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，鉴于大西洋子午线翻转环流(AMOC)在地球气候系统中的重要性，我们应该迅速推进我们对该环流的理解。虽然已经进行了密集的观测工作来描述AMOC路径沿线几个位置的基本结构和(在某些情况下)低频变化，但相对较少的关注查理-吉布斯断裂带(CGFZ)，它是AMOC在大西洋中脊上空温暖和寒冷分支的门户。其结果是，对这种交换流动的最基本特征的描述甚至是不完整的。本项目介绍了CGFZ对AMOC的观测和模拟相结合的研究。主要目标是：(1)改进对通过CGFZ向西输送冰岛-苏格兰溢流水的平均和低频变化的直接估计，以及(2)更好地了解通过CGFZ输送溢出水的低频变化的原因，特别是NAC在产生这种变化中的作用。从2010年开始，将在CGFZ安装一个由8个海流计和水文系泊装置组成的阵列，用于测量海底至500米之间的水流和水性质。这个阵列将提供对CGFZ上空向西和向东流动的第一次长期、同步观测。还将对CGFZ中的昼夜混合强度进行探索性研究。拟议工作的建模部分将被理想化，以解决有关斜压能量流如何在大洋中脊的一个或多个狭窄缝隙之间分配的基本动力学问题。模型和数据之间的联系将通过感兴趣的现象学建立，即变化的空间和时间尺度，以及单个空隙上垂直方向和缝隙之间的子午线之间的耦合。更广泛的影响：通过提供对AMOC温暖和寒冷分支横跨中大西洋脊处的强度和变化的更好理解，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帕金斯盲人学校的持续合作，为盲人和视障初中生和高中生的科学素养做出贡献。这项工作的主要目标是通过与与学生有共同残疾的在职研究人员进行面对面和在线互动来激发人们对地球科学的兴趣，并开发可供视障教师与帕金斯和马萨诸塞州公立学校的学生一起使用的可获得的物理和虚拟工具。

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.