This study utilized electrical resistivity imaging (ERI) to investigate subsurface characteristics near Nicolaus Copernicus University Polar Station on the western Spitsbergen-Kaffi & oslash;yra Plain island in the Svalbard archipelago. Surveys along two lines, LN (148 m) collected in 2022 and 2023, and ST (40 m) collected in 2023, were conducted to assess resistivity and its correlation with ground temperatures. The LN line revealed a 1- to 2-m-thick resistive unsaturated outwash sediment layer, potentially indicative of permafrost. Comparing the LN resistivity result between 2022 and 2023, a 600 Ohm.m decrease in the unsaturated active layer in 2023 was observed, attributed to a 5.8 degrees C temperature increase, suggesting a link to global warming. ERI along the ST line depicted resistivity, reaching its minimum at approximately 1.6 m, rising to over 200 Ohm.m at 4 m, and slightly decreasing to around 150 Ohm.m at 7 m. Temperature measurements from the ST line's monitoring strongly confirmed that the active layer extends to around 1.6 m, with permafrost located at greater depths. Additionally, water content distribution in the ST line was estimated after temperature correction, revealing a groundwater depth of approximately 1.06 m, consistent with measurements from the S4 borehole on the ST line. This study provides valuable insights into Arctic subsurface dynamics, emphasizing the sensitivity of resistivity patterns to climate change and offering a comprehensive understanding of permafrost behavior in the region.

Reconstructing historical climate change from deep ground temperature measurements in cold regions is often complicated by the presence of permafrost. Existing methods are typically unable to account for latent heat effects due to the freezing and thawing of the active layer. In this work, we propose a novel method for reconstructing historical ground surface temperature (GST) from borehole temperature measurements that accounts for seasonal thawing and refreezing of the active layer. Our method couples a recently developed fast numerical modeling scheme for two-phase heat transport in permafrost soils with an ensemble-based method for approximate Bayesian inference. We evaluate our method on two synthetic test cases covering both cold and warm permafrost conditions as well as using real data from a 100 m deep borehole on Sardakh Island in northeastern Siberia. Our analysis of the Sardakh Island borehole data confirms previous findings that GST in the region have likely risen by 5-9 degrees C between the pre-industrial period of 1750-1855 and 2012. We also show that latent heat effects due to seasonal freeze-thaw have a substantial impact on the resulting reconstructed surface temperatures. We find that neglecting the thermal dynamics of the active layer can result in biases of roughly -1 degrees C in cold conditions (i.e., mean annual ground temperature below -5 degrees C) and as much as -2.6 degrees C in warmer conditions where substantial active layer thickening (>200 cm) has occurred. Our results highlight the importance of considering seasonal freeze-thaw in GST reconstructions from permafrost boreholes. Plain Language Summary Long-term changes in the temperature of the atmosphere are recorded in the solid Earth due to the insulating properties of soil and rock. As a result, it is possible to estimate past changes in temperature at the interface between the ground and the atmosphere by measuring ground temperatures deep below Earth's surface. In cold regions, the presence of permafrost, that is, ground that remains frozen throughout the year, complicates such analyses due to the effects of water freezing and thawing in the soil. In this work, we present a new method for reconstructing past changes in ground surface temperature from boreholes situated in permafrost using a computational model of heat flow that accounts for these effects. We evaluate our method on both synthetic test cases as well as real data from a 100 m deep borehole in northeastern Siberia. Our results demonstrate that annual freezing and thawing of water near the surface has a substantial impact on the reconstructed ground surface temperature (GST), especially in regions where permafrost is thawing. The proposed method is the first to be widely applicable to ground temperatures measured in permafrost and thus constitutes a valuable new tool for understanding past and present climate change in cold regions.

Ytymdja depression is one of the Mesozoic structures with discovered large coal deposits of the Aldan Upland. Lack of industrial development and farness from agglomerations explain the knowledge gap about the environmental conditions of the Ytymdja depression. A field monitoring network with existing deep boreholes was absorbed to investigate permafrost conditions and to assess potential impacts of local factors and climate change. This paper describes analyse temperatures at the depth down to 240 m by these boreholes with air and ground temperatures of the Ytymdja depression to determinate permafrost conditions. The research was carried out in a 1800 km(2) area of the South Yakutia, Siberia, using satellite imagery-based classification. The field investigations and analysis of ground temperatures indicated that permafrost underlies of the ground entire area of Ytymdja depression, but likely absent under large rivers. Permanent negative temperatures have been detected in the borehole, which shows evidence of the existing of widespread permafrost conditions nowadays in the coal basins in Siberia. Permafrost temperatures vary between -3.1 degrees C and -1.5 degrees C at 35 m below the surface, and annual ground temperatures at 1 m depth ranged from -4.9 degrees C to -1.2 degrees C. Thermal conductivity of rocks determined by individual core samples varies from 1.1 to 2.9 W m(-1) degrees C-1 with geothermal heat flux in the permafrost zone of 0.02 Wm(-2) and an increase in the zone below permafrost to 0.03 Wm(-2). Spatial modelling for the entire territory of the Ytymdja depression deduced a continuous permafrost distribution with a thickness between 106 and 251 m. The considerable thickness of permafrost probably prevents the emission of greenhouse gases from coal seams into the atmosphere, but detailed studies in this direction have yet to be carried out. (C) 2021 Elsevier B.V. All rights reserved.

In deglaciating environments, rock mass weakening and potential formation of rock slope instabilities is driven by long-term and seasonal changes in thermal- and hydraulic- boundary conditions, combined with unloading due to ice melting. However, in-situ observations are rare. In this study, we present new monitoring data from three highly instrumented boreholes, and numerical simulations to investigate rock slope temperature evolution and micrometer-scale deformation during deglaciation. Our results show that the subsurface temperatures are adjusting to a new, warmer surface temperature following ice retreat. Heat conduction is identified as the dominant heat transfer process at sites with intact rock. Observed non-conductive processes are related to groundwater exchange with cold subglacial water, snowmelt infiltration, or creek water infiltration. Our strain data shows that annual surface temperature cycles cause thermoelastic deformation that dominate the strain signals in the shallow thermally active layer at our stable rock slope locations. At deeper sensors, reversible strain signals correlating with pore pressure fluctuations dominate. Irreversible deformation, which we relate with progressive rock mass damage, occurs as short-term (hours to weeks) strain events and as slower, continuous strain trends. The majority of the short-term irreversible strain events coincides with precipitation events or pore pressure changes. Longer-term trends in the strain time series and a minority of short-term strain events cannot directly be related to any of the investigated drivers. We propose that the observed increased damage accumulation close to the glacier margin can significantly contribute to the long-term formation of paraglacial rock slope instabilities during multiple glacial cycles.

Temperature measurements in boreholes are the most common method allowing the quantitative and direct observation of permafrost evolution in the context of climate change. Existing boreholes and monitoring networks often emerged in a scientific context targeting different objectives and with different setups. A standardized, well-planned and robust instrumentation of boreholes for long-term operation is crucial to deliver comparable, high-quality data for scientific analyses and assessments. However, only a limited number of guidelines are available, particularly for mountain regions. In this paper, we discuss challenges and devise best practice recommendations for permafrost temperature measurements at single sites as well as in a network, based on two decades of experience gained in the framework of the Swiss Permafrost Monitoring Network PERMOS. These recommendations apply to permafrost observations in mountain regions, although many aspects also apply to polar lowlands. The main recommendations are (1) to thoroughly consider criteria for site selection based on the objective of the measurements as well as on preliminary studies and available data, (2) to define the sampling strategy during planification, (3) to engage experienced drilling teams who can cope with inhomogeneous and potentially unstable subsurface material, (4) to select standardized and robust instrumentation with high accuracy temperature sensors and excellent long-term stability when calibrated at 0 degrees C, ideally with double sensors at key depths for validation and substitution of questionable data, (5) to apply standardized maintenance procedures allowing maximum comparability and minimum data processing, (6) to implement regular data control procedures, and (7) to ensure remote data access allowing for rapid trouble shooting and timely reporting. Data gaps can be avoided by timely planning of replacement boreholes. Recommendations for standardized procedures regarding data quality documentation, processing and final publication will follow later.

Multiple studies demonstrate Northwest Alaska and the Alaskan North Slope are warming. Melting permafrost causes surface destabilization and ecological changes. Here, we use thermistors permanently installed in 1996 in a borehole in northwestern Alaska to study past, present, and future ground and subsurface temperature change, and from this, forecast future permafrost degradation in the region. We measure and model Ground Surface Temperature (GST) warming trends for a 10 year period using equilibrium Temperature-Depth (TD) measurements from borehole T96-012, located near the Red Dog Mine in northwestern Alaska part of the Arctic ecosystem where a continuous permafrost layer exists. Temperature measurements from 1996 to 2006 indicate the subsurface has clearly warmed at depths shallower than 70 m. Seasonal climate effects are visible in the data to a depth of 30 m based on a visible sinusoidal pattern in the TD plots that correlate with season patterns. Using numerical models constrained by thermal conductivity and temperature measurements at the site, we show that steady warming at depths of similar to 30 to 70 m is most likely the direct result of longer term (decadal-scale) surface warming. The analysis indicates the GST in the region is warming at similar to 0.44 +/- 0.05 degrees C/decade, a value consistent with Surface Air Temperature (SAT) warming of similar to 1.0 +/- 0.8 degrees C/decade observed at Red Dog Mine, but with much lower uncertainty. The high annual variability in the SAT signal produces significant uncertainty in SAT trends. The high annual variability is filtered out of the GST signal by the low thermal diffusivity of the subsurface. Comparison of our results to recent permafrost monitoring studies suggests changes in latitude in the polar regions significantly impacts warming rates. North Slope average GST warming is similar to 0.9 +/- 0.5 degrees C/decade, double our observations at RDM, but within error. The RDM warming rate is within the warming variation observed in eastern Alaska, 0.36-0.71 degrees C/decade, which suggests changes in longitude produce a smaller impact but have warming variability likely related to ecosystem, elevation, microclimates, etc. changes. We also forward model future warming by assuming a 1D diffusive heat flow model and incorporating latent heat effects for permafrost melting. Our analysis indicates similar to 1 to 4 m of loss at the upper permafrost boundary, a similar to 145 +/- 100% increase in the active layer thickness by 2055. If warming continues at a constant rate of similar to 0.44 +/- 0.05 degrees C/decade, we estimate the 125 m thick zone of permafrost at this site will completely melt by similar to 2150. Permafrost is expected to melt by similar to 2200, similar to 2110, or similar to 2080, if the rate of warming is altered to 0.25, 0.90, or 2.0 degrees C/decade, respectively, as an array of different climate models suggest. Since our model assumes no advection of heat (a more efficient heat transport mechanism), and no accelerated warming, our current prediction of complete permafrost loss by 2150 may overestimate the residence time of permafrost in this region of Northwest Alaska. (C) 2016 The Authors. Published by Elsevier B.V.

Recent ground temperature records from the 100-m-deep borehole near the Tarfala Research Station in northern Sweden reveal that permafrost is warming at a pace consistent with the rate of measured air temperature increase at the site. Here we investigate whether air temperature increase is the main driver of the observed change in the permafrost thermal regime using a non-isothermal hydrogeological numerical model for partially frozen ground. The local site is investigated with different ground surface temperature scenarios representing different integrated effects of surficial heat attenuation processes. Results indicate that despite a short-term sensitivity to heat attenuation processes including snow conditions, the main driver of change in the permafrost thermal regime during the past decade is warming air temperatures. Additionally, the approach used here is shown to be particularly pertinent for modelling warming trends, despite limited prior knowledge of site-specific conditions and geological properties. Understanding the main driving mechanisms of changing permafrost is useful for assessing the suitability of borehole temperature records as proxies for past environmental conditions as well as for modelling possible future climatic impacts.

Three temperature depth profiles recorded in permafrost in northern Quebec, Canada, were used to infer the ground surface temperature history (GSTH) of the region. The site is located in a barren rock desert on the Katinniq plateau at an elevation of 600 m, near the northern tip of the Ungava Peninsula. The boreholes were logged more than 3 yr after drilling was completed, insuring that the holes had returned to thermal equilibrium. Thermal conductivity measurements were made on core samples. Radiogenic heat production is small and can be neglected. The temperature depth profiles show marked deviations from steady state in the upper 200 in that are assumed to be caused by recent (<300 yr) variations in ground surface temperature. The GSTHs obtained by inversion of the three temperature profiles consistently show warming by similar to 2.5 K, but differ significantly in the details. One profile which is least affected by topographic effects and thermal conductivity changes was analyzed in great details with different inversion methods; direct methods were also used to verify how well the GSTH can be resolved by the data. The results show a marked warming (approximate to 1.4 K) between the mid-1700s and 1940, followed by a cooling episode ( approximate to 0.4 K) which lasted 40-50 yr, followed by a sharp approximate to 1.7 K warming over the past 15 yr. The borehole temperature measurements suggest that most of this warming occurred over the past 15 yr. These results are in agreement with the available meteorological records and proxy data. (c) 2007 Elsevier B.V All rights reserved.

The Geological Survey of Canada (GSC), in collaboration with other government partners, has been developing and maintaining a network of active-layer and permafrost thermal monitoring sites which contribute to the Canadian Permafrost Monitoring Network and the Global Terrestrial Network for Permafrost. Recent results from the thermal monitoring sites maintained by the GSC and other federal government agencies are presented. These results indicate that the response of permafrost temperature to recent climate change and variability varies across the Canadian permafrost region. Warming of shallow permafrost temperatures of between 0.3 and 0.6 degrees C per decade has occurred since the mid- to late 1980s in the central and northern Mackenzie region in response to a general increase in air temperature. No significant warming (less than 0.1 degrees C per decade) of permafrost is observed in the southern Mackenzie valley. Warming of shallow permafrost of between 1.0 and 4.0 degrees C per decade is also observed in the eastern and high Arctic, but this mainly occurred in the late 1990s. These trends in permafrost temperature are consistent with trends in air temperature observed since the 1970s. Local conditions however, influence the response of the permafrost thermal regime to these changes in air temperature. Copyright (c) 2005 John Wiley & Sons, Ltd.

Borehole temperature-depth profiles contain a record of surface ground temperature (SGT) changes with time and complement surface air temperature (SAT) analysis to infer climate change over multiple centuries. Ground temperatures are generally warmer than air temperatures due to solar radiation effects in the summer and the insulating effect of snow cover during the winter. The low thermal diffusivity of snow damps surface temperature variations; snow effectively acts as an insulator of the ground during the coldest part of the year. A numerical model of snow-ground thermal interactions is developed to investigate the effect of seasonal snow cover on annual ground temperatures. The model is parameterized in terms of three snow event parameters: onset time of the annual snow event, duration of the event, and depth of snow during the event. These parameters are commonly available from meteorological and remotely sensed data making the model broadly applicable. The model is validated using SAT, subsurface temperature from a depth of 10 cm, and snow depth data from the 6 years of observations at Emigrant Pass climate observatory in northwestern Utah and 217 station years of National Weather Service data from sites across North America. Measured subsurface temperature-time series are compared to changes predicted by the model. The model consistently predicts ground temperature changes that compare well with those observed. Sensitivity analysis of the model leads to a nonlinear relationship between the three snow event parameters (onset, duration, and depth of the annual snow event) and the influence snow has on mean annual SGT.