冰川变化及其水文效应的模型集成研究—以长江源区冬克玛底冰川为例

Glacier, as the solid reservoir, has larger runoff coefficient than non-glacier areas. And more importantly, glacier regulates runoff temporal variation, by storing snowfall in wet years and releasing the melting water in dry years. However, climate change results in severe glacier retreat and glacier mass balance loss, which significantly impact the amount of glacier runoff and its function to regulate precipitation fluctuation, and increase the risk on water security in downstream. The systematic and integrated modelling framework of “climate change – glacier mass balance loss – glacier area and volume change – hydrological effect” is vital to improve our understanding and predicting the impact of climate change on glacier variation and water resources. In this project, we intend to select the Dongkemadi Glacier in the headwater of Yangtze River as a case study, to conduct the following research: 1) based on the FLEXG model, which was developed by the applicant, to couple the glacier mass balance model in the FLEXG with 5 glacier response models, to simulate the “climate change-glacier variation-hydrological effect” system; 2) with the integrated model, to predict the effect of climate change on glacier variation and its impact on hydrology in the Dongkemadi Glacier River basin; 3) to systematically estimate the uncertainty of glacier response models, expecting to optimize a model which has the potential to be used in large scale and ungagged basins. This study will deepen our understanding of the mechanism of “atmosphere-glacier-hydrology” coupling system, allowing us to predict the impact of climate change on glacier variation in the inner Tibetan Plateau and its impact on water resources, and eventually benefit decision making on the adaption of climate change and its effect on water resources management in Western China.

冰川作为固体水库，不仅产流系数远高于非冰川区，还具有调丰补枯的作用。气候变化导致的物质平衡损失及面积变化，严重影响了冰川融水对河川径流的补给和调节作用。因此“气候变化-冰川物质平衡变化-冰川形态与面积变化-冰川融水径流变化”的集成模拟，对科学认识和预估气候变化对冰川和水资源影响起着关键作用。本项目拟以长江源区冬克玛底冰川为研究区①基于申请人自主研建的冰川水文模型FLEXG，进行“气候-冰川-水文”模型集成研究，重点放在把FLEXG中的冰川物质平衡模型与5种冰川响应模型进行无缝连接；②采用集成模型对冰川未来变化以及融水拐点出现时间进行预估；③系统分析冰川响应模型的不确定性，以期优化出适合大尺度推广和缺资料地区应用的模型。该研究将有助于我们进一步科学认识“气-冰-水”变化机制，预估气候变化对青藏高原核心区冰冻圈及水资源的影响，为气候变化适应性决策和西部水资源管理和调控提供科学支撑。

科学认识和预估气候变化对冰川和水资源影响对我国气候变化适应性决策和西部水资源管理调控有重要意义。“气候变化-冰川物质平衡变化-冰川形态与面积变化-冰川融水径流变化”集成模型，为冰冻圈水文模拟提供了重要科学工具。依托本项目取得的主要成果有：1）自主研发了冰川水文与冰川响应耦合模型FLEXG-Δh，并成功应用于乌鲁木齐河源1号冰川和青藏高原冬克玛底冰川流域模拟，采用最新的气候变化CMIP6多模型预估结果，预估了未来流域水资源峰值出现时间。成果发表在一区期刊STE，被IPCC海洋和冰冻圈特别报告引用。2）冰川积雪遥感信息有效减少了水文模型不确定性，对无/缺资料地区的水文模拟有重要的辅助作用；3）原创性地从生态水文视角基于新的地形指数HAND，提出了新的地形驱动水文模型HSC。HSC模型通过简单而具有大样本生态观测数据支持的假设，建立了以地形为基础的土壤含水量和变源产流面积间的非线性关系。新模型不仅无需率定产流参数，还可以模拟变源产流面积的空间和时序变化，而且在模拟效果上比传统模型有明显改进。