Abstract Collapse of permafrost coasts delivers large quantities of particulate organic carbon (POC) to Arctic coastal areas. With rapidly changing environmental conditions, sediment and organic carbon (OC) mobilization and transport pathways are also changing. Here, we assess the sources and sinks of POC in the highly dynamic nearshore zone of Herschel Island‐Qikiqtaruk (Yukon, Canada). Our results show that POC concentrations sharply decrease, from 15.9 to 0.3 mg L−1, within the first 100–300 m offshore. Simultaneously, radiocarbon ages of POC drop from 16,400 to 3,600 14C years, indicating rapid settling of old permafrost POC to underlying sediments. This suggests that permafrost OC is, apart from a very narrow resuspension zone (<5 m water depth), predominantly deposited in nearshore sediments. While long‐term storage of permafrost OC in marine sediments potentially limits biodegradation and its subsequent release as greenhouse gas, resuspension of fine‐grained, OC‐rich sediments in the nearshore zone potentially enhances OC turnover.

中文翻译：

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近岸带动力学决定了侵蚀永久冻土海岸的有机碳的途径

摘要 永久冻土海岸的坍塌向北极沿海地区提供了大量的颗粒有机碳 (POC)。随着环境条件的迅速变化，沉积物和有机碳 (OC) 的动员和运输途径也在发生变化。在这里，我们评估了 Herschel Island-Qikiqtaruk（加拿大育空地区）的高度动态近岸区域中 POC 的源和汇。我们的结果表明，在离岸的前 100-300 m 内，POC 浓度急剧下降，从 15.9 到 0.3 mg L-1。同时，POC 的放射性碳年龄从 16,400 年下降到 3,600 14C 年，表明旧的永久冻土 POC 快速沉降到下伏沉积物中。这表明，除了非常狭窄的再悬浮区（<5 m 水深）外，永久冻土 OC 主要沉积在近岸沉积物中。