Abstract Arctic warming may induce slope failure in upland permafrost soils. These landslide-like events, referred to as active layer detachments (ALDs), redistribute soil material into hydrological networks during spring melt and heavy rainfall. In 2011, 2013 and 2014, fluvial sediments from the West River at the Cape Bounty Arctic Watershed Observatory were sampled where ALDs occurred in 2007–2008. Two ALD-impacted subcatchments were examined exhibiting either continuing disturbance or short-term stabilization. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and targeted biomarker analysis via gas chromatography–mass spectrometry were used to investigate shifts in organic matter (OM) composition. Additionally, radiocarbon ages were determined using accelerator mass spectrometry. Biomarker concentrations and O-alkyl carbon assessed via NMR were both lower in sediments nearest the active disturbance and increased in sediments downstream where other aquatic inputs became more dominant. This suggests immobilization of recalcitrant OM near the ALD and the sustained transport of labile ALD-derived OM further downstream. Shifts toward older radiocarbon dates along the river between 2011 and 2014 suggest the continued transport of permafrost-derived OM downstream. The stabilizing subcatchment revealed high O-alkyl carbon via NMR and increased concentrations of unaltered terrestrial-derived biomarkers indicative of enhanced OM accumulation following ALD activity. The relatively young radiocarbon ages from these sediments suggest accumulation from contemporary sources and potential burial of the previously dispersed ALD inputs. Within the broader context of Arctic climate change, these results portray a complex environmental trajectory for thaw-released permafrost-derived OM and highlight uncertainty in the relationship between lability and persistence upon release by permafrost disturbance.

中文翻译：

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受局部斜坡扰动影响的北极高流域河流沉积有机质组成的时空变化

摘要 北极变暖可能会导致高地多年冻土的斜坡失稳。这些类似滑坡的事件，称为活动层脱离 (ALD)，在春季融化和强降雨期间将土壤材料重新分配到水文网络中。2011 年、2013 年和 2014 年，在 2007-2008 年发生 ALD 的地方，在 Cape Bounty 北极流域观测站对西河的河流沉积物进行了采样。检查了两个受 ALD 影响的子汇水面积，表现出持续干扰或短期稳定。固态 13C 核磁共振 (NMR) 光谱和通过气相色谱-质谱法进行的靶向生物标志物分析用于研究有机物 (OM) 组成的变化。此外，使用加速器质谱法确定放射性碳年龄。通过 NMR 评估的生物标志物浓度和 O-烷基碳在最接近活动扰动的沉积物中均较低，而在其他水生输入变得更加占优势的下游沉积物中则增加。这表明在 ALD 附近将顽固的 OM 固定化，并且不稳定的 ALD 衍生的 OM 持续运输到更远的下游。2011 年至 2014 年间沿河流向较旧放射性碳日期的转变表明永久冻土衍生的 OM 继续向下游输送。稳定的子汇水面积通过 NMR 显示高 O-烷基碳和增加的未改变的陆地衍生生物标志物浓度，表明 ALD 活动后 OM 积累增强。这些沉积物中相对年轻的放射性碳年龄表明来自当代来源的积累和先前分散的 ALD 输入的潜在掩埋。