# Effects of Cyclical Climate Change on Water Temperature Characteristics of Permafrost Slopes
## 3 Results and Discussion
### Long-Term Water Temperature Characteristics
In comparison, deep-layer soil shows higher thermal stability due to the thermal diffusion effect, and the decrease in temperature gradient inhibits water migration, resulting in relatively stable water changes. This hydrothermal interaction not only reveals the depth-lag effect of temperature and water migration but also emphasizes the dual influence of hydrothermal coupling on soil stability: shallow-layer soil is easily damaged by freeze-thaw cycles, while deep-layer soil provides relatively stable conditions for engineering foundations. The temperature variation with depth at different freeze-thaw cycle counts, as shown in Figure 7, is divided into three stages: early freezing (a), stable freezing (b), and thawing (c). During the early freezing stage, the temperature drops rapidly, with the surface layer beginning to freeze, and the temperature gradient is relatively large. In the stable freezing stage, the temperature levels off, the freezing layer reaches its maximum depth, and the heat conduction rate slows down. During the thawing stage, the temperature gradually rises, and heat is transferred from the surface to deeper layers, causing the frozen layer to melt progressively. Additionally, the figure illustrates the suppressive effect of phase  
Figure 6: Changes in water content of slopes and foundations. change latent heat on temperature variation, the depth-lag effect in temperature changes, and the potential impact of freeze-thaw cycles on soil moisture content [11]. Figure 8 shows the soil moisture content profiles at different freeze-thaw cycle counts and stages. In panel (a), representing the early freezing stage, the moisture content increases gradually with depth, starting from nearly 0% at the top (2 m deep) and reaching about 0.28% at the bottom (\(-\)3 m deep). This phenomenon can be attributed to the initial freezing of moisture at the surface due to exposure to low temperatures, resulting in a low moisture content near the surface. In contrast, the bottom region experiences a delayed freezing process due to the lag in heat transfer, maintaining a relatively higher moisture content. Panel (b) shows the stable freezing stage, where the curve demonstrates a gradual change from approximately 0.10% moisture content at 2 m depth to about 0.30% at \(-\)3 m depth. This stage indicates that thermal and moisture migration within the system have reached a relatively stable equilibrium, with the moisture content variations between different depths significantly reduced, resulting in a more stable distribution. Panel (c), representing the thawing stage, shows a more complex curve. Starting from about 0.12% moisture content at 2 m depth, the curve initially rises, forming a small peak of around 0.24% near the 0-m depth, and then gradually decreases to about 0.27% at \(-\)3 m depth. This complex variation reflects the interplay of several factors, such as the uneven temperature gradient and moisture redistribution during the thawing process, leading to non-monotonic changes in moisture content at different depths and significant peak fluctuations at specific depths [3]. Figure 7: The temperature profiles at the center of the slope at different freeze–thaw stages.