Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost
Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost
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DOI：
10.1073/pnas.1811797116
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发表时间：
2019-05
影响因子：
11.1
通讯作者：
B. Wild;A. Andersson;L. Bröder;J. Vonk;G. Hugelius;J. McClelland;Wenjun Song;P. Raymond;Ö. Gustaf
中科院分区：
文献类型：
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作者：
B. Wild;A. Andersson;L. Bröder;J. Vonk;G. Hugelius;J. McClelland;Wenjun Song;P. Raymond;Ö. Gustaf
高纬度永久冻土和泥炭沉积物含有大量休眠碳，在变暖时，可能部分降解为CO2和CH 4，部分可能进入河流。考虑到西伯利亚北极的规模和异质性，整个大陆的解冻和再动员模式一直难以约束。这项研究将四条大型西伯利亚河流有机碳中14 C的长达十年的观测记录与广泛的14 C源指纹数据库结合到一个统计模型中，以提供河流流动有机碳部分的定量分区，这些有机碳特别来自永久冻土和泥炭沉积物，并分别用于溶解和颗粒载体，横跨西伯利亚北极，揭示了不同的空间和季节系统模式的碳再活化。气候变暖预计将调动北方永久冻土和泥炭有机碳（PP-C），但即使是目前的释放量和系统的具体情况也没有受到很好的限制。虽然部分PP-C将在解冻时降解为CO2和CH 4，直接放大全球变暖，但另一部分将进入河流网络，可能为观察大规模PP-C再活化模式提供窗口。在这里，我们采用了长达十年的，高时间分辨率的14 C溶解和颗粒有机碳（DOC和POC，分别）deconvolute PP-C释放在西伯利亚的河流的大流域：鄂毕河，叶尼塞河，莉娜，科雷马。14 C限制的PP-C输出估计值仅相当于河流有机碳总量的17 ± 8%，可作为监测北极变暖时河流PP-C再活化变化的基准。DOC主要由近期有机碳和示踪较差的PP-C（12 ± 8%）组成，而POC具有更强的PP-C特征（63 ± 10%），代表了检测PP-C释放时空动态的最佳窗口。不同的季节模式表明，虽然DOC主要源于表层土壤的逐渐沥滤，POC反映了更深层次的存款突然崩溃。Ob和Yenisey较高的溶解PP-C出口与促进沥滤的不连续永久冻土一致，而Lena和Kolyma较高的颗粒PP-C出口可能与更新世沉积物的热岩溶引起的坍塌相呼应。因此，基于14 C的河流有机碳定量指纹提供了一个机会，以阐明大规模的PP-C再活化的动态响应北极变暖。
Significance High-latitude permafrost and peat deposits contain a large reservoir of dormant carbon that, upon warming, may partly degrade to CO2 and CH4 at site and may partly enter rivers. Given the scale and heterogeneity of the Siberian Arctic, continent-wide patterns of thaw and remobilization have been challenging to constrain. This study combines a decade-long observational record of 14C in organic carbon of four large Siberian rivers with an extensive 14C source fingerprint database into a statistical model to provide a quantitative partitioning of the fraction of fluvially mobilized organic carbon that specifically stems from permafrost and peat deposits, and separately for dissolved and particulate vectors, across the Siberian Arctic, revealing distinct spatial and seasonal system patterns in carbon remobilization. Climate warming is expected to mobilize northern permafrost and peat organic carbon (PP-C), yet magnitudes and system specifics of even current releases are poorly constrained. While part of the PP-C will degrade at point of thaw to CO2 and CH4 to directly amplify global warming, another part will enter the fluvial network, potentially providing a window to observe large-scale PP-C remobilization patterns. Here, we employ a decade-long, high-temporal resolution record of 14C in dissolved and particulate organic carbon (DOC and POC, respectively) to deconvolute PP-C release in the large drainage basins of rivers across Siberia: Ob, Yenisey, Lena, and Kolyma. The 14C-constrained estimate of export specifically from PP-C corresponds to only 17 ± 8% of total fluvial organic carbon and serves as a benchmark for monitoring changes to fluvial PP-C remobilization in a warming Arctic. Whereas DOC was dominated by recent organic carbon and poorly traced PP-C (12 ± 8%), POC carried a much stronger signature of PP-C (63 ± 10%) and represents the best window to detect spatial and temporal dynamics of PP-C release. Distinct seasonal patterns suggest that while DOC primarily stems from gradual leaching of surface soils, POC reflects abrupt collapse of deeper deposits. Higher dissolved PP-C export by Ob and Yenisey aligns with discontinuous permafrost that facilitates leaching, whereas higher particulate PP-C export by Lena and Kolyma likely echoes the thermokarst-induced collapse of Pleistocene deposits. Quantitative 14C-based fingerprinting of fluvial organic carbon thus provides an opportunity to elucidate large-scale dynamics of PP-C remobilization in response to Arctic warming.