Ytymdja depression is one of the Mesozoic structures with discovered large coal deposits of the Aldan Upland. Lack of industrial development and farness from agglomerations explain the knowledge gap about the environmental conditions of the Ytymdja depression. A field monitoring network with existing deep boreholes was absorbed to investigate permafrost conditions and to assess potential impacts of local factors and climate change. This paper describes analyse temperatures at the depth down to 240 m by these boreholes with air and ground temperatures of the Ytymdja depression to determinate permafrost conditions. The research was carried out in a 1800 km(2) area of the South Yakutia, Siberia, using satellite imagery-based classification. The field investigations and analysis of ground temperatures indicated that permafrost underlies of the ground entire area of Ytymdja depression, but likely absent under large rivers. Permanent negative temperatures have been detected in the borehole, which shows evidence of the existing of widespread permafrost conditions nowadays in the coal basins in Siberia. Permafrost temperatures vary between -3.1 degrees C and -1.5 degrees C at 35 m below the surface, and annual ground temperatures at 1 m depth ranged from -4.9 degrees C to -1.2 degrees C. Thermal conductivity of rocks determined by individual core samples varies from 1.1 to 2.9 W m(-1) degrees C-1 with geothermal heat flux in the permafrost zone of 0.02 Wm(-2) and an increase in the zone below permafrost to 0.03 Wm(-2). Spatial modelling for the entire territory of the Ytymdja depression deduced a continuous permafrost distribution with a thickness between 106 and 251 m. The considerable thickness of permafrost probably prevents the emission of greenhouse gases from coal seams into the atmosphere, but detailed studies in this direction have yet to be carried out. (C) 2021 Elsevier B.V. All rights reserved.

A characteristic of frozen ground is a tendency to form banded sequences of particle-free ice lenses separated by layers of ice-infiltrated soil, which produce frost heave. In permafrost, the deformation of the ground surface caused by segregated ice harms engineering facilities and has considerable influences on regional hydrology, ecology, and climate changes. For predicting the impacts of permafrost degradation under global warming and segregated ice transformation on engineering and environmental, establishing appropriate mathematical models to describe water migration and ice behavior in frozen soil is necessary. This requires an essential understanding of water migration and segregated ice formation in frozen ground. This article reviewed mechanisms of water migration and ice formation in frozen soils and their model construction and introduced the effects of segregated ice on the permafrost environment included landforms, regional hydrological patterns, and ecosystems. Currently, the soil water potential has been widely accepted to characterize the energy state of liquid water, to further study the direction and water flux of water moisture migration. Models aimed to describe the dynamics of ice formation have successfully predicted the macroscopic processes of segregated ice, such as the rigid ice model and segregation potential model, which has been widely used and further developed. However, some difficulties to describe their theoretical basis of microscope physics still need further study. Besides, how to describe the ice lens in the landscape models is another interesting challenge that helps to understand the interaction between soil ice segregation and the permafrost environment. In the final of this review, some concerns overlooked by current research have been summarized which should be the central focus in future study.

Climate models project considerable ranges and uncertainties in future climatic changes. To assess the potential impacts of climatic changes on mountain permafrost within these ranges of uncertainty, this study presents a sensitivity analysis using a permafrost process model combined with climate input based on delta-change approaches. Delta values comprise a multitude of coupled air temperature and precipitation changes to analyse long-term, seasonal and seasonal extreme changes on a typical low-ice content mountain permafrost location in the Swiss Alps. The results show that seasonal changes in autumn (SON) have the largest impact on the near-surface permafrost thermal regime in the model, and lowest impacts in winter (DJF). For most of the variability, snow cover duration and timing are the most important factors, whereas maximum snow height only plays a secondary role unless maximum snow heights are very small. At least for the low-ice content site of this study, extreme events have only short-term effects and have less impact on permafrost than long-term air temperature trends.

In recent years successful attempts have been made to develop and improve spatial modelling of mountain permafrost distribution. Work package 4 of the PACE project (Permafrost and Climate in Europe) sought to provide the essential basis not only of present-day modelling capability, but also of future enhancements in modelling methodology. This paper briefly outlines the currently available typology of models, which involve various levels of sophistication at different spatio-temporal scales. Appropriate models may be applied to a range of environmental issues in cold mountain areas, including engineering applications, climate-change scenarios, large-scale mapping, studies of surface processes or environmental concerns. Special emphasis is given here to aspects of energy exchange at the surface and within the active layer. Such energy fluxes remain poorly understood but play an essential role in process-oriented research and sensitivity studies with respect to complex interactions and feedbacks within the system. In contrast to relatively flat permafrost areas in polar and subpolar lowlands, circulation of water and air can cause important lateral fluxes of matter and energy within coarse blocks on steep slopes and result in highly variable and sometimes extreme thermal offsets between the ground surface and the permafrost table. Measuring and numerically modelling such fluxes together with coupling time-dependent surface and subsurface ground thermal conditions in characteristic materials (bedrock, ice-rich debris, fine-grained deposits) constitute the main challenge for research in the near future. Copyright (C) 2001 John Wiley & Sons, Ltd.