An Investigation of Abyssal Mixing and Interior Transports in the North Atlantic

北大西洋深渊混合和内部运输的调查

• 批准号: 0926848
• 负责人: Ruth Curry
• 金额: $ 310.63万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-11-01 至 2014-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0926848&HistoricalAwards=false
• 关键词: Investigation; Abyssal; Mixing; Interior; Transports

Ongoing efforts to develop a quantitative picture of the Atlantic meridional overturning circulation (AMOC) have largely focused on the western boundary current system and transports of water masses formed by buoyancy loss in the northern seas. By contrast, the structure and strength of the interior abyssal circulation and its buoyancy gain have been poorly sampled and are not known in much detail. These are, however, fundamentally important to the global ocean circulation and to ocean budgets of mass, heat and tracers. A process study will be conducted to provide quantitative estimates of abyssal mixing and circulation in order to assess the strength of, and linkages between, the horizontal and vertical components of the North Atlantic interior abyssal circulation. Analysis of climatological property fields suggests that a logical region to accomplish this lies along the eastern flank of Bermuda Rise and in the topographic basin to its southeast. Several lines of evidence suggest that these interior flows are highly structured and remarkably vigorous, and by implication, that the diapycnal mixing feeding them is particularly strong. That source region is situated on the western flank of the mid Atlantic Ridge (MAR) where rugged topography provides conditions favorable for mixing. The project is comprised of two elements: 1) An array of moored profilers designed to measure the geostrophic transports along the southeastern flank of Bermuda Rise, a primary pathway for the interior circulation, and 2) A shipboard survey to obtain microstructure and velocity profiles, plus detailed bathymetry. These will be used to construct estimates of turbulent buoyancy fluxes across a range of topographic features and a characterization of the basin-wide diapycnal forcing field.Intellectual meritEach component of the proposed experiment will provide direct measurements of a poorly quantified portion of the interior abyssal ocean, i.e., the structure and strength of horizontal flows along Bermuda Rise, and the diapycnal forcing that feeds those flows. Together, they will provide a basis for evaluating consistency between the observed circulations and the underlying dynamical theory. This attention to the interior basin will both complement and supplement the emerging quantitative picture of the AMOC.Specifically the process study will accomplish the following:1 Quantify the structure, strength, and variability of the intermediate-to-abyssal interior flow field along Bermuda Rise. Diagnose the relative contributions of northern (high tracer concentration and low nutrients) and southern (low tracer concentrations and high nutrients) sources to these flows. 2 Assess the regional structure and strength of turbulent mixing that feeds the interior flow field. Apply these to improve dynamically-based parameterizations of diapycnal forcing.3 Evaluate consistency between the magnitudes of the observed vertical and horizontal fluxes.4 Synthesize transports from various measurement programs in temperature and density classes, to construct volume flux budgets for cold to warm limb transformation and abyssal circulation in the western North Atlantic basins.Broader impactsThe results of this process study and synthesis will provide benchmarks for evaluation of ocean assimilation and reanalysis products. None of the current ocean models and analysis products exhibits much structure below 4000 m. Abyssal geostrophic flow fields in general circulation models have been shown to improve significantly when realistic representations of diapycnal mixing are incorporated. This effort will provide regional constraints for a dynamical parameterization of diapycnal forcing designed for testing and use in ocean models. Finally, the project will provide opportunities for student participation in the field and in the analysis of observational data.

正在进行的努力制定大西洋子午倾覆循环（AMOC）的定量图片，主要集中在西部边界电流系统和北部海洋浮力损失形成的水质量的运输上。相比之下，内部深渊循环的结构和强度及其浮力增益的采样较差，尚不清楚。但是，这些对于全球海洋循环和质量，热量和示踪剂的海洋预算至关重要。将进行一项过程研究，以提供深渊混合和循环的定量估计，以评估北大西洋内部深渊循环的水平和垂直成分之间的强度和联系。对气候特性领域的分析表明，实现这一目标的逻辑区域沿百慕大东部侧面以及向东南的地形盆地的东部侧面。几条证据表明，这些内部流动是高度结构化的，并且非常有剧烈，并暗示着喂养它们的二比元素混合特别强。该源区域位于大西洋山脊（MAR）的西部侧面，崎toprice的地形可提供有利于混合的条件。该项目由两个要素组成：1）旨在测量沿百慕大东南侧面的地球传输量的系列系列的剖记者，这是内部循环的主要途径，2）船上调查以获得微观结构和速度配置文件，以及详细的耳样。这些将用于构建一系列地形特征的湍流浮力通量的估计以及对盆地范围内的二比强迫场的表征。拟议的实验的智能熟悉的熟悉概要分量将直接测量不足量化的部分内部尺寸尺寸的室内大洋，即沿着水平的散布，并为贝尔多姆（Beryta）提供了良好的水平和强度。他们将共同为评估观察到的循环与潜在动力学理论之间的一致性提供基础。对内部盆地的这种关注将补充和补充AMOC的新兴定量图片。特定的过程研究将完成以下方面：1量化了沿百慕大升级的中间到Abyssal内部流动场的结构，强度和可变性。诊断北部（较高的示踪剂浓度和低营养素）和南部（低示踪剂浓度和高养分）对这些流的相对贡献。 2评估驱动内部流场的湍流混合的区域结构和强度。 3评估观察到的垂直和水平通量的大小之间的一致性。4合成的运输综合，从温度和密度类别中的各种测量程序中进行运输，以构建较冷的肢体变换的寒冷预算，以使其在北部的北部地区循环和构造的基础上构成了basins andlanty contrance.basins。海洋同化和重新分析产物的评估。当前的海洋模型和分析产品均未表现出低于4000 m的结构。一般循环模型中的深渊地质流动场已被证明是在纳入二细混合的现实表示时会显着改善。这项工作将为区域限制提供用于测试和在海洋模型中使用的Diapynal强迫的动态参数化。最后，该项目将为学生参与该领域和观察数据分析提供机会。