Small modular reactors (SMRs) are an alternative for clean energy solutions in Canada's remote northern communities, owing to their safety, flexibility, and reduced capital requirements. Currently, these communities are heavily reliant on fossil fuels, and the transition to cleaner energy sources, such as SMRs, becomes imperative for Canada to achieve its ambitious net-zero emissions target by 2050. However, applying SMR technology in permafrost regions affected by climate change presents unique challenges. The degradation of permafrost can lead to significant deformations and settlements, which can result in increased maintenance expenses and reduced structural resilience of SMR infrastructure. In this paper, we studied the combined effect of climate nonstationarity in terms of ground surface temperature and heat dissipation from SMR reactor cores for the first time in two distinct locations in Canada's North: Salluit in Quebec and Inuvik in the Northwest Territories. It was shown that these combined effects can make significant changes to the ground thermal conditions within a radius of 15-20 m around the reactor core. The change in the ground thermal conditions poses a threat to the integrity of the permafrost table. The implementation of mitigation strategies is imperative to maintain the structural integrity of the nuclear infrastructure in permafrost regions. The thermal modeling presented in this study paves the way for the development of advanced coupled thermo-hydromechanical models to examine the impact of SMRs and climate nonstationarity on permafrost degradation.

Small topographic features below the resolution of existing orbital data sets may create micro ultra-cold traps within the larger permanently shadowed regions that are present at the lunar poles. These ultra-cold traps are protected from the major primary and secondary illumination sources, and thus would create surfaces that are much colder than lower-resolution temperature maps would indicate. We examine this effect by creating a high resolution (1 m pix(-1)) terrain map based on upscaled data from the Lunar Orbiter Laser Altimeter. This map is illuminated by scattered sunlight and infrared emissions from sunlit terrain, which are then run through a thermal model to determine temperatures. We find that while most of the terrain experiences maximum temperatures around 50 K, there are a number of 1-30 m-scale ultra-cold traps with maximum temperatures as low as 20-30 K. By comparing our modeled ultra-cold trapping area to volatile abundances measured by Lunar Crater Observation and Sensing Satellite (LCROSS), we reveal a diverse environment where the surficial abundances necessary to explain the LCROSS results are strongly dependent on precisely where the impact occurred.

The risk of frost damage to building materials is strongly dependent on the water content, particularly when the water content is high. Therefore, to understand the moisture behavior of materials with high water content is essential to predict the frost damage risks of buildings. While little liquid water transfer takes place over the capillary saturation under unfrozen conditions, the pressure drop of the unfrozen water contained in the frozen domain (cryosuction) may be a strong driving force for water transfer during the freezing processes. Therefore, in this study, we investigated water transfer in a building material over capillary saturation during freezing through a one-dimensional freezing experiment using the gamma-ray attenuation method and hygrothermal simulations. In the experiment, an aerated concrete specimen, with a water content greater than the capillary saturation, was subjected to a temperature gradient by cooling the specimen bottom to the freezing temperature. The results show that significant water transfer occurred even in the capillary-saturated material during freezing and thawing. Water moved to the cold side in the material and the most significant water accumulation was observed at a position where the temperature was close to 0 degrees C. The hygrothermal simulation, including the freezing processes, confirmed that cryosuction was a dominant driving force of water movement and accumulation in the material compared with other driving forces, such as gravity and temperature gradient. Moreover, mechanism of the water accumulation at a position where the temperature was close to 0 degrees C was discussed from the perspective of water chemical potential distribution and water conductivity of the material. The findings of this study will help develop a more reliable model for evaluating moisture damage risks by considering the hygrothermal behaviors of building envelopes.

Climate warming is causing significant changes in the Arctic, leading to increased temperatures and permafrost instability. The active layer has been shown to be affected by climate change, where warmer ground surface temperatures result in progressive permafrost thaw and a deepening active layer. This study assessed the effects of thermal modeling parameters on permafrost ground response to climate warming using the fifth phase of the Coupled Model Intercomparison Project (CMIP5) and TEMP/W software. We analyzed how variations in depth, water content, and soil type affect predictions of future active layer depths and settlement under various climate scenarios using the soil characteristics along Hudson Bay Railway corridor. The results indicate that, for finegrained soils, the depth of the model is a more significant parameter than for coarse-grained soils. The water content of all soil types is a critical factor in determining the time at which permafrost thaws and the depth at which the active layer is located, as higher water content leads to larger active layer changes and more settlement in most cases. Our findings have important implications for infrastructure and land use management in the Arctic region.

Lunar collapse pits and possible caves have been suggested as ideal locations for the storage and protection of lunar water ice deposits, due to their potential to create permanently shadowed regions (PSRs) at high latitudes and ability to protect ice from destructive surface processes. However, the thermal environments of these features have not been investigated at high latitudes, and it remains unclear what effects pit latitude and geometry would have on interior temperatures and ice stability. We create a 3D thermal and volatile transport model and use it to characterize the thermal environments and volatile-trapping potential within lunar collapse pits and caves. We model the thermal behavior of lunar pits as it varies with latitude for several different pit geometries. We then apply the thermal model results to the volatile transport model and calculate water loss rates to space given an initial ice deposit. The model shows that in general, high-latitude pits make poor cold traps for ice because their enclosed geometry increases the ability of multiple-scattered infrared radiation to elevate pit interior temperatures. Although, the enclosed geometry of a cave might help trap volatiles in theory, in practice ice stability within pits and caves is primarily controlled by temperature and not geometric effects. We find that ice loss rates are higher within pits and caves than within PSRs of craters at similar latitudes. Nevertheless, some specific situations arise where pits can act as effective cold traps, such as when pits lie within PSRs created by exterior topography.

Arctic regions are highly impacted by the global temperature rising and its consequences and influences on the thermo-hydro processes and their feedbacks. Theses processes are especially not very well understood in the context of river-permafrost interactions and permafrost degradation. This paper focuses on the thermal characterization of a river-valley system in a continuous permafrost area (Syrdakh, Yakutia, Eastern Siberia) that is subject to intense thawing, with major consequences on water resources and quality. We investigated this Yakutian area through two transects crossing the river using classical tools such as in-situ temperature measurements, direct active layer thickness estimations, unscrewed aerial vehicle (UAV) imagery, heat transfer numerical experiments, Ground-Penetrating Radar (GPR), and Electrical Resistivity Tomography (ERT). Of these two transects, one was closely investigated with a long-term temperature time series from 2012 to 2018, while both of them were surveyed by geophysical and UAV data acquisition in 2017 and 2018. Thermodynamical numerical simulations were run based on the long-term temperature series and are in agreement with river thermal influence on permafrost and active layer extensions retrieved from GPR and ERT profiles. An electrical resistivity-temperature relationship highlights the predominant role of water in such a complicated system and paves the way to coupled thermo-hydro-geophysical modeling for understanding permafrost-river system evolution.

Simulations with a one-dimensional heat transfer model (TONE) were performed to reproduce the near surface ground temperature regime in the four main types of soil profiles found in Narsajuaq River Valley (Nunavik, Canada) for the period 1990-2100. The permafrost thermal regime was simulated using climate data from a reanalysis (1948-2002), climate stations (1989-1991, 2002-2019) and simulations based on climate warming scenarios RCP4.5 and RCP8.5 (2019-2100). The model was calibrated based on extensive field measurements made between 1989 and 2019. The results were used to estimate when soil thermal contraction cracking will eventually stop and to forecast the melting of ice wedges due to active-layer thickening. For the period 1990-2019, all soil profiles experienced cracking every year until 2006, when cracking became intermittent during a warm period before completely stopping in 2009-2010, after which cracking resumed during colder years. Ice-wedge tops melted from 1992 to 2010 as the active layer thickened, indicating that top-down ice-wedge degradation can occur simultaneously with cracking and growth in width. Our predictions show that ice wedges in the valley will completely stop cracking between 2024 and 2096, first in sandy soils and later in soils with thicker organic horizons. The timing will also depend on greenhouse gas concentration trajectories. All ice wedges in the study area will probably experience some degradation of their main body before the end of the century, causing their roots to become relict ice by the end of the 21st century.

A physically based one-dimensional sharp-interface model of active layer evolution and permafrost thaw is presented. This computationally efficient, semianalytical, nonequilibrium solution to soil freeze-thaw problems in partially saturated media is proposed as a component of hydrological models to describe seasonal ground ice, active layer evolution, and changes in permafrost temperature and extent. The model is developed and validated against the analytical Stefan solution and a finite volume coupled heat and mass transfer model of freeze-thaw in unsaturated porous media. Unlike analytic models, the interface model provides a nonequilibrium solution to the heat equation while permitting a wide range of temporally variable boundary conditions and supporting the simulation of multiple interfaces between frozen and unfrozen soils. The model is implemented for use in discontinuous permafrost peatlands where soil properties are highly dependent on soil ice content and infiltration capacity is high. It is demonstrated that the model is suitable for the representation of variably saturated active layer and permafrost evolution in cases both with and without a talik.

It is essential to monitor the ground temperature over large areas to understand and predict the effects of climate change on permafrost due to its rapid warming on the Qinghai-Tibet Plateau (QTP). Land surface temperature (LST) is an important parameter for the energy budget of permafrost environments. Moderate Resolution Imaging Spectroradiometer (MODIS) LST products are especially valuable for detecting permafrost thermal dynamics across the QTP. This study presents a comparison of MODIS-LST values with in situ near-surface air temperature (T-a), and ground surface temperature (GST) obtained from 2014 to 2016 at five sites in Beiluhe basin, a representative permafrost region on the QTP. Furthermore, the performance of the thermal permafrost model forced by MODIS-LSTs was studied. Averaged LSTs are found to strongly correlated with T-a and GST with R-2 values being around 0.9. There is a significant warm bias (4.43-4.67 degrees C) between averaged LST and T-a, and a slight warm bias (0.67-2.66 degrees C) between averaged LST and GST. This study indicates that averaged MODIS-LST is supposed to be a useful data source for permafrost monitoring. The modeled ground temperatures and active-layer thickness have a good agreement with the measurements, with a difference of less than 1.0 degrees C and 0.4 m, respectively.

Hydrothermal processes are key components of permafrost dynamics and hydrological and carbon cycles in northern forest ecosystems. A forest hydrology model. ForHyM, was used to evaluate these processes by determining how the depth and duration of frost penetration into the soil would vary daily over the course of several decades. This was done for chosen upland/wetland conditions within the Mackenzie Plain south of Fort Simpson, where permafrost is currently sporadic to discontinuous. The model calculations were done using daily weather records from November 1963 to 2010, starting with a hypothetical no-frost condition within the soil and subsoil. Model performance was evaluated by comparing modeled and measured temperatures at different soil depths (upland and peat plateau modelling, R-2 = 0.95 and 0.94, respectively). It was found that well-drained upland forests within the general area would experience deep and complete freeze thaw cycles each year. In contrast, poorly drained wetlands would develop gradually deepening permafrost that would at first stabilize in depth over the course of 10 to 20 y, with thaw depth limited to <1 m each year. However, recent increases in recorded air temperature (more so in winter than in summer) would destabilize the pennafrost layer, and this would especially occur in areas with insufficient surface insulation by local peat, moss, forest litter, and snow accumulations. These estimates are consistent with (i) reported thawing depths and the widening encroachment of collapse scars towards the poorly drained portions of the South Mackenzie Plain.