Patterns and rates of riverbank erosion involving ice-rich permafrost (yedoma) in northern Alaska
Patterns and rates of riverbank erosion involving ice-rich permafrost (yedoma) in northern Alaska
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DOI：
10.1016/j.geomorph.2015.10.023
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发表时间：
2016-01-15
期刊：
影响因子：
3.9
通讯作者：
Vasiliev, Alexander
中科院分区：
文献类型：
--
作者：
Kanevskiy, Mikhail;Shur, Yuri;Vasiliev, Alexander
Yedoma是一套同生冻结的粉质冰和富含有机物的沉积物，在晚更新世积累了大量冰楔，由于冰含量极高，很容易受到热降解和侵蚀。这种退化可能导致显著的地表沉降和海岸峭壁和河岸的退缩，对景观演变、基础设施破坏和水质造成严重后果。我们使用遥感和实地观察，以评估在35米高的活跃yedoma海崖在北方阿拉斯加的Itkillik河的河岸侵蚀的模式和速率。总体积的地面冰含量，包括楔形，分离，和孔隙冰，估计是类似的86%。河岸侵蚀和稳定过程包括三个主要阶段：（1）热侵蚀与热剥蚀相结合，（2）热剥蚀，（3）斜坡稳定。主要研究地点的活跃河岸侵蚀开始于1995年7月，当Itkillik河改变了它的通道。在1995-2010年期间，在海崖的不同段内，河岸的总后退量从180米到280米不等;河岸侵蚀最活跃的部分的平均后退速率几乎为19米/年。从2007年8月到2011年8月，总后退量从10米到近100米不等。整个680米长的陡海崖的平均后退速率为11米/年。对于海崖最活跃的侵蚀中心部分（150米长），它是20米/年，范围从16到24米/年。每年有超过180，000 m3的冰和富含有机物的冻土，或近70，000公吨（t）的土壤固体，包括880吨有机碳，从后退的河岸被运送到河流。这项研究报告了在欧亚大陆和北美的永久冻土地区观察到的最高的长期河岸侵蚀率。(C)2015 Elsevier B. V.版权所有。
Yedoma, a suite of syngenetically frozen silty ice- and organic-rich deposits with large ice wedges that accumulated during the late Pleistocene, is vulnerable to thermal degradation and erosion because of the extremely high ice contents. This degradation can result in significant surface subsidence and retreat of coastal bluffs and riverbanks with large consequences to landscape evolution, infrastructure damage, and water quality. We used remote sensing and field observations to assess patterns and rates of riverbank erosion at a 35-m-high active yedoma bluff along the Itkillik River in northern Alaska. The total volumetric ground-ice content including wedge, segregated, and pore ice-was estimated to be similar to 86%. The process of riverbank erosion and stabilization include three main stages typical of the areas with ice-rich permafrost: (1) thermal erosion combined with thermal denudation, (2) thermal denudation, and (3) slope stabilization.Active riverbank erosion at the main study site started in July 1995, when the Itkillik River changed its channel. The total retreat of the riverbank during 1995-2010 within different segments of the bluff varied from 180 to 280 m; the average retreat rate for the most actively eroded part of the riverbank was almost 19 m/y. From August 2007 to August 2011, the total retreat varied from 10 to almost 100 m. The average retreat rate for the whole 680-m-long bluff was 11 m/y. For the most actively eroded central part of the bluff (150 m long) it was 20 m/y, ranging from 16 to 24 m/y. More than 180,000 m(3) of ground ice and organic-rich frozen soil, or almost 70,000 metric tons (t) of soil solids including 880 t of organic carbon, were transported to the river from the retreating bank annually. This study reports the highest long-term rates of riverbank erosion ever observed in permafrost regions of Eurasia and North America. (C) 2015 Elsevier B.V. All rights reserved.