Collaborative Proposal: Estimation of particle aggregation and disaggregation rates from the inversion of chemical tracer data

合作提案：通过化学示踪数据反演估计颗粒聚集和解聚率

• 批准号: 1829790
• 负责人: Olivier Marchal
• 金额: $ 45.52万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829790&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Estimation; particle; aggregation

The biological carbon pump in the ocean is an important process by which atmospheric carbon dioxide (CO2) is effectively transported from the surface ocean to the deep ocean, and thereby removing CO2 from the atmosphere. This transport occurs in a multi-step process. First, phytoplankton carry out photosynthesis in the surface, sunlit waters of the ocean, taking up atmospheric CO2 and fixing it into particulate organic carbon. A portion of the organic carbon contained in the phytoplankton is packaged into larger clusters (aggregates) that can sink to the deep ocean. The deeper these aggregates sink, the longer the carbon contained in them is removed from the atmosphere. The depth to which aggregates sink varies greatly over time and space and are difficult to predict. In general, larger aggregates sink more quickly, and thus more deeply, than smaller particles. Processes that promote aggregation to larger particles should enhance the biological pump, and processes that promote disaggregation (breakdown of particle clusters) and regeneration (decomposition) of the organic carbon should decrease the strength and efficiency of the biological pump. Particle aggregation and disaggregation rates are thus crucial to understanding the variability of the biological pump, but are very difficult to measure directly. This project will use chemical tracers and a modeling approach to quantify the rates of these important processes. The investigators will apply the approach to a variety of oceanic environments and provide the first large-scale effort to quantify these rates in the upper 500 meters of the ocean. As part of this project, they will interface with the CalTeach program, which is a University of California Science and Math Initiative to place university science, math, and engineering majors in K-12 classrooms. Many of these CalTeach interns go on to become K-12 science teachers in California. Two undergraduate students enrolled in the CalTeach program at the University of California, Santa Cruz (UCSC) will participate as laboratory assistants and develop a hands-on teaching module on the carbon cycle and biological pump for K-12 classrooms. Scientists from the University of California at Santa Cruz and Woods Hole Oceanographic Institution propose to estimate the rates of particle aggregation and disaggregation in the mesopelagic zone through the inversion of observations of three chemical tracers, namely thorium (Th)-234, lithogenic particles, and particulate organic carbon (POC) distributed between small, suspended particles and large, sinking particles. The isotopes of Th have long been used to estimate rates of particle dynamics processes because of their known source function and particle-reactive behavior. Previous work has shown that lithogenic particles act as an inert, passive tracer of particle dynamics. The investigators will couple thorium and lithogenic particle measurements to measurements of POC to estimate particle aggregation and disaggregation rates from a wide range of oceanographic environments. Estimates of particle cycling rates deduced from the inversion of chemical tracer data provide a crucial quantitative constraint to which rates derived from other approaches can be compared. The main objective of this work is to estimate depth- varying (dis-) aggregation rates at each station of the EXPORTS and GEOTRACES cruises that are most consistent with the tracer data. This work will also produce depth-varying estimates of POC remineralization rates and particle sinking rates.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.

海洋中的生物碳泵是一个重要的过程，通过该过程将大气二氧化碳（CO2）有效地从地面海洋传输到深海，从而从大气中取出了二氧化碳。该运输发生在多步骤过程中。首先，浮游植物在地表，阳光海水的水域进行光合作用，占据大气中的二氧化碳并将其固定在颗粒有机碳中。浮游植物中包含的有机碳的一部分被包装成较大的簇（聚集体），可以沉入深海。这些聚集体越深，从大气中除去其中包含的碳的时间越长。聚集体下沉的深度随时间和空间而变化很大，很难预测。通常，较大的聚集体比较小的颗粒更快，因此更深入。促进较大颗粒聚集的过程应增强生物泵，以及促进有机碳的分解（粒子簇的分解）和再生（分解）的过程应降低生物泵的强度和效率。因此，粒子聚集和分解速率对于了解生物泵的变异性至关重要，但很难直接测量。该项目将使用化学示踪剂和建模方法来量化这些重要过程的速率。研究人员将将方法应用于各种海洋环境，并提供第一个大规模的努力，以量化海洋上500米的上限。作为该项目的一部分，他们将与Calteach计划进行交互，该计划是加利福尼亚大学科学与数学大学的一项计划，旨在将大学科学，数学和工程专业的大满贯在K-12教室中。这些Calteach实习生中有许多继续成为加利福尼亚州的K-12科学老师。加利福尼亚大学圣克鲁斯分校（UCSC）参加CALTEACH计划的两名本科生将作为实验室助理参加，并在K-12教室的碳循环和生物泵上开发一个动手教学模块。加利福尼亚大学圣克鲁斯大学和伍兹孔海洋学机构的科学家提议通过三个化学示踪剂的观察结果（即thore thorium thorium（th）-234，岩性颗粒，以及岩性颗粒，以及岩性颗粒，以及岩性颗粒，以及颗粒有机碳（POC）分布在小的，悬浮的颗粒和大的下沉颗粒之间。由于已知的源函数和粒子反应性行为，TH的同位素长期以来一直用于估计粒子动力学过程的速率。先前的工作表明，岩性颗粒充当颗粒动力学的惰性，被动示踪剂。研究人员将将thor和岩性颗粒测量结果与POC的测量进行杂交，以估算从广泛的海洋环境中的颗粒聚集和分解速率。从化学示踪剂数据反转推导出的粒子循环速率的估计值提供了至关重要的定量约束，可以比较从其他方法中获得的速率。这项工作的主要目的是估计出口的每个站点的深度（dis-）聚集率，而地理位置巡航则与示踪剂数据最一致。这项工作还将产生对POC回忆率和粒子下沉率的深度变化的估计。该奖项反映了NSF的法定任务，并认为使用基金会的知识分子优点和更广泛的影响审查标准，认为值得通过评估来获得支持。