This paper describes the results of ground penetrating radar (GPR) research combined with geocryological data collected from the Circumpolar Active Layer Monitoring (CALM) testing sites in Kashin and Kumzha in August 2015, 2016, and 2017. The study area was located on the Pechora River delta. Both sites were composed of sandy ground and the permafrost depth at the different sites ranged from 20 cm to 8–9 m. The combination of optimum offset and multifold GPR methods showed promising results in these investigations of sandy permafrost geological profiles. According to direct and indirect observations after the abnormally warm conditions in 2016, the thickness and water content of the active layer in 2017 almost returned to the values in 2015 in the Kashin area. In contrast, the lowering of the permafrost table continued at Kumzha, and lenses of thin frozen rocks that were observed in the thawed layer in August of 2015 and 2017 were absent in 2016. According to recent geocryological and geophysical observations, increasing permafrost degradation might be occurring in the Pechora River delta due to the instability of the thermal state of the permafrost.

Climate warming in the Russian Arctic over the past 40 years shows a variety of patterns at different locations and time periods. In the second half of the 20th century, the maximum rates of warming were characteristic of the subarctic permafrost regions of Russia. But in the 21st century, the locations of the greatest rates of climate warming moved to the Arctic zone of Russia. It was one of the reasons for a sharp increase in permafrost temperatures, an increase in the depth of seasonal thaw, and the formation of closed taliks. It was found that as a result of climate change, the differences in permafrost temperatures between different cryogenic landscapes in the area of continuous and discontinuous permafrost distribution have decreased, and in the area of sporadic permafrost distribution are now practically absent. The thermal regime of the ground shows dramatic changes everywhere with a pronounced reduction in the depth of zero annual amplitude.

Typical tree health assessment methods are destructive. Non-destructive Ground Penetrating Radar (GPR) technique can provide a diagnostic tool for assessing the health status of live tree trunks based on internal dielectric permittivity distribution. Typical GPR acquisition technique—common-offset—is not helpful in providing robust and high-resolution quantitative results. In the current work we evaluate the capabilities of GPR tomography on locating tree-decays in a number of different tree species, imaging the interval structure of a healthy tree and quantitative estimation of moisture content (MC) based on distribution of dielectric permittivity, directly related to MC. The measurements described in this work were made on the trunks of live trees of different species in different conditions: a "healthy" English oak (Quercus robur), a "dry" Siberian fir (Picea obovata), a Horse chestnut (Castanea dentata) and a European aspen (Populus tremula) with rot inside. The results of the suggested approach were confirmed by resistography. Different parts of the trunk (bark, core, sapwood), as well as healthy and affected areas differ in moisture content, so the method of GPR tomography allowed us to see both the structure of the trunk of a healthy tree, and the presence and dimensions of defects.

— The water phase transition divides two approximation areas of ground from the standpoint of its elastic properties. It is of interest to study the changes of the acoustic characteristics,...

Геофизические методы в геокриологическом мониторинге