A Quantitative Graph-Based Approach to Monitoring Ice-Wedge Trough Dynamics in Polygonal Permafrost Landscapes
A Quantitative Graph-Based Approach to Monitoring Ice-Wedge Trough Dynamics in Polygonal Permafrost Landscapes
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DOI：
10.3390/rs13163098
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发表时间：
2021-08
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影响因子：
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通讯作者：
Tabea Rettelbach;M. Langer;Ingmar Nitze;B. Jones;V. Helm;J. Freytag;G. Grosse
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文献类型：
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作者：
Tabea Rettelbach;M. Langer;Ingmar Nitze;B. Jones;V. Helm;J. Freytag;G. Grosse
随着北极气温的升高，富含冰的永久冻土景观正在发生快速变化。在冻土低地，多边形冰楔特别容易退化。冰楔的融化导致了冰槽的加深和低中心冰楔多边形向高中心冰楔多边形的转变。这一过程对地表水文学具有重要意义，因为这些沟槽的连通性决定了这些低地景观的排水速率。在这项研究中，我们提出了一个全面的、模块化的、高度自动化的工作流程来提取、表示和分析遥感冰楔多边形槽网作为一个图（即网络结构）。利用计算机视觉方法，我们有效地从高分辨率数字高程模型中提取槽位及其槽深和槽宽的地貌学信息，并将这些数据链接到图中。此外，我们提出并讨论了图形分析算法在描述这种受融化影响的景观的侵蚀发展方面的好处。根据我们的图表分析，我们展示了美国阿拉斯加州北部阿纳克图夫克河火灾疤痕燃烧后，2009年至2019年期间融化沉降的进展情况。我们观察到研究区域内可识别的波谷数量大幅增加，而与此同时，断开网络的数量从2009年的54个小网络减少到2019年的6个相当大的断开网络。槽的宽度平均增加了13.86%，槽的深度平均减少了10.31%。总的来说，我们的新自动化方法允许以前所未有的空间细节监测冰楔动态，同时将数据简化为可量化的几何测量和空间关系。
In response to increasing Arctic temperatures, ice-rich permafrost landscapes are undergoing rapid changes. In permafrost lowlands, polygonal ice wedges are especially prone to degradation. Melting of ice wedges results in deepening troughs and the transition from low-centered to high-centered ice-wedge polygons. This process has important implications for surface hydrology, as the connectivity of such troughs determines the rate of drainage for these lowland landscapes. In this study, we present a comprehensive, modular, and highly automated workflow to extract, to represent, and to analyze remotely sensed ice-wedge polygonal trough networks as a graph (i.e., network structure). With computer vision methods, we efficiently extract the trough locations as well as their geomorphometric information on trough depth and width from high-resolution digital elevation models and link these data within the graph. Further, we present and discuss the benefits of graph analysis algorithms for characterizing the erosional development of such thaw-affected landscapes. Based on our graph analysis, we show how thaw subsidence has progressed between 2009 and 2019 following burning at the Anaktuvuk River fire scar in northern Alaska, USA. We observed a considerable increase in the number of discernible troughs within the study area, while simultaneously the number of disconnected networks decreased from 54 small networks in 2009 to only six considerably larger disconnected networks in 2019. On average, the width of the troughs has increased by 13.86%, while the average depth has slightly decreased by 10.31%. Overall, our new automated approach allows for monitoring ice-wedge dynamics in unprecedented spatial detail, while simultaneously reducing the data to quantifiable geometric measures and spatial relationships.