利用Cryosat-2测高数据研究北极波弗特海海冰干舷变化

发布时间：2018-07-03 01:50

本文选题：北极 + 波弗特海　；参考：《武汉大学》2017年硕士论文

【摘要】：海冰是地球科学研究的重要对象之一,海冰的变化与全球气候变化息息相关并相互影响。北极海冰作为全球的冷源,对全球气候系统具有重要影响,对气候系统的调制作用也是不可或缺的,因此也成为科学家最为关注的海冰研究区域。数十年的研究记录表明,在全球变暖、极端气候频发的背景下,北极海冰覆盖范围和厚度也在持续性的减少,并引发了北极的剧烈增暖和一系列气候变化,极区环境也受到严重影响。同时北极海冰屡次出现历史新低,在2007年9月创下有卫星记录以来海冰覆盖范围的最小值,在2017年1月份创下了北极海冰量历史新低,加快对北极海冰变化的研究显得刻不容缓。受北极特殊的地理位置和气候条件的限制,对北极海冰的研究进展相对缓慢,很多观测手段都无法获取北极地区大范围长时间尺度的观测数据,导致对北极海冰整体的变化特征和趋势了解并不充分,卫星测高技术的提出与发展,使得对北极海冰进行时空连续观测成为可能。CryoSat-2是欧空局根据极地冰盖和海冰测量的需求设计的测高卫星,相比于之前的测高卫星精度和测量范围有明显提升。本文使用CryoSat-2卫星2010年8月至2013年12月的L2级测高数据对北极波弗特海区域进行海冰干舷提取,首先使用BRAT软件对原始数据进行提取,对提取得到的数据进行预处理并计算剩余高程,选取阈值和中误差对剩余高程数据进行异常值剔除,再根据沿轨分布进行相对海平面提取,最后得到海冰干舷提取结果。将得到的结果与Beaufort Gyre Exploration Project(波弗特海环流计划)的仰视声呐数据进行比较,根据海冰干舷提取结果对波弗特海区域的海冰干舷分布情况、海冰干舷变化趋势及海冰干舷季节性变化和年际性变化进行了分析。结果显示:(1)波弗特海区域海冰干舷高度分布情况和纬度具有高度相关性,研究区域内海冰干舷高度值随着纬度的升高而增大,同时波弗特海区域不同的海域之间海冰干舷高度变化速率不同。(2)波弗特海区域海冰干舷高度变化具有明显的季节性特征,在北极的冬季1月份至3月份海冰干舷高度处于上升阶段,在3月份达到一年中海冰干舷高度平均值最大值,4月份至9月份是北极的春季和夏季,海冰不断融化,海冰干舷高度也持续减少,通常在9月份达到全年最低水平,10月份至12月份是北极的秋天,海冰开始冻结海冰干舷高度重新开始增长。(3)2010至2012年的8月份至12月份,波弗特海区域海冰干舷高度平均值处于持续减少的状态,2013年海冰干舷平均值高于2010年至2012年。2012年波弗特海海冰干舷高度年平均值低于2011年,2013年高于2011年,海冰干舷高度的变化与气温变化高度吻合。
[Abstract]:Sea ice is one of the most important objects in earth science research. The change of sea ice is closely related to global climate change and affects each other. Arctic sea ice, as a global cold source, has an important impact on the global climate system and is indispensable to the modulation of climate system. Therefore, Arctic sea ice has become the research area of sea ice that scientists pay most attention to. Decades of research records show that against the backdrop of global warming and frequent extreme weather, Arctic sea ice cover and thickness are also steadily decreasing, triggering a sharp increase in the Arctic and a series of climate changes. The polar environment is also severely affected. At the same time, Arctic sea ice has repeatedly been at record lows, with the lowest sea ice coverage since satellite records in September 2007 and a record low in Arctic sea ice volume in January 2017. It is urgent to speed up the study of Arctic sea ice change. Limited by the special geographical location and climatic conditions of the Arctic, the research on Arctic sea ice is relatively slow. As a result of insufficient understanding of the changing characteristics and trends of the Arctic sea ice as a whole, satellite altimetry technology has been proposed and developed. CryoSat-2 is an altimeter designed by ESA according to the requirements of polar ice cap and sea ice measurement. Compared with previous altimetric satellites, CryoSat-2 is much more accurate than previous altimetric satellites. In this paper, the L2 altimetry data of CryoSat-2 satellite from August 2010 to December 2013 are used to extract the sea ice freeboard in the Beaufort Sea area of the Arctic, and the original data are extracted by BRAT software. The extracted data are preprocessed and the residual elevation is calculated. The outliers of the residual elevation data are eliminated by selecting the threshold and the median error, and then the relative sea level is extracted according to the distribution along the orbit. Finally, the freeboard extraction results of sea ice are obtained. The results obtained are compared with the elevation sonar data of Beaufort Gyre Exploration Project, and the freeboard distribution of sea ice in the Beaufort Gyre Exploration Project is analyzed according to the results of sea ice freeboard extraction. The variation trend of sea ice freeboard, seasonal variation and interannual variation of sea ice freeboard are analyzed. The results show that: (1) the sea ice freeboard height distribution in the Beaufort Sea area is highly correlated with the latitude, and the sea ice freeboard height increases with the increase of latitude in the study area. At the same time, the sea ice freeboard height varies with different sea areas in the Beaufort Sea area. (2) the sea ice freeboard height variation in the Beaufort Sea area has obvious seasonal characteristics. The freeboard height of sea ice is on the rise in the Arctic winter from January to March, reaching the maximum of the average freeboard height in a year in March. During the spring and summer of the Arctic from April to September, the sea ice melts continuously. The freeboard height of sea ice also continues to decrease, usually reaching its lowest level for the year in September-October to December is the autumn of the Arctic, and the freeboard height of sea ice begins to freeze again. (3) August to December, 2010 to 2012. The average sea ice freeboard height in the Beaufort Sea region is in a state of continuous decrease, and the average sea ice freeboard height in 2013 is higher than that in 2010-2012. The annual average of sea ice freeboard height in 2012 is lower than that in 2011, and the average freeboard height in 2013 is higher than that in 2011. The variation of freeboard height of sea ice coincides with that of air temperature.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P731.15;P714.1

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