Abstract Ongoing permafrost thaw in the Arctic may remobilize large amounts of old organic matter. Upon transport to the Siberian shelf seas, this material may be degraded and released to the atmosphere, exported off‐shelf, or buried in the sediments. While our understanding of the fate of permafrost‐derived organic matter in shelf waters is improving, poor constraints remain regarding degradation in sediments. Here we use an extensive data set of organic carbon concentrations and isotopes (n = 109) to inventory terrigenous organic carbon (terrOC) in surficial sediments of the Laptev and East Siberian Seas (LS + ESS). Of these ~2.7 Tg terrOC about 55% appear resistant to degradation on a millennial timescale. A first‐order degradation rate constant of 1.5 kyr−1 is derived by combining a previously established relationship between water depth and cross‐shelf sediment‐terrOC transport time with mineral‐associated terrOC loadings. This yields a terrOC degradation flux of ~1.7 Gg/year from surficial sediments during cross‐shelf transport, which is orders of magnitude lower than earlier estimates for degradation fluxes of dissolved and particulate terrOC in the water column of the LS + ESS. The difference is mainly due to the low degradation rate constant of sedimentary terrOC, likely caused by a combination of factors: (i) the lower availability of oxygen in the sediments compared to fully oxygenated waters, (ii) the stabilizing role of terrOC‐mineral associations, and (iii) the higher proportion of material that is intrinsically recalcitrant due to its chemical/molecular structure in sediments. Sequestration of permafrost‐released terrOC in shelf sediments may thereby attenuate the otherwise expected permafrost carbon‐climate feedback.

中文翻译：

---

量化拉普捷夫和东西伯利亚海表层沉积物中陆源有机碳的退化损失

摘要 北极持续的永久冻土融化可能会重新激活大量旧有机物。在运输到西伯利亚陆架海后，这种材料可能会降解并释放到大气中、直接出口或埋在沉积物中。虽然我们对陆架水域中永久冻土来源的有机物的命运的了解正在不断改善，但沉积物降解方面仍然存在有限的限制。在这里，我们使用有机碳浓度和同位素 (n = 109) 的广泛数据集来清查拉普捷夫海和东西伯利亚海 (LS + ESS) 表层沉积物中的陆源有机碳 (terrOC)。其中约 2.7 Tg terrOC 中的约 55% 似乎在千年时间尺度上具有抗降解性。通过将先前建立的水深和跨陆架沉积物-terrOC 传输时间与矿物相关的 terrOC 负荷之间的关系相结合，得出 1.5 kyr−1 的一级降解速率常数。在跨陆架运输过程中，地表沉积物产生约 1.7 Gg/年的 terrOC 降解通量，这比早期对 LS + ESS 水柱中溶解和颗粒 terrOC 降解通量的估计低几个数量级。这种差异主要是由于沉积物 terrOC 的降解速率常数较低，这可能是由多种因素造成的：(i) 与完全含氧的水相比，沉积物中氧气的可用性较低，(ii) terrOC-矿物质的稳定作用(iii) 由于沉积物中的化学/分子结构，本质上顽抗的物质比例较高。陆架沉积物中永久冻土释放的陆地碳的封存可能会减弱原本预期的永久冻土碳气候反馈。