Climate Change: Evidence from Historical Soil Temperature Measurements in the Russian Arctic and Subarctic

Changes in the near-surface soil temperature have direct impacts on carbon exchange, ecosystems, the active layer and permafrost, and other hydrologic, physical, and biological processes. In this presentation, we document long-term changes in the near-surface soil temperature from 250 stations in the Russian Arctic and subarctic. Mean annual soil temperatures at 40 cm depth have increased about 0.9 to 1.0 degree C from 1930 to 1990. The increase is more pronounced from 1970-1990. Soil temperature increases are greatest during winter months (DJF), at about 1.8 degree C, or 0.030 degree C/year over the period of record. This is followed by spring (MAM), which shows changes of about 1.0 degree C or 0.016 degree C/year. Corresponding changes in summer (JJA) and autumn (SON) are slightly less than 0.4 degree C with a rate of 0.006 degree C/year. The observed increases in soil temperature during winter months are related to increases in both air temperature and precipitation (presumably snowfall). Variations in snow cover thickness have an overall positive impact on soil temperature due to its insulating effects. During spring months, air temperature may play a major role but the timing of snowmelt and soil moisture may also be important. The small changes in soil temperature during summer and autumn are in accord with the only small changes in air temperature although changes in precipitation are substantial. Overall, this study indicates that changes in soil temperature in the Russian Arctic and subarctic are probably controlled by changes in air temperature, with some modification by precipitation. However, at individual stations, this may be not true; changes in snow cover in winter months and rainfall in summer months may have opposing effects. Further study is needed to improve our understanding of soil temperature fluctuation and its potential environmental impact, and to expand analysis to the entire Arctic and subarctic region.