Submesoscale frontal dynamics

在不同温度和盐度的水域相遇的地方，海洋锋面就会形成。锋面在上层海洋中无处不在，包括墨西哥湾流等大尺度洋流系统和较小的短暂特征。锋面是极具活力和活力的环境，对当地生物和全球碳循环有重要影响。根据定义，锋面是密度面或等水晶面从海洋分层的内部露出的地方。最近的证据表明，这些露头的等鳞石提供了一条途径，允许重要的示踪剂，如溶解碳、氧和营养物质在海洋表面和内陆之间直接和快速地转移。海洋表面和内陆之间的水交换速度反过来又影响海洋调节地球气候变化的能力。尽管它们具有全球意义，但许多关于战线的根本性问题仍然没有得到回答。为什么前线的生物生产力往往比周围地区高得多？锋面如何改变湍流混合的强度？是什么物理过程平衡了锋面上会聚的表面流动，最终决定了它们的宽度和强度？在这个项目中，学生将使用数值模拟、数学理论和现场数据的组合来回答这些重要的问题。基于几个海洋锋面的可用水文剖面，我们将确定重要的参数，包括密度对比度、混合层深度和锋面的垂直范围。然后，我们将建立和分析一套数值模拟，以研究不同参数范围内锋面的演变。线性稳定性分析将使我们能够识别最终发展为锋面涡旋的扰动。最后，我们将把我们的结果与现有的和新的观测数据进行比较。我们将根据结果和学生的兴趣调整方法，项目将有开放探索的余地。

Ocean fronts develop where waters with different temperature and salinity meet. Fronts, which include large-scale current systems such as the Gulf Stream and smaller ephemeral features, are ubiquitous in the upper ocean. Fronts are extremely energetic and dynamic environments with important influences on the local biology and the global carbon cycle. By definition, fronts are places where density surfaces, or isopycnals, outcrop from the ocean's stratified interior. Recent evidence indicates that these outcropping isopycnals provide a pathway that allows direct and rapid transfer of important tracers such as dissolved carbon, oxygen, and nutrients between the ocean surface and interior. The rate of exchange of water between the ocean surface and interior in turn affects the ability of the ocean to mediate changes in the earth's climate. Despite their global significance, many fundamental questions about fronts remain unanswered. Why are fronts often much more biologically productive than surrounding areas? How do fronts modify the intensity of turbulent mixing? What physical processes balance the convergent surface flow at fronts, ultimately determining their width and strength?For this project, the student will use a combination of numerical simulations, mathematical theory, and field data to answer these important problems. Based on available hydrographic sections taken across several ocean fronts, we will identify important parameters including the density contrast, mixed layer depth, and vertical extent of the front. We will then build and analyse a suite of numerical simulations to study the evolution of fronts in different parameter ranges. A linear stability analysis will allow us to identify the disturbances that eventually develop into frontal eddies. Finally, we will compare our results with existing and new observational data. We will adapt the approach based on the results and the interests of the student and the project will have scope for open exploration of the topic.