青藏高原多年冻土融化及其对湖泊储量变化影响的数值模拟研究

NUMERICAL SIMULATION OF PERMAFROST THAWING AND ITS IMPACT ON CHANGES OF LAKE RESERVES IN QINGHAI-TIBET PLATEAU

纪舒婷

11849078

硕士

环境工程

梁修雨

2020-05-25

2020-07-09

哈尔滨工业大学

深圳

由于全球气候变暖，青藏高原地区的气温以0.3 °C/10a的速度增温。随着气温升高，大量分布在青藏高原地区的冻土逐渐融化，青藏高原多年冻土的面积在过去30年里减少了18.6%。青藏高原分布着大量的内流湖泊，从1980年以来，青藏高原的湖泊面积总体上不断扩大，湖泊总面积已由1980年的4×104 km3增加至2018年的5×104 km3，增加了约25%。呈现扩大趋势的湖泊多分布在青藏高原的内流区，而这些区域也是多年冻土的主要分布地区。青藏高原地区湖泊面积持续增大的现象已引起广泛的关注，针对湖泊面积增大的原因也有大量的研究，但主要集中考虑降雨、蒸散发和冰川等影响因素，而很少考虑冻土融化对湖泊面积增大的影响。为了探究气候变暖条件下，冻土融化与青藏高原湖泊面积（储量）变化的关系，本文选取了青藏高原3个典型大型湖泊：色林错、纳木错和扎日南木错，及1个小型湖泊当穹错为研究对象，基于气象和遥感数据，分别建立了4个流域典型剖面的变密度地下水及热量运移的耦合模型，模拟了1982 ~ 2011年冻土融化过程，定量估算了冻土融化对湖泊储量的贡献，预测了考虑气温持续升高条件下未来100年冻土融化及其对湖泊储量的影响。结果表明：在气候变暖的背景下，1982 ~ 2011年青藏高原4个湖泊流域的多年冻土均存在不同程度的退化，活动层厚度经历了先变大后又减小的过程，融区逐渐形成并不断扩大，最厚可达32 m；4个流域内地下水均流入湖泊，地下水年均入湖量约占湖泊年均补给量的5.72% ~ 16.37%，随着冻土逐渐融化，地下水入湖量逐渐增大，至2011年最大增长了3.5倍；通过未来100年情景预测，若维持气温增长率，多年冻土将经历更加剧烈的退化，融区最深可达68 m；且未来冬天只有地表至地下5 m以上的区域会产生季节性冻结，地下水入湖排泄量将不断增加，地下水入湖量对湖泊补给的贡献率达到22.31%。

Due to global warming, the temperature of the Qinghai-Tibet Plateau (QTP) is also increasing at a rate of 0.3 °C/10a. As the temperature is rising, a large amount of permafrost distributed in the QTP gradually thawed, and the area of permafrost in China has decreased by 18.6% during the past 30 years. There are a large number of inflow lakes on the QTP, but the lake area of the QTP has generally expanded since 1980, and the total area of lakes on the QTP has increased from 40,000 km3 in 1980 to 50,000 km3 in 2018, an increase of about 25%. The lakes showing an increasing trend are mostly distributed in the inner area of the QTP, that is, areas where permafrost is widely distributed. The continuous increase of lake area in the QTP has attracted wide attention, and there are many studies concentrating on research of its reasons, but most of them are paying more attention on the factors like precipitaion, evaporation, and glacial melting, and the influence of permafrost melting is given less consideration. In order to explore the relationship between the degradation of permafrost and the changes in lake area (reserves) on the QTP under the impact of climate change, this paper chose three large lakes Selinco, Namco, Zhari Namco and a small lake Dangqiongco as study areas. Based on meteorological data as well as remote sensing data, four typical cross-sections of lake basins were established respectively, which coupled variable density groundwater and heat transfer, simulating the process of permafrost melting from 1982 to 2011, evaluating the contribution of permafrost melting to the lake reserves quantitatively, and predicting the influence of permafrost melting on lake reserves in the next 100 years under the condition of continuous temperature growth. Through simulation and analysis, this article mainly draws the following conclusions: under climate change, the permafrost in four basins in QTP degraded consistently during 1982 to 2011, and during this time the thickness of active layer experienced a process of increasing and then decreasing, and the talik emerged and then kept expending, which can up to 32 m; The groundwater of these four basins all entered the lakes, and the discharge of groundwater accounted for 5.72% ~ 16.37% of the average annual lake recharge; With permafrost gradually thawing, the discharge of groundwater kept growing, which has increased by 3.5 times until 2011; According to the scenario prediction in the next 100 years, if the temperature growth rate is unchanged, the permafrost will undergo more severe degradation, and the thickness of talik can reach 68 m, and in the future, only the area from land surface to 5 m above will seasonally freeze in winter, and the discharge of groundwater into the lake will continue to increase. As a result, the contribution of groundwater into the lake to the water balance of the lake will reach 22.31%.

气候变化 青藏高原 湖泊储量 冻土退化 地下水补给 水流-热量耦合模拟

climate change Qinghai-Tibet Plateau water storage permafrost degradation groundwater discharge water and heat coupled modeling

中文

联合培养

南方科技大学

纪舒婷. 青藏高原多年冻土融化及其对湖泊储量变化影响的数值模拟研究[D]. 深圳. 哈尔滨工业大学,2020.