ABSTRACT Pingos and related permafrost mounds are widespread periglacial landforms in Arctic environments that are ice‐rich on the one hand and contain taliks on the other, making them vulnerable to climate change. So far, the interior, geophysical characteristics, and distribution of ground ice within these dome‐ or cone‐shaped features have not been sufficiently investigated, and more in situ observations and multidimensional insights are required. This study presents two‐ and three‐dimensional Electrical Resistivity Tomography (ERT) results from numerous pingos and permafrost mounds investigated in the Ogilvie Mountains and on the Tuktoyaktuk Peninsula, northwest Canada. The measurements cover single features and assemblages of varying sizes and shapes, in mountain valleys, on slopes and at riversides, in drained lakes, and at lakeshores. Resistivities are compared based on representative zones of interest within 2D profiles, and large quasi‐3D grids were set up to test the capabilities of 2D ERT and especially 3D ERT for the investigation of pingos and permafrost mounds. Using this data, the study helps to decipher the origin and development of the landforms, exemplified for specific sites in mountainous vs. coastal environments by additionally considering their complex hydrological settings. The pingos reveal median interior electrical resistivities of 5–50 kΩm, and all have maximum resistivities exceeding 10 kΩm. The bigger ones feature cores of far beyond 100 kΩm, which contrasts with the often more conductive interiors of smaller or different types of permafrost mounds. Difficulties arise when deriving a common resistivity threshold for massive pingo ice. ERT is a powerful tool to three‐dimensionally display the interior of pingos, to detect potential talik areas, and to help to distinguish pingos from other mound landforms based on geoelectrical properties. It enables the estimation of the upper limit and the lateral extent of massive ice cores, but in many cases struggles to provide reliable information on structures below massive ice. Investigating pingos using ERT, therefore, requires careful evaluation of the model sensitivity. The ERT findings and hydrological discussion underline the probable co‐existence of hydraulic and hydrostatic pingos in mountain valleys, and reveal similar characteristics and positions of permafrost mounds as of open‐system pingos. However, the position, lateral extent, and electrical properties of internal massive ice vary between sites and even within single assemblages. Specifically, within the biggest investigated pingo on the Tuktoyaktuk Peninsula, the extent of the detected ice core hardly explains the size and surface appearance of the landform, whereas conductive, likely unfrozen or solute‐rich pockets in the flanks cause an even more heterogeneous internal structure. The investigated examples paint a much more complex picture of the pingo architecture and genesis than traditional models have suggested to date.
ABSTRACT Understanding fine‐scale surface changes is crucial for quantifying ecosystem dynamics and detecting landscape changes. Palsas, comparably small peatland elevations with an ice‐rich permafrost core, undergo natural cycles of growth and degradation. They can also serve as indicators of climate change in subarctic regions. Because they typically cover an area of only a few hundred square metres at most, satellite remote sensing is insufficient for monitoring their detailed development. Unoccupied aerial systems (UAS) and ground‐based remote sensing provide the necessary spatial resolution, and combining multiple sensor types can further improve data quality. In this study, we monitored the annual surface changes of two degrading palsas in northern Finnish Lapland from 2022 to 2024. We captured UAS RGB‐based structure‐from‐motion (SfM), UAS LiDAR and terrestrial laser scanning (TLS) point clouds and validated the resulting digital terrain models (DTMs) using RTK‐GNSS reference measurements. Active layer thickness (ALT) was measured at each GNSS point to characterize thaw depth and to delineate an ALT‐constrained frozen extent. Based on the DTMs, we quantified changes in palsa area, mean height, and volume above a predefined palsa base. These DTM‐based metrics were evaluated for the entire palsa surface and, separately, for the part of the palsa where ALT measurements indicated the presence of a remaining frozen core. The accuracy assessment shows clear advantages of merging SfM point clouds with LiDAR‐ or TLS‐derived datasets. The highest accuracy was achieved at the smaller and flatter palsa, suggesting that high point cloud density and low surface complexity increase accuracy. UAS LiDAR showed a consistent positive elevation bias, likely reflecting a combination of slope‐ and footprint‐related effects and limited penetration of moist moss and peat surfaces. Both palsas lost volume, area and average height during the study period. The larger palsa decreased in total volume by 20% across its entire extent and by 23% within the ALT‐constrained frozen extent; the smaller palsa lost 13% and 18%, respectively. These results underscore the acceleration of palsa degradation under current climatic conditions and demonstrate that multisensor approaches significantly improve high‐resolution monitoring of palsa surface change in permafrost landscapes.
ABSTRACT Pingos are large mounds with cores formed of intrusive ice that form in periglacial landscapes. These ice structures can form in regions of discontinuous permafrost, commonly as hydraulic or open‐system pingos, or in locations of continuous permafrost, commonly as hydrostatic or closed‐system pingos. Using C‐band Interferometric Synthetic Aperture Radar (InSAR) data from the Sentinel‐1 constellation acquired between 2017 and 2025 over the Alaskan North Slope, we quantified interannual surface deformation trends over several hydrostatic pingos. Eight of the 11 pingos analyzed experienced cumulative uplift ranging from 1.49 to 11.35 cm over an 8‐year period, two experienced cumulative subsidence ranging from 0.57 to 2.46 cm, and two experienced no statistically significant surface‐height change. All of the cumulatively uplifting pingos exhibited surface‐height time series proportional to a square‐root dependence with time, which is physically consistent with an aggradational process via Stefan's equation. Ground penetrating radar profiles acquired over select pingos revealed subsurface reflector structures consistent with massive ice cores, reinforcing the hypothesis that the observed surface uplift is driven by intrusive ice formation mediated by elevated hydrostatic pressure due to permafrost aggradation. These results demonstrate that InSAR methods can resolve subtle geodetic signals associated with pingo topographic change, such as from pingo growth due to permafrost aggradation. InSAR observations can thus yield process‐scale insights into the dynamic evolution of pingos and associated periglacial landforms.
ABSTRACT Freeze–thaw processes cause periglacial creep (otherwise known as solifluction) which forms solifluction lobes. These are lobate features characterized by a steep riser (front) and a smooth tread (body). Despite the widespread occurrence of these lobes, the controls on their morphometry remain poorly understood. Research into solifluction lobe morphometry is crucial for understanding their role in landscape evolution, hydrology and sediment budgets and providing microhabitats in a warming climate. We mapped geomorphic and vegetation properties of 40 solifluction lobes in the Turtmann Valley, Swiss Alps, and recorded soil moisture and temperature with a TOMST TMS4 logger at a 10‐min interval for nearly 2 years. We combined these data with derivatives of a high‐resolution digital elevation model and conducted a Spearman ranked correlation test. Our results revealed that (i) the largest lobes, with the highest risers occur in areas with high flow accumulation ( ρ = 0.40–0.75). (ii) Wider, lobate lobes dominate at higher elevations ( ρ = 0.49) on north‐exposed slopes ( ρ = 0.53) with long snow ( ρ = 0.47–0.58) and sparse vegetation cover, while narrow, tongue‐shaped lobes occur at lower elevations with high vegetation cover ( ρ = 0.38–0.55), suggesting a strong topoclimatic control. (iii) Lobes in the Turtmann Valley are longer and more tongue‐shaped, with higher risers and on steeper slopes, than many lobes previously studied. Overall, our results suggest that Alpine solifluction lobe dimensions and shape are controlled by different set of environmental factors than Arctic lobes, possibly due to effects of stronger topoclimatic gradients, steeper slopes and higher flow accumulation on mountain slopes.
Due to its subsurface nature, permafrost cannot be directly observed with the naked eye or optical remote sensing. Consequently, accurately describing its distribution and thermal state is challenging. This is especially true in vast, remote environments, where obtaining comprehensive field data is demanding or improbable. This results in a reliance on models, which are constrained by limited, spatiotemporally fragmented baseline data, and which are rarely validated against actual field data. While such models may be sufficient in homogeneous permafrost environments, or to capture general trends over large areas, their accuracy is limited at finer scales in thermally heterogeneous environments. To explore and conceptualize this issue, we conducted a field sampling campaign in two thermally complex valleys in the Ogilvie Mountains. The study area exhibits strong ground temperature variability over short distances due to surface-based temperature inversions, extreme aspects, and complex land cover types. Our objective was to qualitatively assess our ability to collect in situ permafrost thermal data ("testability") using simple, repeatable, low-cost methods. Although the study area is located within the zone of continuous permafrost, only nine (18.3%) of the 49 Cryotic Assessment Sites (CAS) produced cryotic temperatures in situ, due to substrate clast density and active layer thickness. Testability outcomes were used to develop a generalized linear model (P TEST), which predicts low testability at higher elevations and higher testability in valley bottoms, indicating a substantial potential sampling bias for model calibration and validation. Comparisons with two local permafrost models highlight persistent uncertainty in permafrost characterization in mountainous environments.
Permafrost in northern peatlands occurs within individual palsas or extensive peat plateaus and controls local carbon storage. These permafrost landforms are complex, and their internal structure remains poorly understood. We used quasi-3D electrical resistivity tomography (ERT) measurements, supported by UAV-LiDAR topography, frost probing, and borehole drilling, to map the internal structure of two geomorphologically distinct palsas (dome-shaped and plateau-shaped) within Sweden's largest coherent palsa complex, Viss & aacute;tvuopmi. The results suggest that the 5 m tall dome-shaped palsa contains permafrost up to 20-m-thick beneath elevated areas, whereas permafrost is thin or absent in the surrounding lower-relief areas on the palsa. In contrast, the plateau-shaped palsa seems to contain widespread boulders, with the top of this material identified at depths between 3.8 and 5.5 m below the surface, creating large resistivity anomalies and likely limiting frost heave. The permafrost base is difficult to delineate in the plateau-shaped palsa because of the complex subsurface and limited depth sensitivity. Together, these results support the idea that palsas in deposits lacking boulders can heave into taller domes, whereas boulder-rich substrates experience less frost heave and produce flatter plateau forms. This strong control of subsurface composition on permafrost structure highlights the need for detailed baseline knowledge, which is important for predicting palsa responses to future climate warming.
Arctic permafrost soils and sediments store vast amounts of organic carbon. With global warming intensifying, these soils are increasingly exposed to microbial decomposition. Further, Arctic warming and longer growing seasons drive regional greening, potentially accelerating the degradation of the previously frozen organic matter through rhizosphere priming of the soil microbial community. However, little is known about how fresh plant-derived inputs shape microbial functioning in thawing and eroding Yedoma deposits. We simulated vegetation inputs to sediments from a retrogressive thaw slump in northeast Siberia in two thaw mounds (Pleistocene Yedoma) and one slump-floor site (mixed Yedoma and Holocene material). The microbial response to two substrate levels (1% and 4% of total organic carbon) was evaluated in a 7-week aerobic incubation by measuring heterotrophic respiration, bacterial and fungal growth rates, extracellular enzyme activities, and carbon use efficiency (CUE). Overall, substrate additions stimulated respiration, bacterial growth, and enzyme production, consistent with microbial activation, while microbial CUE remained unaffected. Growth responses shifted in favor of bacteria despite the high C:N ratio and mostly polymeric nature of the substrate mixture. Throughout the incubation, however, fungal growth increased as labile substrates were likely depleted. In addition, sustained increases in nutrient-acquiring enzymes suggest that nutrient-mining-induced priming of native soil organic matter may have occurred. Both thaw mounds showed varying microbial activity, likely reflecting differences in organic matter quality, whereas the slump floor was characterized by a stronger emphasis on resource acquisition than growth, likely linked to more acidic conditions. Together, these results support microbial activation and nutrient mining theories and suggest that plant-derived inputs may enhance microbial processing of thawed Yedoma carbon, while site-specific conditions shape distinct microbial activities.
This study investigates the multi-decadal evolution of a glacier forefield under permafrost conditions in the Combins Massif (western Swiss Alps). A multi-method approach based on historical and recent datasets is used to analyze its landform components. To better understand the complex dynamics of landforms and their interactions in environments shaped by glacial and periglacial processes, this study seeks to foster the use and application of a multi-method approach to capture the multi-decadal evolution of glacier-permafrost interactions in a high-mountain alpine environment. Spatial and temporal surface changes are evaluated on the basis of archive aerial photographs and recent uncrewed aerial vehicle (UAV) surveys, as well as detailed in situ differential global navigation satellite systems (dGNSS) measurements. The long-term kinematic evolution of the landforms within the forefield is investigated with an emphasis on the processes contributing to surface lowering. The evolution of the extent and properties of ground ice and debris-covered surface ice is assessed by geophysical surveys and ground surface temperature measurements. Our observations indicate a general down-wasting trend among the investigated landforms, including two back-creeping push moraines, a glacier forefield-connected rock glacier, and a debris-covered glacier tongue. The greatest morphological and surface elevation changes, which are partly due to ice melt-induced subsidence, have been observed in areas where ice from glacier origin is present. Furthermore, these changes have been enhanced over the last two decades. A notable decline in resistivity has been documented between earlier (1997) and more recent (2020) geophysical surveys conducted in the push-moraines (-54.02%), the rock glacier rooting zone (-73.71%), and the margins of the debris-covered glacier tongue (-57.69%). This decrease is likely to be the result of an increased water-to-ice ratio due to permafrost degradation, as well as melting and thinning of massive ice of glacial origin. In the debris-covered glacier tongue, resistivity changes are the lowest, which can be attributed to unchanged properties of the cold ice, with the only significant change being its reduced thickness. These findings contribute to a better understanding of glacier-permafrost interactions under climate warming and demonstrate the value of integrated, multi-method monitoring for capturing the long-term geomorphic evolution of high-mountain environments.
The Hurd Rock Glacier, located on Livingston Island (South Shetland Islands archipelago, Maritime Antarctica), is a tongue-shaped feature composed of angular boulders, displaying transverse ridges and furrows, and featuring lobate structures, which are more prominently developed in its frontal sector. At the top, an inactive glacier moraine overlies the rock glacier body. To understand the recent evolution of this system, a geochronological survey has been carried out through a combination of three dating techniques: (i) Cosmic-ray exposure (CRE) dating based on the 36Cl cosmonuclide applied to six boulders from the rock glacier frontal lobes; (ii) lichenometric dating, using Rhizocarpon geographicum species, of the upper glacier moraine; and (iii) 12 weathering measurements performed with a Schmidt hammer on the rock glacier lobes as well as on the glacier moraine. The results support an evolutionary model involving the following phases: (i) stabilization of the rock glacier front and/or a reduction in its kinematics around 3-4 ka; (ii) a progressive stabilization or slowing down of the rock glacier suggested by decreasing Schmidt-hammer exposure-age dating (SHD) values with increasing distance (and elevation) from the rock glacier front; and (iii) a very recent abandonment age of approximately 66 years for the upper moraine. These findings are consistent with the glacial and periglacial dynamics documented in this region of maritime Antarctica over the last few millennia.
The existence of permafrost was explored at tropical latitude on Nevado Coropuna (southern Peruvian Andes) using a combination of ground-penetrating radar (GPR) and vertical electrical sounding (VES) in order to strengthen the mutual validation of data processing and interpretation. Two GPR surveys (25 and 10 MHz unshielded antennas) and two VES measurements were conducted on the unglaciated eastern flank of the mountain, exploring the internal structure of a rock glacier and the debris slope adjacent to the rock glacier. According to several longitudinal and transverse GPR profiles, a 15-20 m thick permafrost layer was identified beneath 2-4 m thick unfrozen sediments in the rock glacier and adjacent debris slope. The permafrost layer shows a homogeneous distribution within the rock glacier's subsurface, with maximum values reached in the middle and frontal areas, where radar data indicate the potential existence of buried massive ice. This evidence corresponds to the presence of a well-developed frozen layer with significant lateral continuity and a minimum discontinuous permafrost limit in this area at 5090 m.a.s.l. The extensive unglaciated area at this altitude and with a similar aspect indicates that Nevado Coropuna hosts one of the largest tropical permafrost areas in the world, emphasizing the strategic importance of assessing the extent of the permafrost water reservoir in this Andean region, which is affected by dry conditions and prolonged drought.
Aufeis is a sheetlike or layered accumulation of ice that forms on the ground surface or on top of river and lake ice when groundwater or surface water repeatedly discharges and freezes during the cold season. In the northern Da Xing'anling Mountains of Northeast China, the occurrence and distribution of aufeis are regulated by the coupled influences of hydroclimate, ground thermal conditions, topography, geomorphology, and hydrology. However, the interactions among these factors are highly complex, making it difficult to clearly resolve the spatial patterns and driving mechanisms of aufeis development. Focusing on the G111 National Highway corridor between Jagdaqi and Mo ' he, this study integrates spatial autocorrelation analysis with the Geodetector model to identify clustering characteristics, quantify dominant controls, and evaluate the synergistic effects of multiple environmental factors on aufeis formation and distribution. Field investigations identified 61 individual aufeis features, which exhibit significant spatial clustering. Geodetector analyses of 15 factors show that precipitation (mean q = 0.216), snow depth (q = 0.205), soil moisture (q = 0.183), and air temperature (q = 0.144) are the dominant controls at the regional scale. Among factor interactions, precipitation and slope aspect jointly provide the strongest explanatory power (q = 0.650). At the local scale, snow depth (q = 0.482), slope angle (0.438), and proximity to rivers (0.405) exert the strongest influences. Additional variables, including distance to faults, slope aspect, and slope angle, act as important modulators that selectively enhance spatial differentiation. Moreover, nonlinear interactions among factors substantially strengthen their explanatory power for aufeis distribution. Two years of field observations further indicate that aufeis exhibits marked spatial mobility and temporal periodicity. These findings highlight the coupled roles of climate, topography, hydrology, and permafrost-related environmental conditions in shaping aufeis formation and distribution and provide a scientific basis for infrastructure planning, ecological conservation, and water resource management in cold-region environments.
Using a large and novel array of instruments on five rockwalls in northern Gaspesia, their respective surface energy balances were calculated and their thermal regimes were measured and modeled to depths exceeding the seasonal frost penetration. A parametric analysis of the thermal properties and structural characteristics of the instrumented rockwalls was then performed. The roles of solar radiation exposure, surface thermal absorptivity, lithology, and fracture pattern on the distribution of episodic freeze-thaw cycles and on the seasonal frost distribution over a winter were quantified. The fine spatiotemporal scale of our measurements and models revealed complex thermal configurations in the first meters of rockwalls, including frozen layers sandwiched between thawed ones and vice versa. Freeze-thaw cycle frequency was primarily driven by solar radiation exposure and surface absorptivity, while seasonal frost penetration was strongly influenced by lithology and fracture pattern. The parametric analysis based on thermal and structural properties representative of the study area enabled us to extrapolate a local thermal regime model to a regional scale without needing to instrument as many sites as there is diversity in exposure, absorptivity, lithology, and fracture patterns. Other parameters, such as slope inclination, snow accumulation, and climate warming, can also be tested with this approach. This hybrid method, which combines field measurements and modeling, is intended to quantify the thermal regime of multiple rockwalls more accurately than spatial modeling and climate reanalyzes, while drastically reducing the effort, cost, and risk of conventional instrumentation. It could represent a valuable tool for regional hazard management strategies.
Glacier foreland and permafrost microbiomes exhibit distinct taxonomic and functional specialization adapted to extreme cold. Metagenomic analysis reveals dominance of Thermoproteota and Methanobacteriota in archaea, Ascomycota and Basidiomycota in eukaryotes, and enriched Actinomycetota, Planctomycetota, and Gemmatimonadota in bacteria, compared to temperate sediments. Genus-level distributions further reflect niche partitioning, with cold-adapted taxa such as Pseudogymnoascus (fungi) and pigment-producing/cold-shock protein-encoding bacteria enriched in frozen habitats. Genetically, these communities are fortified with DNA repair, osmoregulation, and cold-shock genes, supporting resilience under UV, osmotic, and freezing stress. Functionally, they show enhanced polysaccharide degradation and Type II methanotrophy but constrained denitrification. Network analysis identified four microbial modules, each representing specialized strategies for nutrient cycling, methane metabolism, phototrophic symbiosis, and resource scavenging in cold environments through cross-domain collaboration and metabolic complementarity. Collectively, this study advances our understanding of extremophile life by demonstrating that microbial survival in cryospheric ecosystems is orchestrated through a sophisticated integration of community composition, genetic inventory, and interspecies cooperation. These insights are essential for predicting the ecological responses and climate feedbacks of cryospheric ecosystems under global warming.
The progressive weakening of alpine rockwalls through subcritical cracking, driven by repeated low-magnitude stress processes, plays a key role in alpine rock weathering. Laboratory studies using acoustic emission (AE) monitoring have shown that thermal stresses from freeze-thaw cycling induce crack propagation, with recent work highlighting the influence of rock moisture saturation. However, the role of moisture availability and movement within the outer rockwall remains poorly constrained. To address this gap, we conducted laboratory experiments on 40 & times; 20 & times; 20 cm samples of Wetterstein limestone (Northern Calcareous Alps), using AE sensors to track subcritical cracking during repeated diurnal and 72-h freeze-thaw cycles between 7 degrees C and -8 degrees C. Initial rock moisture saturation was varied across runs, and moisture redistribution was monitored via electrical resistance measurements. Our results show that while higher saturation generally enhances rock weathering, maximum crack intensity occurs at 70%-75% saturation, challenging the assumption that > 91% saturation represents optimal conditions. Among moisture-driven processes, volumetric expansion produced the highest weathering intensities (but for a shorter period of time), whereas ice segregation generated greater cumulative subcritical cracking due to the longer duration. Based on these findings and evidence of ice segregation, we propose a refined frost cracking window of -4 degrees C to -9 degrees C for Wetterstein limestone. These insights advance our understanding of the coupled role of rock moisture and temperature in alpine rockwall preconditioning for rockfall, though further work is needed to assess the impact of wet-dry weathering during freeze-thaw cycles and the role of increased surface moisture availability.
Periglacial landforms able to hold permafrost or seasonal ice are key elements for high mountain hydrological dynamics, which support societies in arid-semiarid regions and for aquatic biodiversity adapted to low water temperatures. However, the detection of potential internal permafrost still represents a challenge, mainly in regions with limited economic resources, like Southern South America. In Argentina, periglacial landforms containing permafrost are protected under national environmental legislation, as they are considered strategic water reserves, although this legal framework is currently under discussion. In the present study, we surveyed macroinvertebrates and physicochemical variables in 17 springs originating from periglacial landforms (classified into: rock glaciers, solifluction lobes, and debris slopes) located in the alpine zone of four Patagonia Andes mountains (above 1500 m a.s.l.). In our first hypothesis (H1), we tested if springs from periglacial landforms control water quality and aquatic macroinvertebrate diversity, while in our second hypothesis (H2), we evaluated the performance of freshwater macroinvertebrate communities as cost-effective bioindicators of ice meltwater within periglacial landform (intact or relict landforms) and their water quality. We found that periglacial landform type was a weak predictor of springs water quality and macroinvertebrate composition. In contrast, when we classified springs based on macroinvertebrate assemblages (biotic classification), we detected a potential altitude line (1819 m a.s.l.) splitting two main groups of springs, regardless of landform type. Moreover, springs located at higher elevations, characterized by specific Plecoptera, Trichoptera, and Diptera compositions, released water temperatures indicative of potential ice meltwater from permafrost or seasonal ice (values < 4 degrees C). In the context of regional climate change, characterized by rising temperatures and declining precipitation, the altitudinal limit of permafrost is expected to shift upward in the coming decades, and such changes could be efficiently monitored through macroinvertebrate assemblages.
Under continued climate warming, understanding present-day permafrost distribution and the controls on ground thaw are critical for predicting permafrost thaw trajectories and associated implications. This study presents a high-resolution investigation of permafrost extent and active layer thickness (ALT) across a coniferous forested hillslope in the discontinuous permafrost zone near Yellowknife, Northwest Territories, Canada. Using ground-penetrating radar (GPR), electrical resistivity tomography (ERT), and frost probing, spatial patterns of permafrost distribution and ALT were mapped and evaluated in relation to key environmental factors. Seasonal thaw patterns revealed greater early-season thaw at hillslope margins, whereas end-of-season variability was primarily governed by topographic gradients. Although ALT was correlated with multiple surface and subsurface characteristics, wet soil conditions at the hillslope base emerged as the dominant control on hillslope-scale ALT variability. Permafrost occurred in isolated patches along the transition from forested terrain to exposed bedrock, where shallow overburden constrained permafrost development. At the forest to wetland transition, increased ALT and indications of suprapermafrost taliks suggest that elevated soil moisture and associated latent heat inhibit complete refreezing to the permafrost table, highlighting the critical role of moisture in regulating permafrost stability. These results showcase substantial ALT variability over small spatial scales and demonstrate the influence of adjacent land covers in governing permafrost distribution within forested hillslopes. By characterizing high-resolution spatial patterns of ALT and contemporary permafrost occurrence within a representative regional land cover, this study provides key insights to improve permafrost modeling and vulnerability assessments under continued climate warming.
The spatial distribution of permafrost in mountainous regions is influenced by various factors such as topography, climate, vegetation, and substrate. Despite the existence of comprehensive permafrost maps at national and global levels, they fail to accurately represent the patch-scale (e.g., < 25 m) permafrost distribution in characteristic landforms of alpine zones, such as talus slopes, moraines, and rock glaciers. This study aims to improve the understanding of permafrost distribution in these environments, focusing on patch-scale variability and the influence of sediment size. By using data-driven techniques (i.e., logistic regression, support vector machines, and random forests), the spatial distribution of permafrost in six alpine basins within the Canadian Rockies was examined. The results indicate that the enhanced vegetation index, sediment size, and slope angle are the most important variables for predicting permafrost at the patch scale. However, the influence of the predicting variables strongly varied across different sites. Although the models trained with data from all sites effectively capture site-specific features and provide accurate representations of permafrost distribution, their applicability is limited in areas where predictor values fall outside the training domain. Nevertheless, this study contributes to understanding the factors influencing permafrost distribution at different scales, emphasizing the importance of including sediment size in predictive models.
Large periglacial block deposits are found in the mountains of southeastern Australia. Despite their widespread distribution, their mode of formation and age are poorly understood. These landforms hold considerable potential to shed light on the nature of cooling during glacial periods. In this paper we present a new study of block deposits in the mountains of Victoria, Australia. We describe the surface architecture, microrelief, slope profiles, texture, block shape and morphology of the blockstreams and block aprons. We present 14 new cosmogenic nuclide exposure ages (10Be and 36Cl) from four sites to extend existing chronologies and explore the use of weathering rinds to establish relative age. We find that formation of the deposits spans the last glacial cycle, with ages ranging from 93.1 +/- 13.5 to 10.5 +/- 2.0 ka. Weathering rind thickness showed no relationship with age or distance downslope and is likely saturated. We present a conceptual model where a combination of frost creep and hydraulic pressure explain the flow and the morphology of the blockstreams. Based on analogs in North America, mean annual air temperature was 10.2 degrees C +/- 1.3 degrees C colder than present. The high magnitude of temperature change is similar to Australian continental and Antarctic estimates and indicates that the LGM had a significant impact on the landscape.
High-resolution mapping of permafrost in ecologically and topographically complex landscapes remains a major challenge. Existing models of permafrost extent often rely on equilibrium assumptions, which can misrepresent conditions in regions where permafrost persists largely due to ecosystem structure. In such disequilibrium settings, climate-driven approaches alone tend to underpredict permafrost distribution, underscoring the need for methods that integrate both ecological and climatic controls. This study presents a hybrid framework that combines a binary logistic regression model, calibrated with community-based active layer and permafrost surveys, with the temperature at the top of permafrost (TTOP) model. By leveraging the strengths of each approach, the hybrid model improves prediction of permafrost probability relative to TTOP alone, with the clearest gains in burn scars and some mixed-wood forest classes, while hydrologically complex wetlands remain areas of weaker performance, and it maintains the ability to be driven by climate scenarios. Overall classification accuracy of the hybrid model is comparable to that of the TTOP implementation and slightly lower than that of the existing logistic regression model, reflecting a trade-off between maximal present-day accuracy and enhanced capacity for spatial extrapolation and temporal projection. The model was trained and validated using 139 cryotic assessment sites (CAS), along with high-resolution meteorological and ground temperature data. Results demonstrate that the hybrid approach better aligns climate-driven predictions with observed ecosystem-modified permafrost and provides equilibrium-based scenarios under future climate forcings. This study highlights the potential of hybridized approaches for advancing permafrost mapping in heterogeneous boreal landscapes and offers a practical tool to support community planning and adaptation in northern regions facing rapid climate change.
Isolated patches of permafrost, where ground thermal changes are affected by ecosystem factors such as vegetation cover rather than climate, may be vulnerable to environmental disturbances in semiarid regions. However, the impacts of ecosystem factors remain underevaluated in Mongolia. This study monitored changes in the ground surface temperature with respect to vegetation biomass and snow thickness and characterized the ground temperature dynamics at five boreholes in a wetland. Dense vegetation at the permafrost sites cooled the ground surface, resulting in a smaller positive surface offset (S O). Conversely, sparse and dry vegetation warmed the ground surface, leading to a larger positive S O. At the permafrost sites, the negative thermal offset was greater than that at the permafrost-free sites because of the latent heat flux in the water-saturated soil beneath the peat layer. The permafrost-free sites had shorter zero curtains with mineral soils compared with wetter soils underlain by isolated permafrost. Ecosystem-driven permafrost formed in the semiarid region impeded water penetration, increasing soil moisture and fostering peat soil development due to a slower decomposition rate. These processes reduced ground temperatures. These processes were associated with vegetation-soil negative feedback, ultimately enhancing the resilience of isolated patches of permafrost to climate change.
