Parameterizations of Salt Fingers in the Ocean

海洋盐指的参数化

• 批准号: 1433132
• 负责人: Raymond Schmitt
• 金额: $ 58.59万
• 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: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1433132&HistoricalAwards=false
• 关键词: Parameterizations; Salt; Fingers; Ocean

The ultimate goal of this research is to advance our understanding of double diffusion from salt fingers in the ocean so that field observations can be properly interpreted and new representations of this phenomenon can be developed for inclusion in large-scale ocean circulation models. Salt fingering is an ocean mixing process that occurs in tropical and sub-tropical regions where warm and salty water overlies colder and fresher water. It is driven by the fact that, in water, heat diffuses faster than salt. A small parcel of warm, salty water sinking downwards into a colder, fresher region will lose its heat before losing its salt, making the parcel of water increasingly denser than the water around it and sinking further. Likewise, a small parcel of colder, fresher water will be displaced upwards and gain heat by diffusion from surrounding water, which will then make it lighter than the surrounding waters, and cause it to rise further. Locations where salt fingers are present may increase the ability of the oceans to absorb and transport heat, freshwater and nutrients than turbulent mixing in the abyss. Thus, it is very important to develop the tools necessary to quantify salt finger fluxes. The evidence that salt finger intensity is a strong function of density ratio and can feedback on the ocean's stratification is now quite abundant. This project aims to build on new theoretical results and high quality data sets to better quantify the mixing due to salt fingers in the ocean and hasten the progress toward a plausible representation in numerical models of the ocean circulation, which have a demonstrated sensitivity to double diffusion. This project will also contribute to the general knowledge of double-diffusive systems which are now recognized to be important in fields as diverse as astrophysics and magmas. The investigator plans to participate in a proposed multi-disciplinary workshop on "The Mathematics of Layers and Interfaces" in 2015. The project will also contribute to the educational development of undergraduate Summer Student Fellows at the Woods Hole Oceanographic Institution who will participate in the project as part of their summer research projects. Many of the excellent students in that program go on to become very successful graduate students.Analysis of finestructure, microstructure and tracer data will conducted along with theoretical analysis and numerical simulations in order to better understand the role of salt fingers in oceanic mixing. Evidence for the importance of salt fingers is now clear; it is the dominant thermocline mixing process in some regions and a significant contributor in many others. The fact that heat and salt are transported at different rates has a variety of consequences for thermohaline structure and ocean dynamics. There are four main elements to this project. First, a parameterization of salt fingers using microstructure data from the Salt Finger Tracer Release Experiment (SFTRE) as well as other cruises will be developed to test consistency with the new salt finger equilibration model. Second, the properties of the SFTRE thermohaline staircase will be analyzed using the Moored Profiler time series data. The analysis of layer properties in Theta-S space will be used to evaluate the viability of an existing flux divergence model. In addition, this analysis will help test the layer formation and thickness models which rely on a decreasing finger flux ratio with increasing density ratio. Third, a study of shear dispersion and lateral mixing in the staircase will be conducted using the tracer data in conjunction with the remarkably consistent Theta-S properties of the layers. This will locate any one layer observation within the overall meridional gradients of the region and permit the investigator to establish the lateral dispersion of the deliberate tracer. This analysis will allow the assessment of the displacement of layers relative to one another, and improve estimates of both vertical and lateral diffusivities. Fourth, an analysis of fingers in unstable stratifications will be done. Theory and numerical modeling will be used to help understand how a new parameter regime based on recent experimental results has the potential to affect "mixed" layer stratifications in the ocean. Overall, this project will contribute to improvement of the general circulation models used for climate prediction and ecosystem dynamics, both tasks of great importance to society.

这项研究的最终目标是促进我们对海洋中盐指双扩散的理解，以便能够正确解释现场观测，并开发这种现象的新表示方法，以便纳入大规模海洋环流模型。盐指是一种海洋混合过程，发生在热带和亚热带地区，温暖和咸的水覆盖在寒冷和新鲜的水上。这是因为在水中，热量的扩散速度比盐快。一小块温暖的咸水下沉到一个更冷、更新鲜的区域，在失去盐之前会失去热量，使水的密度比周围的水更大，下沉得更深。同样，一小块较冷、较新鲜的水将向上移动，并通过周围水的扩散获得热量，这将使它比周围的沃茨轻，并使它进一步上升。盐指存在的地方可能会增加海洋吸收和输送热量、淡水和营养物质的能力，而不是深渊中的湍流混合。因此，开发量化盐指通量所需的工具非常重要。盐指强度是密度比的一个强函数，并且可以反馈海洋分层的证据现在相当丰富。该项目旨在建立新的理论结果和高质量的数据集，以更好地量化海洋中盐指的混合，并加快海洋环流数值模型中合理表示的进展，该模型对双重扩散具有明显的敏感性。这个项目也将有助于双扩散系统的一般知识，现在被认为是重要的领域，如天体物理学和岩浆。研究人员计划在2015年参加一个关于“层和界面的数学”的多学科研讨会。该项目还将促进伍兹霍尔海洋学研究所暑期本科生研究员的教育发展，他们将参加该项目，作为其暑期研究项目的一部分。该项目的许多优秀学生后来成为非常成功的研究生。精细结构，微观结构和示踪剂数据的分析将与理论分析和数值模拟沿着进行，以便更好地了解盐指在海洋混合中的作用。盐指的重要性的证据现在很清楚;它是一些区域的主要温跃层混合过程，也是许多其他区域的重要贡献者。热量和盐分以不同的速率输送，这一事实对温盐结构和海洋动力学产生了各种影响。这个项目有四个主要内容。首先，盐指示踪剂释放实验（SFTRE）以及其他巡航的微观结构数据的参数化盐指将开发测试与新的盐指平衡模型的一致性。其次，将使用系泊剖面仪时间序列数据分析SFTRE温盐阶梯的特性。在Theta-S空间中对层特性的分析将用于评估现有通量发散模型的可行性。此外，这种分析将有助于测试层的形成和厚度模型，依赖于一个减少手指通量比与密度比增加。第三，将使用示踪剂数据结合各层非常一致的Theta-S特性，对楼梯中的剪切分散和横向混合进行研究。这将在该区域的整体纬向梯度内定位任何一层观测，并允许研究人员确定有意示踪剂的横向分散。这种分析将允许层相对于彼此的位移的评估，并提高垂直和横向扩散率的估计。第四，分析手指在不稳定分层。理论和数值模拟将被用来帮助了解一个新的参数制度的基础上最近的实验结果有可能影响“混合”层分层在海洋中。总的来说，该项目将有助于改进用于气候预测和生态系统动态的大气环流模型，这两项任务对社会都非常重要。