Multidirectional Changes in Temperature of Permafrost-Affected Soils during the Growing Season against the Background Increase in the Mean Annual Air Temperature

Abstract

Data on air and soil temperatures at the Verkhoyansk and Oymyakon weather stations in the East Siberian permafrost-taiga region are analyzed. The soils are represented by permafrost-affected sandy podzolized podbur (Verkhoyansk) and loamy soddy soil (Oymyakon). Recent decades have been the period of steady warming; average annual air temperature in 2001–2010 exceeded the climatological normal (1961–1990) by 1.4–1.5°C. An increase in air temperature is observed both in the cold and warm seasons. The temperature response of sandy and loamy soils to this warming is different. In the cold season, both soils are characterized by some rise in temperatures. In the warm season, the sandy soil demonstrates an increase in temperature and in the seasonal thawing depth, whereas the loamy soil is characterized by some a decrease in temperature and in the thawing depth. The importance of the snow cover as a factor slowing down soil freezing in the fall and soil thawing in the spring is demonstrated. The soil water and ice contents are also important factors affecting soil temperatures. It is shown that the freezing of both soils and their preservation in the frozen state take place at temperatures established at the snow/soil contact. In the coldest month (January), these temperatures in Verkhoyansk and Oymyakon are 12.6 and 14.3°C higher than air temperatures and 14.9 and 16.0°C higher than temperatures at the surface of the snow cover, respectively. The decrease in summer temperatures of the permafrost-affected loamy soil is explained by a higher heat consumption for the ice–water phase transition during the soil thawing.