气候变化下的青藏高原冻土脆弱性区域模拟研究

Permafrost and seasonally freezing ground play a crucial role in the land surface system of the Tibetan Plateau (TP) due to the close associations between the freezing ground and the energy/water balances over land surface. However, it is quite difficult to accurately project the stability and trend of the TP permafrost due to its high spatial heterogeneity...Therefore, this study is to investigate the stability and vulnerability of the TP permafrost under current and future climate changes. To address this issue, one process-based permafrost model (the Geophysical Institute Permafrost Lab, GIPL2.0) will be improved according to the in-situ observed thermal-water features of the TP permafrost. To simulate the permafrost process and variation of the whole TP using the improved permafrost model, the in-situ and multiple satellite observation will be integrated to construct the grid-based (1-km) parameters and driving-variables for the GIPL2.0 model in the TP. The future scenario of land surface temperature and soil moisture will be designed based on the actual surface conditions during the last five years. Then the improved GIPL2.0 will be run to map the permafrost and stability for the whole TP. The permafrost vulnerabilities will also be projected under different climate scenarios. These simulations can clarify the trend of TP permafrost and its response to climate changes. With the method of vulnerability evaluation put forward by IPCC, the simulated characteristics of permafrost and seasonally frozen ground in TP will be detailedly investigated. Therefore, this study will improve our understanding of the mechanism of TP permafrost in response to climate change, and thus help human in the TP and neighboring regions to well adapt to these changes.

冻土，是青藏高原地表系统中的一个关键因子，同近地表水热平衡互为因果紧密耦合，使得地表系统对气候变化的响应更为敏感和复杂。在当前气候变化下，青藏高原冻土呈区域性退化趋势，但由于其空间分异强烈，在区域尺度上详尽地辨析其对气候变化的脆弱性，具有较大难度。.. 为此，本项目将针对气候变化下的青藏高原冻土脆弱性：1)结合冻土水热过程观测和一个高纬点尺度冻土模型，构建青藏高原区域冻土模型；2)利用融合的地面和多源遥感观测资料，模拟青藏高原详尽的冻土空间分布及变化等特征因子；3)并借鉴IPCC脆弱性框架，设计基于冻土模拟及遥感观测的冻土脆弱性评价方案，旨在：据此评估当前及气候情景下青藏高原的冻土脆弱性，以增强对青藏高原冻土变化的理解及适应能力。该研究工作，将增强对气候变化下青藏高原冻土稳定性和脆弱性的理解，帮助科学判断其未来趋势，有助于提高对冻土变化环境效应的适应性。

本项目根据申请内容和任务书，研究了科学问题——“气候变化下的青藏高原冻土脆弱性”，在区域尺度上研究青藏高原冻土在气候变化形势下的脆弱性及环境效应：1）结合当前气候形势下的近地表土壤热状态变化，选择冻土面积比重差异显著的两个典型寒区流域，对比分析其径流演变特征，探讨了冻土水文对气候变化的响应规律；2）并利用PWBM和VIC两个陆面水文模型，评估了气候情景下研究区冻土水文过程的未来可能变化；3）基于星地多源观测资料，剖析了研究区内近地表土壤的冻融过程；4）改进冻土过程模型PWBM，探究了环境条件对土壤冻融过程的影响；5）结合过程模型和卫星遥感反演，分析评估了长江源区冻土特征及变化。..本项目研究，揭示了青藏高原典型寒区流域的冻土水文对气候变暖响应敏感，并且同冻土覆盖面积比重紧密关联。因此，在分析评估气候变化形势下的青藏高原水文水资源变化时，应重视和充分考虑流域冻土特征及变化，有助于提高对径流及水资源变化情势的适应性。强调了土壤水分在冻土敏感性评估中的重要性，有助于增强对青藏高原近地表土壤冻融机制的理解，为预估青藏高原冻土对气候变化敏感性及其对水文生态等过程的影响提供了方法支撑。