Cascading of Ocean Waters at the Continental Shelf Edge: Winds, Cooling and Stability

大陆架边缘海水的层叠：风、冷却和稳定性

• 批准号: 1433953
• 负责人: Kenneth Brink
• 金额: $ 42.16万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1433953&HistoricalAwards=false
• 关键词: Cascading; Ocean; Waters; Continental; Shelf

Cascading refers to the process by which dense continental shelf waters pass onto the continental slope and then sink to an equilibrium depth. This is the way that much of the ocean's deepest waters are formed, for example in the Weddell Sea off Antarctica. As such, it is important for shaping the global meridional overturning circulation, and thus it is influential for climate in general. It is argued that in most cases, cascading occurs in settings where current variability is dominated by the eddy field. This study seeks to understand cascading in the presence of wind and/or topographic effects. This work will support the PhD research and career preparation of a graduate student. When water becomes denser over the shelf (due to cooling, brine rejection or evaporation), the resulting convection and cross-shelf density gradient lead to an eddy field that drives cascading across the shelf edge. This process is well understood in simple geometries when there are no complicating effects due to winds. Also, the behavior of dense slope currents (and their related eddies), such as those generated at the Denmark Strait or at Gibraltar, is also well-studied. This project will focus on two other aspects of the cascading problem. 1) A shelf-edge alongshore current is found off East Greenland, and these flow features are not uncommon globally. This project will address the stability of these currents, and, more importantly, the ability of the resulting eddy field to expedite cascading. 2) Winds are an important driver over much of the coastal ocean, so it makes sense to ask how they affect cross-shelf transports in a region where intense surface cooling creates eddies that contribute to cascading. It appears likely that wind and buoyancy forcing will couple nonlinearly, so that we should not think about a simple linear superposition of the two effects. Thus, this project will attack the question of how these two important forcing agents (plus irregular topography) affect each other. The approach used to address these problems involves multiple runs of idealized (meaning, for example, simple geometries, but using a realistic range of parameters such as forcing amplitude) numerical models, followed by a dynamically based scaling analysis that encapsulates the results quantitatively and that clarifies the processes involved.

层叠是指密集的大陆架沃茨通过大陆坡，然后下沉到平衡深度的过程。海洋中最深的沃茨就是这样形成的，例如南极洲外的威德尔海。因此，它对形成全球纬向翻转环流很重要，因此对气候有影响。 有人认为，在大多数情况下，级联发生在电流的变化是由涡流场为主的设置。本研究旨在了解级联存在风和/或地形的影响。 这项工作将支持博士研究和研究生的职业准备。 当水在大陆架上变得更密集时（由于冷却、盐水排斥或蒸发），所产生的对流和跨大陆架密度梯度导致涡流场，驱动跨大陆架边缘的级联。当没有风的复杂影响时，这个过程在简单的几何形状中很好地理解。此外，密集斜坡流（及其相关涡流）的行为，如在丹麦海峡或直布罗陀产生的行为，也得到了很好的研究。这个项目将集中在级联问题的另外两个方面。1)在东格陵兰发现了一个陆架边缘沿岸流，这些流动特征在全球并不罕见。该项目将解决这些电流的稳定性，更重要的是，所产生的涡流场加速级联的能力。2)风是大部分沿海海洋的重要驱动力，因此在强烈的表面冷却产生有助于级联的漩涡的地区，询问它们如何影响跨大陆架运输是有意义的。看来风和浮力作用力很可能是非线性耦合的，所以我们不应该认为这两种效应是简单的线性叠加。因此，这个项目将攻击这两个重要的强迫剂（加上不规则地形）如何相互影响的问题。 用于解决这些问题的方法包括多次运行的理想化（即，例如，简单的几何形状，但使用一个现实的参数范围，如强迫振幅）的数值模型，其次是一个基于动态的缩放分析，定量封装的结果，并澄清所涉及的过程。