中文摘要：

北极海冰变化受全球气候变化影响明显,海冰的变化不仅体现在面积上,而且也体现在厚度上。利用海冰干舷高度可以反演海冰厚度,冰、云和陆地高程卫星/地球科学激光测高系统（ice,cloud and land elevation satellite/geoscience laser altimeter system,ICESat/GLAS）提供了高精度的海冰高程信息。利用ICESat/GLAS测高数据,提取了2003～2008年部分时间段北极区域海冰的干舷高度,分析了2003～2008年间北极海冰季节性以及年际变化特征。结果表明,北极海冰干舷高度呈下降趋势,并且在2007年夏季减少趋势最为明显。对北极海冰在2007年迅速减少的原因进行了探讨,并利用仰视声呐实测数据对干舷高提取算法存在的系统性偏差进行了讨论与分析。

英文摘要：

Changes in both the area and thickness of Arctic sea iceare significantly influenced by global climate change the rapid decline in Arctic sea ice during the summer of 2007 is analyzed empirically in our research.Sea ice thickness can be retrieved from the sea ice freeboard heights.As ICESat/GLAS（ice,cloud and land elevation satellite/geoscience laser altimeter system）provide high-precision sea ice elevation information,therefore we could extract the freeboard heights of the Arctic sea ice from ICESat/GLAS datasets spanning from 2003 to 2008to analyze seasonal and inter-annual variation in Arctic sea ice.The results show that the Arctic sea ice freeboard heights have been decreasing during2003-2008,especially in the summer of 2007.Systematic deviationsin the retrieved results are discussed and analyzed based on the ULS（Upward Looking Sonar）field data.