Hillslope patterns in thaw-freeze cycle and hydrothermal regimes on Tibetan Plateau

A significant portion of the Tibetan Plateau is underlain by permafrost, making investigation of related thaw-freeze cycle and hydrothermal conditions very important within earth system research. However, complex surface environments result in strong spatial heterogeneity of thaw-freeze processes and water/thermal exchange on the plateau. Thus, hillslope study is essential for exploring land surface variability. Therefore in this paper, ground penetrating radar (GPR) is used and its data evaluated for permafrost hydrology investigation. The spatial distribution of soil moisture and thaw/freeze conditions along south- and north-facing slopes is illustrated on the basis of various survey methods. In addition, sensitivity experiments reveal that the responses of frost depth and soil moisture vary with periods, depths and slopes under ground surface warming conditions, especially for freeze days and ratios. The significant feedback of warming to soil moisture is simulated. Moisture variation in the upper part of the soil is more significant, and the response of the north-facing slope is stronger. These results offer a detailed description of thaw/freeze cycle and water/thermal exchange at hillslope scales, which would be useful for studying frozen ground response to climatic warming and its spatial pattern on the Tibetan Plateau.