Environmental changes, such as climate warming and higher herbivory pressure, are altering the carbon balance of Arctic ecosystems; yet, how these drivers modify the carbon balance among different habitats remains uncertain. This hampers our ability to predict changes in the carbon sink strength of tundra ecosystems. We investigated how spring goose grubbing and summer warming-two key environmental-change drivers in the Arctic-alter CO2 fluxes in three tundra habitats varying in soil moisture and plant-community composition. In a full-factorial experiment in high-Arctic Svalbard, we simulated grubbing and warming over two years and determined summer net ecosystem exchange (NEE) alongside its components: gross ecosystem productivity (GEP) and ecosystem respiration (ER). After two years, we found net CO2 uptake to be suppressed by both drivers depending on habitat. CO2 uptake was reduced by warming in mesic habitats, by warming and grubbing in moist habitats, and by grubbing in wet habitats. In mesic habitats, warming stimulated ER (+75%) more than GEP (+30%), leading to a 7.5-fold increase in their CO2 source strength. In moist habitats, grubbing decreased GEP and ER by similar to 55%, while warming increased them by similar to 35%, with no changes in summer-long NEE. Nevertheless, grubbing offset peak summer CO2 uptake and warming led to a twofold increase in late summer CO2 source strength. In wet habitats, grubbing reduced GEP (-40%) more than ER (-30%), weakening their CO2 sink strength by 70%. One-year CO2-flux responses were similar to two-year responses, and the effect of simulated grubbing was consistent with that of natural grubbing. CO2-flux rates were positively related to aboveground net primary productivity and temperature. Net ecosystem CO2 uptake started occurring above similar to 70% soil moisture content, primarily due to a decline in ER. Herein, we reveal that key environmental-change drivers-goose grubbing by decreasing GEP more than ER and warming by enhancing ER more than GEP-consistently suppress net tundra CO2 uptake, although their relative strength differs among habitats. By identifying how and where grubbing and higher temperatures alter CO2 fluxes across the heterogeneous Arctic landscape, our results have implications for predicting the tundra carbon balance under increasing numbers of geese in a warmer Arctic.

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.

Svalbards permafrost is thawing as a direct consequence of climate change. In the Low Arctic, vegetation has been shown to slow down and reduce the active layer thaw, yet it is unknown whether this also applies to High Arctic regions like Svalbard where vegetation is smaller, sparser, and thus likely less able to insulate the soil. Therefore, it remains unknown which components of High Arctic vegetation impact active layer thaw and at which temporal scale this insulation could be effective. Such knowledge is necessary to predict and understand future changes in active layer in a changing Arctic. In this study we used frost tubes placed in study grids located in Svalbard with known vegetation composition, to monitor the progression of active layer thaw and analyze the relationship between vegetation composition, vegetation structure and snow conditions, and active layer thaw early in summer. We found that moss thickness, shrub and forb height, and vascular vegetation cover delayed soil thaw immediately after snow melt. These insulating effects attenuated as thaw progressed, until no effect on thaw depth was present after 8 weeks. High Arctic mosses are expected to decline due to climate change, which could lead to a loss in insulating capacity, potentially accelerating early summer active layer thaw. This may have important repercussions for a wide range of ecosystem functions such as plant phenology and decomposition processes. Temperatures are rising in the Arctic, causing increased thaw of the layer of soil located above the permanently frozen ground. In Low Arctic regions vegetation cools the soil, which reduces the thawing. So far, we do not know whether the small plants growing in the High Arctic may be able to slow or reduce thaw. We measured soil thaw throughout the summer in High Arctic Svalbard in locations where vegetation composition is known. We also measured thickness of the moss layer, height of plants and snow depth. We found that moss thickness was the strongest factor in insulating the soil. Also the cover of plants, height of shrubs and forbs, and height of grass-like plants slowed soil thaw in the early summer. The insulating effects became less over time and no effects were found 8 weeks after onset of thaw. As climate change is causing changes in the Arctic vegetation, mosses and small shrubs are expected to decrease. As we found these to be the most important factors in insulating the soil, a future decrease in mosses and small shrubs may cause accelerated soil thaw at the start of summer. High Arctic vegetation slows active layer thaw in early summer after snow melt Mosses show a stronger negative relation with thaw depth than vascular vegetation Factors influencing active layer thaw change over time in early summer

Permafrost warming has been observed all around the Arctic, however, variations in temperature trends and their drivers remain poorly understood. We present a comprehensive analysis of climatic changes spanning 25 years (1998-2023) at Bayelva (78.92094 degrees N, 11.83333 degrees E) on Spitzbergen, Svalbard. The quality controlled hourly data set includes air temperature, radiation fluxes, snow depth, rainfall, active layer temperature and moisture, and, since 2009, permafrost temperature. Our Bayesian trend analysis reveals an annual air temperature increase of 0.9 +/- 0.5 degrees C/decade and strongest warming in September and October. We observed a significant shortening of the snow cover by -14 +/- 8 days/decade, coupled with reduced winter snow depth. The active layer simultaneously warmed by 0.6 +/- 0.7 degrees C/decade at the top and 0.8 +/- 0.5 degrees C/decade at the bottom. While the soil surface got drier, in particular during summer, soil moisture below increased in accordance with the longer unfrozen period and higher winter temperatures. The thawed period prolonged by 10-15 days/decade at different depths. In contrast to earlier top-soil warming, we observed stable temperatures since 2010 and only little permafrost warming (0.14 +/- 0.13 degrees C/decade). This is likely due to recently stable winter air temperature and continuously decreasing winter snow depth. This recent development highlights a complex interplay among climate and soil variables. Our distinctive long-term data set underscores (a) the changes in seasonal warming patterns, (b) the influential role of snow cover decline, and (c) that air temperature alone is not a sufficient indicator of change in permafrost environments, thereby highlighting the importance of investigating a wider range of parameters, such as soil moisture and snow characteristics. Permafrost is warming across the Arctic, but it is not yet well understood why temperature trends vary and what affects them the most. Our detailed study investigates 25 years (1998-2023) of data at the Bayelva permafrost observatory on Svalbard. We analyzed a quality-controlled data set, including hourly measurements of air temperature, radiation, snow depth, rainfall, permafrost temperature, and active layer conditions. We looked beyond annual averages, examining changes in each month. The air warmed strongly by 0.9 degrees C/decade and even stronger in September and October. Continuous snow cover shortened by -14 days/decade and winter snow depth decreased. Simultaneously, the active layer warmed by 0.6 degrees C/decade at the top and 0.8 degrees C/decade at the bottom. While the surface dried in summer, deeper soil layers became moister due to a longer unfrozen period and higher temperatures in winter. The thawed period extended by 10-15 days/decade, with slightly stronger changes toward later freezing in autumn. We found that soil warming stopped in recent years and attributed this effect to the lower winter snow depth since 2010. Therefore, if we want to know how permafrost warms or cools in the future, we need to consider additional measurements such as soil moisture and snow properties. Snow cover thinning and winter air temperature variability are the most important drivers of trends in permafrost temperature While mean annual air temperature continues to increase, the top soil at Bayelva, Svalbard, stopped warming since 2010 The fully snow-covered season shortened by -14 days per decade since 1998, which led to longer unfrozen conditions in the active layer

Ground temperature measurements are crucial for a better understanding of changes in the natural environment, especially in the Arctic. Previous measurement systems provided accurate measurements; however, their most significant disadvantage was the relatively low spatial resolution, including in the vertical profile. The aim of this work was to develop and initially validate a new, original temperature measurement system based on the photonic sensing technique of optical frequency-domain reflectometry (OFDR). The system consists of a fibre-optic sensor, an interrogator, and an automatic data acquisition system. Such fibre-optic sensors allow a significant increase in spatial resolution. Data on precise temperature distribution in the ground profile will allow for a detailed determination of the changes in the thickness of the permafrost active layer (PAL) and, as a consequence, a better description of the current state of the permafrost and the layers above it in relation to their progressive degradation. In the longer term, it will make a better prediction of the pace of possible changes in the polar environment and will open up previously unavailable opportunities in the field of climate change monitoring and forecasting.

Arctic wetlands are a globally significant store of soil organic carbon. They are often characterized by ice-wedge polygons, which are diagnostic of lowland permafrost, and which greatly influence wetland hydrology and biogeochemistry during summer. The degradation of ice-wedge polygons, which can occur in response to climate change or local disturbance, has poorly understood consequences for biogeochemical processes. We therefore used geochemical analyses from the active layer and top permafrost to identify and compare the dominant biogeochemical processes in high-centered (degraded) and low-centered (pristine) polygons situated in the raised beach sediments and valley-infill sediments of Adventdalen, Central Svalbard. We found similar organic-rich sediments in both cases (up to 38 dry wt.%), but while low-centered polygons were water-saturated, their high-centered counterparts had a relatively dry active layer. Consequently, low-centered polygons showed evidence of iron and sulfate reduction leading to the precipitation of pyrite and siderite, whilst the high-centered polygons demonstrated more oxidizing conditions, with decreased iron oxidation and low preservation of iron and sulfate reduction products in the sediments. This study thus demonstrates the profound effect of ice-wedge polygon degradation on the redox chemistry of the host sediment and porewater, namely more oxidizing conditions, a decrease in iron reduction, and a decrease in the preservation of iron and sulfate reduction products.

The soils of Arctic regions are of great interest due to their high sensitivity to climate change. Kvartsittsletta coast in the vicinity of the Baranowski Research Station of the University of Wroclaw constitutes a sequence of differently aged sea terraces covered with different fractions of beach material. It is a parent material for several developing soil types. Despite the low intensity of the modern soil-forming processes, the soil cover is characterized by high diversity. Soil properties are formed mainly by geological and geomorphological factors, which are superimposed by the influence of climate and living organisms. The degree of development of soil is usually an indicator of its relative age. This article highlights the dominant influence of lithology and microrelief over other soilforming factors, including the duration for which the parent material was exposed to external factors. The soils on the highest (oldest) terrace steps of the Kvartsittsletta rarely showed deep signs of soil-forming processes other than cryoturbations. On the youngest terraces, deep-reaching effects of soil processes associated with a relatively warm climate, including the occurrence of cambic horizons, were observed. Their presence in Arctic regions carries important environmental information and may be relevant to studies of climate change.

Permafrost degradation is one of the most pressing issues in the modern cryosphere related to climate change. Most attention is paid to the degradation of the top of the active permafrost associated with contemporary climate. This is the most popular issue because in the subsurface part of it there is usually the greatest accumulation of ground ice in direct relation to the changes taking place. The melting of ground ice is the cause of the greatest changes related to subsidence and other mass-wasting processes. The degradation of the subsurface permafrost layer is also responsible for the increased emission of CO2 and methane. However, this is not a fully comprehensive look at the issue of permafrost degradation, because depending on its thickness, changes in its thermal properties may occur more or less intensively throughout its entire profile, also reaching the base of permafrost. These changes can degrade permafrost throughout its profile. The article presents the basic principles of permafrost degradation in its overall approach. Both the melting of the ground ice and the thermal degradation of permafrost, as manifested in an increase in its temperature in part or all of the permafrost profile, are discussed. However, special attention is paid to the degradation characteristics from the permafrost base. In the case of moderately thick and warm permafrost in the zone of its sporadic and discontinuous occurrence, this type of degradation may particularly contribute to its disappearance, and surficial consequences of such degradation may be more serious than we expect on the basis of available research and data now. A special case of such degradation is the permafrost located in the coastal zone in the vicinity of the Hornsund Spitsbergen, where a multidirectional thermal impact is noted, also causing similar degradation of permafrost: from the top, side and bottom. Especially the degradation of permafrost from the permafrost base upwards is an entirely new issue in considering the evolution of permafrost due to climate change. Due to the difficulties in its detection, this process may contribute to the threats that are difficult to estimate in the areas of discontinuous and sporadic permafrost.

The active layer of permafrost in Ny angstrom lesund, Svalbard (79 degrees N) around the Bayelva River in the Leirhaugen glacier moraine is measured as a small net carbon sink at the brink of becoming a carbon source. In many permafrost-dominating ecosystems, microbes in the active layers have been shown to drive organic matter degradation and greenhouse gas production, creating positive feedback on climate change. However, the microbial metabolisms linking the environmental geochemical processes and the populations that perform them have not been fully characterized. In this paper, we present geochemical, enzymatic, and isotopic data paired with 10 Pseudomonas sp. cultures and metagenomic libraries of two active layer soil cores (BPF1 and BPF2) from Ny angstrom lesund, Svalbard, (79 degrees N). Relative to BPF1, BPF2 had statistically higher C/N ratios (15 +/- 1 for BPF1 vs. 29 +/- 10 for BPF2; n = 30, p < 10(-5)), statistically lower organic carbon (2% +/- 0.6% for BPF1 vs. 1.6% +/- 0.4% for BPF2, p < 0.02), statistically lower nitrogen (0.1% +/- 0.03% for BPF1 vs. 0.07% +/- 0.02% for BPF2, p < 10(-6)). The d(13)C values for inorganic carbon did not correlate with those of organic carbon in BPF2, suggesting lower heterotrophic respiration. An increase in the delta C-13 of inorganic carbon with depth either reflects an autotrophic signal or mixing between a heterotrophic source at the surface and a lithotrophic source at depth. Potential enzyme activity of xylosidase and N-acetyl-beta-D-glucosaminidase increases twofold at 15 degrees C, relative to 25 degrees C, indicating cold adaptation in the cultures and bulk soil. Potential enzyme activity of leucine aminopeptidase across soils and cultures was two orders of magnitude higher than other tested enzymes, implying that organisms use leucine as a nitrogen and carbon source in this nutrient-limited environment. Besides demonstrating large variability in carbon compositions of permafrost active layer soils only similar to 84 m apart, results suggest that the Svalbard active layer microbes are often limited by organic carbon or nitrogen availability and have adaptations to the current environment, and metabolic flexibility to adapt to the warming climate.

Direct Current (DC) Resistivity and Induced Polarization (IP) response of six profiles were measured using the Gradient electrode configuration in Adventdalen, Svalbard, to characterise the near-surface stratigraphy of the soil and to account for geotechnical and environmental aspects of global warming in the arctic region. In addition, Wenner array data was collected for the selected profiles to examine its effectiveness as compared to the Gradient array, given the characteristics of the study site. Two commercial inversion software programs, Res2DINV and AarhusINV, were used for the inversion of the DC resistivity and IP data, to compare the software. Physical soil properties, including porosity, water saturation, water salinity, freezing temperature and grain size distribution, previously measured from samples retrieved from wells along the studied profiles, were integrated in this study to investigate the correlation with geoelectrical properties of the sediments inferred from the DC resistivity and IP data. Results from processing of the Wenner array DC resistivity data provided higher resolution as compared to the Gradient array data, especially from deeper parts of the models, due to its higher signal-to-noise ratio. The Wenner array data also indicated better inversion result for the IP data as distinctive anomalies were better indicated in data from Wenner array survey. The Wenner array data also provided a realistic trend for the anomalies, thanks to the symmetrical geometry of the electrodes during the survey, although at the cost of time and higher expenses. Inversion results proved that AarhusINV resolved the geometry of the subsurface layers with higher resolution compared with the Res2DINV. However, the two inversion algorithms use slightly different parameters for the processing and for presenting the results, thus only allowing qualitative comparison. Based on the interpretations of the DC resistivity and IP data, four distinctive zones were identified from the surface to the maximum depth of 26 m, consisting of (i) unfrozen active-layer-(silts and sands), with intermediate resistivity values 200-300 omega center dot m; (ii) frozen soil with 3-10 m thickness and resistivity values between 2500 and 5000 omega center dot m; (iii) unfrozen soil (cryopeg) with high salinity and low resistivity of 40 omega center dot m; and finally (iv) clayey unfrozen soil sediments with low resistivity ranging 10-20 omega center dot m, at depths between 13 and 26 m. The IP data allowed for the delineation of a low chargeability zone near the surface and a high chargeability zone at greater depth which denote the active layer, lower parts of unfrozen soil sediments and cryopeg respectively, within the top 10 m of the subsurface. The 3D subsurface model of the study area was created based on interpretations of the DC resistivity and IP data and was constrained by the description of the subsurface stratigraphy from nearby wells, which provided detailed information about the vertical stratigraphy of the study area. In addition, a good correlation was observed between the studied physical properties of the sediments and the DC resistivity data for the intersecting profile SVAER04, as the interface between high and low resistivity data at ca. 10 m depth coincided the sedimentary formation with intermediate-fine grain size, high porosity, high water saturation and high salt content. Our findings show that joint application of the geoelectrical surveys and laboratory analysis of soil samples are an efficient complement to each other. These methods can be used as an alternative to each other to investigate larger areas where achieving high resolution data is not necessary.