel seismic reflection data

Cited by 37 publications

References 46 publications

Submarine Permafrost Map in the Arctic Modeled Using 1‐D Transient Heat Flux (SuPerMAP)

Submarine Permafrost Map in the Arctic Modeled Using 1‐D Transient Heat Flux (SuPerMAP)

Subsea ice‐bearing permafrost on the U.S. Beaufort Margin: 2. Borehole constraints

The interaction of climate change and methane hydrates

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