Multi-temporal, multi-sensor investigations of supra-glacial lakes on the Greenland Ice Sheet
Multi-temporal, multi-sensor investigations of supra-glacial lakes on the Greenland Ice Sheet
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格陵兰冰盖冰上湖泊的多时相、多传感器研究
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发表时间：
2011
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通讯作者：
P. Jansson
中科院分区：
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作者：
M. Johansson;I. Brown;P. Jansson
格陵兰冰盖是北方最大的冰盖。冰盖的持续融化，导致相对于长期趋势的质量损失增加，引起了人们对冰盖稳定性的担忧。地表产生的融水暂时储存在冰盖上的冰上湖泊中。融水的产生、储存和冰盖动态之间的联系突出了地表水文系统的重要性，在这篇论文中，我们使用不同的方法来提高我们观察格陵兰岛西部冰盖上的冰上湖泊系统的能力。格陵兰冰盖的这一地区拥有最广泛的冰上水文系统，有密集的溪流网络连接面积可超过几平方公里的湖泊。合成孔径雷达（SAR）和可见光近红外（VNIR）图像被用来探索不同的传感器系统定期观测冰上湖泊的潜力。SAR图像被认为是一个有用的补充VNIR数据。来自中等分辨率传感器的VNIR数据是优选的，因为这些提供了高时间分辨率数据，改善了云覆盖的问题。湖泊的动态性质使得自动分类困难，手动制图已被广泛使用。这里提出了一种新的方法，通过自动识别和分类湖泊，并通过引入一个灵活的系统，可以捕捉到所有的湖泊形式，改进现有的方法。应用我们的新方法，我们能够更好地分析湖泊的演变在一些融化的季节。我们发现，湖泊开始后，大约40积极度天。大多数湖泊存在不到20天，然后排水，或在本赛季后期，并不经常，冻结。使用本论文中开发的自动化方法，湖泊已被映射在图像从2001年至2010年在大约五天的时间间隔。
The Greenland Ice Sheet is the largest ice sheet in the northern hemisphere. Ongoing melting of the ice sheet, resulting in increased mass loss relative to the longer term trend, has raised concerns about the stability of the ice sheet. Melt water generated at the surface is temporarily stored in supra-glacial lakes on the ice sheet. Connections between melt water generation, storage and ice sheet dynamics highlight the importance of the surface hydrological system.In this thesis different methods are used that improve our ability to observe the supra-glacial lake system on the west Greenland Ice Sheet. This region of the Greenland Ice Sheet has the most extensive supra-glacial hydrological system with a dense network of streams connecting lakes that can exceed several square kilometres in area. Synthetic Aperture Radar (SAR) and visible-near infrared (VNIR) images are used to explore the potential of different sensor systems for regular observations of the supra-glacial lakes. SAR imagery is found to be a useful complement to VNIR data. VNIR data from moderate resolution sensors are preferred as these provide high temporal resolution data, ameliorating problems with cloud cover.The dynamic nature of the lakes makes automated classification difficult and manual mapping has been widely used. Here a new method is proposed that improves on existing methods by automating the identification and classification of lakes, and by introducing a flexible system that can capture the full range of lake forms. Applying our new method we are better able to analyse the evolution of lakes over a number of melt seasons. We find that lakes initiate after approximately 40 positive degree days. Most lakes exist for less than 20 days before draining, or later in the season, and less often, freezing over. Using the automated method developed in this thesis lakes have been mapped in imagery from 2001–2010 at approximately five day intervals.