| 摘要: |
| 全球增温导致青藏高原湖泊热力学特征发生显著变化，对于湖泊生态系统和水质变化具有重要影响。本研究以西藏第一大湖—色林错为研究对象，开展了连续的湖泊水温和气象观测，揭示了色林错年内热力学动态变化特征以及对气象条件的响应过程。结果表明：基于2021年6月至2022年12月水温剖面的连续观测，显示色林错属于双对流混合型湖泊，热力学状态可分为冬季结冰期（12月初至次年4月底）、春季混合期（4月中下旬至5月中旬）、夏季分层期（5月中旬至11月中旬）和秋季混合期（11月中旬至12月中旬）四个阶段。色林错于结冰期（3月中旬）开始进入热力学分层状态，随着冰面融化，进入湖水的辐射增强以及高盐度导致冰下水体快速稳定分层，表层水体得以快速升温。但色林错可能由于盐度梯度的存在，整个水柱在春季未发生完全混合，混合现象只局限在表层0-30 m的水体，底部水体一直保持缓慢的增温现象。色林错湖泊稳定度指标施密特稳定度（Schmidt Stability）变化范围为0至520J/m2。从温跃层的特征来看，2021年和2022年温跃层的变化规律非常相似，夏季分层期温跃层最大深度在17 m左右。风速与净辐射对于色林错不同时期热分层的驱动机制不同，风力和辐射在形成期共同主导了热分层的形成，而辐射减弱是导致热力学分层消失的主要原因。通过对比分析发现，气温变化相比较于表层水温变化幅度更大，表层水温滞后于气温21天左右。本研究首次开展了色林错湖水热力学特征及其影响因素研究，为深入理解青藏高原内陆湖泊水温变化及对区域气候变化的响应和湖泊模型研究提供了科学依据。 |
| 关键词: 热力学分层 水温变化 双循环湖泊 青藏高原 色林错 |
| DOI： |
| 分类号: |
| 基金项目: |
|
| The seasonal variations on thermodynamics in Selin Co, the largest lake in Southern Tibetan Plateau: dimictic and its influencing factors |
|
Qin Xuan1, Wang Junbo2, Ye Chuanyong3, Kai Jinlei4, Wang Hua4, Wang Zha5, Ju Jianting4, Zhu Liping4
|
|
1.School of Ecology and Environment,Tibet University;2.Institute of Tibetan Plateau Research Chinese Academy of Sciences;3.Institute of Mineral Resources，Chinese Academy of Geological Sciences;4.Institute of Tibetan Plateau Research, Chinese Academy of Sciences;5.School of Ecology and Environment, Tibet University, Lhasa 850000, P.R.China
|
| Abstract: |
| Global warming has led to significant changes in the thermodynamic characteristics of lakes on the Tibetan Plateau, resulting in vital impact on lake ecosystem and water quality changes. In this study, continuous observations of lake water temperature and meteorological conditions were carried out in the largest lake—Selin Co, Tibet, the characteristics of intra-annual thermodynamic dynamic of Selin Co and its responding to meteorological conditions are revealed. The results show that Selin Co is a dimictic lake based on continuous observations of water temperature profiles from June 2021 to December 2022. The thermodynamic state can be divided into four phases: winter freezing, spring mixing, summer stratification and fall mixing. Selin Co starts to stratify during the freezing period (mid-March). The melting of the lake ice, the enhanced radiation penetrating the ice and the high salinity resulted in a rapid and stable stratification of the water column under the ice. However, Selin Co did not undergo complete mixing of the water column in the spring, probably due to the salinity gradient, and the mixing phenomenon was confined to the surface 0-30 m, with the bottom waters remaining slowly warmed.The Schmidt Stability ranged from 0 to 520J/m2 in Selin Co. From the characteristics of the thermocline, the daily variation patterns of the thermocline in 2021 and 2022 are very similar, with the maximum depth of the thermocline around 17 m during the summer stratification period. Wind speed and radiation have different driving mechanisms for thermal stratification during different periods. Wind and radiation contribute concurrently to thermal stratification during the formation period, and weakening radiation being the main cause of the disappearance of thermodynamic stratification. Comparative analysis showed that air temperature changes were more variable than surface water temperature, which lagged air temperature by about 21 days. This study conducted the observation and research on the thermodynamic characteristics of Selin Co and its influencing factors for the first time, providing a scientific basis for an in-depth understanding of the changes in water temperature of inland lakes on the Tibetan Plateau and their response to regional climate change, as well as lake modeling research. |
| Key words: Thermal stratification Water temperature variations Dimictic lake Tibetan Plateau Selin Co |
