Spatial heterogeneity of sedimentary organic carbon accumulation and degradation along the Arctic continental margins

The warming climate has led to the translocation of a large amount of terrestrial organic carbon (TerrOC) from permafrost into the Arctic Ocean through river transport and coastal erosion. The fate of sedimentary organic carbon (SOC) varies dramatically and thus affects climate-carbon feedback. We analyzed the spatial heterogeneity of SOC sources and degradation along the East Siberian Arctic Shelf (ESAS) with bulk parameters (total organic carbon, δ13C) and a biomarker (lignin) for comparison of the spatial heterogeneity of TerrOC degradation between the broad ESAS and the narrow Amerasian continental shelf. The results show that the relative importance of river runoff, coastal erosion, and primary productivity causes alongshore variations in organic carbon (OC) sources within the ESAS, highlighting the effects of land-based inputs and ocean currents. Meanwhile, the variations of OC sources show gradually diminishing terrestrial signals in the seaward direction. The simultaneous offshore decrease in OC loadings and increase in lignin degradation indicate that the degradation of TerrOC within a water depth of 100 m is a key mechanism driving the cross-shelf loss of OC in the ESAS. Compared to the broad ESAS, the inconspicuous variations in Λ8/SSA and 3,5-Bd/V across the narrow Amerasian margin suggest that the width of the continental shelf is vital in determining the fate of TerrOC, despite greater levels of recalcitrant petrogenic OC in the Beaufort Sea. In general, the insights have profound implications for evaluating the coastal remobilization and preservation of SOC and its climate-carbon feedback across diverse pan-Arctic continental shelves.

全球气候变暖导致大量陆地有机碳（TerrOC）通过河流运输和海岸侵蚀从永久冻土区迁移至北极海洋。沉积有机碳（SOC）的归宿差异显著，进而影响气候-碳反馈。本研究通过分析东西伯利亚大陆架（ESAS）沿线的SOC来源及其降解的空间异质性，利用总量参数（总有机碳、δ13C）和生物标志物（木质素）对ESAS广阔区域与狭窄的美洲大陆架之间TerrOC降解的空间异质性进行比较。研究结果表明，河流径流、海岸侵蚀和初级生产力的相对重要性导致了ESAS内有机碳（OC）来源的沿岸变化，凸显了陆地输入和海洋流的影响。同时，OC来源的变化显示出 seaward 方向陆地信号的逐渐减弱。OC负载量的同步 offshore 减少以及木质素降解的增加表明，在100米水深范围内TerrOC的降解是驱动ESAS横跨大陆架OC损失的关键机制。与广阔的ESAS相比，在狭窄的美洲大陆架边缘Λ8/SSA和3,5-Bd/V的无明显变化表明，大陆架的宽度在决定TerrOC的归宿中至关重要，尽管波弗特海中存在更高水平的抗性有机碳。总体而言，这些发现对于评估不同泛北极大陆架上SOC的沿海再动员和保存及其气候-碳反馈具有深远的启示意义。