Deciphering the physical controls on the fate of terrestrially-derived organic carbon in a high-yield tectonically-active margin

破译高产构造活跃边缘中陆源有机碳命运的物理控制

• 批准号: 2324953
• 负责人: Steven Kuehl
• 金额: $ 26.47万
• 依托单位: College of William & Mary Virginia Institute of Marine Science
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2324953&HistoricalAwards=false
• 关键词: Deciphering; physical; controls; fate; terrestrially

Sediment carried by large rivers accumulates on the adjacent continental shelves forming major deposits of mineral and associated organic matter. Globally, these deposits represent the major burial sites for organic matter in the ocean and help to regulate atmospheric CO2. The amount of carbon preserved in a paticular shelf deposit depends on how fast the sediment is buried. When sediment is buried faster, more organic carbon is removed. In very energetic shelf settings, however, waves and tides can cause sediment resuspension. This resuspension leads to oxidation and breakdown of organic matter that releases CO2 to the atmosphere. The Ayeyarwady-Thanlwin river system in the northern Andaman Sea is the third largest globally but has not previously been assessed for its carbon sequestration potential. It is the only remaining large river system in Asia that has not been severely affected by human activity. Humans have altered the delivery of river sediment to the ocean in many systems with unknown consequence on the global carbon budget. This study uses an existing set of core samples and other data collectd during a 2017 research cruise. The goal is to examine the transformation of organic matter from the rivers to the ocean. The study also explores the physical processes that determine the burial efficiency for orgainc carbon. This will be determined through modeling of ocean currents, waves, tides and storms. The results of this study will provide a baseline for future changes, including planned major dam construction on these rivers. With increasing human modifications to this system and increased storm frequency driven by climate change, this research will help better understand the future of this heavily populated and environmentally sensitive system. This project will support a Ph.D. student and a post-doctoral scientist. In addition, the models developed for this project will be available for community modeling efforts.Continental margins are the primary depocenters of mud delivered by rivers, record a rich history of terrestrial and oceanographic conditions, and account for most of the organic carbon (OC) burial in the ocean. The Ayeyarwady and Thanlwin rivers enter an active margin in the northern Andaman Sea and eastern Bay of Bengal. Relatively understudied, their combined inputs rank in the top three of the world’s river systems in terms of sediment and OC supply. A 2017 research cruise conducted by the PIs recovered a unique and unprecedented set of observations and sediment samples, and this study leverages these existing samples and modifies a numerical model to address exciting new questions regarding the dispersal and fate of sediment and OC in this globally important system. Specifically: 1) what is the residence time of sediment in the Gulf and mechanism(s) for transfer of this material to the basin depocenter?, 2) how do the associated physical processes affect the transformation and sequestration of organic carbon as it transits the shallow shelf to the basin?, and 3) what are the relative roles of seasonal (monsoonal) oceanographic conditions and episodic events (cyclones) in affecting sediment dispersal to the depocenter and northwestern shelf. At the time of the 2017 cruise, the Ayeyarwady and Thanlwin were the last free-flowing mega-rivers in tropical and subtropical Asia. Therefore, this study provides a baseline for certain future change. Numerical models developed for this project will be available for application to other river-influenced margins via community modeling efforts. This research supports the education of a promising Ph.D. candidate who will focus on the organic geochemistry proposed herein, and a post-doctoral scientist who will focus on the potentially critical role of fluid mud transport in this system. The PIs forged strong relationships with the Myanmar research community during the previous project, and propose to continue this engagement through joint participation at an international meeting. With rapidly increasing human modifications to the A-T system and predictions of future increased cyclone frequency driven by climate change, this research will be instrumental in understanding the future trajectory of this heavily populated and environmentally sensitive system.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

大河流携带的沉积物堆积在邻近的大陆架上，形成了全球范围内的主要矿物和相关有机物沉积物，这些沉积物是海洋中有机物的主要埋藏地，有助于调节大气中二氧化碳的含量。特定的陆架沉积物取决于沉积物埋藏的速度。然而，在充满活力的陆架环境中，当沉积物埋藏速度更快时，更多的有机碳会被去除，这种再悬浮会导致沉积物氧化和沉积。安达曼海北部的伊洛瓦底江-坦温河流域是全球第三大河流系统，但此前尚未对其碳封存潜力进行过评估，它是亚洲仅存的大型河流系统。人类活动并未受到人类活动的严重影响。人类在许多系统中改变了河流沉积物向海洋的输送，这对全球碳预算产生了未知的影响。这项研究使用了一组现有的核心样本和 2017 年研究期间收集的其他数据。该研究的目标是研究有机物从河流到海洋的转化，这将通过洋流、波浪、潮汐和风暴的建模来确定。这项研究的结果将为未来的变化提供基准，包括计划在这些河流上建设大型水坝，随着人类对该系统的改造不断增加以及气候变化导致的风暴频率增加，这项研究将有助于更好地了解这一严重的未来。该项目人口稠密且环境敏感。此外，为该项目开发的模型将可用于社区建模工作。大陆边缘是河流输送的泥浆的主要沉积中心，记录了丰富的陆地历史。伊洛瓦底江和坦温河进入安达曼海北部和孟加拉湾东部的活跃边缘，占海洋中大部分有机碳的埋藏量。就沉积物和有机碳供应而言，综合输入量位居世界河流系统前三名。 2017 年，PI 进行的一项研究巡游回收了一组独特且前所未有的观测结果和沉积物样本，本研究利用了这些现有样本并修改了模型。数值模型来解决有关这个全球重要系统中沉积物和有机碳的扩散和归宿的令人兴奋的新问题，具体来说：1）沉积物在海湾中的停留时间以及该物质转移到盆地的机制。沉积中心？，​​2）当有机碳从浅陆架转移到盆地时，相关的物理过程如何影响有机碳的转化和封存？以及3）季节性（季风）海洋条件和偶发事件（气旋）的相对作用是什么？ ）影响沉积物向沉积中心和西北陆架的扩散。2017 年航行时，伊洛瓦底江和萨尔文河是热带和热带地区最后一条自由流动的巨型河流。因此，本研究为该项目开发的某些未来变化提供了基准，该模型将可通过社区建模工作应用于其他受河流影响的边缘地区。一位博士后科学家将重点研究本文提出的有机地球化学，一位博士后科学家将重点研究流体泥浆输送在该系统中的潜在关键作用。 PI 在之前的项目中与缅甸研究界建立了牢固的关系，并提议：通过联合继续这种接触随着人类对 A-T 系统的改造迅速增加，以及对气候变化导致的未来气旋频率增加的预测，这项研究将有助于了解这个人口稠密且环境敏感的系统的未来轨迹。该奖项反映了 NSF 的贡献法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。