Engineering carbon emissions induced by permafrost degradation and mitigation strategy: Insights from the Qinghai–Tibet Highway

Permafrost degradation and its’ carbon feedback is an important issue in global carbon cycle. However, the engineering carbon emissions of infrastructure caused by permafrost degradation remain a critical but poorly constrained variable. In this study, the degrading rate of permafrost along the Qinghai–Tibet Highway (QTH) was simulated using a hydro-thermo-vapor coupled model. Based on the lifespan replacement model and the emission factor method, the engineering carbon emissions caused by permafrost degradation were quantified, the mitigation effect of various cooling embankments was evaluated, and a low-carbon strategy was proposed. The results indicate that, the permafrost table beneath the QTH remarkable declines with an average rate of 30.1 cm per year from 1985 to 2035. Affected by permafrost degradation, the engineering carbon emissions in this period amount to 5.16 Mt. Aiming to low emissions, the cooling measures have been optimized for each section, and the optimization strategy can reduce the emissions by 59.3%. The engineering emissions account for 27.3% of the decomposed SOC from thawed permafrost and 82.2% of carbon emissions from thermokarst lakes along the QTH, which are substantial. This study underscores the imperative of embedding engineering carbon emissions into regional carbon budgets to advances our understanding of permafrost carbon feedbacks and guide low-carbon adaptation for permafrost infrastructure under climate warming.