基于大地测量方法研究南极冰盖底部质量变化

In the past few decades, domestic and foreign had done the massive research on mass balance of Antarctic ice sheet, the results show that the factor that the basal ice flux beneath ice sheet is the biggest uncertainty and the least understood in study of Antarctic ice sheet mass balance. For now, due to the limited of the development level of observation techniques and the special circumstances in Antarctic, researches in this respect only in typical ice shelf. Against this background, this project brings forward the scientific proposition of "investigation on the basal mass variations beneath Antarctic ice sheet using the method of geodesy", it aims at the study of the forward and inversion theoretical method between potential field variations and ice sheet mass variation; refining and assimilating the multi-source and multi-generation satellite altimetry and satellite gravity data; meanwhile, extracting the geometrical and physical factor of ice sheet mass change and finding the main influencing factor of mass variations beneath ice sheet, then detecting the basal mass variations using satellite gravity and altimetry from geometric and physical aspects respectively, so that breaking through the quantitative evaluation of basal mass variations beneath Antarctic ice sheet "bottleneck" . What's more, the project will obtain and analyze the mass variation rate and spatial/temporal distribution of bottom of Antarctic ice sheet, and set up a complete academic system of study basal mass change beneath ice sheet based on geodesy. As a consequence, the program will provide high-quality data source for determine the direct contributions of basal mass variations in ice sheet mass balance, and enhance understanding of the mechanism underlying and the correlation between polar ice sheet and sea level change.

国内外对南极冰盖物质平衡做了大量研究工作，表明冰盖底部通量是南极冰盖物质平衡研究中最大的不确定性，也是目前了解最少的分量，限于技术及南极特殊环境，目前研究仅在典型冰架进行。在此背景下，本项目提出用大地测量手段研究南极冰盖底部质量变化这一科学命题，旨在通过深入研究重力位场变化与南极冰盖质量变化的正反演理论与方法，精化和融合多源卫星测高、卫星重力资料，提取冰盖质量变化几何与物理因子，分离冰盖底部物质变化的主要影响因素，从几何与物理角度综合利用卫星重力、卫星测高等空间大地测量技术突破定量评估南极冰盖底部质量变化瓶颈，开展冰盖底部质量变化的重力位场反演与解释，分析南极冰盖底部质量变化速率及时空分布，形成大地测量研究冰盖底部质量变化较为完整的理论体系。为揭示南极冰盖底部冻融过程对南极冰盖质量平衡的直接贡献提供高质量的数据源，提升对极地冰盖变化与全球海平面变化的相互关系及其内在机理的科学认识。

本项目研究利用大地测量手段探索南极冰盖底部质量变化，深入研究了重力位场变化与南极冰盖质量变化的正反演理论与方法，提出了综合利用GRACE卫星重力、ICESsat卫星激光测高等空间大地测量数据，估算南极冰盖底部质量变化的两种方法。提出了基于GRACE数据反演陆地型冰川质量变化的块域拟合法和块域正演迭代法。首次将Slepian空间谱集中法应用于求解南极冰盖质量变化。基于MODIS卫星遥感数据以及降雪量、风速等资料，研究构建了南极表层粒雪密度改进模型。基于GRACE数据研究构建了新型大尺度重力场时变统一模型。提出了联合GRACE、ICESat、GPS等数据分离南极冰川均衡调整(GIA)信号方法，构建了南极GIA改正模型。研究分析了ICESsat卫星激光测高各项误差对估算南极冰盖表层质量变化的影响，以及GRACE卫星重力各项误差对估算南极冰盖整体质量变化的影响。利用2003-2010年间（ICESat与GRACE在轨重合时间段）的数据资料推算得到南极冰盖底部质量变化，分析了底部质量变化速率及时空分布。为揭示南极冰盖底部冻融过程对南极冰盖质量平衡的直接贡献提供可靠的科学参考，提升对极地冰盖变化与全球海平面变化的相互关系及其内在机理的科学认识。