Combined Geophysical Measurements Provide Evidence for Unfrozen Water in Permafrost in the Adventdalen Valley in Svalbard

Keating, Kristina; Binley, Andrew; Bense, Victor; Dam, Remke L. Van; Christiansen, Hanne H.

doi:10.1029/2017gl076508

Cited by 40 publications

(22 citation statements)

References 40 publications

(52 reference statements)

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“…The consistency of our full-year results with previous studies in more easily accessible alpine and polar regions (e.g., Hilbich et al, 2011;Supper et al, 2014;Keuschnig et al, 2017;Tomaskovicova, 2018;Oldenborger and LeBlanc, 2018) suggests that the detailed studies of the Alps can be transferred to setups in very remote environments, which would allow for integrative process studies as well as coupled modeling of A-ERT data with existing water content and temperature monitoring systems in Antarctica. Examples of such studies include the combination of data processing techniques, petrophysical models and supporting information to estimate unfrozen water content from electrical resistivity data (e.g., Hauck, 2002;Fortier et al, 2008;Grimm and Stillman, 2015;Dafflon et al, 2016) or combining electrical resistivity data with seismic refraction data in a joint petrophysical model to estimate ice and water content (e.g., Hauck et al, 2011).…”

Section: Discussionsupporting

confidence: 80%

“…The black line delineates the cut-off value of 13 k m, and the white dashed line shows the 0 • C isotherm from the borehole temperatures at S 3,3 . studies where stronger lateral variations along the ERT transects are usually more evident (i.e., Hilbich et al, 2011;Supper et al, 2014;Keuschnig et al, 2017). In contrast, large lateral resistivity changes are visible during the extreme short-lived meteorological events.…”

Section: Discussionmentioning

confidence: 99%

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Detailed detection of active layer freeze–thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

et al. 2020

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Abstract. Climate-induced warming of permafrost soils is a global phenomenon, with regional and site-specific variations which are not fully understood. In this context, a 2-D automated electrical resistivity tomography (A-ERT) system was installed for the first time in Antarctica at Deception Island, associated to the existing Crater Lake site of the Circumpolar Active Layer Monitoring – South Program (CALM-S) – site. This setup aims to (i) monitor subsurface freezing and thawing processes on a daily and seasonal basis and map the spatial and temporal variability in thaw depth and to (ii) study the impact of short-lived extreme meteorological events on active layer dynamics. In addition, the feasibility of installing and running autonomous ERT monitoring stations in remote and extreme environments such as Antarctica was evaluated for the first time. Measurements were repeated at 4 h intervals during a full year, enabling the detection of seasonal trends and short-lived resistivity changes reflecting individual meteorological events. The latter is important for distinguishing between (1) long-term climatic trends and (2) the impact of anomalous seasons on the ground thermal regime. Our full-year dataset shows large and fast temporal resistivity changes during the seasonal active layer freezing and thawing and indicates that our system setup can resolve spatiotemporal thaw depth variability along the experimental transect at very high temporal resolution. The largest resistivity changes took place during the freezing season in April, when low temperatures induce an abrupt phase change in the active layer in the absence of snow cover. The seasonal thawing of the active layer is associated with a slower resistivity decrease during October due to the presence of snow cover and the corresponding zero-curtain effect. Detailed investigation of the daily resistivity variations reveals several periods with rapid and sharp resistivity changes of the near-surface layers due to the brief surficial refreezing of the active layer in summer or brief thawing of the active layer during winter as a consequence of short-lived meteorological extreme events. These results emphasize the significance of the continuous A-ERT monitoring setup which enables detecting fast changes in the active layer during short-lived extreme meteorological events. Based on this first complete year-round A-ERT monitoring dataset on Deception Island, we believe that this system shows high potential for autonomous applications in remote and harsh polar environments such as Antarctica. The monitoring system can be used with larger electrode spacing to investigate greater depths, providing adequate monitoring at sites and depths where boreholes are very costly and the ecosystem is very sensitive to invasive techniques. Further applications may be the estimation of ice and water contents through petrophysical models or the calibration and validation of heat transfer models between the active layer and permafrost.

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Section: Discussionsupporting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Detailed detection of active layer freeze–thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

et al. 2020

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“…Surface NMR has been used for almost three decades study groundwater (e.g., Trushkin et al, 1995) and cryosphere systems (e.g., Legchenko et al, 2014;Lehmann-Horn et al, 2011), as well as freeze-thaw dynamics in permafrost (Keating et al, 2018;Parsekian et al, 2013Parsekian et al, , 2019. While GPR measurements allow fast acquisition of high-resolution profile lines, surface NMR is typically implemented as a static measurement, with data averaging at one location to generate an individual sounding.…”

Section: Geophysical Differentiation Of Frozen and Unfrozen Groundmentioning

confidence: 99%

“…Given the successful performance of NMR during maximum freeze, it is likely that NMR would also be helpful for delineating the AP boundary during maximum thaw at the Kuparuk site. Indeed, surface (Keating et al, 2018;Parsekian et al, 2019) and borehole (Kass et al, 2017;Minsley et al, 2016) NMR has seen growing use for observing freeze-thaw dynamics in the Arctic.…”

Section: Delineating the Active Layer To Permafrost Boundary During Mmentioning

confidence: 99%

Seasonal Subsurface Thaw Dynamics of an Aufeis Feature Inferred From Geophysical Methods

Terry¹,

Grunewald

Briggs³

et al. 2020

JGR Earth Surface

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Aufeis are sheets of ice unique to cold regions that originate from repeated flooding and freezing events during the winter. They have hydrological importance associated with summer flows and winter insulation, but little is known about the seasonal dynamics of the unfrozen sediment layer beneath them. This layer may support perennial groundwater flow in regions with otherwise continuous permafrost. For this study, ground penetrating radar (GPR) were collected in September 2016 (maximum thaw) and April 2017 (maximum frozen) at the Kuparuk aufeis field on the North Slope of Alaska. Supporting surface nuclear magnetic resonance data were collected during the maximum frozen campaign. These point‐in‐time geophysical data sets were augmented by continuous subsurface temperature data and periodic Structure‐from‐Motion digital elevation models collected seasonally. GPR and difference digital elevation model data showed up to 6 m of ice over the sediment surface. Below the ice, GPR and nuclear magnetic resonance identified regions of permafrost and regions of seasonally frozen sediment (i.e., the active layer) underlain by a substantial lateral talik that reached >13‐m thickness. The seasonally frozen cobble layer above the talik was typically 3‐ to 5‐m thick, with freezing apparently enabled by relatively high thermal diffusivity of the overlying ice and rock cobbles. The large talik suggests that year‐round groundwater flow and coupled heat transport occurs beneath much of the feature. Highly permeable alluvial material and discrete zones of apparent groundwater upwelling indicated by geophysical and ground temperature data allows direct connection between the aufeis and the talik below.

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“…The dependence of the methane concentration upon Cl -, δ 18 O-H 2 O and δD-H 2 O is therefore consistent with the expulsion of pore waters from the uplifted marine sediments contributing directly to the high methane concentrations seen in the pingo springs. It is also possible that the cryopegs which contain unfrozen brines with a high salt content (Keating et al, 2018) enhance the mobility of the groundwaters flowing towards the pingos. These processes are most obvious towards the former marine limit up-valley, because downstream, the system is increasingly diluted by a fresh groundwater with a more depleted (lower) δ 18 O-H 2 O and δD-H 2 O signature that is typical of snow and ice melt from the mountains (Yde et al, 2008).…”

Section: Groundwater Geochemical Environment and Methane Concentrationsmentioning

confidence: 99%

Open system pingos as hotspots for sub-permafrost methane emission in Svalbard

Hodson¹,

Nowak²,

Senger³

et al. 2020

Preprint

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Abstract. Methane release from beneath lowland permafrost represents an important uncertainty in the Arctic greenhouse gas budget. Our current knowledge is arguably best-developed in settings where permafrost is being inundated by rising sea level, which means much of the methane is oxidised in the water column before it reaches the atmosphere. Here we provide a different process perspective that is appropriate for Arctic fjord valleys, where local deglaciation causes isostatic uplift to out-pace rising sea level. We show how the uplift induces permafrost aggradation in former marine sediments, whose pressurisation results in methane escape directly to the atmosphere via ground water springs. In Adventdalen, Central Spitsbergen, we show how the springs are historic features, responsible for the formation of open system pingos, and capable of discharging brackish waters enriched with high concentrations of mostly biogenic methane (average 18 mg L−1). Thermodynamic calculations show that the methane concentrations sometimes marginally exceed the solubility limit for methane in water at 0 °C (41 mg L−1). In our case study, emissions from just four pingo springs with a combined discharge of less than 2 L s−1 increase the land-atmosphere methane flux by 16 %. This confirms that sub-permafrost methane migration deserves more attention for improved forecasting of Arctic greenhouse gas emissions.

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Combined Geophysical Measurements Provide Evidence for Unfrozen Water in Permafrost in the Adventdalen Valley in Svalbard

Cited by 40 publications

References 40 publications

Detailed detection of active layer freeze–thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

Detailed detection of active layer freeze–thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

Seasonal Subsurface Thaw Dynamics of an Aufeis Feature Inferred From Geophysical Methods

Open system pingos as hotspots for sub-permafrost methane emission in Svalbard

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