Boundary Layer Effects on Flow and Mixing in Deep Ocean Canyons

边界层对深海峡谷流动和混合的影响

• 批准号: 1357078
• 负责人: Ian Eisenman
• 金额: $ 22.31万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 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: 2014-04-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1357078&HistoricalAwards=false
• 关键词: Boundary; Layer; Effects; Flow; Mixing

Overview: The main reasons to identify the spatial and temporal distribution of mixing and upwelling in the deep ocean are to understand its energy budget, to close the overturning circulation and to understand deep currents and the transport of heat, fresh water, dissolved carbon, geochemical tracers, and nutrients. Observations suggest that the majority of deep-ocean mixing happens over rough topography, like the flanks of the world's mid-ocean ridges. Though tidally-driven internal waves are the most commonly discussed explanation for this mixing, a number of observations suggest that mixing and upwelling within the ridge flank canyons is significant, and that it is not fully explained by internal wave processes. There are about 1,000 mid-ocean ridge flank canyons in the deep ocean, and the canyon to be studied in this project is representative of many or most of them. Therefore, if boundary layer processes are shown to be significant in this canyon, they are expected to be significant throughout much of the world's oceans. This study presents a novel hypothesis for the mechanism behind an important process (abyssal mixing), developed with physical models, and which can be feasibly and cleanly tested with an observational program.Intellectual Merit: A novel mechanism for abyssal mixing and upwelling is proposed: diffusion-driven boundary layers interacting with complicated topography. Though it occurs in conjunction with tidally-driven mixing, this mechanism may significantly change the expected distribution of deep-ocean mixing. This project investigates whether boundary layers are driving the circulation within a canyon in the South Atlantic using a series of modeling experiments to elucidate how these boundary layers interact with complicated topography and affect bulk properties of the ocean. The approach consists of a hierarchy of models with increasing complexity, from canyons with constant cross-sections to fully-realistic three-dimensional topography. A key deliverable is a set of metrics for the total impact of the boundary layers on the density field far from the boundary. These metrics will be related to the characteristics of the topography as a first step toward mixing parameterizations that do not collapse all topographic effects into a single roughness parameter. Broader Impacts: This project will improve our understanding of mixing and upwelling throughout the deep ocean. A key goal of the modeling portion of this study is beginning to develop mixing parameterizations for global models that take into account boundary layer and mixing processes within canyons and are based on both models and observations. This project will also form a central portion of the training of a postdoctoral researcher.

概述：识别深海混合和上升流的空间和时间分布的主要原因是了解其能量预算，关闭倾覆的循环，了解深水，淡水，淡水，淡水，溶解碳，地球化学示踪剂和营养。观察结果表明，大多数深海洋混合发生在粗糙的地形上，例如世界中山脊的侧面。尽管潮汐驱动的内波是这种混合的最常见的解释，但许多观察结果表明，在山脊侧面峡谷内的混合和上升流是很重要的，并且没有通过内部波过程来充分解释。在深海中大约有1,000个中山山脊侧峡谷，该项目中要研究的峡谷代表了其中许多或大多数。因此，如果在此峡谷中证明边界层过程很重要，则预计它们在世界上许多海洋中都会很重要。这项研究提出了一个新的假设，该假设是通过物理模型开发的重要过程（深处混合）背后的机制，并且可以通过观察程序进行可靠，清洁测试。IntlectualFure：提出了一种新颖的深渊混合和上升的机制：提议：提议：扩散驱动的边界层与复杂的地形相互作用。尽管它与潮汐驱动的混合结合发生，但该机制可能会显着改变深洋混合的预期分布。该项目研究了边界层是否使用一系列建模实验来驱动南大西洋峡谷内的循环，以阐明这些边界层如何与复杂的地形相互作用并影响海洋的批量特性。该方法包括一个模型的层次结构，从具有恒定横截面到完全现实的三维地形的峡谷，其复杂性越来越高。一个关键可交付的是一组指标，用于边界层对远离边界的密度场的总影响。 这些指标将与地形的特征有关，这是混合参数化的第一步，这些参数不会使所有地形效应崩溃为单个粗糙度参数。更广泛的影响：该项目将提高我们对整个深海混合和上升流的理解。本研究的建模部分的一个关键目标开始开发用于考虑边界层和峡谷内混合过程的全局模型的混合参数化，并基于模型和观察值。该项目还将构成博士后研究人员培训的中心部分。