Remote Monitoring of Freeze–Thaw Transitions in Arctic Soils Using the Complex Resistivity Method

Abstract

Our ability to monitor freeze–thaw transitions is critical to developing a predictive understanding of biogeochemical transitions and carbon dynamics in high latitude environments. In this study, we conducted laboratory column experiments to explore the potential of the complex resistivity method for monitoring the freeze–thaw transitions of the arctic permafrost soils. Samples for the experiment were collected from the upper active layer of Gelisol soils at the Barrow Environmental Observatory (BEO) in Barrow, Alaska. Freeze–thaw transitions were induced through exposing the soil column to controlled temperature environments at 4 and −20°C. Complex resistivity and temperature measurements were collected regularly during the freeze–thaw transitions using electrodes and temperature sensors installed along the column. During the experiments, over two orders of magnitude of resistivity variations were observed when the temperature was increased or decreased between −20 and 0°C. Smaller resistivity variations were also observed during the isothermal thawing or freezing processes that occurred near 0°C. Single frequency electrical phase response and imaginary conductivity at 1 Hz were found to be exclusively related to the unfrozen water in the soil matrix, suggesting that these geophysical attributes can be used as a proxy for the monitoring of the onset and progression of the freeze–thaw transitions. Spectral electrical responses and fitted Cole–Cole parameters contained additional information about the freeze–thaw transition affected by the soil grain size distribution. Specifically, a shift of the observed spectral response to lower frequency was observed during the isothermal thawing process, which we interpret to be due to sequential thawing, first from fine particles and then to coarse particles within the soil matrix. Our study demonstrates the potential of the complex resistivity method for remote monitoring of freeze–thaw transitions in arctic soils. Although conducted at the laboratory scale, this study provides the foundation for exploring the potential of the complex resistivity signals for monitoring spatiotemporal variations of freeze–thaw transitions over field‐relevant scales.

Coincident aboveground and belowground autonomous monitoring to quantify covariability in permafrost, soil, and vegetation properties in Arctic tundra

“…Examples include the spatial distribution of various lithological units [e.g., Yoshikawa et al ., ; Overduin et al ., ], active layer properties such as thickness and water content [ Hubbard et al ., ], and permafrost properties such as bulk resistivity, ice content, and salinity [e.g., Fortier et al ., ; Dafflon et al ., ]. ERT data have also been used to constrain thermal simulation [ McClymont et al ., ] and to investigate the dynamics of freeze‐thaw processes and water‐to‐ice transitions [ Overduin et al ., ; Wu et al ., ]. Autonomous acquisition of ERT time lapse data has been used to monitor freeze‐thaw dynamics in alpine permafrost environments [e.g., Hauck , ] and in seasonally frozen Arctic environments [e.g., Doetsch et al ., ].…”

Geophysical estimation of shallow permafrost distribution and properties in an ice-wedge polygon-dominated Arctic tundra region

“…The ERT approach has been applied widely to investigate the spatial and temporal distribution of EC in permafrost systems, in alpine (e.g., Hauck, 2002;Krautblatter et al, 2010) and in Arctic environments (e.g., Yoshikawa et al, 2006;. ERT surveys in an Arctic environment enabled investigators to characterize the spatial distribution of various lithologic units (Yoshikawa et al, 2004), to estimate active layer properties , to estimate water content in permafrost (Fortier et al, 2008), and to investigate the dynamics of freeze-thaw processes and water-to-ice transitions (Overduin et al, 2012;Wu et al, 2013).…”

“…In the presence of freshwater and negligible salinity, an exponential relation has been commonly used to relate resistivity to temperature (McGinnis et al, 1973). This representation has led to satisfactory results for loose soils (e.g., Hauck, 2002;Wu et al, 2013), although being inappropriate for low-permeability rocks (e.g., Krautblatter et al, 2010). If salinity is nonnegligible, part of the fluid will freeze into pure ice, whereas the solutes are rejected and migrate into the unfrozen fluid, increasing the salinity of the unfrozen fluid and thus creating a highly saline solute with strong depression of its freezing point (Aksenov et al, 2011).…”

Special Section: Progress in Modeling and Characterization of Frozen Soil Processes

“…Surface geophysical methods offer effective tools for mapping subsurface information (e.g., frozen and unfrozen water content) over a relatively large scale (10 1 to 10 2 m). Wu et al (2013) investigated how the magnitude and phase angle of complex resistivity change during freeze– thaw cycles using soil samples collected from a permafrost study site in Barrow, Alaska. The sandy clay loam soil was packed in a column (5‐cm diameter, 12‐cm length) equipped with four electrodes and eight temperature sensors and subjected to controlled temperatures at −20 and 4°C.…”