土壤热状态是指示多年冻土存在及其热稳定性的最关键指标。为探究黄河源头区冻土热 状态的较长期变化，首先构建了土壤热传导数学模型并基于HYDRUS-1D模型求解，经参数率定 验证，表明该模型具有较好的可靠性和适用性，然后利用中国区域地面气象要素驱动数据集 （CMFD）驱动模拟了黄河源头区6 个钻孔1979—2018 年冻土地温的变化。结果表明，黄河源头区 冻土热状态在1999 年发生转变：1999 年前温度变化速率为-0.037~0.026 °C/a，1999 年后升温速率 为0.006~0.120 °C/a。分析表明1998 年的气候变暖突变及1999 年的极端气候灾害突变是黄河源头 区冻土地温在1999 年发生突变的主要原因；冻土地温升高，冻土热稳定性下降，将深刻影响冻土水 源涵养功能。该研究可厘清高原冻土对气候变化的响应规律，为加强黄河源头区生态环境分区管 控提供科技支撑。

Abstract：The thermal regime of soil is vital for indicating the presence and thermal stability of permafrost. To investigate the long-term changes in the thermal regime of permafrost in the Headwater Area of the Yellow River (HAYR), we first constructed a mathematical model for soil heat transfer to simulate the dynamics of ground temperatures at six boreholes using the HYDRUS-1D model. The reliability and applicability of the model were confirmed through parameter calibration procedures. Subsequently, the changes in permafrost thermal regime from 1979 to 2018 in the HAYR were simulated using monthly air temperature data extracted from the China Meteorological Forcing Dataset (CMFD). The model simulations revealed an abrupt change in mean annual ground temperature in the HAYR after 1999. Prior to 1999, the changing rates were from ?0.037 to 0.026 °C/a, whereas after 1999, they ranged from 0.006 to 0.120 °C/a. The abrupt increase in mean annual air temperature in 1998 and the occurrence of extreme climate disasters in 1999 were identified as the primary reasons for the sudden changes in permafrost thermal regime in 1999. The rise in permafrost temperature and the decrease in its thermal stability are expected to have various impacts on the water resources conservation function and biogeochemical cycle. This study can provide scientific and technological support for clarifying the response patterns of plateau permafrost to climate change and for strengthening zoning and control of the ecological environment in the HAYR.