Detecting unfrozen sediments below thermokarst lakes with surface nuclear magnetic resonance

Parsekian, Andrew D.; Grosse, Guido; Walbrecker, Jan O.; Müller‐Petke, Mike; Keating, Kristina; Liu, Lin; Jones, Benjamin M.; Knight, Rosemary

doi:10.1002/grl.50137

Cited by 51 publications

(40 citation statements)

References 23 publications

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“…The nuclear magnetic resonance depth of investigation is limited to 60 m, despite the use of a 90‐m‐diameter loop, due to the high inclination of the background magnetic field (80°). Parsekian et al () encountered similar reductions in depth of penetration in their investigation of talik thickness using NMR at a location farther south outside of Fairbanks, AK. This reduced depth of investigation at Peatball Lake means that surface NMR cannot resolve the bottom of the talik at this site.…”

Section: Discussionmentioning

confidence: 79%

Transient Electromagnetic Surveys for the Determination of Talik Depth and Geometry Beneath Thermokarst Lakes

et al. 2018

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Thermokarst lakes are prevalent in Arctic coastal lowland regions and sublake permafrost degradation and talik development contributes to greenhouse gas emissions by tapping the large permafrost carbon pool. Whereas lateral thermokarst lake expansion is readily apparent through remote sensing and shoreline measurements, sublake thawed sediment conditions and talik growth are difficult to measure. Here we combine transient electromagnetic surveys with thermal modeling, backed up by measured permafrost properties and radiocarbon ages, to reveal closed‐talik geometry associated with a thermokarst lake in continuous permafrost. To improve access to talik geometry data, we conducted surveys along three transient electromagnetic transects perpendicular to lakeshores with different decadal‐scale expansion rates of 0.16, 0.38, and 0.58 m/year. We modeled thermal development of the talik using boundary conditions based on field data from the lake, surrounding permafrost and a borehole, independent of the transient electromagnetics. A talik depth of 91 m was determined from analysis of the transient electromagnetic surveys. Using a lake initiation age of 1400 years before present and available subsurface properties the results from thermal modeling of the lake center arrived at a best estimate talk depth of 80 m, which is on the same order of magnitude as the results from the transient electromagnetic survey. Our approach has provided a noninvasive estimate of talik geometry suitable for comparable settings throughout circum‐Arctic coastal lowland regions.

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Section: Discussionmentioning

confidence: 79%

Transient Electromagnetic Surveys for the Determination of Talik Depth and Geometry Beneath Thermokarst Lakes

et al. 2018

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“…The technique has proven useful in unconsolidated aquifers and in a variety of soil types (e.g., Legchenko et al, 2004;Knight et al, 2012;Behroozmand et al, 2015;Parsekian et al, 2015). NMR is also applied to multiphase systems (e.g., water-petroleum, water-air, and now water-ice) with success (e.g., Song, 2010;Parsekian et al, 2013;Walsh et al, 2014).…”

Section: Borehole Nmrmentioning

confidence: 99%

In situ nuclear magnetic resonance response of permafrost and active layer soil in boreal and tundra ecosystems

et al. 2017

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Abstract. Characterization of permafrost, particularly warm and near-surface permafrost which can contain significant liquid water, is critical to understanding complex interrelationships with climate change, ecosystems, and disturbances such as wildfires. Understanding the vulnerability and resilience of permafrost requires an interdisciplinary approach, relying on (for example) geophysical investigations, ecological characterization, direct observations, remote sensing, and more. As part of a multiyear investigation into the impacts of wildfires on permafrost, we have collected in situ measurements of the nuclear magnetic resonance (NMR) response of the active layer and permafrost in a variety of soil conditions, types, and saturations. In this paper, we summarize the NMR data and present quantitative relationships between active layer and permafrost liquid water content and pore sizes and show the efficacy of borehole NMR (bNMR) to permafrost studies. Through statistical analyses and synthetic freezing simulations, we also demonstrate that borehole NMR is sensitive to the nucleation of ice within soil pore spaces.

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“…Geophysical methods are necessary for investigating subsurface physical properties over large and/or remote areas. Recent examples of geophysical surveys aimed at characterizing permafrost in Alaska include an airborne electromagnetic (AEM) survey used to delineate geologic and permafrost distributions in an area of discontinuous permafrost (Minsley et al, 2012), ground-based electrical measurements used to assess shallow permafrost aggradation near recently receded lakes (Briggs et al, 2014), electrical and electromagnetic surveys used to characterize shallow active layer thickness and subsurface salinity , and surface nuclear magnetic resonance soundings used to infer the thickness of unfrozen sediments beneath lakes (Parsekian et al, 2013). A challenge with geophysical methods, however, is that geophysical properties (e.g., electrical resistivity) are only indirectly sensitive to physical properties of interest (e.g., lithology, water content, thermal state).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of airborne geophysical data to sublacustrine and near-surface permafrost thaw

Minsley¹,

Wellman²,

Walvoord

et al. 2015

The Cryosphere

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Abstract.A coupled hydrogeophysical forward and inverse modeling approach is developed to illustrate the ability of frequency-domain airborne electromagnetic (AEM) data to characterize subsurface physical properties associated with sublacustrine permafrost thaw during lake-talik formation. Numerical modeling scenarios are evaluated that consider non-isothermal hydrologic responses to variable forcing from different lake depths and for different hydrologic gradients. A novel physical property relationship connects the dynamic distribution of electrical resistivity to ice saturation and temperature outputs from the SUTRA groundwater simulator with freeze-thaw physics. The influence of lithology on electrical resistivity is controlled by a surface conduction term in the physical property relationship. Resistivity models, which reflect changes in subsurface conditions, are used as inputs to simulate AEM data in order to explore the sensitivity of geophysical observations to permafrost thaw. Simulations of sublacustrine talik formation over a 1000-year period are modeled after conditions found in the Yukon Flats, Alaska. Synthetic AEM data are analyzed with a Bayesian Markov chain Monte Carlo algorithm that quantifies geophysical parameter uncertainty and resolution. Major lithological and permafrost features are well resolved by AEM data in the examples considered. The subtle geometry of partial ice saturation beneath lakes during talik formation cannot be resolved using AEM data, but the gross characteristics of sub-lake resistivity models reflect bulk changes in ice content and can identify the presence of a talik. A final synthetic example compares AEM and ground-based electromagnetic responses for their ability to resolve shallow permafrost and thaw features in the upper 1-2 m below ground outside the lake margin.

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Detecting unfrozen sediments below thermokarst lakes with surface nuclear magnetic resonance

Cited by 51 publications

References 23 publications

Transient Electromagnetic Surveys for the Determination of Talik Depth and Geometry Beneath Thermokarst Lakes

Transient Electromagnetic Surveys for the Determination of Talik Depth and Geometry Beneath Thermokarst Lakes

In situ nuclear magnetic resonance response of permafrost and active layer soil in boreal and tundra ecosystems

Sensitivity of airborne geophysical data to sublacustrine and near-surface permafrost thaw

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