The Zonal Overturning Circulation

海洋中的垂直输送是耦合气候系统的一个重要组成部分，因为它们能够将热量、碳、营养物质和其他示踪剂移入和移出表面混合层，在那里它们可以与大气交换。几乎所有关于海洋翻转环流的研究都集中在二维经向翻转环流上，这是一个二维纬度/深度投影。实际上，翻转环流是三维的，在垂直输送和底辟输送中有很大的纬向变化，通常在不同的纬度，由纬向流连接。本计画将检视纬向翻转环流，即二维经向翻转的三维非纬向平均现象。主要重点将放在预期的上升流沿着中纬度西部边界，这是预计反映下降流沿着东部边界已在过去的检查，都与沿岸压力梯度。在几个模型中发现了这种上升流，其输送量很大，影响到中层至上层水柱，并可能影响这些沃茨暴露于大气、海气交换、热量和盐的储存和变化。该项目将使用高分辨率理想化数值模式、低分辨率和高分辨率现实状态估计以及边界层理论，将上升流区域的幅度、水平和垂直尺度与其基本驱动机制、表面风应力和浮力强迫联系起来。这项工作将深入了解西部边界上升流在全球气候系统中的作用，支持研究生，为研究生和本科生的课程内容做出贡献，包括WHOI GFD暑期学校和U。特拉华州，并通过WHOI暑期学生研究员计划和美国大学生。del. REU程序。公众宣传计划通过网页和美国。del.拟议研究的主要目标是：应用理想化模型和边界层理论的层次结构，从根本上了解是什么维持了沿中纬度西部边界沿着观测到的压力梯度，以及这与三维海洋环流和热量输送的关系;在现实的低分辨率和高分辨率海洋状态估计中诊断垂直运输和浮力预算，并将这些发现与理想化的建模和理论联系起来;并使用拉格朗日诊断法诊断西部边界附近涌上的沃茨水源区域及其涌上后的命运，包括可能夹带到表面混合层中以及对海气相互作用的影响。理想化建模将基于HYCOM原始方程模型，其可以被配置为纯等密度、z坐标、sigma坐标或这些坐标系的组合。该模式将应用于日益复杂的配置，以便更好地分离和了解控制纬向翻转环流的源沃茨的物理现象。现实的建模将包括来自"估计海洋环流和气候"联合会的两个海洋状态估计：低分辨率、无涡流分辨率的ECCO第4版（ECCO v4）;以及允许涡流的ECCO第二阶段（ECCO 2）。除了检查控制上升流的动力学，模型还将用于探索上升水的来源和命运，在一系列初始深度引入示踪剂和浮子。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Vertical transports in the ocean are an important component of the coupled climate system because they are able to move heat, carbon, nutrients, and other tracers into and out of the surface mixed layer, where they can be exchanged with the atmosphere. Almost all research on the Ocean’s overturning circulation has focused on the two-dimensional Meridional Overturning Circulation, a two-dimensional latitude/depth projection. In reality the overturning circulation is three-dimensional, with large zonal variations in vertical and diapycnal transports, often at different latitudes, that are connected by zonal flows. This project would examine this Zonal Overturning Circulation, the three-dimensional non-zonally averaged aspects of the two-dimensional Meridional Overturning. The primary focus will be on the expected upwelling along midlatitude western boundaries, which is expected to mirror the downwelling along eastern boundaries that has been examined in the past, both associated with alongshore pressure gradients. This upwelling is found in several models at significant transport magnitudes, affecting the middle to upper water column and potentially influencing the exposure of those waters to the atmosphere, air-sea exchange, heat and salt storage and variability. The project will relate the magnitude, horizontal, and vertical scales of the upwelling regions to their fundamental driving mechanisms, surface wind stress, and buoyancy forcing, using high resolution idealized numerical models, low and high resolution realistic state estimates, and boundary layer theory. The work will provide insight into the role of western boundary upwelling in the global climate system, support a graduate student, contribute to graduate and undergraduate course content, including the WHOI GFD summer school and classes at U. Delaware, and involve undergraduates through the WHOI summer student fellow program and the U. Del. REU program. Public outreach is planned through webpages and the U. Del. annual Coast Day presentations.The primary objectives of the proposed study are: to apply a hierarchy of idealized models and boundary layer theory to gain a fundamental understanding of what maintains the observed pressure gradient along mid-latitude western boundaries and how this connects to the three-dimensional ocean circulation and heat transport; to diagnose vertical transports and buoyancy budgets in realistic low- and high-resolution ocean state estimates and relate these findings to the idealized modeling and theory; and to use Lagrangian diagnostics to diagnose the source regions of waters upwelled near the western boundary and their fate after upwelling, including possible entrainment into the surface mixed layer and influence on air-sea interaction. Idealized modeling will be based on the HYCOM primitive equation model, which can be configured as purely isopycnal, z-coordinate, sigma-coordinate, or a combination of these coordinate systems. The model will be applied in increasingly complex configurations in order to better isolate and understand the physics controlling the source waters for the zonal overturning circulation. Realistic modeling will include two ocean state estimates from the “Estimating the Circulation and Climate of the Ocean (ECCO)” consortium: the low-resolution, non-eddy resolving ECCO version 4 (ECCO v4); and the eddy-permitting ECCO, phase II (ECCO2). In addition to examining the dynamics controlling upwelling, the models will also be used to explore the source and fate of upwelled water, using the introduction of both tracers and floats at a range of initial depths.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.