Collaborative Research: Investigating the Dynamics in Deep Valleys on the Seafloor With Numerical Experiments and Data Analysis

合作研究：通过数值实验和数据分析研究海底深谷的动力学

• 批准号: 0752018
• 负责人: Tamay Ozgokmen
• 金额: $ 30.41万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0752018&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Dynamics; Deep

In order to close the global overturning circulation of the ocean, the production and sinking of dense water at high latitudes must be balanced elsewhere by buoyancy gain and upwelling. Both these processes are intimately linked to diapycnal mixing, which implies that mixing processes are fundamentally important in the Earth's climate system. Additionally, vertical motion is a primary driver for the abyssal circulation, which implies that its spatial distribution must be known in order to understand and model the circulation. Observations collected during the last few decades indicate that the strongest mixing in the deep ocean is primarily found near the rough topography of mid-ocean ridges (MORs), which cover more than 50% of the entire sea-floor. Of particular interest are the many ridge-flank canyons (fracture zones) that incise the flanks of slow-spreading ridges every 50 km or so. Not only are these canyons the main sites of strong mixing, they are also strikingly regular and self similar, with persistent up-flank flows and overflows across the ubiquitous bathymetric hills that act as sills for the along-axial flows. In spite of the observational advances regarding the spatial distribution of mixing and the circulations in ridge-flank canyons, virtually nothing is known about the spatial distribution of vertical motion in the ocean. While current high resolution ocean models have made significant strides towards realism in many areas, the accuracy of the upwelling field remains as one of the important outstanding problems. The dynamics acting near MORs, and in particular the flows in the ridge flank canyons will be investigated by using numerical modeling and analysis of existing observations. In addition to improving our understanding of the lateral circulation and the mixing near rough topography, one could expect insights from this study to contribute towards developing more accurate representations of upwelling and the resulting abyssal circulations in ocean general circulation models.Intellectual Merits: Turbulent flows are strongly dependent on the details of domain geometry. Even the highest resolution large-scale ocean models cannot adequately resolve all the fine-scale features of bottom topography. As such, parameterization and modeling of upwelling induced by rough topography poses a fundamental challenge. The self-similar, regular nature of the geometry of the ridge-flank canyons and the associated flows may greatly facilitate representation of the associated drag and mixing in large-scale models. The numerical modeling of these flows is a novel undertaking, which will reveal the importance of form drag, hydraulic control and time-dependent forcing in stratified flows over multiple sills.Broader Impacts: The results from this project will be disseminated in the form of articles in journals, presentations in national and international scientific meetings, and via a project website. Ultimately, a better understanding of flow dynamics on MORs will lead to an improved understanding and modeling of the ocean general circulation. As ocean models are used to predict circulation patterns at a variety of scales, the results from this study may have the broader impact of aiding climate modeling, which can ultimately impact society by influencing policy. The results from this project may also help improve our understanding on the dispersal of hydrothermal "products", including heat, geochemical tracers and animal larvae. The study will provide support for both a PhD student and a female PhD recipient in physical oceanography.

为了关闭全球倾覆的海洋循环，必须通过浮力增长和上升的在其他地方平衡在高纬度地区的密集水的产量和下沉。这两个过程都与Diapynal混合密切相关，这意味着混合过程在地球气候系统中至关重要。另外，垂直运动是深渊循环的主要驱动力，这意味着必须知道其空间分布才能理解和建模循环。在过去的几十年中收集的观察结果表明，深海中最强的混合主要是在中山脊（MORS）的粗糙地形附近发现的，覆盖了整个海底的50％以上。尤其令人感兴趣的是许多山脊 - 弗兰克峡谷（裂缝区），它们每50公里左右切开慢速山脊的侧面。这些峡谷不仅是强烈混合的主要地点，而且它们也非常规律和自我相似，在无处不在的小山丘上持续存在的上流流和溢流，这些山丘充当了沿海流的把架。尽管关于混合的空间分布和山脊 - 弗兰克峡谷的循环的观察进步，但实际上对海洋中垂直运动的空间分布一无所知。尽管当前的高分辨率海洋模型在许多领域都取得了重大改善，但上升流域的准确性仍然是重要的杰出问题之一。将通过数值建模和现有观测值分析来研究近距离作用的动力学，尤其是脊侧峡谷中的流动。除了提高我们对横向循环和近乎粗糙地形的混合的理解外，人们还可以期望这项研究的见解有助于开发上上升的更准确的表示，以及在海洋一般循环模型中产生的深渊循环。即使是最高分辨率的大规模海洋模型也无法充分解决底部地形的所有精细特征。因此，由粗糙地形引起的上升流的参数化和建模构成了一个基本挑战。山脊峡谷和相关流的几何形状的自相似，规则性质可能会极大地促进大型模型中相关的阻力和混合的表示。这些流的数值建模是一项新颖的事业，它将揭示形式阻力，液压控制和时间依赖性强迫在多个窗台上的影响：该项目的影响：该项目的结果将以期刊和国际科学会议的期刊演示以及通过项目网站的形式传播。最终，对MOR的流动动态的更好理解将导致对海洋一般循环的理解和建模。由于海洋模型用于预测各种尺度的循环模式，因此这项研究的结果可能会产生帮助气候建模的更广泛影响，这最终可以通过影响政策来影响社会。该项目的结果还可能有助于提高我们对水热“产品”的分散的理解，包括热，地球化学示踪剂和动物幼虫。该研究将为博士生和物理海洋学的女性博士学位接受者提供支持。