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This paper documents the first comprehensive inventory of thermokarst and thaw-sensitive terrain indicators for a 2 million km2 region of northwestern Canada. This is accomplished through the Thermokarst Mapping Collective (TMC), a research collaborative to systematically inventory indicators of permafrost thaw sensitivity by mapping and aerial assessments across the Northwest Territories (NT), Canada. The increase in NT-based permafrost capacity has fostered science leadership and collaboration with government, academic, and community researchers to enable project implementation. Ongoing communications and outreach have informed study design and strengthened Indigenous and stakeholder relationships. Documentation of theme-based methods supported mapper training, and flexible data infrastructure facilitated progress by Canada-wide researchers throughout the COVID-19 pandemic. The TMC inventory of thermokarst and thaw-sensitive landforms agree well with fine-scale empirical mapping (69%–84% accuracy) and aerial inventory (74%–96% accuracy) datasets. National- and circumpolar-scale modelling of sensitive permafrost terrain contrasts significantly with TMC outputs, highlighting their limitations and the value of empirically based mapping approaches. We demonstrate that the multiparameter TMC outputs support a holistic understanding and refined depictions of permafrost terrain sensitivity, provide novel opportunities for regional syntheses, and inform future modelling approaches, which are urgently required to comprehend better what permafrost thaw means for Canada's North.

There are different ideas about the classification and distribution of permafrost in Mongolia. Terms such as continuous, discontinuous, sporadic, and isolated permafrost are inconsistently applied; hence, maps of permafrost display different distribution patterns. Particularly, the southern border of the Siberian permafrost in Mongolia is still debated. Furthermore, comparing these maps is challenging when studying impacts of climate change on permafrost. While, without a doubt, Mongolia's permafrost is in a stage of significant degradation and has receded from vast regions, telling this story is difficult when data are not easily comparable. Today, all permafrost is restricted to Mongolia's mountains. To better describe permafrost that depends on orography and elevation, we propose to use the more appropriate term 'mountain permafrost.' Surprisingly, the term 'periglacial' is mostly absent in the literature on Mongolia's permafrost. We here aim to clarify definitions of terms and hope that future studies will pay attention to both periglacial environments and mountain permafrost. [ABSTRACT FROM AUTHOR]

The Essential Climate Variable (ECV) Permafrost is currently undergoing strong changes due to rising ground and air temperatures. Surface movement, forming characteristic landforms such as rock glaciers, is one key indicator for mountain permafrost. Monitoring this movement can indicate ongoing changes in permafrost; therefore, rock glacier velocity (RGV) has recently been added as an ECV product. Despite the increased understanding of rock glacier dynamics in recent years, most observations are either limited in terms of the spatial coverage or temporal resolution. According to recent studies, Sentinel-1 (C-band) Differential SAR Interferometry (DInSAR) has potential for monitoring RGVs at high spatial and temporal resolutions. However, the suitability of DInSAR for the detection of heterogeneous small-scale spatial patterns of rock glacier velocities was never at the center of these studies. We address this shortcoming by generating and analyzing Sentinel-1 DInSAR time series over five years to detect small-scale displacement patterns of five high alpine permafrost environments located in the Central European Alps on a weekly basis at a range of a few millimeters. Our approach is based on a semi-automated procedure using open-source programs (SNAP, pyrate) and provides East-West displacement and elevation change with a ground sampling distance of 5 m. Comparison with annual movement derived from orthophotos and unpiloted aerial vehicle (UAV) data shows that DInSAR covers about one third of the total movement, which represents the proportion of the year suited for DInSAR, and shows good spatial agreement (Pearson R: 0.42–0.74, RMSE: 4.7–11.6 cm/a) except for areas with phase unwrapping errors. Moreover, the DInSAR time series unveils spatio-temporal variations and distinct seasonal movement dynamics related to different drivers and processes as well as internal structures. Combining our approach with in situ observations could help to achieve a more holistic understanding of rock glacier dynamics and to assess the future evolution of permafrost under changing climatic conditions. [ABSTRACT FROM AUTHOR]

Talus slopes are a common sedimentary formation both in polar and high-mountain areas, but their development is still not sufficiently understood. This article discusses the environmental factors that have been influencing development of talus slopes since the deglaciation and their impact on the internal structure of slopes. Case studies of the slopes from SW Spitsbergen and the Tatra Mountains in Poland were compared in order to explore different evolution stages. Slopes’ structure was analysed using geophysical surveys based on two-dimensional electrical resistivity tomography (ERT) with a Wenner-Schlumberger array and an electrode spacing of 5 m, combined with geomorphological observations. The investigated talus slopes represent the paraglacial, periglacial and talus-alluvial environments. New data on the internal structure of talus slopes developing in the present or past glaciated areas adds to understanding talus slope evolution. There are many different views concerning the development of slopes during the paraglacial period, whose analysis seems to be crucial in the background of climate change and their record in slope structures. In addition, the study provided valuable information on the development and degradation of permafrost in slope materials.

Hourly ground temperature measurements from the highest shallow ground temperature monitoring system on Earth and sedimentological data were used to construct a thermal model at the Ojos del Salado, in the Dry Andes (5830 m a.s.l.). The results were used to investigate daily temperature fluctuations and the phase changes of water in the regolith, where the permafrost and ground ice are present. Model results reveal that the thermal evolution of the ground and the speed of phase changes are determined by the differing thermal properties of liquid and solid water, and change in their vertical distribution over time. At the start of summer, the increasing ratio of liquid water near the surface insulates deeper layers, and thus, melting is delayed and daily temperature fluctuations are damped in the regolith. The approach of the present study includes testing how simple, relatively low processing power required data analysis might be applied for Mars in the future. Periglacial and aeolian landforms were also surveyed, with a focus on thermo- and cryokarstic features, as previous studies have shown that patterned ground structures are rare in the region due to the highly porous nature of the dry regolith. Besides the wealth of aeolian features, gravel mantled megaripples, solifluction lobes, and thermo- and cryokarstic depressions, were found. In the case of the former, a close association with ephemeral ponds—hosting extremophilic microorganisms—was found, highlighting the fact that meltwater percolates horizontally even in this extremely dry environment. The thermo- and cryokarstic depressions also reveal the role of melting and its intricate connection to sublimation. As these features indicate degrading permafrost, closer investigation may provide useful analogs for earlier and contemporary climatic changes on Mars. [ABSTRACT FROM AUTHOR]

Six hundred sixty‐one rock glaciers in the northern Absaroka and Beartooth Ranges of south‐central Montana were digitized and evaluated using geographic information systems technology and an array of topographic and environmental parameters. Beartooth rock glaciers are larger, occur at higher elevations, receive more precipitation, and are subject to lower temperatures than northern Absaroka rock glaciers. Elevation is strongly correlated with rock glacier activity. Comparative analysis of these adjacent mountain ranges indicates that Beartooth geomorphic landscapes are shifting from predominantly glacial to periglacial regimes, and that the northern Absarokas have largely completed this transition. Because glaciers are declining in response to climate warming, rock glaciers could soon become the most important source of ice in the region. [ABSTRACT FROM AUTHOR]

Abstract Proxy data from pollen and mollusc indicator species, periglacial phenomena, changes in geometry of mountain palaeoglaciers and based on selected lithological and geomorphological features enabled reconstruction of the Late Pleistocene climate characteristics in Poland and adjacent areas. Climate during the Eemian was generally stable but with a distinct west-east gradient in summer. Strong influence of the Atlantic air masses moving to the east resulted in the annual precipitation over 600 mm. Climate instability in the late Eemian as well as during stadials and interstadials of the Early Weichselian was expressed by progressive cooling and increasing temperature difference between winters and summers, reflecting stronger continentalism towards the west, accompanied by decreased precipitation. Periglacial frost crackings and polygonal patterns indicated occurrence of permafrost in Poland already at about 49 ka BP and its occurrence until the termination of the last glaciation. These periglacial structures have developed at mean annual temperatures from −9 to −4 °C, with winter extremes up to about −25 °C. Mean summer temperature reached likely around 10 °C as suggested by palaeobotanic record. Palaeoglaciological studies of mountain glaciers across Europe allowed inferring their activity and sensitivity to climatic fluctuations during the Late Weichselian. The Weichselian of central Europe was controlled mostly by the southerly and easterly circulation dominated by climate cyclones and anticyclones, respectively. An inflow of air masses from the west was significantly limited and concentrated mainly within the so-called periglacial corridor between the Scandinavian ice sheet and the Alps. Such circulation pattern determined serious reduction of precipitation during the Last Glacial Maximum that reached 60% in relation to modern conditions. The following Late Pleistocene cold phases (Oldest and Younger Dryas) were slightly warmer and wetter with increasing contribution of the westerlies that were strongly dependent on progressing shrinkage of the Northern Hemisphere ice sheets. [ABSTRACT FROM AUTHOR]

Abstract The extent to which deposition within river systems is driven by climate over glacial-interglacial timescales, and the nature of such linkages, is much debated. Answering such questions from the geological record is often limited by a lack of geochronological precision. Numerical modelling allows us to scale up what we know of climate response on short timescales to these longer timescales. To generate a robust reconstruction, relevant parameters need to be included in the model setup, and model output needs to be evaluated against the geological record. Here we introduce the model C leopatra (CybErosion-based Landscape Evolution On Periglacially Altered TeRrAin), the first reduced complexity model to include periglacial processes explicitly within a river catchment. We also use a pattern-oriented sampling approach to model evaluation and introduce innovative methods, particularly the quantification of the comparison of synthetic borehole data with geological sequences using Spearman rank correlation. Sediment starvation is observed within the model compared with the geological data, suggesting either the importance of sediment reworking within the catchment or that we have yet to specify the full complexity of periglacial processes in the model. In this sediment-starved situation, gelifluxion drives sediment supply but climate is less important in dictating the timing of aggradation and incision than intrinsic controls and elapsed time. [ABSTRACT FROM AUTHOR]

Abstract Two loess-paleosol sequences from the Heilbronn Basin in southwestern Germany, Frankenbach and Talheim, have been investigated to gain information about environmental conditions during the last interglacial-glacial cycle. Since paleoenvironmental research on terrestrial archives is crucial for a better understanding of past climatic and environmental conditions, the profiles were studied using a multi-proxy approach. Applied methods include the analyses of grain-size distribution, element contents, sediment color, rock magnetism, micromorphology, and black carbon (BC) via benzene polycarboxylic acids (BPCA). The data reveal that the two profiles show large variations in conservation due to their different geomorphologic positions. Moreover, the results imply a subarctic climate with stable conditions during the Middle Pleniglacial (MIS 3) in-situ soil formation phase while the Lower Pleniglacial (MIS 4) was characterized by erosion and reworking of Eemian and Early Glacial (MIS 5) material but also by accumulation of aeolian material during the late Lower Pleniglacial (MIS 4) in Frankenbach. The results further suggest that the Rhine River floodplain has been a major source for the accumulated material in the two profiles, which indicates westerly wind directions during the time of accumulation. The low GSI and U-Ratio of Upper Pleniglacial (MIS 2) sediments, supported by the overall high content of fine material, imply a larger distance to the source area. We give an overview of loess in the Heilbronn Basin and place it in a wider context of loess in Western Europe. Highlights • Two loess-paleosol sequences of the Heilbronn Basin have been investigated. • Preservation of loess-paleosol archives strongly depends on geomorphological settings. • Westerly wind direction are proposed for the last interglacial-glacial cycle. • A multi-proxy approach is essential to avoid misleading results. [ABSTRACT FROM AUTHOR]

The most important stratified screes of the Iberian Range are found in Sierra de Albarracín. These slope deposits have been traditionally considered, without absolute datings, as having been formed during various Pleistocene cold phases. The aim of this paper is to establish the sedimentological, morphological, chronological, and paleoenvironmental characteristics of these deposits through the study of four profiles recorded in the Calomarde canyon (El Rollo, El Molino, and Royuela) and Toril. The most representative profile is that of El Rollo as it is formed by basal tufa and stratified scree layers separated by paleosoils. Radiocarbon datings obtained from paleosoil samples show that the sequence ranges between the early and middle Holocene. The profiles from El Molino and Royuela, as well as the upper levels of Toril, complete the sequence showing deposits from upper Holocene (Bronze Age and ‘Little Ice Age’). These data show the oscillations during the Holocene between colder phases, represented by the stratified screes, and warmer–wetter phases with soil development and local tufa deposits. This geomorphological and pedological response to the Holocene climatic variability shows its clearest records in the canyons. However, there are almost no Pleistocene accumulations – with the exception of that of Toril (minimum age of <43.5 ka BP). The possibility of relating this succession of Holocene environmental changes to known regional and global climatic stages converts these accumulations into the most important Holocene paleoenvironmental record from the Iberian Ranges and the most complete sequence of Holocene stratified screes from the Mediterranean area. [ABSTRACT FROM AUTHOR]

Proglacial systems are amongst the most rapidly changing landscapes on Earth, as glacier mass loss, permafrost degradation and more episodes of intense rainfall progress with climate change. This review addresses the urgent need to quantitatively define proglacial systems not only in terms of spatial extent but also in terms of functional processes. It firstly provides a critical appraisal of prevailing conceptual models of proglacial systems, and uses this to justify compiling data on rates of landform change in terms of planform, horizontal motion, elevation changes and sediment budgets. These data permit us to produce novel summary conceptual diagrams that consider proglacial landscape evolution in terms of a balance of longitudinal and lateral water and sediment fluxes. Throughout, we give examples of newly emerging datasets and data processing methods because these have the potential to assist with the issues of: (i) a lack of knowledge of proglacial systems within high-mountain, arctic and polar regions, (ii) considerable inter- and intra-catchment variability in the geomorphology and functioning of proglacial systems, (iii) problems with the magnitude of short-term geomorphological changes being at the threshold of detection, (iv) separating short-term variability from longer-term trends, and (v) of the representativeness of plot-scale field measurements for regionalisation and for upscaling. We consider that understanding of future climate change effects on proglacial systems requires holistic process-based modelling to explicitly consider feedbacks and linkages, especially between hillslope and valley-floor components. Such modelling must be informed by a new generation of repeated distributed topographic surveys to detect and quantify short-term geomorphological changes. [ABSTRACT FROM AUTHOR]

Fan-shaped landforms occur in all climatic regions on Earth. They have been extensively studied in many of these regions, but there are few studies on fans in periglacial, Arctic and Antarctic regions. Fans in such regions are exposed to many site-specific environmental conditions in addition to their geological and topographic setting: there can be continuous to discontinuous permafrost and snow avalanches and freeze–thaw cycles can be frequent. We study fans in the high-Arctic environment of Svalbard to (1) increase our fundamental knowledge on the morphology and morphometry of fans in periglacial environments, and (2) to identify the specific influence of periglacial conditions on fans in these environments. Snow avalanches have a large geomorphic effect on fans on Svalbard: the morphology of colluvial fans is mainly determined by frequent snow avalanches (e.g., flattened cross-profiles, exposed fine-grained talus on the proximal fan domain, debris horns and tails). As a result, there are only few fans with a rockfall-dominated morphology, in contrast to most other regions on Earth. Slush avalanches contribute significant amounts of sediment to the studied alluvial fans. The inactive surfaces of many alluvial fans are rapidly beveled and leveled by snow avalanches, solifluction and frost weathering. Additionally, periglacial reworking of the fan surface often modifies the original morphology of inactive fan surfaces, for example by the formation of ice-wedge polygons and hummocks. Permafrost lowers the precipitation threshold for debris-flow initiation, but limits debris-flow volumes. Global warming-induced permafrost degradation will likely increase debris-flow activity and -magnitude on fans in periglacial environments. Geomorphic activity on snow avalanche-dominated colluvial fans will probably increase due to future increases in precipitation, but depends locally on climate-induced changes in dominant wind direction. [ABSTRACT FROM AUTHOR]

Intense glaciation during the end of Cryogenian time (∼635 million years ago) marks the coldest climate state in Earth history – a time when glacial deposits accumulated at low, tropical paleolatitudes. The leading idea to explain these deposits, the snowball Earth hypothesis, predicts globally frozen surface conditions and subfreezing temperatures, with global climate models placing surface temperatures in the tropics between −20 °C and −60 °C. However, precise paleosurface temperatures based upon geologic constraints have remained elusive and the global severity of the glaciation undetermined. Here we make new geologic observations of tropical periglacial, aeolian and fluvial sedimentary structures formed during the end-Cryogenian, Marinoan glaciation in South Australia; these observations allow us to constrain ancient surface temperatures. We find periglacial sand wedges and associated deformation suggest that ground temperatures were sufficiently warm to allow for ductile deformation of a sandy regolith. The wide range of deformation structures likely indicate the presence of a paleoactive layer that penetrated 2–4 m below the ground surface. These observations, paired with a model of ground temperature forced by solar insolation, constrain the local mean annual surface temperature to within a few degrees of freezing. This temperature constraint matches well with our observations of fluvial deposits, which require temperatures sufficiently warm for surface runoff. Although this estimate coincides with one of the coldest near sea-level tropical temperatures in Earth history, if these structures represent peak Marinaon glacial conditions, they do not support the persistent deep freeze of the snowball Earth hypothesis. Rather, surface temperatures near 0 °C allow for regions of seasonal surface melting, atmosphere–ocean coupling and possible tropical refugia for early metazoans. If instead these structures formed during glacial onset or deglaciation, then they have implications for the timescale and character for the transition into or out of a snowball state. [ABSTRACT FROM AUTHOR]

We report on the key physical features of an active rock glacier that influence the distribution of plants and arthropods. We also perform a comparison with neighboring scree slope and alpine grassland to test whether the environmental features of the rock glacier drive the presence of specific species assemblages. Compared with scree slope and grassland, the studied rock glacier provides particular physical features that determine the presence of unique species. Plant distribution is mainly driven by grain size. Arthropod distribution is linked to grain size, with cold-adapted species found on areas with coarse-grained deep debris, which also shows a distinctive temperature regime with very low values throughout the year. On the basis of these findings, we advance the hypothesis that rock glaciers provide specific ecological conditions creating potential refugia for cold-demanding species during warm climatic periods. [ABSTRACT FROM PUBLISHER]

Sand dune stratigraphy, radiocarbon-dated charcoal layers, palaeosol development and luminescence dating are used to reconstruct the Holocene environmental history of the dune fields in Finnish Lapland since deglaciation in the early Holocene (~10,900–10,200 cal. BP). After rapid formation and stabilisation of parabolic dunes and the immigration of Scots pine (Pinus sylvestris), forest fires are inferred to have played a key role in triggering episodes of aeolian erosion of the dunes (deflation) leading to 16 sand dune re-activation events. These events were widespread in the dune fields from ~8300 cal. BP and occurred with increasing frequency towards the late Holocene. Each event is interpreted as relating to local fires that occurred up to 100–400 years after the date of each charcoal layer; the radiocarbon age of the charcoal being affected by the age of the wood when burned, and the accumulation and/or recycling of charcoal from earlier fires. Well-developed buried iron podzols, which can develop within 500–1000 years, indicate prolonged phases of dune stability, four of which are dated to between 4500 and 1050 cal. BP. Indirect associations are evident between the sand dune re-activation events and climatic phases that were relatively cold and/or wet. These associations are explained by a conceptual geo-ecological model in which the effects of century- to millennial-scale climatic variability are modulated by the interactions between fire and vegetation. Thus, the subarctic dune field is viewed as a heterogeneous landscape of stable and unstable areas in space and through time. The unstable elements of this spatial mosaic become more extensive at times when the climatic environment promotes fire and deflation. [ABSTRACT FROM PUBLISHER]

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Recent research on slope processes and weathering on Marion Island has highlighted distinctive attributes of the maritime Subantarctic periglacial environment, compared to other periglacial environments. This is reflected morphologically by sorted stripe characteristics and stratified solifluction forms, but the wind factor and low diurnal temperature range also results in differences with other diurnal frost environments. Its hyper-maritime setting at low mean annual temperatures results in very high frost cycle frequencies, with associated effectiveness in surface sediment transport and patterned ground development. In addition, a high frequency of wetting and drying cycles is observed in rocks. Small seasonal temperature ranges and steep temperature profiles indicate a high sensitivity to climate change in the Subantarctic, as reflected in a rich relict periglacial record on most islands. This sensitivity appears absent in high tropical environments of low annual temperature range. [Copyright &y& Elsevier]

Only a few very young landforms are the result of currently operating geomorphic processes. Because the time scale for landscape evolution is much longer than the time scale for late Cenozoic climate changes, almost all landscapes are palimpsests, written over repeatedly by various combinations of climate-determined processes. Relict glacial and periglacial landforms are widely identified in mid-latitude regions that have been traditionally described as having been shaped by the “normal” processes of fluvial erosion. Less confidently, deeply weathered regolith and associated relict landforms in the middle and high latitudes are attributed to early Tertiary warmth. However, assemblages of geomorphic processes specific to certain climatic regions, like faunal and floral assemblages, cannot be translated across latitude, so in spite of the many books about the geomorphology of specific modern climate regions, there are few sources that discuss former warm high-latitude, or cold low-latitude, low-altitude geomorphic processes that have no modern analogs. Students and teachers alike who attempt to interpret landforms by extrapolating modern climatic conditions to other latitudinal zones will find their outlook broadened, and they become better prepared to consider the geomorphic impacts of global climate change. [Copyright &y& Elsevier]