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

层叠是指密集的大陆架水进入大陆坡，然后下沉到平衡深度的过程。这就是许多海洋最深的水域形成的方式，例如在南极洲附近的韦德尔海。因此，它对塑造全球经向翻转环流很重要，因此它对整个气候都有影响。有人认为，在大多数情况下，级联发生在电流变化由涡场主导的环境中。这项研究试图了解在风和/或地形影响下的级联。这项工作将为研究生的博士研究和职业准备提供支持。当水在货架上变得更稠密时(由于冷却、盐水拒绝或蒸发)，所产生的对流和跨货架密度梯度导致涡流场，从而驱动沿货架边缘的级联。当没有风的复杂影响时，这个过程在简单的几何中是很好理解的。此外，密集的坡流(及其相关的涡流)的行为也得到了很好的研究，例如在丹麦海峡或直布罗陀产生的那些。本项目将关注级联问题的另外两个方面。1)东格陵兰外海存在陆架边缘沿岸流，这种流动特征在全球范围内并不少见。这个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，在一个表面强烈冷却产生涡流并促成级联的地区，风如何影响跨陆架运输是有意义的。风和浮力的强迫很可能是非线性耦合的，所以我们不应该考虑这两种效应的简单线性叠加。因此，这个项目将解决这两个重要的强迫因素(加上不规则的地形)如何相互影响的问题。用于解决这些问题的办法涉及多次理想化(例如，意味着简单的几何形状，但使用了实际范围的参数，如强迫幅度)数值模型，然后进行基于动态的比例分析，该分析量化地概括了结果，并澄清了所涉及的过程。

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.