Clustering of Floating Tracers in the Ocean

海洋中漂浮示踪剂的聚集

• 批准号: 2478905
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2478905
• 关键词: Clustering; Floating; Tracers; Ocean

The Project is mostly motivated by marine plastic pollution and the need to understand and mitigate it. Ocean circulation is characterized by complicated mesoscale and submesoscale eddying motions (i.e., eddies) acting on length scales from a few to hundreds of kilometres, and on timescales from days to many months - these phenomena feed an active research scope involving many fundamental and practical aspects. The eddies affect many tracers and substances floating on the ocean surface: plastic pollution (including litter and microplastic), oil spills, sargassum, plankton, ice and wreckage debris. Our main focus is on the plastic pollution, which is one of the largest environmental threats. In a complicated and poorly understood way, the floating materials are constantly moved around, redistributed and clustered by the large-scale ocean circulation, eddies and smaller-scale flow features. Here, by clustering we refer to the process of accumulation and aggregation of material properties in structured and temporally evolving spatial patterns. This process is practically important, because different floating and neutrally buoyant tracers, including nutrients and biomass, cluster differently - this has profound effect on their interactions; e.g., positive correlations between clusters of pollution and marine life have enhanced adverse effect on the latter. In the Project we aim to understand some fundamentals of the clustering. There are many practical needs for accurate predictions of distributions and transport pathways of the floating tracers, but there are also many theoretical aspects involved, which shape up the research design and aims of the Project. These aspects can be grouped as the following: (1) Most of the marine plastic and oil is floating, and the plastic is also made up of finite-size particles - this results in significant non-passive and non-Lagrangian properties of these tracers. As a result, their common approximations in terms of passive-tracer concentrations or ensembles of Lagrangian particles have systematic errors and biases. The Project will estimate the latter and explore more accurate approximations for floating tracers. (2) Most of the spatio-temporal variability of the tracers is driven by the mesoscale and sub-mesoscale eddy fields, which are routinely either unresolved or underresolved in general circulation models and field observations. Thus, progress in predictive understanding of floating tracers is hindered by the lack of (inherently expensive) in situ observations and by the enormous computational burden required for brute-force resolution of mesoscale and submesoscale eddies in operating general circulation models. This puts theoretical understanding of the involved mechanisms and tracer behaviours at the research frontline, as outlined in the Project. (3) To a large degree the clustering process is induced by the multiscale and weak, surface velocity divergence, that is difficult to observe and model, because it is induced and controlled by different physical processes with poorly understood contributions and complicated mutual feedbacks. In a systematic way the Project aims to sort out clustering contributions of the underlying physical processes. (4) In connection with (1)-(3), the Project also aims to develop efficient methodologies for clustering analyses, as well as mathematical models of clustering for practical applications. It is expected that theoretical results of the Project will be useful for the existing and upcoming observational programs, as well as for many researchers dealing with marine pollution and material transport in the ocean. Links to relevant working groups and missions have been thought out, and support from Erik van Sebille, who coordinates the global research on marine plastic pollution, has been secured. Alignment to EPSRC's strategic theme and research areas: fluid dynamics, mathematical physics, nonlinear systems, living with environmental change.

该项目的主要动机是海洋塑料污染以及了解和减轻污染的必要性。海洋环流的特征是复杂的中尺度和亚中尺度涡旋运动（即，这些现象的长度从几公里到几百公里不等，时间从几天到几个月不等，为涉及许多基本和实际方面的积极研究提供了素材。这些漩涡会影响许多漂浮在海洋表面的示踪物和物质：塑料污染（包括垃圾和微塑料）、石油泄漏、马尾藻、浮游生物、冰和残骸碎片。我们的主要重点是塑料污染，这是最大的环境威胁之一。漂浮物以一种复杂且知之甚少的方式不断地四处移动，通过大规模的海洋环流，漩涡和小规模的流动特征重新分布和聚集。在这里，通过聚类，我们指的是在结构化和时间演变的空间模式中材料属性的积累和聚集的过程。这个过程实际上很重要，因为不同的漂浮和中性浮力示踪剂，包括营养物质和生物质，聚集的方式不同--这对它们的相互作用有深远的影响;例如，污染集群与海洋生物之间的正相关性增强了对海洋生物的不利影响。在这个项目中，我们的目标是了解集群的一些基本原理。准确预测漂浮示踪剂的分布和传输路径有许多实际需求，但也涉及许多理论方面，这些方面形成了该项目的研究设计和目标。这些方面可以分为以下几类：（1）大多数海洋塑料和石油是漂浮的，塑料也是由有限尺寸的颗粒组成的-这导致这些示踪剂具有显着的非被动和非拉格朗日特性。因此，他们常用的被动示踪剂浓度或拉格朗日粒子系综的近似值存在系统误差和偏差。该项目将估计后者，并探索更准确的浮动示踪剂近似值。(2)大多数的时空变化的示踪剂是由中尺度和亚中尺度涡动场，这是经常未解决或欠解决的大气环流模式和现场观测。因此，在预测性的理解浮动示踪剂的进展是阻碍了缺乏（固有的昂贵）的原位观测和巨大的计算负担所需的蛮力分辨率的中尺度和亚中尺度涡旋在操作的大气环流模式。正如项目中所概述的那样，这将对所涉及的机制和示踪剂行为的理论理解置于研究前沿。(3)在很大程度上的聚类过程是由多尺度和弱，表面速度的分歧，这是很难观察和建模，因为它是由不同的物理过程引起和控制的知之甚少的贡献和复杂的相互反馈。该项目旨在以系统的方式整理出潜在物理过程的聚类贡献。(4)关于（1）-（3），本项目还旨在开发有效的聚类分析方法，以及用于实际应用的聚类数学模型。预计该项目的理论结果将对现有和即将开展的观测计划以及许多研究海洋污染和海洋物质运输的研究人员有用。与相关工作组和任务的联系已经考虑好了，并得到了协调全球海洋塑料污染研究的Erik货车Sebille的支持。符合EPSRC的战略主题和研究领域：流体动力学，数学物理，非线性系统，与环境变化的生活。