Response of Seasonal Soil Freeze Depth to Climate Change across China

The response of seasonal soil freeze depth to climate change has repercussions for the surface energy and water balance, ecosystems, the carbon cycle, and soil nutrient exchange. In this study, we use data from 845 meteorological stations to investigate the response of variations in soil freeze depth to climate change across China. Observations include daily air temperature, daily soil temperatures at various depths, mean monthly gridded air temperature, and Normalized Difference Vegetation Index. Results show that soil freeze depth decreased significantly at a rate of −0.18 cm/year, resulting in a net decrease of 8.05 cm over 1967–2012 across China. On the regional scale, soil freeze depth decreases varied between 0.0 and 0.4 cm/year in most parts of China from 1950 to 2009. Combining climatic and non-climatic factors with soil freeze depth, we conclude that air temperature increases are responsible for the decrease in soil seasonal freeze depth during this period. Changes in snow depth and vegetation are negatively correlated with soil freeze depth. These results are important for understanding the soil freeze/thaw dynamics and the impacts of soil freeze depth on ecosystem and hydrological process.