Topographic Dynamics of the Gulf Stream

本文对从查尔斯顿凸起到哈特拉斯角地区的次表层墨西哥湾流进行了理论和数值研究。墨西哥湾流是北大西洋环流的中心要素，事实证明，在海洋环流环境中模拟这种环流是微妙的。这项工作将巩固目前对墨西哥湾流动力学的理解，特别是关于哈特拉斯角与海岸的强劲分离，这仍然是数值模式的一个顽固问题。此外，这项研究将隔离和确定哈特拉斯角附近墨西哥湾流脱离地球自转压力梯度和力之间的地转平衡的位置。从平衡流动到较小尺度、耗散和混合的能量损失也将在这些地区量化，这是结束海洋能源循环的重要一步。这些位置的确定可以为未来对涉及失去平衡和非静力现象的过程的观测研究提供选址信息。除了通过期刊出版物和在国家和国际会议上作介绍来传播成果的通常方法外，还将对一名研究生进行多尺度计算海洋学和大中尺度海洋动力学方面的培训。他们的博士研究将从这份提案中概述的一个主题中提取。此外，还将与FSU数学、科学和工程女性(WIMSE)计划联系起来，招聘一名本科生从事地形数据集的开发和分析软件的开发。这将导致与本科生在主要海洋期刊上联合发表文章。将创建一个网站来托管和维护建模结果和软件，从而将它们提供给更广泛的社区使用。他们的目标是在完成实验后的六个月内下载所有的数值数据。这项研究的动机来自于最近强调该地区对北大西洋大气环流的动力重要性的结果，以及关于墨西哥湾流能量学、局部地形控制和混合的未决问题。提出的假设是：(1)墨西哥湾流-地形相互作用促进次表层‘失去平衡’并随后产生亚中尺度现象；(2)发生在哈特拉斯角的等深辐合是墨西哥湾流与沿海分离的主要控制因素；(3)非静力现象，包括密度反转，经常在该地区产生。这个项目将在墨西哥湾流的数值和理论研究的范围内检验这些假设。将采用的主要工具是区域嵌入和缩小尺度的数值模型，并结合分析和面向过程的分析。该项目的目标是定位和描述与区域失去平衡和亚中尺度产生相关的现象，并提供从墨西哥湾流到不平衡的亚中尺度运动的区域能量消耗的定量估计。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This is a theoretical and numerical study of the subsurface Gulf Stream from the Charleston Bump to the Cape Hatteras region. The Gulf Stream is a central element of the North Atlantic circulation that has proven subtle to model in ocean general circulation settings. This work will solidify current understanding of Gulf Stream dynamics, particularly with regards to the robust separation from the coast at Cape Hatteras which remains a stubborn problem for numerical models. In addition, this study will isolate and define the locations in the vicinity of Cape Hatteras where the Gulf Stream comes out of geostrophic balance between the pressure gradients and forces due to the rotation of the Earth. The loss of energy from balanced flows to smaller scales, dissipation, and mixing, will also be quantified in these areas, an important step to closing the oceanic energy cycle. The identification of these locations can inform site selection for future observational studies of processes involved in loss of balance and non-hydrostatic phenomena. In addition to the usual methods for disseminating results by means of journal publications and presentations at national and international meetings, a graduate student will be trained in multi-scale computational oceanography and large and mesoscale ocean dynamics. Their Ph.D. research will be drawn from one of the topics outlined in this proposal. Also, a connection with the FSU Women in Mathematics, Science and Engineering (WIMSE) program will be engaged to recruit an undergraduate to work on the development of topographic datasets, and the development of analysis software. This will result in publications joint with the undergraduate in major oceanographic journals. A website will be created to host and maintain the modeling results and software, thereby making them available to the broader community for their use. The goal is to have all the numerical data available for download within six months of completing the experiments.The motivations for the study come from recent results emphasizing the dynamical importance of this region to the North Atlantic general circulation and open questions about Gulf Stream energetics, local topographic controls and mixing. The presented hypotheses are: (1) Gulf Stream -topography interaction promotes subsurface ''loss of balance'' and subsequently the generation of submesoscale phenomena, (2) the isobath convergence occurring at Cape Hatteras is a major control on Gulf Stream separation from the coast and (3) non-hydrostatic phenomena, including density inversions, are routinely generated in this area. This project will examine these hypotheses within the confines of a numerical and theoretical study of the Gulf Stream. The primary tools to be employed are regional embedded and downscaled numerical models, combined with analytical and process-oriented analyses. The goals of the project are to locate and describe the phenomena associated with regional loss of balance and submesoscale generation and provide quantitative estimates of the regional energy drain from the Gulf Stream to unbalanced, submesoscale motions.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.