Scale‐Dependent Influence of Permafrost on Riverbank Erosion Rates
Scale‐Dependent Influence of Permafrost on Riverbank Erosion Rates
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DOI：
10.1029/2023jf007101
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发表时间：
2023-07
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通讯作者：
J. Rowland;Jon Schwenk;E. Shelef;J. Muss;Daniela Ahrens;S. Stauffer;Anastasia Pilliouras;B. Crosby;A. Chadwick;M. Douglas;P. Kemeny;M. Lamb;Gen K. Li;L. Vulis
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作者：
J. Rowland;Jon Schwenk;E. Shelef;J. Muss;Daniela Ahrens;S. Stauffer;Anastasia Pilliouras;B. Crosby;A. Chadwick;M. Douglas;P. Kemeny;M. Lamb;Gen K. Li;L. Vulis
永久冻土是否系统地改变河岸侵蚀的速率是一个基本的地貌问题，对高纬度流域的基础设施，水质和地球化学具有重要意义。四十多年来，由于缺乏数据，这个问题一直没有答案。利用遥感图像，我们解决了这一知识差距，量化整个北极和亚北极地区的河岸侵蚀率。为了将这些速率与非永久冻土河流进行比较，我们收集了已发布的河岸侵蚀速率的全球数据集。我们发现，受永久冻土影响的河流的侵蚀速率平均比非永久冻土系统低9倍;对于最大的河流，侵蚀速率差异增加到40倍。为了检验观测到的侵蚀速率差异的替代假设，我们研究了这些河流和非永久冻土河流之间的总水量和侵蚀效率的差异。这些因素和河流泥沙负荷的差异都没有提供令人信服的替代解释，这使我们得出结论，永久冻土限制了河岸侵蚀速率。这一结论得到了支持的速率和模式的侵蚀沿着三条河流流经阿拉斯加的不连续永久冻土的实地调查。我们的研究结果表明，永久冻土限制了河流功率大于900 Wm−1的河流的最大河岸侵蚀率。然而，在较小的河流，水文，而不是解冻率可能是主要控制银行侵蚀。我们的研究结果表明，北极变暖和水文变化应增加银行侵蚀率的大型河流，但可能会降低率的河流流域面积小于几千平方公里。
Whether permafrost systematically alters the rate of riverbank erosion is a fundamental geomorphic question with significant importance to infrastructure, water quality, and biogeochemistry of high‐latitude watersheds. For over four decades, this question has remained unanswered due to a lack of data. Using remotely sensed imagery, we addressed this knowledge gap by quantifying riverbank erosion rates across the Arctic and subarctic. To compare these rates to non‐permafrost rivers, we assembled a global data set of published riverbank erosion rates. We found that erosion rates in rivers influenced by permafrost are on average nine times lower than non‐permafrost systems; erosion rate differences increase up to 40 times for the largest rivers. To test alternative hypotheses for the observed erosion rate difference, we examined differences in total water yield and erosional efficiency between these rivers and non‐permafrost rivers. Neither of these factors nor differences in river sediment loads provided compelling alternative explanations, leading us to conclude that permafrost limits riverbank erosion rates. This conclusion was supported by field investigations of rates and patterns of erosion along three rivers flowing through discontinuous permafrost in Alaska. Our results show that permafrost limits maximum bank erosion rates on rivers with stream powers greater than 900 Wm−1. On smaller rivers, however, hydrology rather than thaw rate may be the dominant control on bank erosion. Our findings suggest that Arctic warming and hydrological changes should increase bank erosion rates on large rivers but may reduce rates on rivers with drainage areas less than a few thousand km2.