The role of snow in soil thermal dynamics of the Arctic terrestrial ecosystems

The vast area of permanent or seasonal snow cover is an essential component of terrestrial ecosystems in northern mid-to-high latitudes (45-90°N), which has insulation effects on the soil layer beneath it. The affected soil thermal regimes will impact soil carbon dynamics. Recent observations indicate that there are substantial changes in both snow cover extent and duration due to climate change in the area. It is important to understand the insulation effect historically so as to better quantify its role in affecting ecosystem carbon dynamics under changing climate in the future. This study incorporates the snow insulation effect by introducing a snow model into an existing soil thermal model in a biogeochemistry modeling framework, the Terrestrial Ecosystem Model (TEM). The coupled model is used to evaluate the effects of snow dynamics on thermal regimes in the pan-Arctic for the period 2003-2010. Available satellite snow-cover data and site-level data are used to calibrate and evaluate the modeling system for the historical period. The study demonstrates that the revised model reproduces the top-soil layers’ thermal regime and freeze/thaw status reasonably well for the region. The study finds that the insulation effect of snow can alter soil thermal regime. The soil temperature estimations at 5cm and 20cm depths using the satellite snow data are in general 5? warmer in winters compared to those using the previous version of the model. There is a lag of soil cooling rate in early winter and a lag of soil warming rate in late spring. The study also finds that the insulation effect of snow can influence ground freeze/thaw status. The frozen line estimated by the revised model moves slightly southward in late spring and slightly northward in early winter. This study suggests that future analysis of soil thermal and carbon dynamics should take snow dynamics into account for the region