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.

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.

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.