【作者】 黄海兰；

【导师】 晁定波； 李建成；

【作者基本信息】 武汉大学 ， 大地测量学与测量工程， 2011， 博士

【摘要】 全球气候变化是大气和海洋科学以及固体地球物理学等的交叉研究领域。评价地球如何随着全球变暖而变化,一个有效可行的方法是研究极地冰盖的变化以及冰盖与海洋和大气之间的相互作用。冰盖消融是影响全球气候变化的重要因素,研究表明冰盖的演化对全球海平面变化有较大的影响,这种影响目前表现为平均海面上升,正在威胁人口集中的沿海陆地和南太平洋某些岛国的生存环境。尽管较大范围的融化不会马上来临,但是冰盖的持续变化影响着全球气候变化的进程和全球的温室效应。冰盖和海洋之间的年质量交换大约相当于全球海平面高度的8mm的海水质量,因此即使是小的质量交换比率的变化也是很重要的。1992年IPCC(政府间气候变化专门委员会)关于气候变化的科学评估增刊中谈到,关于海平面高在认识上最大的不确定性,在于未能充分理解反映气候变化,同时也影响海面高预测的极地冰盖。美国国家科学院(1990)也指出,格陵兰岛和南极冰盖质量平衡中的变化是我们了解全球气候变化和海平面升高的关键,也是海平面高预测量化和精化的关键。由于冰盖质量平衡的不确定性直接影响全球海面变化率的不确定性,因此,极地冰盖的量化监测和评估非常重要。研究冰盖对于气候变化的响应需要高精度的观测数据集和均衡的冰面覆盖。ICESat激光测高卫星是NASA对地观测系统的一部分,ICESat卫星上的地学激光测高系统可以年际和长时间尺度监测极地冰盖高程变化,量化极地冰盖质量变化和质量平衡的改变。本论文主要研究内容为利用ICESat激光测高卫星观测数据联合GRACE卫星重力数据研究年际和长周期的极地冰盖变化,探讨极地冰盖总量平衡和对海平面变化的贡献；获取预测冰盖总量和海平面变化所需的关键数据；研究质量平衡改变的原因以及它们对全球海平面和全球气候变化的影响。本文的主要研究内容和成果包括：(1)从全球气候变化、海平面上升及冰盖冰川消融三者的关系出发,综述了冰盖冰川的消融现状及南极洲和格陵兰岛冰盖的质量平衡进程,阐述了监测冰盖表面高程及质量变化的相关技术和方法；(2)总结和评述了ICESat激光测高技术的应用及ICESat卫星的在轨性能,分析了激光测高监测冰盖表面高程变化的优势,对ICESat上搭载的唯一有效载荷即地学激光测高系统(GLAS)的波形和测高精度进行了分析；分析了激光测的误差来源,及相关地球物理改正；(3)详细描述了GRACE数据产品构成,总结并研究了利用GRACE时变重力场反演地球表面质量变化的基本理论；(4)研究并实施了ICESat卫星激光测高数据预处理,给出了交叉点计算方法,获得了“净化”的可靠数据集；(5)较系统地研究了三种数据内插方法,包括Shepard方法和连续曲率张力样条法及Kriging方法,利用实测数据,通过对三种内插方法的多项实例分析比较,提出确认连续曲率张力样条方法更适合于极地冰盖数据的内插；(6)利用交叉点计算得到的高程差与时间差的导数计算平均高程变化率,分析了冰盖变化趋势,探讨了影响冰盖高程变化的因素；(7)利用GRACE卫星观测数据反演了南极洲和格陵兰岛冰盖的质量变化,分析了冰盖质量变化的时间特征及其与气候变化的关系；(8)对比分析了ICESat数据与GRACE数据所得极地冰盖变化结果,揭示了极地冰盖质量平衡与全球海平面变化之间的相关性。综上所述,本文的主要研究成果包括：ICESat激光测高数据的预处理技术；数字地面高程模型的高精度插值方法；基于ICESat测高数据建立了极地高精度高分辨率冰面数字高程模型；基于交叉点算法获取了极地冰盖高程变化时间序列；利用GRACE时变重力位模型反演了极地冰盖质量变化；对比分析ICESat与GRACE数据所得极地冰盖变化结果；揭示了极地冰盖质量平衡与全球海平面变化之间的相关性；研制了可联合卫星重力数据和激光测高数据推求极地冰盖变化与水质量变化的多功能软件系统。更多还原

【Abstract】 Climate change studies require scientific evidence from a network of atmospheric and oceanic sciences as well as solid earth geophysics. One possible way to assess how the Earth changes due to global warming is by studying ice sheet changes and the interaction among ice sheet, ocean and atmosphere. Melting of ice sheet is a key factor which influences the global climate change. Research has showed that the evolution of ice sheet, which now has been making the mean sea level rise and severely threatening the continent where human survive, has major effect on global sea level change. Although major melting is not imminent, the continuous changes of ice sheets impact on the processes of global climate change and greenhouse effect. Since the annual mass exchange between the ice sheets and the ocean is about 8 mm/year of global sea level equivalent, small changes in this rate are significant.1992 IPCC Supplement on Scientific Assessment of Climate Change noted that the largest uncertainty about sea level is "rooted in our inadequate understanding of polar ice sheets whose response to climate change also affects predictions of sea level rise". The National Academy of Sciences(1990) stated "possible changes in the mass balance of the Greenland and Antarctic ice sheets are fundamental gaps in our understanding and are crucial to the quantification and refinement of sea-level forecasts". Quantifying the state of the polar ice sheet is of great importance since uncertainty in ice sheet mass balance directly affects uncertainty of the global sea level change rate. Studies on ice sheet response to climate change require data sets with high accuracy and uniform ice-sheet coverage.The Ice, Cloud and land Elevation Satellite (ICESat), as part of NASA’s Earth Observing System program to study the Earth atmosphere and cryosphere, was launched in Jan 2003. The GLAS(Geoscience Laser Altimeter System) on the ICESat can determine the inter-annual and long-term changes in polar ice sheet mass, and quantify the change of polar ice sheet mass and its equilibrium. The aim of this dissertation is to investigate the inter-annual and long-term changes of polar ice sheets and the contribution of the total mass balance of polar ice sheets to global sea level rise using combined ICESat observation data and GRACE gravity data; to obtain key data necessary for predicting the change of total ice sheets mass and the change of sea level; and to investigate the causes of changes in mass balance as well as their impacts on global sea level and global climate.Main contents and achievements of this paper include:(1) Originating from the relationships among global climate change, sea level rise as well as ablation of ice sheets and glaciers, ablation status of ice sheets and glaciers, together with ice sheets mass balance progress in Anactica and Greenland, has been illustrated in detail, and techniques of monitoring surface elevation change and quality change of ice sheet have been studied;(2) The application of ICESat laser altimetry and on-orbit performance of ICESat have been summarized, then the advantage of monitoring ice sheet surface elevation change using laser altimetry has been analyzed, together with waveform and altimetry precision of GLAS; error sources of laser altimetry have been analyzed, and corresponding corrections have been given;(3) GRACE data products and development of GRACE gravity field have been described in detail, and the methods of determining earth gravity model using GRACE data, as well as the theory of determining mass change of earth surface using GRACE time-variable gravity field, have been studied;(4) "Clean"and reliable data set was obtained by studying and realizing the techniques of pre-processing, refining ICESat laser altimetry data with which the cross-over point algorithm was described;(5) The interpolation methods, such as Shephard, continuous curvature splines in tension and Kriging method, have been studied with the conclusion that continuous curvature splines in tension is more suitable for data interpolatation of polar ice sheet;(6) Through the average chang rate of elevation computed by derivatives of elevation difference and time difference obtained from cross-over point algorithm, change tendency of ice sheet mass and its precision were analysized, the factors affect elevation change of ice sheet were revealed;(7) Ice sheet mass changes of Antarctica and Greenland were deduced by using GRACE observations;(8) Through comparing the results of polar ice sheet changes obtained from ICESat data and GRACE data, correlation between polar ice sheet mass balance and sea level change was revealed.In conclusion, the main achievements of this dissertation includes:ICESat laser altimetry data pre-processing and refinement techniques; high-precision digital terrain elevation model interpolation method; a high-precision and high-resolution polar ice DEM was established based on ICESat altimetry data; time series of the polar ice sheets elevation change were obtained via cross-over point algorithm; the changes of polar ice sheet mass were deduced by utilizing GRACE time-varible gravity data; correlation between polar ice sheet mass balance and sea level change was revealed through comparing the results of polar ice sheet changes obtained from ICESat data and GRACE data; the multi-functional software system with independent intellectual property rights was developed for calculating polar ice mass changes and water storage change by combining satellite gravity data and laser altimetry data.更多还原