利用ICESat数据确定北极冰雪消融方法的研究

发布时间：2018-08-24 14:49

【摘要】：极地是全球气候的冷源,对于调节全球气候和环境变化具有重要的驱动作用,两极地区大气、海洋以及冰川的变化会直接或间接地引起全球尺度的大气环流、海洋环流的变化,因此,极地研究对于理解和监测全球气候环境变化具有重要意义。在全球气候变暖的背景下,北极气候系统显得异常脆弱,气温升高的速度远远高于全球平均水平,更凸显了北极研究的重要性和紧迫性。气候变暖对北极带来的显著影响是冰雪的消融,尤其是在进入21世纪后,北冰洋海冰的退缩和格陵兰冰盖消融速度都明显加速。海冰是北极气候系统中的关键因素,海冰在北冰洋上形成的冰雪层不仅减少了北极通过太阳辐射获得的热量,而且能够阻隔海洋与大气之间的热量交换,帮助北极保持低温的气候。海冰的变化能够强烈影响极地大气和海洋环流,从而导致全球的气候变化。冰盖消融的影响更加直接,格陵兰冰盖完全融解可以引起全球海平面升高约7m,对人类的生存环境带来巨大的冲击。尽管目前格陵兰冰盖的消融速度引起的海平面变化仅为约0.5mm/yr,但不断增加的消融速度却令人担忧,人口集中的沿海城市以及南太平洋的一些岛国都已经受到了威胁。卫星技术的发展为极地研究带来了突破,特别是卫星遥感技术在海冰覆盖范围、冰盖消融面积以及大气环境等方面的大范围、长期监测极大的推动了极地研究的发展。ICESat卫星激光测高技术的出现则为极地研究提供了新的角度和方法,相比于传统的卫星雷达测高,激光脉冲光斑小、不穿透雪层的特点以及受坡度影响较小的优势使得ICESat能够以前所未有的精度获取两极的高程信息,为海冰厚度和冰盖高程变化的确定提供了可靠的数据。本论文的主要内容是利用ICESat数据分析北极地区冰雪存量的变化,对北极ICESat数据的精度和误差来源进行分析,研究利用ICESat获取海冰干舷高和冰盖高程变化的方法,在此基础上确定北冰洋海面高以及海冰干舷高,探讨北冰洋海冰厚度的变化趋势,确定格陵兰冰盖高程和体积变化趋势,分析冰盖质量损失的情况。具体内容包括：1)分析了近年来北冰洋海冰和格陵兰冰盖的变化趋势,阐述了海冰形成和发展的过程以及与北极气候环境相互作用的模式,论述了格陵兰冰盖表面消融和质量损失的机制；总结了海冰和冰盖研究的相关技术和研究现状。2)阐述了ICESat卫星激光测高的基本原理,分析讨论了ICESat测高的主要误差源以及任务期偏差,探讨了ICESat冰面观测值的数据编辑方法和准则,对了ICESat测高的精度进行了估计。3)研究了利用ICESat数据确定海冰覆盖区域海面高的最低面滤波法和经验关系法,并通过对ICESat海冰测高数据波形特征和高程变化的分析,提出确定海面高的波形高程法。通过对数据处理过程中产生的系统误差进行分析和研究,探讨了一些关键参数的最优取值。4)利用2003-2008年ICESat北极海冰测高数据确定北冰洋平均海平面,获得的海面高模型与DTU13海面高模型的差值为9.9±7.1 cm,这一结果相比国外类似研究的精度更高。同时,利用ICESat数据获得的北冰洋海面高季节变化与验潮站结果一致,验证了ICESat确定海冰覆盖的海平面高的能力。由平均海面高和大地水准面得到北冰洋的海面动力地形,结果有效的反应了北极海流的主要特征。5)确定2003-2008年北冰洋海冰干舷高变化,并对其变化趋势进行了分析。根据海冰干舷高的概率密度分布,结合北极气候变化情况,分析了一年冰与多年冰组成比例的变化。研究了利用干舷高确定海冰厚度的方法,确定北冰洋海冰厚度的变化趋势,结果表明北冰洋多年冰厚度以约15cm/yr的速度减少,而一年冰厚度减少的速度则不到4cm/yr。6)研究了利用ICESat轨迹交叉点和重复轨道数据确定冰盖高程变化的方法。通过不同方法的对比,分析了高程变化确定中地面坡度、轨迹排列顺序等对计算结果的影响。7)利用ICESat重复轨道数据获得了2003-2009年格陵兰冰盖高程/体积变化,结果表明格陵兰冰盖高程以16.12 cm/yr的速度减少,相当于289.39 km3/yr的体积损失。根据格陵兰冰盖的自然流域划分,详细分析格陵兰冰盖的变化,探讨冰盖流失的具体情况。
[Abstract]:Polar region is the cold source of global climate, which plays an important driving role in regulating global climate and environmental change. The changes of atmosphere, ocean and glacier in polar regions will directly or indirectly cause global atmospheric circulation and ocean circulation changes. Therefore, polar research is important for understanding and monitoring global climate and environmental change. Significance. In the context of global warming, the Arctic climate system appears extremely fragile, and the rate of temperature rise is much higher than the global average, which highlights the importance and urgency of Arctic research. The melting rate of the Greenland ice sheet has accelerated significantly. Sea ice is a key factor in the Arctic climate system. The ice and snow layers formed by sea ice in the Arctic Ocean not only reduce the Arctic heat from solar radiation, but also block the exchange of heat between the ocean and the atmosphere and help the Arctic maintain a cold climate. The melting of the Greenland ice sheet can cause a global sea-level rise of about 7m, with a huge impact on the human environment. Although the current melting rate of the Greenland ice sheet causes a sea-level change of only about 0.5mm/yr, The development of satellite technology has brought breakthroughs in polar research, especially in the areas of sea ice cover, ice sheet ablation area and atmospheric environment. The emergence of ICESat satellite laser altimetry technology provides a new angle and method for polar research. Compared with traditional satellite radar altimetry, ICESat has the advantages of small laser pulse spot, non-penetrating snow layer and less slope influence, which makes ICESat able to obtain unprecedented precision. Elevation information of the two poles provides reliable data for the determination of sea ice thickness and ice sheet elevation changes. The main content of this paper is to analyze the changes of ice and snow stock in the Arctic region by ICESat data analysis, to analyze the accuracy and error sources of the Arctic ICESat data, and to study the use of ICESat to obtain sea ice freeboard height and ice sheet elevation changes. Methods On this basis, the sea surface height and sea ice freeboard height in the Arctic Ocean were determined, the variation trend of sea ice thickness in the Arctic Ocean was discussed, the variation trend of ice sheet height and volume in Greenland was determined, and the mass loss of ice sheet was analyzed. The process of formation and development and the model of interaction with Arctic climate and environment are discussed. The mechanism of surface melting and mass loss of Greenland ice sheet is discussed. The related technologies and research status of sea ice and ice sheet are summarized. 2) The basic principle of ICESat satellite laser altimetry is expounded, and the main error sources of ICESat altimetry are analyzed and discussed. The method and criterion of ICESat ice surface observation data editing are discussed, and the accuracy of ICESat altimetry is estimated. 3) The lowest surface filtering method and empirical relation method for determining sea surface height in sea ice covered area by ICESat data are studied, and the waveform characteristics and elevation changes of ICESat sea ice altimetry data are analyzed. A waveform elevation method for determining sea surface height is proposed. The optimum values of some key parameters are discussed by analyzing and studying the systematic errors produced in the data processing. 4) The mean sea level of the Arctic Ocean is determined by using the ICESat Arctic sea ice altimetry data from 2003 to 2008. The difference between the sea surface elevation model and the DTU13 sea surface elevation model is 9.9 At the same time, the high seasonal variation of the Arctic Ocean sea surface obtained from ICESat data coincides with the tidal station results, which verifies the ICESat's ability to determine the sea level height covered by sea ice. According to the probability density distribution of sea ice freeboard height and the Arctic climate change, the variation of the composition ratio of annual ice to perennial ice is analyzed. The variation trend of sea ice thickness in the Arctic Ocean is determined. The results show that the perennial ice thickness in the Arctic Ocean decreases at a speed of about 15cm/yr, while the annual ice thickness decreases at a speed of less than 4cm/yr. The results show that the Greenland ice sheet height decreases at a speed of 16.12 cm/yr, equivalent to 289.39 km 3/yr. According to the natural watershed division of the Greenland ice sheet The change of Greenland ice sheet is analyzed in detail, and the specific situation of ice sheet loss is discussed.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P343.3;P225

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