青藏工程走廊热融湖湖底热状态

热融湖塘对寒区环境可产生较大影响, 其侧向热侵蚀会诱发冻土工程病害.选取青藏工程走廊热融湖塘分布密集的楚玛尔河、五道梁、北麓河3个亚区, 于2009—2010年通过HOBO水位传感器对4个固定湖塘的连续监测和大量湖塘的随机观测, 探讨了不同季节、不同水深湖底的热状态.在结冰期的1月中旬, 楚玛尔河90%以上的湖塘湖底温度都在0 ℃以下, 主要与湖塘较浅和湖水高矿化度有关.五道梁和北麓河湖底温度相对较高, 只有约20%的湖底温度低于0 ℃, 这些湖水深小于最大冻结冰层厚度; 最高温度高于4 ℃, 主要与湖较深有关.但3个亚区湖底温度均随着水深增加而增加.在6~9月融冰期, 湖底温度普遍增加, 最高达到18 ℃以上, 浅湖增温快于深湖, 湖底温度随着水深增加而递减.湖底温度年际变化近似为正弦曲线, 在1~2月, 湖底温度最低, 之后逐渐升高, 到7~8月, 湖底温度达到最高. 

Thermal Regime at Bottom of Thermokarst Lakes along Qinghai-Tibet Engineering Corridor

Thermokarst lakes have greatly influenced landscapes in cold regions, and the thermal erosion of their lakeshores may induce ground instability that affects infrastructure. Our study area includes three sub-regions where thermokarst lakes have obviously extended: the Chumaerhe high plateau, Wudaoliang basin, and Beiluhe basin. Based on continual monitoring of four lakes, and sporadic observation of lake-bottom temperatures of many lakes using HOBO Sensors in 2009—2010, the thermal regime of lake bottoms and the relation between lake-bottom temperature and water depth are examined. The results show that in January, when ice cover was present, the lake-bottom temperatures at 90% of the lakes in Chumarhe high plateau were below 0 ℃, which is likely because of shallow depths and high salinity of lakes in the region. However, the lake-bottom temperature of most lakes in Wudaoliang and Beiluhe basins were above 0 ℃, except in some lakes shallower than the maximum ice thickness. In general, lake-bottom temperature in the three sub-regions increased with water depth during this period. When lakes were free of ice between June and October, the lake-bottom temperatures in the three sub-regions were all warm and the highest temperature was near 18 ℃. The seasonal increase in lake-bottom temperature in summer is more rapid in shallower lakes, and the temperatures were inversely related to water depth. The annual variation in lake-bottom temperature approximates a sinusoidal curve, with the coldest temperature occurring in January to February and the warmest in July to August.