Riverbank erosion in yedoma regions strongly affects landscape evolution, biogeochemical cycling, sediment transport, and organic and nutrient fluxes to the Arctic Ocean. Since 2006, we have studied the 35-m-high Itkillik River yedoma bluff in northern Alaska, whose retreat rate during 1995–2010 was up to 19 m/yr, which is among the highest rates worldwide. This study extends our previous observations of bluff evolution and shows that average bluff-top retreat rates decreased from 8.7–10.0 m/yr during 2011–2014 to 4.5–5.8 m/yr during 2015–2019, and bluff-base retreat rates for the same time period decreased from 4.7–7.5 m/yr to 1.3–1.7 m/yr, correspondingly. Bluff evolution initially involves rapid fluvio-thermal erosion at the base and block collapse, following by slowdown in river erosion and continuing thermal denudation of the retreating headwall with formation of baydzherakhs. Eventually, input of sediment and water from the headwall diminishes, vegetation develops, and slope gradually stabilizes. The step change in the fluvial–geomorphic system has resulted in a 60% decline in the volumetric mobilization of sediment and organic carbon between 2011 and 2019. Our findings stress the importance of sustained observations at key permafrost region study sites to elucidate critical information related to past and potential landscape evolution in the Arctic.

中文翻译：

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阿拉斯加北部叶多马地区的水热侵蚀和热剥蚀：重新审视伊基利克河的暴露

叶多马地区的河岸侵蚀强烈影响景观演变、生物地球化学循环、沉积物输送以及向北冰洋的有机和营养通量。自 2006 年以来，我们研究了阿拉斯加北部 35 米高的伊基利克河 yedoma 断崖，其 1995-2010 年的退缩率高达 19 米/年，是世界上最高的退缩率之一。本研究扩展了我们之前对断崖演化的观察结果，表明断崖顶部的平均撤退率从 2011-2014 年的 8.7-10.0 米/年下降到 2015-2019 年期间的 4.5-5.8 米/年，断崖底撤退率从 2011-2014 年的 4.5-5.8 米/年下降到同期，相应地从 4.7-7.5 米/年下降到 1.3-1.7 米/年。断崖演化最初涉及底部的快速水热侵蚀和块体坍塌，随后河流侵蚀减缓，后退的端墙持续热剥蚀，形成 baydzherakhs。最终，底壁的泥沙和水的输入减少，植被发育，坡度逐渐稳定。河流-地貌系统的阶跃变化导致 2011 年至 2019 年间沉积物和有机碳的体积流动性下降了 60%。我们的研究结果强调了在关键的永久冻土区研究地点进行持续观测以阐明与北极过去和潜在的景观演变。