Permafrost in the NE European Russian Arctic is suffering from some of the highest degradation rates in the world. The rising mean annual air temperature causes warming permafrost, the increase in the active layer thickness (ALT), and the reduction of the permafrost extent. These phenomena represent a serious risk for infrastructures and human activities. ALT characterization is important to estimate the degree of permafrost degradation. We used a multidisciplinary approach to investigate the ALT distribution in the Khanovey railway station area (close to Vorkuta, Arctic Russia), where thaw subsidence leads to railroad vertical deformations up to 2.5 cm/year. Geocryological surveys, including vegetation analysis and underground temperature measurements, together with the faster and less invasive electrical resistivity tomography (ERT) geophysical method, were used to investigate the frozen/unfrozen ground settings between the railroad and the Vorkuta River. Borehole stratigraphy and landscape microzonation indicated a massive prevalence of clay and silty clay sediments at shallow depths in this area. The complex refractive index method (CRIM) was used to integrate and quantitatively validate the results. The data analysis showed landscape heterogeneity and maximum ALT and permafrost thickness values of about 7 and 50 m, respectively. The active layer was characterized by resistivity values ranging from about 30 to 100 omega m, whereas the underlying permafrost resistivity exceeded 200 omega m, up to a maximum of about 10 k omega m. In the active layer, there was a coexistence of frozen and unfrozen unconsolidated sediments, where the ice content estimated using the CRIM ranged from about 0.3 - 0.4 to 0.9. Moreover, the transition zone between the active layer base and the permafrost table, whose resistivity values ranged from 100 to 200 omega m for this kind of sediments, showed ice contents ranging from 0.9 to 1.0. Taliks were present in some depressions of the study area, characterized by minimum resistivity values lower than 10 omega m. This thermokarst activity was more active close to the railroad because of the absence of insulating vegetation. This study contributes to better understanding of the spatial variability of cryological conditions, and the result is helpful in addressing engineering solutions for the stability of the railway.

The Qinghai-Tibet Plateau is the largest permafrost region at low latitude in the world. Climate warming may lead to permafrost temperature rise, ground ice thawing and permafrost degradation, thus inducing thermal hazards. In this paper, the ARCGIS method is used to calculate the changes of ground ice content and active layer thickness under different climate scenarios on the Qinghai-Tibet Plateau, in the coming decades, thus providing the basis for hazards zonation. The method proposed by Nelson in 2002 was used for hazards zonation after revision, which was based on the changes of active layer thickness and ground ice content. The study shows that permafrost exhibits different degrees of degradation in the different climate scenarios. The thawing of ground ice and the change from low-temperature to high-temperature permafrost were the main permafrost degradation modes. This process, accompanied with thinning permafrost, increases the active layer thickness and the northward movement of the permafrost southern boundary. By 2099, the permafrost area decreases by 46.2, 16.01 and 8.5% under scenarios A2, A1B and B1, respectively. The greatest danger zones are located mainly to the south of the West Kunlun Mountains, the middle of the Qingnan Valley, the southern piedmont of the Gangdise and Nyainqentanglha Mountains and some regions in the southern piedmont of the Himalayas. The Qinghai-Tibet Plateau permafrost region is in the low-risk category. Climate warming exacerbates the development of thermal hazards. In 2099, the permafrost region is mainly in the middle-risk category, and only a small portion is in the low-risk category.

Mountain ecosystems are commonly regarded as being highly sensitive to global change. Due to the system complexity and multifaceted interacting drivers, however, understanding current responses and predicting future changes in these ecosystems is extremely difficult. We aim to discuss potential effects of global change on mountain ecosystems and give examples of the underlying response mechanisms as they are understood at present. Based on the development of scientific global change research in mountains and its recent structures, we identify future research needs, highlighting the major lack and the importance of integrated studies that implement multi-factor, multi-method, multi-scale, and interdisciplinary research.

The permafrost regions currently occupy about one quarter of the Earth's land area. Climate-change scenarios indicate that global warming will be amplified in the polar regions, and could lead to a large reduction in the geographic extent of permafrost. Development of natural resources, transportation networks, and human infrastructure in the high northern latitudes has been extensive during the second half of the twentieth century. In areas underlain by ice-rich permafrost, infrastructure could be damaged severely by thaw-induced settlement of the ground surface accompanying climate change. Permafrost near the current southern margin of its extent is degrading, and this process may involve a northward shift in the southern boundary of permafrost by hundreds of kilometers throughout much of northern North America and Eurasia. A long-term increase in summer temperatures in the high northern latitudes could also result in significant increases in the thickness of the seasonally thawed layer above permafrost, with negative impacts on human infrastructure located on ice-rich terrain. Experiments involving general circulation model scenarios of global climate change, a mathematical solution for the thickness of the active layer, and digital representations of permafrost distribution and ice content indicates potential for severe disruption of human infrastructure in the permafrost regions in response to anthropogenic climate change. A series of hazard zonation maps depicts generalized patterns of susceptibility to thaw subsidence. Areas of greatest hazard potential include coastlines on the Arctic Ocean and parts of Alaska, Canada, and Siberia in which substantial development has occurred in recent decades.