TY  - JOUR
AU  - Ji, Hailong
AU  - Nan, Zhuotong
AU  - Chen, Yuhong
AU  - Chen, Lihua
AU  - Zhao, Shuping
ID  - ref1
ER  - 
TY  - JOUR
PY  - 2026
DA  - 2026//
TI  - Reassessing Alpine Permafrost Thermal State by Accounting for Ground Ice
JO  - Earth's Future
SP  - e2025EF007931
VL  - 14
IS  - 8
AB  - Abstract Permafrost thermal state, representing the stored “cold energy” in the ground, is crucial for assessing permafrost changes. However, the conventional metric, mean annual ground temperature (MAGT), has inherent limitations because it overlooks the thermodynamic contribution of ground ice. To address this, we developed an alternative metric based on enthalpy change (ΔH′), which integrates ground temperature and ice content. Using a process-based model, we designed controlled warming experiments to evaluate the performance of the two metrics. The results show that permafrost traditionally classified as “unstable” (MAGT between −0.5 and 0°C) can persist for 30–100 years under an air warming rate of 0.4°C per decade, largely due to variations in ground ice content. Compared with MAGT, ΔH′ provides a more uniform scale and higher discernibility in indicating potential permafrost duration, and is therefore more suitable for representing permafrost thermal state. Furthermore, using high-resolution gridded data sets, we mapped permafrost thermal state across the Qinghai-Tibet Plateau (QTP) and quantified the spatial discrepancy between the two metrics. The results indicate that permafrost on the western QTP is less stable than suggested by MAGT, whereas permafrost in the southeast and around lakes in the endorheic basins is more stable than MAGT estimates. Explainable machine-learning analyses reveal that precipitation, soil coarse fraction, and solar radiation are the primary factors controlling the spatial heterogeneity of this discrepancy. This study highlights the dominant role of ground ice in regulating permafrost thermal state and calls for greater attention to ground ice in future permafrost projections.
UR  - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2025EF007931
ID  - ref2
ER  -