This research is focused on quantitative assessment of salinity influence on predictions of permafrost temperature on a regional scale. The relevance is determined by the intensive economic development of the Yamal Peninsula and the observed climate change in the Arctic. Reducing the uncertainty in forecast predictions of the permafrost temperature helps to reduce the value of the safety margin when designing the ground foundations of buildings and structures, avoiding the development of negative geoprocesses during their construction and operation. The object of the study is the permafrost of the Yamal Peninsula, which is continuously distributed and forms the foundation of the majority of buildings and structures in operation. The temperature of the saline permafrost is the subject of the study. The methods used combine thermodynamic and mathematical modelling and climate change consideration. The mean annual ground temperature by mid-century is predicted for three regions of the peninsula – north-western and western Yamal as well as the lower course of the Ob River. The temperature of the permafrost was determined by two independent approaches. In the first case, we used the heat-exchange characteristics of rocks which are constant for the forecast period, and in the second case – those that change with the transformation of the water-ionic composition of pore solutions. The minimum difference between the obtained temperature values is 0.1–0.2 °C in the north-western Yamal. The largest discrepancy between the modelling results is observed for the lower Ob River and reaches 0.5–0.6 °С. Neglecting the salinity of the permafrost and its properties for the period of geocryological forecasting leads to an error in determining the mean annual ground temperature of up to 20%. With the increase of pore solution salinity from 35 to 150 g/l, the difference in calculations increases by 15–20%. The mean annual ground temperature obtained with constant heat transfer characteristics turn out to be underestimated in comparison with the results of the problem with time-varying characteristics. Improving the geocryological forecast methodology will make it possible to more reasonably approach the assessment of the future thermal state of saline permafrost under climate change.
