Vegetation-banked terraces (VBTs) with bare treads and vegetated risers occur in periglacial environments characterized by strong winds, shallow ground freezing and frequent freeze-thaw cycles. On lee slopes on Scottish mountains they follow the contour, but as exposure to dominant winds increases they dip windward. Comparative analyses of VBTs on mountains with non-frost-susceptible regolith cover and those on mountains with frost-susceptible soils reveal significant differences in dimensions, associated landforms and current activity. The former are generally smaller, lack over-ridden organic material and are associated with aeolian landforms and deposits. They are apparently static features where present activity is limited to needle-ice creep of debris across terrace treads and over risers. The latter are associated with active vegetation-covered solifluction terraces, have over-run organic material and are currently moving en masse downslope through frost creep and possibly gelifluction. We infer that VBTs on non-frost-susceptible regolith cover formed through the accumulation of debris at the upslope margins of wind stripes that formed due to wind erosion during the Little Ice Age. The latter probably represent Holocene vegetation-covered solifluction terraces from which vegetation has been stripped from treads by turf exfoliation (disruption by needle ice, deflation of fines and undermining of soil scarps).

Schmidt-hammer exposure-age dating (SHD) was applied to similar to 180 medium- to large-scale solifluction features on the northern edge of Juyflye, Jotunheimen (southern Norway) using an electronic Schmidt-hammer (RockSchmidt) and an improved local SHD age-calibration equation. Age estimates from four different types of solifluction landforms were analysed and compared with those from recalibrated estimates from patterned ground previously investigated on Juvflye. Average SHD-age estimates are c. 9.8 and 9.3 ka for the two dominant morphological types of solifluction features ('type A' boulder tongues and 'type B' stone-banked solifluction lobes) and c. 8.6 ka for sorted stripes and circles. Our results indicate that active formation of all investigated types of solifluction features, sorted stripes, and sorted circles ceased in the Early Holocene, prior to the onset of the regional Holocene Thermal Maximum (HTM) at c. 7.7 ka. Formation of all of these periglacial landforms appears to have commenced shortly after local deglaciation (c. 11.4 ka) in water-saturated till. Alternative origins are rejected, including the possibility of development before the last glaciation, survival beneath cold-based glaciers, and exhumation in the Early Holocene. Cessation of activity is attributed to changing ground conditions affecting active layer processes, particularly reduced soil moisture and pore water pressure. Temporal variations of the altitudinal permafrost limits had little or no impact on the timing of either the Early Holocene climax in activity or subsequent stabilisation. Caution is therefore urged in the utilisation of large-scale solifluction and patterned ground landforms as palaeoclimatic indicators.

Solifluction processes in the Arctic are highly complex, introducing uncertainties in estimating current and future soil carbon storage and fluxes, and assessment of hillslope and infrastructure stability. This study aims to enhance our understanding of triggers and drivers of soil movement of permafrost-affected hillslopes in the Arctic. To achieve this, we established an extensive soil deformation and temperature sensor network, covering 48 locations across multiple hillslopes within a 1 km2 watershed on the Seward Peninsula, AK. We report depth-resolved measurements down to 1.8 m depth for May to September 2022, a period conducive to soil movement due to deepening thaw layers and frequent rain events. Over this period, surface movements of up to 334 mm were recorded. In general, these movements occur close to the thawing front, and are initiated as thawing reaches depths of 0.4-0.75 m. The largest movements were observed at the top of the south-east facing slope, where soil temperatures are cold (mean annual soil temperatures averaging -1.13 degrees C) and slopes are steeper than 15 degrees. Our analysis highlights three primary factors influencing movements: slope angle, soil thermal conditions, and thaw depth. The latter two significantly impact the generation of pore water pressures at the thaw-freeze interface. Specifically, soil thermal conditions govern the liquid water content, while thaw depth influences both the height of the water column and, consequently, the pressure at the thawing front. These factors affect soil properties, such as cohesion and internal friction angle, which are crucial determinants of slope stability. This underscores the significance of a precise understanding of subsurface thermal conditions, including spatial and temporal variability in soil temperature and thaw depth, when assessing and predicting slope instabilities. Based on our observations, we developed a factor of safety proxy that consistently falls below the triggering threshold for all probes exhibiting displacements exceeding 50 mm. This study offers novel insights into patterns and triggers of hillslope movements in the Arctic and provides a venue to evaluate their impact on soil redistribution.

Periglacial environments are characterized by highly dynamic landscapes. Freezing and thawing lead to ground movement, associated with cryoturbation and solifluction. These processes are sensitive to climate change and variably distributed depending on multiple environmental factors. In this study, we used multi-geometry Sentinel-1 Synthetic Aperture Radar Interferometry (InSAR) to investigate the spatial distribution of the mean annual ground velocity in a mountainous landscape in Northern Norway. Statistical modeling was employed to examine how periglacial ground velocity is related to environmental variables characterizing the diverse climatic, geomorphic, hydrological and biological conditions within a 148 km(2) study area. Two-dimensional (2D) InSAR results document mean annual ground velocity up to 15 mm/yr. Vertical and horizontal velocity components in the East-West plane show variable spatial distribution, which can be explained by the characteristics of cryoturbation and solifluction operating differently over flat and sloping terrain. Statistical modeling shows that slope angle and mean annual air temperature variables are the most important environmental factors explaining the distribution of the horizontal and vertical components, respectively. Vegetation and snow cover also have a local influence, interpreted as indicators of the ground material and moisture conditions. The results show contrasted model performance depending on the velocity component used as a response variable. In general, our study highlights the potential of integrating radar remote sensing and statistical modeling to investigate mountainous regions and better understand the relations between environmental factors, periglacial processes and ground dynamics.

InSAR time series of surface deformation from 16 yr of Envisat (2003-2011) and Sentinel-1 (2014-2019) ESA satellite radar measurements have been constructed to characterise spatial and temporal dynamics of ground deformation over an 80,000 km(2) area in the permafrost of the northeastern Tibetan Plateau. The regional deformation maps encompass various types of periglacial landforms and show that seasonal thaw effects are controlled by the sediment type and local topography. High seasonal ground movements are concentrated on shallow slopes and poor-drainage areas in unconsolidated, frost-susceptible and fine-grained sediments within glacier outwash plains, braided stream plains, alluvial deposits or floodplains. Fast subsidence due to thaw settlement takes place during June/July while frost heave is intense during December/January when two-sided freezing of pore water under pressure causes prolonged ice segregation near the permafrost table. The analysis reveals pervasive subsidence of the ground of up to similar to 2 cm/yr, and increasing by a factor of 2 to 5 from 2003 to today, in high-relief and well-drained areas. The findings suggest that seasonal thaw increasingly affects ice-rich layers at the permafrost table, as well as high-rates of widespread mass movements of non-consolidated sediments, the latter amplified by an increase of effects from frost heave/thaw settlement. (C) 2020 Elsevier B.V. All rights reserved.

Permafrost decline, observed in the last few decades as a result of climate change, causes an activation of cryogenic landslide processes. This study on Olkhon Island in Lake Baikal (Eastern Siberia), located within the discontinuous permafrost zone, was aimed to determine how strongly the landslide forms found there are associated with climatic conditions and if they can react to climate change. It was also important to identify which type of landslides in this area is the most sensitive indicator of the observed changes and to what extent they can react to them. For this purpose, landslides were identified, and their morphology, geological structure, and thermal parameters were assessed. The results show that the key process is the increase in thickness of the active layer, partly due to the presence of Miocene lake clays and changes in water level in Lake Baikal.

Environmental factors that affect the activity-inactivity variation of periglacial features may differ from those factors that control the distributional patterns of active features. To explore this potential difference, a statistically based modelling approach and comprehensive data on active and inactive cryoturbation and solifluction features from a subarctic area of Finnish Lapland are investigated at a landscape scale. In the cryoturbation modelling, vegetation abundance is the most important environmental variable explaining both the activity-inactivity variation and the distribution of active sites. The next most important variables are soil moisture and (micro)climatological conditions in the activity modelling, and slope angle and ground material in the distribution modelling. For solifluction, the key variables determining the activity-inactivity variation are mean annual air temperature and mean maximum snow depth, whereas vegetation abundance and slope angle control the distribution of active sites. Comparison between the environmental conditions of active and inactive periglacial features may provide new insights into activity-environment relationships, which in turn are valuable when the effects of climate change on periglacial processes are explored. Copyright (c) 2014 John Wiley & Sons, Ltd.

Field data on the rates of solifluction and associated parameters are compiled from the literature, in an attempt to evaluate factors controlling the spatial variability in solifluction processes and landforms, with special attention on the climate-solifluction. relationship. The analyzed data originate from 46 sites over a wide range of periglacial environments, from Antarctic nunataks to tropical high mountains. Solifluction, broadly defined as slow mass wasting resulting from freeze-thaw action in fine-textured soils, involves several components: needle ice creep and diurnal frost creep originating from diurnal freeze-thaw action; annual frost creep, gelifluction and plug-like flow originating from annual freeze-thaw action; and retrograde movement caused by soil cohesion. The depth and thickness of ice lenses and freeze-thaw frequency are the major controls on the spatial variation in solifluction processes. Near the warm margin of the solifluction-affected environment, diurnal freeze-thaw action induces shallow but relatively rapid movement of a superficial layer 5 - 10 cm thick on average, often creating the thin stone-banked lobes typically seen on tropical high mountains. In addition to diurnal movement, annual frost creep and gelifluction may occur on slopes with soil climates of seasonal frost to warm permafrost, dislocating a soil layer shallower than 60 cm at a rate of centimeters per year and eventually producing medium-size solifluction lobes. In High-Arctic cold permafrost regions, two-sided freezing can induce plug-like flow of a soil mass 60 cm or thicker. The correlation between process and landform. suggests that the riser height of lobes is indicative of the maximum depth of movement and prevailing freeze-thaw type. Climate change may result in new different ground freezing conditions, thereby influencing the surface velocity and maximum depth of soil movement. Soil moisture and topography also control solifluction. High moisture availability in the seasonal freezing period enhances diurnal freeze-thaw action and subsequent seasonal frost heaving. The latter contributes to raising the moisture content of the thawed layer and promotes gelifluction during the thawing period. The slope angle defines the upper limit of the surface velocity of solifluction. A diagram correlating the potential frost creep with the actual surface velocity permits an inter-site comparison of the relative magnitude of solifluction components. Physically based modelling of periglacial slope evolution requires synthetic and more detailed field monitoring and laboratory simulations of solifluction processes. (C) 2001 Elsevier Science B.V. All rights reserved.