Petrophysical Joint Inversion Applied to Alpine Permafrost Field Sites to Image Subsurface Ice, Water, Air, and Rock Contents

Mollaret, Coline; Wagner, Florian M.; Hilbich, Christin; Scapozza, Cristian; Hauck, Christian

doi:10.3389/feart.2020.00085

Cited by 52 publications

(74 citation statements)

References 82 publications

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“…Independent of the permeability values, this porous media modeling approach inherently homogenizes the active layer. Borehole geophysics generally only provide limited information about the composition of the active layer of rock glaciers (Haeberli et al, 1988;Vonder Mühll and Holub, 1992;Arenson et al, 2002), geophysics draw a relatively homogenous pattern in terms of the electrical resistivity (Hilbich et al, 2009) and more recent findings suggest that the air content and thus the permeability decreases toward the bottom of the active layer (Mollaret et al, 2020). However, at different sites there is also geophysical evidence for heterogeneous active layers, often depending on 3D topography and differential water infiltration patterns (Scapozza et al, 2015;Halla et al, unpublished).…”

Section: Permeabilitymentioning

confidence: 99%

“…For COR the assumption of a homogenous active layer is less of a simplification than for SBE. The blocks at COR are relatively big (0.4 m up to several meters), the water percolates quickly, the surface is almost always dry (Hanson and Hoelzle, 2004) and geophysical measurements do not show signs of water in the active layer (Hilbich et al, 2009;Mollaret et al, 2020). At SBE less information is available.…”

Section: Permeabilitymentioning

confidence: 99%

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Air Convection in the Active Layer of Rock Glaciers

Wicky

Hauck

2020

Front. Earth Sci.

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Coarse blocks are an abundant surface cover in mountainous permafrost landscapes. In this coarse blocky layer, air convection occurs and has a significant influence on the ground thermal regime of the underlying permafrost. Besides heat transfer through conduction, free convection of air takes place seasonally and leads to a pronounced ground cooling. Air convection has been observed and described in many field studies but is often neglected or parametrized in permafrost modeling. In the present study, air convection in the active layer of rock glaciers is explicitly modeled through a heat conduction equation coupled with Darcy's law over a two-dimensional geometry. With a series of numerical experiments, we show its effects on the thermal regime of the underlying permafrost. The ground permeability and the thermal gradient in the active layer are the most important parameters for air convection in the ground. On field sites with a high ground permeability (order of magnitude 10 −6 m 2), convection plays a crucial role and is required to correctly model measured borehole temperatures. The onset of natural convection occurs at critical Rayleigh numbers and is characterized by an increase of the standard deviation of the direction and the vorticity of the airflow field in the active layer. In the numerical solutions, the internal air circulation in the coarse blocky surface layer leads to an efficient ground cooling.

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Section: Permeabilitymentioning

confidence: 99%

Section: Permeabilitymentioning

confidence: 99%

Air Convection in the Active Layer of Rock Glaciers

Wicky

Hauck

2020

Front. Earth Sci.

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“…The petrophysical joint inversion scheme minimizes the following objective function (Wagner et al, 2019;Mollaret et al, 2020):…”

Section: Petrophysical Joint Inversionmentioning

confidence: 99%

“…A last important parameter to consider in this scheme is porosity initial value and range. Wagner et al (2019), already stressed the importance of a good porosity estimation in order to avoid ambiguity between ice and rock content and in a recent study, Mollaret et al (2020) analyses the influence of the porosity constraint in the petrophysical joint inversion results. Following the approach of this last paper, and accordingly to the previous knowledge from the field site we tested different initial porosity values and ranges (φ min -φ max ) for both rock glaciers.…”

Section: Petrophysical Joint Inversionmentioning

confidence: 99%

“…Joint inversion has become a popular tool in geophysics, providing a formal approach to integrate multiple datasets with the aim of better constraining the model results (Moorkamp et al, 2016). In order to do that, the property models related to the different data sets need to be coupled, either through petrophysical relationships (Wagner et al, 2019;Mollaret et al, 2020) or by structural constraints (Jordi et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Active and inactive Andean rock glacier geophysical signatures by comparing 2D joint inversion routines of electrical resistivity and refraction seismic tomography

Pasquale¹,

Valois²,

Schaffer³

et al. 2020

Preprint

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Abstract. In semi-arid Chile, rock glaciers cover a surface area that is four-times larger than that occupied by glaciers. For this reason, their role in freshwater production, transfer and storage is likely to be of primary importance, especially in this area of increasing human pressure and high rainfall variability. To understand their hydrological role now and in the future it is necessary to characterize their internal structure (e.g., internal boundaries, ice, air, water and rock content). In this paper, we present the results and interpretations of electrical resistivity and refraction seismic tomography profiles on an active (El Ternero) and inactive (El Jote) rock glacier in the Chilean Andes. These are the first in situ measurements in Estero Derecho: a natural reserve at the headwaters of the Elqui River, where the two rock glaciers are located. Within our study, we highlight the strong differences in the geophysical responses between active and inactive rock glaciers through the analysis and comparison of three different inversion schemes: individual dataset inversion, structural and petrophysical joint inversion. Moreover, we propose a diagnostic model representation for the differentiation between active and inactive rock glaciers.

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Best practices for using electrical resistivity tomography to investigate permafrost

Herring,

Lewkowicz,

Hauck

et al. 2023

Permafrost & Periglacial

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Electrical resistivity tomography (ERT) is a minimally invasive geophysical method that produces a model of subsurface resistivity from a large number of electrical resistance measurements. Strong resistivity contrasts usually exist between frozen and unfrozen earth materials, making ERT an effective and increasingly utilized tool in permafrost research. In this paper, we review more than 300 scientific publications dating from 2000 to 2022 to identify the capabilities and limitations of ERT for permafrost applications. The annual publication rate has increased by a factor of 10 over this period, but several unique challenges remain, and best practices for acquiring, processing, and interpreting ERT data in permafrost environments have not been clearly established. In this paper, we make recommendations for ERT surveys of permafrost and highlight recent advances in the field, with the objective of maximizing the utility of existing and future surveys.

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Petrophysical Joint Inversion Applied to Alpine Permafrost Field Sites to Image Subsurface Ice, Water, Air, and Rock Contents

Cited by 52 publications

References 82 publications

Air Convection in the Active Layer of Rock Glaciers

Air Convection in the Active Layer of Rock Glaciers

Active and inactive Andean rock glacier geophysical signatures by comparing 2D joint inversion routines of electrical resistivity and refraction seismic tomography

Best practices for using electrical resistivity tomography to investigate permafrost

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