Collaborative Research: Field and Modeling Studies of the Magnitude and Variability of 234-Th Based Estimates of POC Export Flux and Remineralization in the Upper Ocean

合作研究：基于 234-Th 估计的 POC 输出通量和上层海洋再矿化的幅度和变异性的现场和建模研究

• 批准号: 0327693
• 负责人: Adrian Burd
• 金额: --
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-12-15 至 2008-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0327693&HistoricalAwards=false
• 关键词: Collaborative; Research; Field; Modeling; Studies; Collaborative; Research; Field; Modeling; Studies

ABSTRACTOCE-0327721 / OCE-327644 / OCE-0327693The magnitude of the flux of biogenic particulate organic carbon (POC) exported from the surface waters of the world ocean and remineralized at depth is critical to constraining models of the global carbon cycle, yet remains controversial. Over the past decade, 234Th has been increasingly used as a tracer to estimate POC export from the euphotic zone by multiplying the depth-integrated 234Th flux by the POC/234Th ratio of sinking particles. The accuracy of this technique is highly dependent on the natural variability in the POC/234Th ratio and 234Th flux, yet the significance of this variability to estimates of POC export remains uncertain. The global distribution of 234Th-derived POC export fluxes can vary by 2-10 times or more due solely to variability in the POC/234Th ratio and procedures used to estimate the 234Th flux. Thus, despite over a decade of research, our understanding of the magnitude and variability of 234Th-derived POC export fluxes, and the dominant controlling mechanisms, is not well constrained.In this project field, researchers at the University of Rhode Island, Texas A & M University, and University of Georgia will conduct field and modeling studies to address the following major question: How accurate are 234Th-based estimates of POC export flux from the euphotic to the mesopelagic zone, what are the dominant mechanisms controlling 234Th scavenging and export, and how can this tracer technique be improved? They have two working hypotheses designed to address this central question. Hypothesis 1: Regional variability in the magnitude of 234Th-derived POC export is determined by differences in particle source/organic chemical composition and food web structure. Hypothesis 2: Particle-particle interactions and differential biogeochemical recycling of organic C and 234Th controls POC/234Th ratios and hence the magnitude of 234Th-derived POC export and remineralization. The research strategy is to combine new and existing measurements of sediment trap and particle size-fractionated 234Th, POC and specific organic compounds in the upper ocean (~0-500 m) with newly developed particle coagulation models to validate, test and further develop the proposed working hypotheses. Samples will be collected from three study sites characterized by distinct differences in food-web structure and particle export (Mediterranean, Arctic, NW Atlantic) and designed to provide maximum information on the mechanisms controlling POC/234Th ratios and POC export and remineralization. Model development and testing is a key aspect of the project and serves to guide and validate the field observations and provide information on mechanisms of 234Th estimates upper ocean POC export and remineralization.The intellectual merit of the proposed research bears on a number of national and international carbon cycle research programs (JGOFS, VERTIGO, DYFAMED, CARBOCEAN). Specifically, this proposal has broad intellectual implications for previous and currently NSF funded projects that use (or have used) 234Th to measure POC export fluxes from the upper ocean. For example, POC fluxes obtained during the JGOFS program may need to be revised, and future investigations of the mesopelagic, which will depend on accurate determination of the particle flux entering this region of the ocean, may need to take the results of this work into account. The results could also have implications for the SCOR/IGBP OCEANS initiative of improved understanding of the global ocean carbon cycle.

AbstractOCE-0327721 / OCE-327644 / OCE-03276933生物颗粒有机碳（POC）的通量大小从世界海洋的地表水域导出，并在DEPTH上重新矿化的深度对全球碳循环模型的约束至关重要，但仍存在争议。在过去的十年中，通过将深度集成的第234通量乘以下沉颗粒的POC/234TH比率，将第234次用作示踪剂估计POC从舒适区出口的示踪剂。该技术的准确性高度依赖于POC/234TH和234 FLUX的自然变异性，但是这种变异性与POC导出估计的重要性仍然不确定。 第234个衍生的POC出口通量的全球分布可能仅由于POC/234TH的变化以及用于估计第234次通量的程序而变化2-10倍或更多。因此，尽管进行了十多年的研究，但我们对234个衍生的POC出口通量和主要控制机制的大小和可变性的理解却没有很好的限制。在这个项目领域，罗德岛州罗德岛州A＆M University of Devartive of Texas A＆M University of Develly Island of Decult of Copperip the Inder Inders and Georgia将从下面的研究中进行计算：234的现场和模型的估算。中质区域，控制第234次清除和出口的主要机制是什么？如何改善这种示踪剂技术？ 他们有两个工作假设，旨在解决这个中心问题。假设1：234衍生的POC导出幅度的区域可变性取决于粒子源/有机化学组成和食物网络结构的差异。假设2：有机C和第234个控制POC/234的粒子粒子相互作用和差异生物地球化学回收，因此234衍生的POC出口和回忆性的幅度。该研究策略是将上海（〜0-500 m）中的新的和现有的沉积物陷阱和粒度分级分数的测量结果与新开发的粒子凝结模型相结合，以验证和进一步开发拟议的工作假设。样品将从三个研究地点收集，这些研究地点的特征是食品 - 网络结构和颗粒导出（地中海，北极，西北大西洋）的明显差异，并旨在提供有关控制POC/234th比率以及POC出口和回忆性和回忆性的机制的最大信息。模型开发和测试是该项目的关键方面，旨在指导和验证现场观察结果，并提供有关第234估计机制的信息，估计上海POC的出口和回忆性。拟议的研究的知识分子具有许多国家和国际碳循环研究计划（JGOFS，jgofs，jgofs，vertigo，vertigo，dyffame，dyffame，dyffimed，carbocean）。具体而言，该提案对使用（或已使用）第234个用于测量上海POC出口通量的先前和NSF资助的项目具有广泛的智力含义。例如，可能需要修改JGOFS计划期间获得的POC通量，并且对中质质量的未来研究将取决于对进入海洋该区域的粒子通量的准确确定，可能需要考虑到这项工作的结果。结果也可能对SCOR/IGBP海洋倡议有影响，以提高对全球海洋碳循环的了解。