Influence of climatic changes on geoelectrical parameters grounds of Central Yakutia
The features of seasonal periodic changes of apparent resistivity of the permafrost soil mass were examined basing on field measurements of the surface impedance in the 100-1000 kHz frequency range. The experiments were done at the permanent study plot of the Melnikov Permafrost Institute, SB RAS in the area of the city of Yakutsk in 2006-2012. The conformity of characteristic changes of soil temperature and apparent resistivity to the certain periods of time is given. The apparent resistivity of the permafrost soil mass is shown to conform to the degree of soil freezing. The results of the analysis of experimental data of supervision of changes of geoelectrical parameters under influence of the climatic factors are given. The influence of the climatic factors was estimated by the temperature of the air and soils, thickness of snow cover and quantity of rain deposits in the certain periods of time. It is shown that the seasonal changes of the apparent resistivity by asymptotical meanings reflect, accordingly, four degrees of freezing grounds: winter, spring, summer, and autumn. The levels of apparent resistivity of grounds, appropriate to their established degrees of freezing in the spring, summer and autumn, differ approximately twice. The value of apparent resistivity of the frozen soil mass depends on a degree of ground freezing during the pre-measurement period of cooling or thawing. The seasonal changes of apparent resistivity were within the limits of one order, and for electromagnetic and cross resistance they achieved two orders of the value. The degree of frozen ground freezing depends not only on the solar radiation and the temperature of air, but also on the thickness of the snow cover at a stage of cooling and the amount of rain at a thawing stage. For monitoring the active layer, more acceptable parameters are its cross resistivity or longitudinal conductivity received by interpretation of the radioimpedance or RМТ soundings data.