High-Temporal-Resolution Modeling of Land Surface Temperature and Groundwater Level Impacts on Shallow Aquifer Thermal Regimes

Climate change is recognized to directly and indirectly affect groundwater systems. However, the mechanisms through which climate change influences groundwater temperature (GWT), particularly how seasonal variations mediate these effects, remain incompletely understood. This study utilized high-temporal-resolution (hourly) data by parameterizing groundwater levels (GWLs) and instantaneous temperature gradients to model GWT, establishing the Seasonally Adaptive Thermal Diffusivity Numerical Model (SATDNM). Through scenario analyses, the potential impacts of climate change on GWT were simulated. The results indicate that our model captures seasonal and interannual variations more precisely compared to classical models, revealing the seasonal influence of GWLs and instantaneous temperature gradients on subsurface thermal properties such as advents and wet-season rainfall, as well as long-term surface warming and GWL decline. The key findings include (1) a greater sensitivity to extreme heat during winter, (2) wet-season rainfall potentially stabilizing groundwater temperature, and (3) declining GWLs amplifying GWT fluctuations. By 2100, the projected mean GWT increases under four Shared Socioeconomic Pathway (SSP) scenarios are approximately 0.51 °C (SSP1-2.6), 1.25 °C (SSP2-4.5), 2.19 °C (SSP3-7.0), and 2.87 °C (SSP5-8.5). Under four scenarios of annual GWL decline rates, GWT fluctuations increased by approximately 0.094 °C (0.01 m/year), 0.27 °C (0.02 m/year), 0.44 °C (0.03 m/year), and 0.67 °C (0.04 m/year), respectively. These findings enhance the mechanistic understanding of climate–groundwater thermal interactions and provide new insights for adaptive groundwater management under climate change.