青藏公路沿线热喀斯特湖分布特征及其热效应研究

Distribution of Thermokarst Lakes and Its Thermal Influence on Permafrost along Qinghai-Tibet Highway

热喀斯特湖的出现和发育是多年冻土变暖的指示器,研究热喀斯特湖发育及其热效应是应对青藏高原气候变化和人类活动诱发冻土灾害的基础工作。基于SPOT-5卫星影像资料,在ArcGIS平台下解译遥感影像,获取了青藏公路沿线楚玛尔河至风火山段热喀斯特湖的数量和分布特征,这些热喀斯特湖以楚玛尔河高平原和北麓河盆地为主要分布区,且80%发育于高含冰量多年冻土区。热喀斯特湖通过竖向和侧向2种传热方式影响多年冻土,竖向传热会造成其下部多年冻土融穿,侧向传热会造成湖岸多年冻土增温,扩大热影响范围。通过北麓河地区一典型热喀斯特湖的数值计算,湖全年都在向湖岸放热。当热喀斯特湖离路基较近,将会对公路产生潜在或者直接的危害,其侧向热侵蚀往往会导致冻土路基温度升高,诱发路基病害。

The occurrence of thermokarst lake is an indicator implying the permafrost warming. A study of thermokarst lake and their thermal effect will become an important basic work that responds to the permafrost haz- ards induced by the climate changes and the anthropogenic activities on the Qinghai-Tibet Plateau. Based on SPOT- 5 satellite image data, we interpreted and obtained the area and quantity of thermokarst lakes from Chumaerhe to Fenghuoshan Mountain section along the Qinghai-Tibet Highway under the ArcGIS platform in this paper. The re- sult shows that these thermokarst lakes have mainly spread in Chumaerhe High Plains and Beiluhe Basin and ap- proximately 80% lakes have been developing in rich-ice permafrost regions. The thermokarst lake influences the permafrost through downward and lateral heat transfer. The downward heat transfer accelerates the thawing of per- mafrost and the formation of an open-talik, the lateral heat erosion will cause the permafrost warming at lakeshore and expand the scope of the heat-affected. The modeled result of a typical thermokarst lake in Beiluhe Basin shows that the lake has always released the heat to lakeshore in a whole year. If the thermokarst lake is close to the road- bed, it will cause influence on the stability of roadbed, especially the lateral thermal erosion often leads to the tem- perature increases of frozen soil subgrade and induces the embankment disease.