Rapid Fluvio-Thermal Erosion of a Yedoma Permafrost Cliff in the Lena River Delta
Rapid Fluvio-Thermal Erosion of a Yedoma Permafrost Cliff in the Lena River Delta
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DOI：
10.3389/feart.2020.00336
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发表时间：
2020-08-21
影响因子：
2.9
通讯作者：
Grosse, Guido
中科院分区：
文献类型：
--
作者：
Fuchs, Matthias;Nitze, Ingmar;Grosse, Guido
富冰永久冻土沉积物的退化有可能释放大量先前冻结的碳(C)和氮(N)，对当地产生影响，例如影响河流和近岸生态系统，但也会产生全球影响，例如向大气中释放温室气体。本文采用53年的遥感时间序列分析方法，研究了勒拿河三角洲高27.7 m、长1660 m的索布四色崖的快速侵蚀过程，并计算了勒拿河的年平均泥沙量和碳氮释放量。研究发现，苏博-四色岩壁暴露出富冰晚更新世至全新世沉积物，其平均长期（1965-2018）侵蚀速率为9.1 m yr(-1)，局部和时间变化速率高达22.3 m yr（-1）。这些速率是测量到的永久冻土海岸和河流岸线延伸的最高侵蚀速率之一。河流热侵蚀导致大量C（土壤有机碳和溶解有机碳）和N向水系释放。目前，平均每年（2015-2018年）至少有5.2 x 10(6)kg有机碳和0.4 x 10(6)kg氮被侵蚀到勒拿河。观测到的泥沙和有机质侵蚀在观测期间持续存在，这也与河流流向和崖岸走向的特定配置有关。我们的观察结果强调了进一步研究永久冻土区快速河流-热侵蚀过程的重要性，也因为我们的研究表明，在最近的调查时期，索布-斯塞悬崖的侵蚀率在增加。有机碳和氮从陆地到河流并最终到北冰洋的运输可能对拉普捷夫海近岸地区的生物地球化学和生态以及旧碳和氮向大气的转换和快速释放产生严重影响。
The degradation of ice-rich permafrost deposits has the potential to release large amounts of previously freeze-locked carbon (C) and nitrogen (N) with local implications, such as affecting riverine and near-shore ecosystems, but also global impacts such as the release of greenhouse gases into the atmosphere. Here, we study the rapid erosion of the up to 27.7 m high and 1,660 m long Sobo-Sise yedoma cliff in the Lena River Delta using a remote sensing-based time-series analysis covering 53 years and calculate the mean annual sediment as well as C and N release into the Lena River. We find that the Sobo-Sise yedoma cliff, which exposes ice-rich late Pleistocene to Holocene deposits, had a mean long-term (1965-2018) erosion rate of 9.1 m yr(-1)with locally and temporally varying rates of up to 22.3 m yr(-1). These rates are among the highest measured erosion rates for permafrost coastal and river shoreline stretches. The fluvio-thermal erosion led to the release of substantial amounts of C (soil organic carbon and dissolved organic carbon) and N to the river system. On average, currently at least 5.2 x 10(6)kg organic C and 0.4 x 10(6)kg N were eroded annually (2015-2018) into the Lena River. The observed sediment and organic matter erosion was persistent over the observation period also due to the specific configuration of river flow direction and cliff shore orientation. Our observations highlight the importance to further study rapid fluvio-thermal erosion processes in the permafrost region, also because our study shows increasing erosion rates at Sobo-Sise Cliff in the most recent investigated time periods. The organic C and N transport from land to river and eventually to the Arctic Ocean from this and similar settings may have severe implications on the biogeochemistry and ecology of the near-shore zone of the Laptev Sea as well as for turnover and rapid release of old C and N to the atmosphere.