Changes In Ice Content Research Articles

20-year permafrost evolution documented through petrophysical joint inversion, thermal and soil moisture data

This study investigates the ground characteristics of the high altitude (3410 m a.s.l.) permafrost site Stockhorn in the Swiss Alps using a combination of surface and subsurface temperature, soil moisture, electrical resistivity and P-wave velocity time series data including a novel approach to explicitly quantify changes in ground ice content. This study was motivated by the clear signal of permafrost degradation visible in the full dataset at this long-term monitoring site within the PERMOS (Permafrost Monitoring Switzerland) network. Firstly, we assess the spatio-temporal evolution of the ground ice and water content by a combined analysis of all available in situ thermal (borehole and ground surface temperature), hydrological (soil moisture) and geophysical (geoelectric and seismic refraction) data over two decades (2002–2022) regarding the driving factors for the spatially different warming. Secondly, we explicitly quantify the volumetric water and ice content and their changes in the subsurface from 2015 to 2022 using a time-consistent petrophysical joint inversion scheme within the open-source library pyGIMLi. The petrophysical joint inversion scheme has been improved by constraining the rock content to be constant in time for six subsequent inversions to obtain consistent changes in ice and water content over the monitoring period based on jointly inverted resistivity and traveltime data. All different data show a warming trend of the permafrost. The ice content modeled from the petrophysical joint inversion has decreased by about 15 vol.% between 2015 and 2022. Changes in ice content are first observed in the lower, south-facing part of the profile. As a result, resistivity and P-wave velocity have been decreasing significantly. Permafrost temperatures measured in the boreholes have increased between 0.5 °C and 1 °C in 20 years. Our study shows the high value of joint and quantitative analysis of datasets comprising complementary subsurface variables for long-term permafrost monitoring.

A review on the preparation techniques and geotechnical behaviour of icy lunar regolith simulants

This review provides an in-depth analysis of the methods used to produce icy regolith simulants with a focus on the Moon. Current knowledge of the form and morphology of ice on the Moon is limited, yet a wide range of studies have used ice and regolith analogues to simulate the icy material in lunar cold traps. The physical properties of ice on the Moon may vary significantly depending on its form as either an amorphous or crystalline solid, as well as its physical texture with lunar regolith. As a result, the choice of a particular preparation technique used to create an icy regolith simulant may directly impact the results of a study. It is found that sample preparation techniques can be broadly classified based on the mechanism of ice formation, proposed as either the freezing of liquid to solid, direct deposition (desublimation) of vapor to solid, or the comminution of large blocks to smaller fragments. Secondary growth structures including re-cementation, vapor re-deposition or ductile deformation of ice can also be achieved by post-processing techniques like thermal or pressure-induced metamorphism of the ice. Differences in the form and morphology of icy regolith is also found to significantly influence geotechnical behaviour to a greater extent than changes in ice content, bulk density or temperature. Specifically, vapor-deposited and amorphous ices which best simulate the formation conditions of ice on the Moon are the weakest, whilst ice-cemented ’mud-pies’ which are commonly produced by gradually freezing simulant mixtures containing liquid water, which is not stable on the Moon, can be orders of magnitude stronger. The limitations of current simulants are highlighted, and several opportunities to combine or improve existing techniques are provided. In conclusion, further study using techniques that involve comminution and deposition of ice in the absence of the liquid phase of water are recommended to better emulate the formation and weathering pathways of icy regolith on the Moon, and ultimately its physical properties.

Understanding seismic velocity variations of subsea permafrost: A sensitivity study

Monitoring the change in permafrost conditions and distribution is crucial for forecasting global warming. As seismic velocities increase with ice content, marine seismic surveys can map the top of ice-bearing subsea permafrost on a large scale. However, conventional seismic methods cannot fully map internal velocity variations linked to changes in ice content because the removal of guided waves and multiples is challenging for reflection processing. Nevertheless, these arrivals carry information about velocity variations with depth. We investigate if a joint analysis of various wave arrivals could provide information about velocity variations within permafrost and accurately estimate the permafrost thickness. Through a sensitivity analysis, we estimate the feasibility of using different wave arrivals, such as reflections, refractions, multiples, and guided waves, to better characterize permafrost conditions. We find that guided waves are sensitive to velocity variations within permafrost and can detect the depth of the permafrost’s base under certain geologic conditions. Then, we combine the analysis of all seismic arrivals to derive a subsurface permafrost model for a seismic line collected in the Beaufort Sea. The joint analysis reveals the transitions in depth between ice-bonded and partially ice-bonded permafrost and offers a crude estimate of permafrost thickness.

Quantification of freeze–thaw hysteresis of unfrozen water content and electrical resistivity from time lapse measurements in the active layer and permafrost

AbstractWe quantified seasonal, in‐situ variation in ground electrical resistivity, unfrozen water content, and ground temperature using daily and sub‐daily measurements in active layer and in permafrost on a high‐latitude monitoring site in West Greenland. The in‐situ unfrozen water content in a clayey soil undergoing phase change was 10% higher during freezing than during thawing at the same ground temperature, thus shifting the freezing curve parameterization seasonally. The freeze–thaw unfrozen water content hysteresis was a measurable part of the energy balance of the active layer and corresponds to 12.1% of the total yearly enthalpy change for our field site. We also observed and quantified hysteresis in the relationships between ground electrical resistivity and unfrozen water content, where the inverted resistivities during freezing in the temperature range from 0°C to approximately −4°C were up to one order of magnitude higher than during thawing at the same unfrozen water content. As a result, the petro‐physical models that uniquely derive soil unfrozen water content from bulk soil electrical resistivity measured from ground surface do not fully capture the complexity of the in‐situ processes. The hysteresis should therefore be considered in quantitative interpretation of ground resistivity changes in terms of ground temperature and ice content changes.

Influence of Ground Ice Content on Thawing Depth Road Base

One of the important parameters that determine technical solutions in the design of roads in the permafrost zone is the depth of thawing of the road foundation soils. The aim of the work was to quantify the degree of influence of the ice content in the soil foundations of roads in the permafrost zone on the depth of their seasonal thawing. For the analysis, we used the classical formula for calculating the thawing depth for bodies of plane symmetry, obtained by solving the single-phase Stefan problem. The results of numerical calculations are presented in the form of 2D and 3D graphs, which make it possible to visually assess the effect of ground ice content and the degree of its change during the road operation period on the depth of thawing of the road foundation. It has been established, in particular, that the degree of change in the depth of thawing at the same value of the increase in ice content in different ranges (for example, from 10 to 20% and from 30 to 40%) for the considered typical case of the ground base of the permafrost zone, decreases by almost 1.3 times. It is shown that the greater the initial ice content of the soil, the lower the degree of decrease in the thawing depth when the ice content changes by a constant value.

Calculation of the Fourier criterion in predicting the thermal regime of thawed and frozen dispersed rocks

The purpose of this work was to determine the range of changes in the Fourier criterion (number) when predicting the thermal regime of dispersed rocks in thawed and frozen state. And, also an assessment of the possibility of averaging the thermophysical characteristics of rocks to obtain universal values of Fourier numbers. To achieve this goal, an assessment of the influence of the thermophysical properties of dispersed rocks on the range of changes in the values of the Fourier number used in thermal calculations of technical objects of the cryolithozone is made. The calculation formulas took into account the functional dependence of the coefficient of thermal conductivity, density and specific heat capacity of rocks on humidity (iciness) in the thawed and frozen state. As an example, a mixture of quartz sandstone with water in a thawed and frozen state is considered when the ice content changes from zero (dry quartz sandstone) to full moisture saturation. It is established that the range and nature of the change in Fourier numbers for thawed and frozen dispersed rocks, depending on their humidity (iciness), differs significantly, not only quantitatively, but also qualitatively: for thawed dispersed rocks, the Fourier number decreases with increasing humidity, and for frozen rocks increases. The possibility of averaging the thermophysical characteristics of rocks to obtain universal values of Fourier numbers has been evaluated. It is shown that the use of universal Fourier numbers leads to a significant error for both thawed and frozen rocks and their use in thermal calculations with annual temperature fluctuations is impractical.

The effect of the iciness of the soil on the depth of thawing of the road base

One of the important parameters determining technical solutions in the design of highways in the cryolithozone is the depth of thawing of the soils of the road base. The aim of the work was to quantify the degree of influence of the iciness of the soil foundations of roads in the cryolithozone on the depth of their seasonal thawing. For the analysis, the classical formula for calculating the thawing depth for bodies of plane symmetry, obtained by solving the single-phase Stefan problem, was used. The results of calculations are presented in the form of 2D and 3D graphs, which allow us to visually assess the effect of the iciness of the soil and the degree of its change during the operation of the road on the depth of thawing of the road base. It was found, in particular, that the degree of change in the depth of thawing at the same value of the increase in ice content in different ranges (for example, from 10 to 20% and from 30 to 40%) for the considered typical case of the ground base of the cryolithozone decreases by almost 1.3 times. It is shown that the greater the initial iciness of the soil, the degree of decrease in the depth of thawing when the iciness changes by a constant value will be less. A 3D graph was built to determine the depth of thawing of the soils of the active layer of the road base in a wide range of possible changes in ice content during the construction and use of the highway. The availability of a schedule allows to quickly assess possible options for changing the depth of thawing and make a correct, informed technical decision when designing the road. For example, when assessing the need to use a special heat-protective layer in road clothing. Further directions of research in this area should be aimed at studying the effect of humidity (iciness) of dispersed soils on the depth of thawing of road foundations, taking into account the dependence of the density and thermal conductivity of the soil on the iciness.

Thermal Regime and Properties of Soils and Ice‐Rich Permafrost in Beacon Valley, Antarctica

AbstractSubsurface temperatures in polar environments control geomorphic, hydrologic, and biologic processes and ground ice stability. Most studies of the thermal regime in permafrost areas have been developed for the Arctic where interest and concern focus on permafrost thawing. In contrast, this study focuses on soils in the McMurdo Dry Valleys of Antarctica where conditions are much colder and drier, and long‐term persistence of ground ice is of interest including as an analog site for Mars. The soil temperature in Beacon Valley, one of the McMurdo Dry Valleys, has been modeled using the surface temperature, measured heat capacity, and temperature‐dependent thermal conductivity and compared to continuous, high‐resolution measurements of temperatures for a decade down to 19.6‐m depth. For the temperature range of −47.9 to 7.5 °C at our study site, the heat capacity of the dry soil ranges from 580 to 690 J · kg−1 · K−1, thermal conductivity from 0.22 to 0.27 W · m−1 · K−1, and the calculated thermal diffusivity from 0.23 to 0.25 mm2/s. Both the finite difference method and the finite volume method are used to solve the 1‐D heat diffusion equation; the finite volume method‐modeled temperature most closely approximates the measured temperature at all depths with average differences ranging from 0.01 to 0.03 °C. The latent heat contribution of documented episodic snowmelt events and of modeled changes in ice content due to condensation or sublimation is negligible. This study can be applied readily to thermal regimes of similar systems where subsurface temperature measurements are not available such as on Mars.

Geophysical and cryostratigraphic investigations for road design in northern Alaska

This study used combined geophysical and cryostratigraphic methods for permafrost characterization in Arctic road design and engineering. Two major study areas located in the continuous permafrost zone represented a range of terrain conditions including yedoma (syngenetically frozen ice-rich silts with large ice wedges) plateaus and hills, thaw-lake basins, river terraces, and modern floodplains. Direct-current resistivity - electrical resistivity tomography (DCR-ERT) using a Wenner array was applied over transects. Complementary site data including the results of drilling and active layer depths measurements were also obtained. The boreholes provided cryostratigraphic information on soil texture, cryostructures, ground ice, and gravimetric moisture content of frozen soils. The resistivity data supported evaluation of the presence/absence of permafrost; location and depth of the active and intermediate layers; and in some conditions changes in ice content. In contrast, the cryostratigraphic interpretation generally offered more nuanced analysis of the subsurface, but was limited in its ability to detect unconformities and the depth of drilling. Both techniques were enhanced by the availability of high-resolution geospatial information and can be used to optimize the location and density of the boreholes for road construction.

Determining Soil Ice Contents during Freezing and Thawing with Thermo‐Time Domain Reflectometry

Core Ideas An optimum heat application strategy was established for measuring thermal properties with the heat pulse method in partially frozen soils. At temperatures ≤ −5°C, T‐TDR probes were able to measure soil ice content changes with acceptable accuracy. At temperatures between −5 and 0°C, soil ice contents could be estimated from water content before freezing, TDR measured unfrozen water content, and T‐TDR measured total water content at temperatures below −5°C. Determining soil ice content during freezing and thawing is important and challenging for both engineering and environmental issues. The thermo‐time domain reflectometry (T‐TDR) probe, which can monitor unfrozen soil water content and soil thermal properties simultaneously, has the potential to measure ice content in partially frozen soils. The objective of this study was to identify an optimum heat application strategy for measuring soil thermal properties with T‐TDR probes in partially frozen soil while minimizing ice melting during the process. The optimized heating schemes were then applied for monitoring soil ice content dynamics during freezing and thawing. The results indicated that the heat pulse method failed at temperatures between −5 and 0°C because of temperature field disturbances from latent heat of fusion. When soil temperatures were ≤ −5°C, ice melting during heat pulse applications could be limited effectively with a combination of 60‐s heat‐pulse duration and 450 J m−1 heating strength, or a 90‐s heat‐pulse duration and heating strength of 450 to 900 J m−1. With the optimized heating scheme, T‐TDR probes were able to measure soil ice content changes at ≤ −5°C during freezing and thawing, and the errors were within ±0.05 m3 m−3 in sandy loams and within ±0.1 m3 m−3 in soils with high clay content. At temperatures between −5 and 0°C, soil ice contents could not be measured accurately with the heat‐pulse method directly, but they could be estimated coarsely from water content before freezing, TDR measured unfrozen water content, and T‐TDR measured total water content at temperatures below −5°C.

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

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.

Time-lapse refraction seismic tomography for the detection of ground ice degradation

Abstract. The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM) proved to be a valuable tool for the observation of ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the sensitivity of P-wave velocity of seismic waves to phase changes between unfrozen water and ice is similar to the sensitivity of electric resistivity. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space) remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, a time-lapse refraction seismic tomography (TLST) approach is applied as an independent method to ERTM at two test sites in the Swiss Alps. The approach was tested and validated based on a) the comparison of time-lapse seismograms and analysis of reproducibility of the seismic signal, b) the analysis of time-lapse travel time curves with respect to shifts in travel times and changes in P-wave velocities, and c) the comparison of inverted tomograms including the quantification of velocity changes. Results show a high potential of the TLST approach concerning the detection of altered subsurface conditions caused by freezing and thawing processes. For velocity changes on the order of 3000 m/s even an unambiguous identification of significant ice loss is possible.

Dimensional and ice content changes of hardened concrete at different freezing and thawing temperatures

Samples of concrete at different water-to-cement ratios and air contents subjected to freeze/thaw cycles with the lowest temperature at about -80 degrees C are investigated. By adopting a novel tec ...

Factors influencing the particle size distribution of flaked meat. II. Effect of aperture size, number of cutting stations, rotational speed and impeller design

Summary Diced steer flank and brisket were flaked at a nominal temperature of -4.0°C to investigate the effects of rotational speed (3360 or 5250 r.p.m.), two different impeller designs, aperture size (1.5, 6.1 and 19.0mm) and number of cutting stations on the resulting particle size distribution, measured using video image analysis. Changes in ice content and enthalpy were also calculated from measurements of temperature before and after flaking. The amount of ice which melted, and the corresponding enthalpy change, was significantly greater for the smaller aperture sizes, and the higher speeds. Of the four factors investigated, the most important influence on particle size was that of aperture size. However, under some conditions, the number of cutting stations and the rotational speed also influenced the resulting particle size characteristics, most notably in producing thinner particles.

Development and validation of a simple frozen soil parameterization scheme used for climate model

A simple frozen soil parameterization scheme is developed based on NCAR LSM and the effects of re-vised scheme are investigated using Former Soviet Union (FSU) 6 stations measurement data. In the revised model, soil ice content and the energy change in phase change process is considered; the original soil thermal conductivity scheme is replaced by Johanson scheme and the soil thermal and hydraulic properties is modi-fied depending on soil ice content. The comparison of original model with revised model results indicates that the frozen soil scheme can reasonably simulate the energy budget in soil column and the variation of thermal and hydraulic properties as the soil ice content changes. Soil moisture in spring is decreased because of the reduction of infiltration and increment of runoff. Consequently, the partition of heat flux and surface temperature changes correspondingly.

A Scheme for Parameterizing Ice-Cloud Water Content in General Circulation Models

The optical properties of ice clouds are a primary issue for climate and climate change. Evaluating these optical properties in three-dimensional models for studying climate will require a method to calculate the ice water content of such clouds. A procedure is developed to parameterize ice water content as a function of large-scale meteorological characteristics for use in circulation models in which the ice water content is not calculated by means of a three-dimensional prognostic equation for condensed water. The technique identifies large-scale flows in which ice clouds exist and calculates their ice water content by reconstructing the trajectory associated with cloud formation. As the cloud forms, its ice content changes both by deposition of ice from water vapor and by ice removal by sedimentation. The sedimentation process is found to modify significantly the ice water content expected from deposition alone. Ice water contents predicted by the parameterization are compared with aircraft observations collected in the middle latitudes and the tropics, and show reasonable agreement over four orders-of-magnitude of ice water content. A parameterization for the sublimation of ice crystals settling into ice-subsaturated environments is also presented.