Collaborative Research: Particle Scavenging Controls on Trace Element Distributions

海洋中几乎所有的光合作用都是由被称为浮游植物的微小的单细胞“植物”进行的。浮游植物的光合作用构成了食物链的基础，支撑着海洋中几乎所有的生命。浮游植物需要生长的关键营养物质之一是铁，它在海洋表面水域往往供不应求，会限制浮游植物的生长和光合作用。该项目旨在更好地了解海洋中铁的循环，重点是通过颗粒清除从海洋中去除铁。颗粒清除指的是溶解的铁粘在大的下沉颗粒上，最终将铁移到沉积物中。这项模拟研究将模拟海洋中的铁循环，以及几种不同的金属同位素的循环，这些同位素也会被颗粒清除，但不会作为浮游植物的营养物质。这将有助于将生物对铁分布的影响与颗粒清除和其他物理过程的影响分开。还将评估来自尘埃沉积、海洋沉积物、河流径流和海底热液喷口的海洋铁的外部来源。这项工作对于理解气候变化和人类活动将如何改变铁的循环和影响未来的生物地球化学具有重要意义。该项目还将支持两名研究生和一名本科生研究员。模型模拟将通过与铁和其他关键变量的现场测量进行广泛的比较来评估和约束。GEOTRACES计划最近制作了一套全球船舶测量测量，对许多同位素和微量元素进行了全深度测量，包括铁，这是评估预测海洋模型(共同体地球系统模型(CESM)海洋组成部分)的理想选择。GEOTRACES数据集也是整合到我们的离线反向模型(OCIM，CyCLOCIM)中的理想选择，该模型可以在3D环流和生物地球化学的背景下解释仍然稀少的观测结果。对230Th、232Th、231Pa和Fe循环的模拟将提高对粒子清除的机理的理解，并对海洋中微量元素的外部成因来源的模式和大小施加更强的观测约束。这项研究的结果和产品，以及社区地球系统模型(CESM)的海洋模型部分，将被纳入CESM的未来版本，以提高目前预测海洋生物地球化学和海洋生态系统将如何沿着一系列潜在的未来气候轨迹响应气候变化的能力。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nearly all of the photosynthesis in the oceans is carried out by microscopic, single-cell “plants” called phytoplankton. The photosynthesis by phytoplankton forms the base of the food chain, supporting almost all life in the oceans. One of the key nutrients that phytoplankton need to grow is iron, which is often in short supply in ocean surface waters and can limit the phytoplankton growth and photosynthesis rates. This project seeks to better understand the cycling of iron in the oceans, focusing on the removal of iron from the oceans by particle scavenging. Particle scavenging refers to dissolved iron sticking to large, sinking particles, which ultimately remove iron to the sediments. This modeling study will simulate iron cycling in the oceans, along with the cycling of several different metal isotopes, that are also subject to removal by particles scavenging, but do not act as nutrients for phytoplankton. This will help separate the biological influences on iron distributions, from the impacts of particle scavenging and other physical processes. The external sources of iron to the oceans coming from dust deposition, ocean sediments, river runoff, and the seafloor hydrothermal vents will also be evaluated. This work is important for understanding how climate change and human activities will modify the iron cycle and impact biogeochemistry in the future. This project will also support two graduate students and an undergraduate student researcher. The model simulations will be evaluated and constrained with extensive comparisons to field measurements of iron and the other key variables. The GEOTRACES program has recently produced a global set of ship measurement surveys, with full depth measures of numerous isotopes and trace elements, including iron, that are ideal for evaluating the prognostic ocean model (Community Earth System Model (CESM) ocean component). The GEOTRACES datasets are also ideal for incorporation into our offline, inverse model (OCIM, CYCLOCIM) which can interpret the still sparse observations in the context of 3D circulation and biogeochemistry. The simulations of 230Th, 232Th, 231Pa, and Fe cycling will improve mechanistic understanding of particle scavenging and place stronger observational constraints on the patterns and magnitude of external lithogenic sources of trace elements to the oceans. Results and products from this study, with the ocean model component of the Community Earth System Model (CESM), will be incorporated into future versions of CESM, to improve the current ability to predict how ocean biogeochemistry and marine ecosystems will respond to climate change along a range of potential future climate trajectories.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.