遥感反演2000—2020年青藏高原水储量变化及其驱动机制

Remote sensing retrieval of water storage changes and underlying climatic mechanisms over the Tibetan Plateau during 2000—2020

气候变化对青藏高原的水储量造成显著影响,严重威胁下游地区涉及10亿人口的水资源安全、水灾害防治和水生态保护。本研究集成多源卫星遥感(包括卫星重力、卫星测高、光学影像等)及相关反演融合算法和部分再分析数据,在前期工作基础上延长并生成了2000—2020年青藏高原各类水储量(湖泊、冰川、雪深和雪水当量、总水储量)变化数据,并分析其气候驱动机制。结果表明:(1)2002—2020年间青藏高原外流区总水储量呈显著下降趋势(-10.90 Gt/a),主要由冰川质量损失主导;内流区总水储量呈显著上升趋势(6.40 Gt/a),其中湖泊水量扩张占主导。(2)青藏湖泊整体呈扩张趋势,并分为3个阶段:2000—2012年为平稳增长期(6.35 Gt/a),2012—2017年为相对稳定期(1.42 Gt/a),2017年后进入快速增长期(10.59 Gt/a);湖泊水量变化与降水量变化一致性较高。(3)藏东南地区的冰川呈快速消融趋势(-4.50 Gt/a),气温升高和降水年际波动是近年来该地区冰川后退的主要原因。(4)2016—2020年平均雪水当量较2001—2015年呈增加趋势,积雪变化主要受累积期平均气温和降水影响。

Climate change has profound impacts on water storage over the Tibetan Plateau(TP).This may seriously threaten freshwater availability,disaster prevention,and ecological integrity for about 1 billion people living downstream.Here we integrate multisource remote sensing(including satellite gravity,satellite altimetry,and optical images)and related algorithms that were developed mostly by the authors to estimate changes in various water storage components over the TP during 2000—2020.Estimated water storage includes lake and glacier storage,snow depth and snow water equivalent,and total water storages(TWS).In addition,we examine underlying climatic mechanisms for these storage changes.Results show that:(1)TWS shows a significant decrease(-10.90 Gt/a)for exorheic TP basins dominated by glacier retreat,but a marked increase(6.40 Gt/a)in endorheic basins reflected mostly by lake expansion in recent decades(2002—2020).(2)Lake storage over the TP shows an increasing trend during 2002—2020,and this trend can be divided into a stable growth period(2002—2012,6.35 Gt/a),a relatively stable period(2012—2017,1.42 Gt/a),and a rapid growth period(2017—2020,10.59 Gt/a).Lake water storage changes show high consistency with precipitation variations.(3)Glacier mass over the Southeastern TP declined rapidly during 2002—2019(-4.50 Gt/a).Rising temperatures and interannual variability in precipitation are the dominate climate factors that resulted in glacier retreat over this region.(4)Annual average SWE during 2016—2020 shows an increasing trend compared to that during 2001—2015.Changes in SWE are affected mostly by average temperature and precipitation during the snow accumulation periods.