A two-dimensional (2D) cryo-hydrogeological numerical model of groundwater flow, coupled with advective-conductive heat transport with phase change, has been developed to study permafrost dynamics around an ice-rich permafrost mound in the Tasiapik Valley near Umiujaq, Nunavik (Québec), Canada. Permafrost is degrading in this valley due to climate warming observed in Nunavik over the last two decades. Ground temperatures measured along thermistor cables in the permafrost mound show that permafrost thaw is occurring both at the permafrost table and base, and that heat fluxes at the permafrost base are up to ten times higher than the expected geothermal heat flux. Based on a vertical cross-section extracted from a 3D geological model of the valley, the numerical model was first calibrated using observed temperatures and heat fluxes. Comparing simulations with and without groundwater flow, advective heat transport due to groundwater flow in the subpermafrost aquifer is shown to play a critical role in permafrost dynamics and can explain the high apparent heat flux at the permafrost base. Advective heat transport leads to warmer subsurface temperatures in the recharge area, while the cooled groundwater arriving in the downgradient discharge zone maintains cooler temperatures than those resulting from thermal conduction alone. Predictive simulations incorporating a regional climate-change scenario suggest the active layer thickness will increase over the coming decades by about 12 cm/year, while the depth to the permafrost base will decrease by about 80 cm/year. Permafrost within the valley is predicted to completely thaw by around 2040.

已开发了一个二维（2D）地下水流动的低温水文地质数值模型，并结合了具有相变的对流传导热传输，以研究努纳维克Umiujaq附近Tasiapik谷中富含冰的多年冻土丘周围的多年冻土动力学（加拿大魁北克省。由于过去二十年来在努纳维克观测到的气候变暖，该山谷的多年冻土正在退化。沿永久冻土丘中的热敏电阻电缆测量的地面温度表明，永久冻土台和底部都发生了永久冻土融化，并且永久冻土底部的热通量比预期的地热通量高出十倍。基于从山谷的3D地质模型中提取的垂直横截面，首先使用观察到的温度和热通量对数值模型进行校准。比较有无地下水流的模拟，结果表明，由于多年冻土层中地下水流动而产生的对流热传递在多年冻土动力学中起着至关重要的作用，并且可以解释多年冻土基层的高表观热通量。有利的热传输导致补给区的地下温度升高，而到达降梯度排放区的冷却的地下水保持的温度比仅由热传导产生的温度要低。结合区域气候变化情景的预测模拟表明，在未来几十年中，活动层厚度将增加约12厘米/年，而多年冻土基层的深度将减少约80厘米/年。预计到2040年左右，山谷中的永久冻土将完全融化。地下水在多年冻土层中的流动引起的平流热传递在多年冻土动力学中起着关键作用，可以解释多年冻土基层的高表观热通量。有利的热传输导致补给区的地下温度升高，而到达降梯度排放区的冷却的地下水保持的温度比仅由热传导产生的温度要低。结合区域气候变化情景的预测模拟表明，在未来几十年中，活动层厚度将增加约12厘米/年，而多年冻土基层的深度将减少约80厘米/年。预计到2040年左右，山谷中的永久冻土将完全融化。地下水在多年冻土层中的流动引起的平流热传输在多年冻土动力学中起着关键作用，可以解释多年冻土基层的高表观热通量。有利的热传输导致补给区的地下温度升高，而到达降梯度排放区的冷却的地下水保持的温度比仅由热传导产生的温度要低。结合区域气候变化情景的预测模拟表明，在未来几十年中，活动层厚度将增加约12厘米/年，而多年冻土基层的深度将减少约80厘米/年。预计到2040年左右，山谷中的永久冻土将完全融化。