Numerical Simulation of Thaw Settlement and Permafrost Changes at Three Sites Along the Qinghai‐Tibet Engineering Corridor in a Warming Climate

Thaw settlement caused by permafrost degradation has great impacts on engineering infrastructure, hydrological cycles and ecosystems in recent decades under climate warming. We combined the moving‐grid method (Lagrangian method) with the heat conduction equation to develop a new moving‐grid permafrost model. Our model takes into account not only the cryostratigraphy of permafrost, but also the thaw settlement. We used the model to simulate the thaw settlement and the permafrost changes at the three sites along the Qinghai‐Tibet Engineering Corridor from 1966 to 2018. The monitoring of the ground temperature and the geodetic leveling in situ were used for model validation. The results show that our model can accurately reproduce the observed interannual thaw settlement and ground temperature fields. The risk of thawing settlement in ice‐rich permafrost regions in the zero‐temperature‐gradient stage is high. Plain Language Summary Under climate warming, the thawing of permafrost in Arctic and alpine mountain has induced ground surface settlement (thaw settlement). Thaw settlement may lead to geologic hazards damaging engineering foundation and changing local hydrological cycles and ecosystems. It is essential to accurately assess permafrost changes and thaw settlement by models. Few current permafrost simulations, however, take thaw settlement into account. We developed a new permafrost model based on the moving‐grid method. Our model can quantitatively assess not only permafrost changes but also associated thaw settlement. We used the new model to simulate the permafrost changes and the thaw settlement at three sites along the Qinghai‐Tibet Engineering Corridor (Qinghai‐Tibet Engineering Corridor) over a span of 50 recent years. The monitoring of the ground surface settlement and the ground temperatures in nearly a decade from the three sites were used to validate the simulated results. The simulated results were well consistent with the observations, which indicated that our model could capture thaw settlement processes and permafrost changes in a warming climate. The simulation results show that those permafrost regions with slowly rising ground temperature but quickly ground ice thawing may have a great risk of thawing settlement. Key Points We develop a new moving‐grid permafrost model taking thaw settlement into account based on the Lagrangian moving‐grid method Thaw settlement and permafrost changes at the three sites along the Qinghai‐Tibetan Enginee