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The CryoGrid community model is a flexible toolbox for simulating the ground thermal regime and the ice–water balance for permafrost and glaciers, extending a well-established suite of permafrost models (CryoGrid 1, 2, and 3). The CryoGrid community model can accommodate a wide variety of application scenarios, which is achieved by fully modular structures through object-oriented programming. Different model components, characterized by their process representations and parameterizations, are realized as classes (i.e., objects) in CryoGrid. Standardized communication protocols between these classes ensure that they can be stacked vertically. For example, the CryoGrid community model features several classes with different complexity for the seasonal snow cover, which can be flexibly combined with a range of classes representing subsurface materials, each with their own set of process representations (e.g., soil with and without water balance, glacier ice). We present the CryoGrid architecture as well as the model physics and defining equations for the different model classes, focusing on one-dimensional model configurations which can also interact with external heat and water reservoirs. We illustrate the wide variety of simulation capabilities for a site on Svalbard, with point-scale permafrost simulations using, e.g., different soil freezing characteristics, drainage regimes, and snow representations, as well as simulations for glacier mass balance and a shallow water body. The CryoGrid community model is not intended as a static model framework but aims to provide developers with a flexible platform for efficient model development. In this study, we document both basic and advanced model functionalities to provide a baseline for the future development of novel cryosphere models.

Ground temperatures in coarse, blocky deposits such as mountain blockfields and rock glaciers have long been observed to be lower in comparison with other (sub)surface material. One of the reasons for this negative temperature anomaly is the lower soil moisture content in blocky terrain, which decreases the duration of the zero curtain in autumn. Here we used the CryoGrid community model to simulate the effect of drainage on the ground thermal regime and ground ice in blocky terrain permafrost at two sites in Norway. The model set-up is based on a one-dimensional model domain and features a surface energy balance, heat conduction and advection, as well as a bucket water scheme with adjustable lateral drainage. We used three idealized subsurface stratigraphies, blocks only, blocks with sediment and sediment only, which can be either drained (i.e. with strong lateral subsurface drainage) or undrained (i.e. without drainage), resulting in six scenarios. The main difference between the three stratigraphies is their ability to retain water against drainage: while the blocks only stratigraphy can only hold small amounts of water, much more water is retained within the sediment phase of the two other stratigraphies, which critically modifies the freeze–thaw behaviour. The simulation results show markedly lower ground temperatures in the blocks only, drained scenario compared to other scenarios, with a negative thermal anomaly of up to 2.2 ∘C. For this scenario, the model can in particular simulate the time evolution of ground ice, with build-up during and after snowmelt and spring and gradual lowering of the ice table in the course of the summer season. The thermal anomaly increases with larger amounts of snowfall, showing that well-drained blocky deposits are less sensitive to insulation by snow than other soils. We simulate stable permafrost conditions at the location of a rock glacier in northern Norway with a mean annual ground surface temperature of 2.0–2.5 ∘C in the blocks only, drained simulations. Finally, transient simulations since 1951 at the rock glacier site (starting with permafrost conditions for all stratigraphies) showed a complete loss of perennial ground ice in the upper 5 m of the ground in the blocks with sediment, drained run; a 1.6 m lowering of the ground ice table in the sediment only, drained run; and only 0.1 m lowering in the blocks only, drained run. The interplay between the subsurface water–ice balance and ground freezing/thawing driven by heat conduction can at least partly explain the occurrence of permafrost in coarse blocky terrain below the elevational limit of permafrost in non-blocky sediments. It is thus important to consider the subsurface water–ice balance in blocky terrain in future efforts in permafrost distribution mapping in mountainous areas. Furthermore, an accurate prediction of the evolution of the ground ice table in a future climate can have implications for slope stability, as well as water resources in arid environments.

It is crucial to keep the eastern shore of Khuvsgul Lake, which is differentiated from other parts by its unique characteristics. For this case, it is necessary to study permafrost, which plays a certain role in the component of the uniqueness, of this region. Numerous studies have proven that the current climate change has caused accelerating permafrost loss. Therefore, we initiated a study to understand the permafrost condition on the eastern shore of Khuvsgul Lake. The preliminary findings of the study were presented. Nine locations, which were on the same line but had various natural characteristics, were selected for the study. FDD (freezing degree days) and TDD (thawing degree days) values of the sites as well as changes in the mean annual temperature were analyzed in the study. Between the study sites, the mean annual ground surface temperature ranged from -1.67°C to 1.04°C. For the FDD and TDD values of the studied area, site A-10, which was situated on a south-facing slope, had the higher temperature variations, ranging from -1573.2°C to 1953.1°C, while the study sites in the forest had the lower temperature variations, ranging from -881.3°C to 646.1°C. Also, the differences between the FDD and TDD values were highest and 379.9°C at A-10, whereas, it was lowest and -609.2°C at the valley site A-35, where shrubs were predominated. The temperature variations between winter and summer at the study sites were relatively lower and 17°C in the forested area, whereas relatively higher and 25.5°C in the non-forested area. Хөвсгөл нуурын зүүн эргийн гадаргын температурын анализ ХУРААНГУЙ Хөвсгөл нуурын зүүн эрэг нь өөрийн гэсэн өвөрмөц байгалийн тогтцоороо бусад үзэсгэлэнт газруудаас ялгарсаар ирсэн ба үүнийг зүй зохистой байгалийн унаган төрхөөр нь хадгалж үлдээх нь маш чухал юм. Үүний тулд тэрхүү байгалийн үзэсгэлэнт төрхийг бүрэлдүүлэхэд тодорхой хэмжээний үүрэгтэй оролцдог цэвдгийг тухайн бүс нутагт илүү нарийн судлан шинжлэх шаардлагатай. Сүүлийн жилүүдэд эрчимтэй явагдаж байгаа уур амьсгалын өөрчлөлтийн нөлөөгөөр цэвдгийн алдрал улам ихсэж байгаа нь олон төрлийн судалгаагаар батлагдсаар байна. Иймд бид Хөвсгөл нуурын зүүн эргийн цэвдгийг илүү нарийн судлахаар уг судалгааны ажлыг эхлүүлсэн. Энэхүү өгүүлэлд бидний эхлүүлээд байгаа судалгааны ажлын анхан шатны үр дүнг оруулаад байна. Судалгаанд ашиглахаар 9 ширхэг газрын гадаргын хувьд өөр хоорондоо ялгаатай нэг шугамд байрлах цэгүүдийг сонгож авсан. Тухайн цэгүүдийн жилийн дундаж температур болон FDD болон ТDD утгуудын өөрчлөлтийг судалгаанд оруулсан. Гадаргын жилийн дундаж температур нь -1.67°С-ээс 1.04°С-ийн хооронд судалгааны цэгүүд дээр хэлбэлзэж байна. Харин судалгааны цэгүүдийн FDD болон TDD утгуудын хувьд уулын өвөр энгэрт байрлах А-10 цэгт халалт, хөрөлт хамгийн их буюу -1573.2°С-ээс 1953.1°С-ийн хооронд байгаа бол модтой ар хажууд байрлах цэгүүдэд хамгийн бага буюу -881.3°С-ээс 646.1°С-ийн хооронд байна. Мөн FDD болон ТDD утгуудын зөрүү нь хамгийн их нь өвөр энгэрийн А-10 цэгт 379.9°С байсан бол хамгийн бага нь уулсын хөндийд сөөглөг ургамал голдуу ургасан газарт байрлах А-35 цэгт -609.2°С байгаагаар тус тус тогтоогдсон. Судалгааны талбайн газрын гадарга дээрх нь өвөл, зуны улирлын температурын агуураг ойтой ар хажууд маш бага буюу дунджаар 17°С байгаа бол ойгүй газарт 25.5°С тус тус байна. Түлхүүр үгс: Цэвдэг, ЖДГТ (жилийн дундаж гадрагын температур), ХДХТН (хоногийн дундаж хасах температурын нийлбэр), ХДНТН (хоногийн дундаж нэмэх температурын нийлбэр)

Soils in the northern high latitudes are a key component in the global carbon cycle; the northern permafrost region covers 22 % of the Northern Hemisphere land surface area and holds almost twice as much carbon as the atmosphere. Permafrost soil organic matter stocks represent an enormous long-term carbon sink which is in risk of switching to a net source in the future. Detailed knowledge about the quantity and the mechanisms controlling organic carbon storage is of utmost importance for our understanding of potential impacts of and feedbacks on climate change. Here we present a geospatial dataset of physical and chemical soil properties calculated from 651 soil pedons encompassing more than 6500 samples from 16 different study areas across the northern permafrost region. The aim of our dataset is to provide a basis to describe spatial patterns in soil properties, including quantifying carbon and nitrogen stocks. There is a particular need for spatially distributed datasets of soil properties, including vertical and horizontal distribution patterns, for modeling at local, regional, or global scales. This paper presents this dataset, describes in detail soil sampling; laboratory analysis, and derived soil geochemical parameters; calculations; and data clustering. Moreover, we use this dataset to estimate soil organic carbon and total nitrogen storage estimates in soils in the northern circumpolar permafrost region (17.9×106 km2) using the European Space Agency's (ESA's) Climate Change Initiative (CCI) global land cover dataset at 300 m pixel resolution. We estimate organic carbon and total nitrogen stocks on a circumpolar scale (excluding Tibet) for the 0–100 and 0–300 cm soil depth to be 380 and 813 Pg for carbon, and 21 and 55 Pg for nitrogen, respectively. Our organic carbon estimates agree with previous studies, with most recent estimates of 1000 Pg (−170 to +186 Pg) to 300 cm depth. Two separate datasets are freely available on the Bolin Centre Database repository (https://doi.org/10.17043/palmtag-2022-pedon-1, Palmtag et al., 2022a; and https://doi.org/10.17043/palmtag-2022-spatial-1, Palmtag et al., 2002b).

With the EU-funded PACE project in the turn of this century, several deep boreholes (100 m +) were drilled in European mountain sites, including mainland Norway, Svalbard and Sweden. During other projects from c. 2004 and the International Polar Year (IPY) period in 2006/07, several additional boreholes were drilled in different sites in both Norway and Iceland, measuring temperatures along both altitudinal and latitudinal gradients. At most sites, multi-temporal geophysical soundings are available using seismic and electrical resistivity tomography (ERT). Here we study the development of permafrost and ground temperatures in mainland Norway and Iceland based on these data sets. We document that permafrost in is warming at an high rate, including the development of taliks in both Norway and Iceland in response to climate change during the last 20 years. At most sites ground surface temperature (GST) is apparently increasing stronger than surface air temperature (SAT). Changing snow conditions appear to be the most important factor for the higher GST rates. Modelling exercises also indicate that the talik development can by explained both by higher air temperatures and increasing snow cover.

Arctic permafrost is yet the largest non-seasonal component of Earth's cryosphere and has been proposed as a climate tipping element. Already today, permafrost thaw and ground ice loss have detrimental consequences for Arctic communities and are affecting the global climate via carbon-cycle–feedbacks. However, it is an open question whether climatic changes drive permafrost loss in a way that gives rise to a tipping point, crossing of which would imply abrupt acceleration of thaw and disproportional unfolding of its impacts.Here, we address this question by geospatial analyses and a comprehensive literature review of the mechanisms and feedbacks driving permafrost thaw across spatial scales. We find that neither observation-constrained nor model-based projections of permafrost loss provide evidence for the existence of a global-scale tipping point, and instead suggest a quasi-linear response to global warming. We identify a range of processes that drive rapid permafrost thaw and irreversible ground ice loss on a local scale, but these do not accumulate to a non-linear response beyond regional scales.We emphasize that it is precisely because of this overall linear response, that there is no „safe space“ for Arctic permafrost where its loss could be acceptable. Every additional amount of global warming will proportionally subject additional land areas underlain by permafrost to thaw, implying further local impacts and carbon emissions.

Norway has the third greatest extent of peatlands in Europe, after Finland and Sweden. Norwegian peatlands cover nearly 30 000 km2 or 7.7 percent of Norway’s land area. However, 6500 km2 of these peatlands have been drained for forestry or agriculture and are estimated to emit approximately 6 Mton CO2 annually, accounting for 11 percent of Norway’s total carbon emissions. In 2016, the Norwegian Environment Agency and the Norwegian Directorate of Agriculture embarked on a peatland restoration plan to reduce greenhouse gas emissions and improve the ecological conditions of drained and degraded peatlands in Norway. Since then, over 100 peatland sites have been restored. However, only one of these sites is being actively monitored to determine the effect of restoration on carbon fluxes, making this site critical to understanding carbon dynamics of restored peatlands in Norway. The site, located in the Regnåsen and Hisåsen Nature Reserve (Trysil Municipality, Innlandet county) consists of two study areas that are sub-catchments of the same watershed, cover approximately 0.5 km2, and are separated by 0.5 km. Both areas were drained in the 1960s, with a network of drainage ditches totaling approximately 4000m. One of the areas was restored in 2021 by constructing 318 dams in the drainage ditches, while the other area remains drained as a control. In 2019 eddy covariance towers were installed to track vertical CO2 and CH4 fluxes on each site. In addition, DOC, DIC and water discharge measurements were taken to estimate lateral carbon transport, and soil samples were taken to estimate carbon stocks. Preliminary results indicate that CO2 fluxes have decreased and CH4 fluxes have increased in the restored site as compared to the drained site, and that vertical carbon fluxes account for over 90% of carbon transport on both sites. This project is coordinated by the LATICE (Land-ATmosphere Interactions in Cold Environments) project at University of Oslo. The results of this study will assist the Norwegian Environment Agency in shaping the next phase of the peatland restoration work in Norway.

Extensive regions in the permafrost zone are projected to become climatically unsuitable to sustain permafrost peatlands over the next century, suggesting transformations in these landscapes that can leave large amounts of permafrost carbon vulnerable to post-thaw decomposition. We present three years of eddy covariance measurements of CH4 and CO2 fluxes from the degrading permafrost peatland Iskoras in Northern Norway, which we disaggregate into separate fluxes of palsa, pond, and fen areas using information provided by the dynamic flux footprint in a novel ensemble-based Bayesian deep neural network framework. The three-year mean CO2-equivalent flux is estimated to be 106 gCO2 m-2 yr-1 for palsas, 1780 gCO2 m-2 yr-1 for ponds, and -31 gCO2 m-2 yr-1 for fens, indicating that possible palsa degradation to thermokarst ponds would strengthen the local greenhouse gas forcing by a factor of about 17, while transformation into fens would slightly reduce the current local greenhouse gas forcing.

Peatlands have often been neglected in Earth system models (ESMs). Where they are included, they are usually represented via a separate, prescribed grid cell fraction that is given the physical characteristics of a peat (highly organic) soil. However, in reality soils vary on a spectrum between purely mineral soil (no organic material) and purely organic soil, typically with an organic layer of variable thickness overlying mineral soil below. They are also dynamic, with organic layer thickness and its properties changing over time. Neither the spectrum of soil types nor their dynamic nature can be captured by current ESMs. Here we present a new version of an ESM land surface scheme (Joint UK Land Environment Simulator, JULES) where soil organic matter accumulation – and thus peatland formation, degradation and stability – is integrated in the vertically resolved soil carbon scheme. We also introduce the capacity to track soil carbon age as a function of depth in JULES and compare this to measured peat age–depth profiles. The new scheme is tested and evaluated at northern and temperate sites. This scheme simulates dynamic feedbacks between the soil organic material and its thermal and hydraulic characteristics. We show that draining the peatlands can lead to significant carbon loss, soil compaction and changes in peat properties. However, negative feedbacks can lead to the potential for peatlands to rewet themselves following drainage. These ecohydrological feedbacks can also lead to peatlands maintaining themselves in climates where peat formation would not otherwise initiate in the model, i.e. displaying some degree of resilience. The new model produces similar results to the original model for mineral soils and realistic profiles of soil organic carbon for peatlands. We evaluate the model against typical peat profiles based on 216 northern and temperate sites from a global dataset of peat cores. The root-mean-squared error (RMSE) in the soil carbon profile is reduced by 35 %–80 % in the best-performing JULES-Peat simulations compared with the standard JULES configuration. The RMSE in these JULES-Peat simulations is 7.7–16.7 kg C m−3 depending on climate zone, which is considerably smaller than the soil carbon itself (around 30–60 kg C m−3). The RMSE at mineral soil sites is also reduced in JULES-Peat compared with the original JULES configuration (reduced by ∼ 30 %–50 %). Thus, JULES-Peat can be used as a complete scheme that simulates both organic and mineral soils. It does not require any additional input data and introduces minimal additional variables to the model. This provides a new approach for improving the simulation of organic and peatland soils and associated carbon-cycle feedbacks in ESMs.

In many Arctic regions marine coastlines change rapidly in the currently warming climate. In contrast, coastal rock cliffs on Svalbard are considered to be comparably stable, based on previous studies that considered only a few years and limited coastal reaches. Long-term trends of coastal retreat rates in rock cliffs on Svalbard are unknown so far, but their quantification could improve the understanding of coastal dynamics on the Arctic archipelago. This study presents coastal retreat rates in rock cliffs along several kilometers of the Brøgger peninsula, Svalbard. The work is based on high-resolution orthoimages from 1970, 1990, 2010, and 2021, corroborated by high-precision dGNSS measurements along selected segments of the coastline and by rock surface temperature measurements during the period 2020–2021. Our analysis shows that coastal retreat rates accelerate statistically significant along the Brøgger peninsula in the time period of 2010 to 2021. This is true for both the northeast facing coastline, with retreat rates increasing from 0.04 ± 0.06 m/a (1970–1990) and 0.04 ± 0.04 m/a (1990–2010) to 0.07 ± 0.08 m/a (2010–2021) and the southwest facing coastline, where retreat rates of 0.26 ± 0.06 m/a (1970–1990), 0.24 ± 0.04 m/a (1990–2010) and 0.30 ± 0.08 m/a (2010–2021) are measured. Furthermore, the parts of the coastline affected by erosion increase along the northeast facing coastline from 47 % (1970–1990) to 65 % (2010–2021), while they stay consistently above 90 % along the southwest facing coastline. Measurements of rock surface temperature show mean annual values close to the thaw threshold with −0.49 °C at the southwest facing coastline, while records at the northeast facing coastline are lower with −1.64 °C. The recently accelerated retreat rates coincide with increasing storminess and retreating sea ice, together with increasing ground temperatures, all factors that can enhance coastal erosion.

Due to climate change, the risk of destabilization of soil organic carbon by permafrost thaw has increased dramatically. In many areas, including Norway, permafrost has disappeared entirely which releases stored organic carbon to decomposition and transport. Permafrost regions are estimated to store approximately twice the amount of carbon currently present in our atmosphere and the degradation of these carbon hotspots leads to further emissions of greenhouse gases. Thawing of ice-rich permafrost soils in areas of low relief commonly generates thermokarst ponds, which expose old carbon to degradation and can become hotspots of greenhouse gas (GHG) emissions. These thermokarst pond systems and the surrounding peatlands are hydrologically connected, allowing for the export of organic matter. Here we present our investigations of hydrology, water chemistry and dissolved organic matter (DOM) lability from areas of thawing permafrost and the resulting thermokarst ponds in the Iškoras peat plateau, located in a headwater catchment on the Finnmarksvidda in Northern Norway. A 12-30h dark incubation method is used to estimate DOM lability. Between May 2021 and September 2022, we collected water samples and performed dark incubations on 7 occasions from several thermokarst ponds, wetland streams and a lake. These samples were analyzed for nutrients, greenhouse gas (CO2, CH4 and N2O) and O2 concentrations. Greenhouse gas concentrations in the water samples and at the end of the dark incubations were analyzed by gas chromatography following headspace equilibrium. In addition, floating chambers were deployed to measure diffusive CO2 emissions. High frequency water height and temperature sensors were installed in both ponds and streams in autumn 2021. A preliminary analysis indicates that the thermokarst ponds are high in concentrations of CO2 and CH4 and are key sources of these gases within the landscape when compared to the wetland stream stations. N2O shows seasonal variability and is likely controlled by vegetative uptake of nitrogen although there is still high production in the thermokarst ponds. CO2 productions rates are highest in the ponds, especially those ponds that are darker in color. These data all highlight the lability of the organic matter originating from the permafrost plateau. We aim to observe the seasonal and spatial changes in the lability of organic matter from the thermokarst ponds and the seasonal hydrological connections between the peat plateau and the surrounding wetlands.

The interannual variability of snow cover in alpine areas is increasing, which may affect the tightly coupled cycles of carbon and water through snow-vegetation-atmosphere interactions across a range of spatio-temporal scales. To explore the role of snow cover for the land-atmosphere exchange of CO2 and water vapor in alpine tundra ecosystems, we combined three years (2019–2021) of continuous eddy covariance flux measurements of net ecosystem exchange of CO2 (NEE) and evapotranspiration (ET) from the Finse site in alpine Norway (1210 m a.s.l.) with a ground-based ecosystem-type classification and satellite imagery from Sentinel-2, Landsat 8, and MODIS. While the snow conditions in 2019 and 2021 can be described as site-typical, 2020 features an extreme snow accumulation associated with a strong negative phase of the Scandinavian Pattern of the synoptic atmospheric circulation during spring. This extreme snow accumulation caused a one-month delay in melt-out date, which falls on the 92nd-percentile in the distribution of yearly melt-out dates in the period 2001–2021. The melt-out dates follow a consistent fine-scale spatial relationship with ecosystem types across years. Mountain and lichen heathlands melt out more heterogeneously than fens and flood plains, while late snowbeds melt out up to one month later than the other ecosystem types. While the summertime average Normalized Difference Vegetation Index (NDVI) was reduced considerably during the extreme snow year 2020, it reached the same maximum as in the other years for all but one the ecosystem type (late snowbeds), indicating that the delayed onset of vegetation growth is compensated to the same maximum productivity. Eddy covariance estimates of NEE and ET are gap-filled separately for two wind sectors using a random forest regression model to account for complex and nonlinear ecohydrological interactions. While the two wind sectors differ markedly in vegetation composition and flux magnitudes, their flux response is controlled by the same drivers as estimated by the predictor importance of the random forest model as well as the high correlation of flux magnitudes (correlation coefficient r = 0.92 for NEE and r = 0.89 for ET) between both areas. The one-month delay of the start of the snow-free season in 2020 reduced the total annual ET by 50 % compared to 2019 and 2021, and reduced the growing season carbon assimilation to turn the ecosystem from a moderate annual carbon sink (−31 to −6 gC m−2 yr−1) to a source (34 to 20 gC m−2 yr−1). These results underpin the strong dependence of ecosystem structure and functioning on snow dynamics, whose anomalies can result in important ecological extreme events for alpine ecosystems.

Blockfields remain enigmatic regarding their origin, internal structure, surface processes, and glaciological implications. In Scandinavia, blockfields are found on high-elevation, low-relief mountains (plateaus) across the Arctic and Subarctic. In this study, we present a 1D numerical model that uses near-surface temperatures measured between summer 2018 and summer 2020 to calculate frost-cracking intensities (FCI) within the ground column in three different blockfields in Norway and Svalbard. Eighty-nine miniature temperature loggers were distributed on Tron Mountain (1650 m a.s.l.) in Alvdal, Gamlemsveten (780 m a.s.l.) near Ålesund in southwestern Norway and on Platåberget (460 m a.s.l.) near Longyearbyen, Svalbard. We modelled FCI by scaling the time spent in the frost cracking window (between −3 and −8°C) with the temperature gradient and a penalty function for distance to available water. At Tron and Gamlemsveten, ground temperatures never reached the frost cracking window at one third of our sites due to insulation by a thick snow cover in depressions and on the lee sides of summits. The highest FCI (0.05–0.4 K m) are obtained where the subsurface consists of boulders and stones in a matrix of relatively fine sediment (sand, silt, gravel). In contrast, very low FCI (0.003–0.02 K m) were modelled for blocky layers with large air-filled pores because of the low water availability. On Platåberget, all sensors reached the frost-cracking window during the annual temperature cycle, but FCI are extremely low (0.0004–0.15 K m) as water availability is limited due to (i) permafrost and (ii) near-surface temperatures remaining below the frost-cracking window for 3/4 of the year. This indicates that boulder-rich blockfields with air-filled hollows are preserved in very cold climates, whereas warmer, maritime settings with higher availability of fine interstitial material place blockfields in the fast lane for frost weathering.

Water takes part in most physical processes that shape the mountainous periglacial landscapes and initiation of mass wasting. An observed increase in rockfall activity in several mountainous regions was previously linked to permafrost degradation in high mountains, and water that infiltrates into rock fractures is one of the likely drivers of these processes. However, there is very little knowledge on the quantity and timing of water availability for infiltration in steep rock slopes. This knowledge gap originates from the complex meteorological, hydrological and thermal processes that control snowmelt, and also the challenging access and data acquisition in the extreme alpine environments. Here we use field measurement and numerical modeling to simulate the energy balance and hydrological fluxes in a steep high elevation permafrost affected rock slope at Aiguille du Midi (3842 m a.s.l), in the Mont-Blanc massif. Our results provide new information about water balance at the surface of steep rock slopes. Model results suggest that only ~25 % of the snowfall accumulates in our study site, the remaining ~75 % are redistributed by wind and gravity. Snow accumulation depth is inversely correlated with surface slopes between 40° to 70°. Snowmelt occurs between spring and late summer and most of it does not reach the rock surface due to the formation of an impermeable ice layer at the base of the snowpack. The annual effective snowmelt, that is available for infiltration, is highly variable and ranges over a factor of six with values between 0.05–0.28 m in the years 1959–2021. The onset of the effective snowmelt occurs between May and August, and ends before October. It precedes the first rainfall by one month on average. Sublimation is the main process of snowpack mass loss in our study site. Model simulations at varying elevations show that effective snowmelt is the main source of water for infiltration above 3600 m a.s.l.; below, direct rainfall is the dominant source. The change from snowmelt-dominated to rainfall-dominated water availability is nonlinear and characterized by a rapid increase in water availability for infiltration. We suggest that this elevation of water availability transition is highly sensitive to climate change, if snowmelt-dominated permafrost-affected slopes experience an abrupt increase in water input that can initiate rock slope failure.

Purpose.In this paper we present and validate an analytical model of water inflow and rising level in a flooded mine and examine the model robustness and sensitivity to variations of input data considering the examples of three closed hard-coal mines in Germany. Methods. We used the analytical solution to a boundary value problem of radial ground water flow to the shaft, treated as a big well, and water balance relations for the series of successive stationary positions of a depression cone to simulate a mine water rebound in the mine taking into account vertical distribution of hydraulic conductivity, residual volume of underground workings, and natural pores. Findings. The modeling demonstrated very good agreement with the measured data for all the studied mines. The maximum relative deviation for the mine water level during the measurement period did not exceed 2.1%; the deviation for the inflow rate to a mine before its flooding did not exceed 0.8%. Sensitivity analysis revealed the higher significance of the residual working volume and hydraulic conductivity for mine water rebound in the case of thick overburden and the growing significance of the infiltration rate and the flooded area size in the case of lower overburden thickness. Originality.The developed analytical model allows realistic prediction of transient mine water rebound and inflow into a mine with layered heterogeneity of rocks, irregular form of the drained area, and with the inflow/outflow to a neighboring mine and the volume of voids as a distributed parameter without gridding the flow domain performed in numerical models. Practical implications.The study demonstrated the advantages of analytical modeling as a tool for preliminary evaluation and prediction of flooding indicators and parameters of mined out disturbed rocks. In case of uncertain input data, modeling can be considered as an attractive alternative to usually applied numerical methods of modeling ground and mine water flow.

Long-term measurements of permafrost temperatures do not provide a complete picture of the Arctic subsurface thermal regime. Regions with warmer permafrost often show little to no long-term change in ground temperature due to the uptake and release of latent heat during freezing and thawing. Thus, regions where the least warming is observed may also be the most vulnerable to permafrost degradation. Since direct measurements of ice and liquid water contents in the permafrost layer are not widely available, thermal modeling of the subsurface plays a crucial role in understanding how permafrost responds to changes in the local energy balance. In this work, we first analyze trends in observed air and permafrost temperatures at four sites within the continuous permafrost zone, where we find substantial variation in the apparent relationship between long-term changes in permafrost temperatures (0.02 K yr−1 to 0.16 K yr−1) and air temperature (0.09 K yr−1 to 0.11 K yr−1). We then apply recently developed Bayesian inversion methods to link observed changes in borehole temperatures to unobserved changes in latent heat and thaw depth using a transient model of heat conduction with phase change. Our results suggest that the degree to which recent warming trends correlate with permafrost thaw and variations in latent heat is heavily dependent on both local soil properties as well as historical climatology. At the warmest site, a nine meter borehole near Ny-Ålesund, Svalbard, modeled annual maximum thaw depth increases by an average of (12 ± 1) cm K−1 rise in mean annual ground temperature. In stark contrast, modeled thaw rates for a borehole on Samoylov Island in the Lena River Delta (northeastern Siberia) appear far less sensitive to temperature change, with an almost negligible increase of (1 ± 1) cm K−1. Although our study is limited to just four sites, the results urge caution in the interpretation and comparison of warming trends in Arctic boreholes, indicating substantial uncertainty in their implications for the current and future thermal state of permafrost.

Climate change modifies the water and energy fluxes between the atmosphere and the surface in mountainous regions. This is particularly true over the Qinghai-Tibet Plateau (QTP), a major headwater region of the world, which has shown substantial hydrological changes over the last decades. Among them, the rapid lake level variations observed throughout the plateau remain puzzling and much is still to be understood regarding the spatial distribution of lake level trends (increase/decrease) and paces. The ground across the QTP hosts either permafrost or seasonally frozen ground and both are affected by climate change. In this environment, the ground thermal regime influences liquid water availability, evaporation and runoff. Therefore, climate-driven modifications of the ground thermal regime may contribute to lake level variations. For now, this hypothesis has been overlooked by modelers because of the scarcity of field data and the difficulty to account for the spatial variability of the climate and its influence on the ground thermo-hydrological regime in a numerical framework. This study focuses on the cryo-hydrology of the catchment of Lake Paiku (Southern Tibet) for the 1980–2019 period. We use TopoSCALE and TopoSUB to downscale ERA5 data and capture the spatial variability of the climate in our forcing data. We use a distributed setup of the CryoGrid community model (version 1.0) to quantify thermo-hydrological changes in the ground during the period. Forcing data and simulation outputs are validated with weather station data, surface temperature logger data and the lake level variations. We show that both seasonal frozen ground and permafrost have warmed (1.7 °C per century 2 m deep), increasing the availability of liquid water in the ground and the duration of seasonal thaw. Both phenomena promote evaporation and runoff but ground warming drives a strong increase in subsurface runoff, so that the runoff/(evaporation + runoff) ratio increases over time. Summer evaporation is an important energy sink and we find active layer deepening only where evaporation is limited. The presence of permafrost is found to promote evaporation at the expense of runoff, consistent with recent studies. Yet, this relationship seems to be climate dependent and we show that a colder and wetter climate produces the opposite effect. This ambivalent influence of permafrost may help to understand the contrasting lake level variations observed between the south and north of the QTP, opening new perspectives for future investigations.

Ground temperatures in coarse, blocky deposits such as mountain blockfields and rock glaciers have long been observed to be lower in comparison with other (sub)surface material. One of the reasons for this negative temperature anomaly is the lower soil moisture content in blocky terrain, which decreases the duration of the zero curtain in autumn. Here we used the CryoGrid community model to simulate the effect of drainage in blocky terrain permafrost at two sites in Norway. The model setup features a surface energy balance, heat conduction and advection, as well as a bucket water scheme with adjustable lateral drainage. We used three idealized subsurface stratigraphies, denoted blocks only, blocks with sediment and sediment only and are either drained or undrained of water, resulting in six ‘scenarios’. The main difference between the three stratigraphies is their ability to retain water against drainage: while the blocks only stratigraphy can only hold small amounts of water, much more water is retained within the sediment phase of the two other stratigraphies, which critically modifies the freeze-thaw behaviour. The simulation results show markedly lower ground temperatures in the blocks only, drained scenario compared to other scenarios, with negative thermal anomaly of up to 1.8–2.2 °C. For this scenario, the model can in particular simulate the time evolution of ground ice, with build-up during and after snow melt and spring and gradual lowering of the ice table in the course of the summer season. We simulate stable permafrost conditions at the location of a rock glacier in northern Norway with a mean annual ground surface temperature of 2.0–2.5 °C in the blocks only, drained simulations. Finally, transient simulations at the rock glacier site showed a complete or partial lowering of the ground ice table since 1951 for all simulations except the blocks only, drained run. The interplay between the subsurface water/ice balance and ground freezing/thawing driven by heat conduction can at least partly explain the occurrence of permafrost in coarse blocky terrain below the assumed elevational limit of permafrost. It is thus important to consider this effect in future efforts on permafrost distribution mapping in mountainous areas. Furthermore, an accurate prediction of the evolution of the ground ice table in a future climate can have implications for slope stability, as well as water resources in arid environments.

The importance of frost weathering processes has long been discussed in the context of cold-climate landscape evolution. The 9 % volumetric expansion of in situ water when it freezes to ice was initially held responsible for generating the stresses that create and widen cracks in rocks. This theory has since been challenged by the theory of ice segregation in rocks, in which the growth of ice lenses is supplied by additional water that is drawn to the freezing front. Numerical modelling and laboratory experiments suggest that segregated ice growth can generate enough stress to cause rock damage and is most intense between approximately -8 and -3 ℃ (the precise range depends on rock properties), in the so-called frost cracking window (FCW). The two theories of weathering have different implications for landscape evolution: (1) if in situ volumetric expansion is more important, most frost weathering should occur close to the freezing point, (2) if ice lensing is more important, most frost weathering should occur in the FCW. For the latter theory, several frost weathering indices have been developed based on such factors as the time spent vulnerable to cracking within the FCW, the magnitudes of ground temperature gradients that induce water transport, and other factors that affect water availability. In this study, we model ground temperature using the ground heat flux model CryoGrid 2D (Myhra et al., 2017) and apply the one-dimensional frost weathering index proposed by Rempel et al. (2016), where frost weathering potential is assumed to be correlated with porosity changes that accompany gradients in water flux. Here, we adjust the frost weathering index so that frost weathering potential is modeled in two dimensions. Our results predict spatial and temporal patterns of frost weathering in rock walls that can be tested in the field. References Myhra, K. S., Westermann, S., & Etzelmüller, B. (2017). Modelled distribution and temporal evolution of permafrost in steep rock walls along a latitudinal transect in Norway by CryoGrid 2D. Permafrost and Periglacial Processes, 28(1), 172-182. doi: 10.1002/ppp.1884.Rempel, A. W., Marshall, J. A., & Roering, J. J. (2016). Modeling relative frost weathering rates at geomorphic scales. Earth and Planetary Science Letters, 453, 87-95. doi:10.1016/j.epsl.2016.08.019

Mountain permafrost and rock glaciers have been intensely investigated in Southern Carpathians highest ranges in the last 15 years using thermal, geophysical and remote sensing methods. However, a complete estimation of permafrost area has not been done so far. Thus, using statistical modeling we intend to offer an image of potential permafrost distribution in Southern Carpathians ranges of Făgăraș, Iezer, Parâng, Retezat, Godeanu and Țarcu. Model 1 is based on machine learning algorithms and model 2 is based on Maxent model. Both models use bottom temperature of snow (BTS) data as independent variable and land cover, altitude, slope curvature, solar radiation and snow probability as independent variables. Land cover is considered the key variable as the field methods indicated that permafrost can only be present in the talus deposits that produce negative thermal anomalies in the underground. Results indicated an area of about 45-60 km2 of potential permafrost distribution depending on the BTS threshold used for permafrost presence (-3°C, -2.5°C and -2°C). This represent about 0.01% from a total surface of about 4334 km2 of the six ranges used in this analysis being a typical sporadic mountain permafrost in a marginal periglacial environment.

Understanding the future evolution of permafrost requires a better understanding of its climatological past. This requires permafrost models to efficiently simulate the thermal dynamics of permafrost over the past centuries to millennia, taking into account highly uncertain soil and snow properties. In this study, we present a computationally efficient numerical permafrost model which satisfactorily reproduces the current thermal state of permafrost in the Arctic and its recent trend over the last decade. Also, the active layer dynamics and its trend is realistically captured. The performed simulations provide insights into the evolution of permafrost since the 18th century and show that permafrost on the North American continent is subject to early degradation, while permafrost on the Eurasian continent is relatively stable over the investigated 300-year period. Permafrost warming since industrialization has occurred primarily in three "hotspot" regions in northeastern Canada, northern Alaska, and, to a lesser extent, western Siberia. The extent of near-surface permafrost has changed substantially since the 18th century. In particular, loss of continuous permafrost has accelerated from low (−0.10 × 105 km2 dec−1) to moderate (−0.77 × 105 km2 dec−1) rates for the 18th and 19th centuries, respectively. In the 20th century, the loss rate nearly doubled (−1.36 × 105 km2 dec−1), with the highest near-surface permafrost losses occurring in the last 50 years. Our simulations further indicate that climate disturbances due to large volcanic eruptions in the Northern Hemisphere, can only counteract near-surface permafrost loss for a relatively short period of a few decades. Despite some limitations, the presented model shows great potential for further investigation of the climatological past of permafrost, especially in conjunction with paleoclimate modeling.

Peatlands store large amounts of carbon in terrestrial ecosystems and they are vulnerable to recent warming. The ongoing warming may change their carbon sink capacity and could reduce their potential to sequester carbon. In this study, we simulated peatland carbon dynamics in distinct future climate conditions using the peatland-vegetation model (LPJ-GUESS). The study examined whether less pronounced warming could further enhance the peatland carbon sink capacity and buffer the effects of climate change. It also determined which trajectory peatland carbon balance would follow, what the main drivers were, and which one would dominate in the future. We found that peatlands will largely retain their carbon sink capacity under the climate scenario RCP2.6 to RCP6.0. They are projected to shift from a carbon sink to a carbon-neutral (5–10 gC m−2 yr−1) in RCP8.5. Higher respiration rates will dominate the net productivity in a warmer world leading to a reduction in carbon sink capacity.