How efficient is organic carbon burial in deep-water sediments after the extreme glacial lake outburst flood in Elliott Creek (BC, Canada)

埃利奥特溪（加拿大不列颠哥伦比亚省）极端冰川湖溃决洪水后，深水沉积物中的有机碳埋藏效率如何

• 批准号: NE/W000601/1
• 负责人: Sanem Acikalin
• 金额: $ 6.68万
• 依托单位: Newcastle University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FW000601%2F1
• 关键词: How; efficient; organic; carbon; burial

Previous work suggests that marine fjords are responsible for burying globally significant amounts of organic carbon (OC). Understanding the burial of terrestrial OC in fjords is important on a global scale, as previous work estimated that just the fine-grained fjord sediments are responsible for burying ~11% of global organic carbon flux into the oceans. More recently it was shown that coarse-grained sediment deposited by small rivers floods will significantly increase that amount of OC burial in fjords. Exceptionally large and infrequent floods, like glacial lake outburst floods (GLOFs), are likely to transport and bury larger amounts OC into coarse-grained fjord deposits, however their role remains poorly constrained due to their infrequent nature. Yet, constraining the full OC burial budget in marine sediments is important as these sediments are the second largest sink of atmospheric CO2 and thus contributes to long-term regulation of climate.An exceptional GLOF occurred on 28th Nov 2020 at Elliot Creek (BC, Canada) that now provides us a unique opportunity to study the OC burial efficiency of such extreme events. Reconstruction from the measured 4.9 Mw seismic activity that coincided with the event indicates the original landslide dislodged 30 million tonnes of sediment and triggered a ~100m high displacement-wave in the glacial lake. This wave in turn broke through the lake's moraine-dam, releasing large amounts of water, which powerfully scoured Elliott Creek before entering into the fjord. The event posed a hazard to marine traffic and coastal structures and destroyed significant salmon, wildlife and forest resources of Homalco First Nations. The Elliot Creek event moved large volumes of sediment and OC, which are ultimately deposited in the fjord. Fortuitously, Bute Inlet was previously the site of an extremely detailed time series of seabed surveys, as it was mapped ten times in between 2008 up to 2020. Recent work by our group at Bute Inlet has shown how turbidity currents transport young terrestrial OC from the river mouth down to the deeper fjord waters. The extensive background data on the bathymetry, the current dynamics and the geochemical signatures of the OC in the fjord under normal conditions now enable a unique opportunity to study the OC burial of large GLOFs. This proposal aims to test two hypotheses, which are: 1) large GLOFs can transport vast amounts of sediment and OC to the distal lobe and (2) young terrestrial organic matter can be efficiently buried in these deep water fjord sediment. Here, efficiency refers to direct transport from source to sink, as opposed the normal conditions in which OC only reaches this sink through many staggered smaller transport events. The opportunity is unique due to the combination of an exceptional flood and world-leading baseline data of Bute Inlet, having been repeatedly mapped, monitored and sampled over the last decade. Additionally, this opportunity is time limited, as normal turbidity currents activity returns this spring as the snow start to melt. These activities will start to rework, blur and bury the signature of this GLOF.The hypotheses will be tested by mapping the GLOF-related deposits throughout the fjord and characterising their OC components. Field data collection will be a combination of new bathymetric survey and sediment sampling, which can be compared to pre-event surveys and cores. Sediment and organic carbon characterisation will include grain-size analysis, XRD, total organic carbon, C-N-S, stable carbon isotope and radiocarbon composition as well as ramped pyrolysis-oxidation analysis. Combination of all routine organic geochemistry (TOC, CNS, d13C and 14C) and textural data will be used for initial fingerprinting of OC (marine or terrestrial source). Further separation of OC by RPO coupled with d13C and 14C measurements will detail the OC source, as previously demonstrated by our group.

以前的研究表明，海洋峡湾是全球大量有机碳（OC）的埋藏地。了解峡湾中陆地有机碳的埋藏在全球范围内是很重要的，因为以前的工作估计，只有细粒峡湾沉积物负责将约11%的全球有机碳通量埋藏到海洋中。最近的研究表明，小河流洪水沉积的粗颗粒沉积物将显着增加峡湾中OC埋藏量。异常大和罕见的洪水，如冰湖溃决洪水（GLOFs），可能会运输和掩埋大量的OC到粗粒度的峡湾沉积物中，但由于其罕见的性质，它们的作用仍然受到很大的限制。然而，限制海洋沉积物中OC的全部埋藏预算非常重要，因为这些沉积物是大气CO2的第二大汇，因此有助于长期调节气候。2020年11月28日在加拿大不列颠哥伦比亚省Elliot Creek发生的异常GLOF现在为我们提供了一个独特的机会来研究这种极端事件的OC埋藏效率。根据与该事件同时发生的4.9兆瓦地震活动进行的重建表明，最初的滑坡移动了3000万吨沉积物，并在冰川湖中引发了约100米高的位移波。这波又冲破了湖的冰碛坝，释放出大量的水，在进入峡湾之前强烈地冲刷了埃利奥特溪。这一事件对海上交通和沿海结构构成了危险，并摧毁了霍马科第一民族的大量鲑鱼、野生动物和森林资源。埃利奥特河事件移动了大量的沉积物和有机碳，最终沉积在峡湾。幸运的是，布特湾以前是一个非常详细的海底调查时间序列的地点，因为它在2008年至2020年期间被绘制了十次。我们小组最近在布特湾的工作表明，浊流如何将年轻的陆地有机碳从河口输送到更深的峡湾沃茨。在正常条件下，峡湾中OC的水深测量，当前动态和地球化学特征的广泛的背景数据，现在使一个独特的机会来研究大型GLOFs的OC埋藏。该建议旨在验证两个假设，即：1）大型GLOFs可以将大量沉积物和OC输送到远叶和（2）年轻的陆地有机质可以有效地埋藏在这些深水峡湾沉积物中。在这里，效率是指从源到汇的直接传输，而不是OC仅通过许多交错的较小传输事件到达该汇的正常条件。这是一个独特的机会，因为一个特殊的洪水和世界领先的基线数据的布特湾，已反复映射，监测和采样在过去十年的组合。此外，这个机会是有限的，因为正常的浊流活动返回今年春天的雪开始融化。这些活动将开始返工，模糊和埋葬这个GLOF的签名。将通过绘制整个峡湾的GLOF相关沉积物并描述其OC组件来测试假设。实地数据收集将结合新的测深测量和沉积物取样，可与事件前的测量和岩芯进行比较。沉积物和有机碳的特性鉴定将包括粒度分析、X射线衍射、总有机碳、碳氮硫、稳定碳同位素和放射性碳组成以及斜坡热解-氧化分析。所有常规有机地球化学（TOC、CNS、d13 C和14 C）和结构数据的组合将用于OC（海洋或陆地源）的初始指纹识别。通过RPO结合d13 C和14 C测量进一步分离OC将详细说明OC来源，正如我们小组先前所证明的那样。

项目成果

First source-to-sink monitoring shows dense head controls sediment flux and runout in turbidity currents.

• DOI: 10.1126/sciadv.abj3220
• 发表时间: 2022-05-20
• 期刊: SCIENCE ADVANCES
• 影响因子: 13.6
• 作者: Pope, Ed L.;Cartigny, Matthieu J. B.;Clare, Michael A.;Talling, Peter J.;Lintern, D. Gwyn;Vellinga, Age;Hage, Sophie;Acikalin, Sanem;Bailey, Lewis;Chapplow, Natasha;Chen, Ye;Eggenhuisen, Joris T.;Hendry, Alison;Heerema, Catharina J.;Heijnen, Maarten S.;Hubbard, Stephen M.;Hunt, James E.;McGhee, Claire;Parsons, Daniel R.;Simmons, Stephen M.;Stacey, Cooper D.;Vendettuoli, Daniela
• 通讯作者: Vendettuoli, Daniela