A Crossroads of the Atlantic Meridional Overturning Circulation: The Charlie-Gibbs Fracture Zone

学术价值：最近，海洋学界一致认为，我们应该迅速推进对大西洋经向翻转环流（AMOC）的理解，认识到它在地球气候系统中的重要性。虽然人们已经进行了大量的观测工作，以描述AMOC路径沿线几个地点的基本结构和（在某些情况下）低频变化，但对查理-吉布斯断裂带（CGFZ）的关注相对较少，该断裂带是AMOC在大西洋中脊上方的冷暖分支的门户。其结果是，即使是对这种交换流最基本特征的描述也不完整。本项目对三峡库区AMOC进行了观测和模拟相结合的研究。主要目标是：(1)对冰岛-苏格兰溢流通过CGFZ向西深层输送的平均和低频变率进行改进的直接估计；(2)更好地了解溢流通过CGFZ输送的低频变率的原因，特别是NAC在产生这种变率中的作用。从2010年开始的两年时间里，将在CGFZ上安装由8个流速计和水文测量系缆组成的阵列，测量海底至500米之间的水流和水的特性。该阵列将提供第一次长期、同时观测CGFZ上空的西向和东向气流。此外，还将对CGFZ内的横向混合强度进行探索性研究。为了解决关于斜压、高能流如何在洋中脊的一个或多个狭窄间隙之间划分的基本动力学问题，所提出的工作的建模部分将被理想化。模型和数据之间的联系将通过感兴趣的现象学来实现，即变异性的空间和时间尺度以及在单个间隙上的垂直和间隙之间的子午线上的耦合。更广泛的影响：通过更好地了解大西洋暖流和寒流的强度和变动性，这项研究将有助于厘清海洋在全球气候中的作用，并为气候模型的关键评估提供一个运输基准。该项目还将通过与马萨诸塞州珀金斯盲人学校的持续合作，为盲人和视力受损的初高中学生的科学素养做出贡献。这项工作的主要目标是通过与一位在职研究人员的面对面和在线互动来激发人们对地球科学的兴趣，这位研究人员分享了学生的特殊残疾，并为珀金斯和马萨诸塞州公立学校的视障教师开发了可访问的物理和虚拟工具。

Intellectual Merit: Recently the oceanographic community has agreed that we should work quickly to advance our understanding of the Atlantic Meridional Overturning Circulation (AMOC) in recognition of its importance in Earth's climate system. While intense observational effort has been made to describe the basic structure and (in some cases) low-frequency variability at a few locations along the paths of the AMOC, relatively little attention has been paid to the Charlie-Gibbs Fracture Zone (CGFZ), a gateway for both the warm and cold limbs of the AMOC over the Mid-Atlantic Ridge. The result is an incomplete description of even the most fundamental characteristics of this exchange flow. This project presents a combined observational and modeling study of the AMOC at the CGFZ. The primary objectives are:(1) to obtain an improved direct estimate of the mean and low frequency variability of the deep westward transport of Iceland-Scotland Overflow Water through the CGFZ, and(2) to gain a better understanding of the causes of the low-frequency variability in the transport of overflow waters through the CGFZ, especially of the role of the NAC in generating this variability.An array of eight current meter and hydrographic moorings will be installed across the CGFZ that will measure the currents and water properties between the bottom and 500 m for two years beginning in 2010. This array will provide the first long-term, simultaneous observations of both the westward and eastward flows over the CGFZ. An exploratory study of diapycnal mixing intensity in the CGFZ will also be conducted. The modeling component of the proposed work will be idealized in order to address basic dynamical questions about how baroclinic, energetic flows are partitioned between one or more narrow gaps in mid-ocean ridges. The connection between model and data will be made through the phenomenology of interest, i.e., the space and time scales of the variability and the coupling in both the vertical over a single gap and meridionally between gaps.Broader Impacts: By providing an improved understanding of the strength and variability of the warm and cold limbs of the AMOC where they cross over the Mid-Atlantic Ridge, the research will help to sort out the ocean's role in global climate and provide a transport benchmark for critical evaluation of climate models. This project will also contribute to the scientific literacy of blind and visually impaired middle and high school students through a continuing collaboration with the Perkins School for the Blind in Massachusetts. The primary objectives of this effort are to stimulate interest in the earth sciences through face-to-face and online interaction with a working researcher who shares the students' particular disability and to develop accessible physical and virtual tools for teachers of the visually impaired to use with students at Perkins and in the Massachusetts public schools.