CAREER: A new perspective on the transformation of internal waves on the inner shelf

在像海洋这样的分层流体中，波浪可以出现在不同密度的水层之间的界面上。这些被称为内波，它们在深海盆地和中到外大陆架区域得到了大量研究。然而，陡峭的内波在内大陆架中很常见，可以改变湍流混合、跨大陆架的物质交换和沿海水域的生物生产力。本研究将进行密集的野外活动和数值模拟，旨在解决大陆架内波的转换，包括破碎和耗散。从历史上看，内波是通过在固定位置使用系泊或垂直温度剖面进行的地下海洋温度观测来探测的，每种观测在分辨率上都有自己的局限性。这项研究使用了光纤分布式温度传感（DTS）系统，这是一种新的方法，可以提供大面积（公里）的大陆架测量，具有高空间（1米）和时间分辨率。这些测量将与更传统的水文和湍流变量点测量相结合。这项工作的结果将有助于深入了解底栖生态、营养物质和污染物的跨大陆架交换、湍流混合、幼虫连通性、沿海缺氧和海洋酸化。这个CAREER项目的教育部分是基于这样一种理念，即帮助学生在科学领域取得成功并塑造下一代创新者的最好方法之一就是激发对科学的热情。这是通过整合研究、教学和活动来实现的，这些活动将课程概念与激发学生兴趣的社会问题联系起来，并通过展示毅力是成功的重要组成部分。在大学一级，课程将重新设计，以包括：(i)与正在进行的研究有关的社会科学问题；（ii）鼓励冒险和坚持不懈的积极学习技术，作为通往科学发现的建设性途径。在小学和中学教育阶段，研究者将开发一个导师工具包，以帮助STEM职业的专业人士，他们希望成为榜样，但缺乏基础教育培训，最有效地沟通他们通往科学的道路以及他们在此过程中面临和克服的困难。实际上，内大陆架是一个非线性内波（NLIWs）的“冲刷区”，它们的间歇性和小时空尺度给观测带来了挑战。因此，很少有内陆架nliw的综合现场测量来验证从大量实验室和数值研究中得出的动力学理论。该项目将使用高分辨率DTS测量，再加上密集的水文仪器和湍流测量，以捕捉NLIWs跨大陆架演变的连续视图。在中国南海进行的一项初步研究结果表明，DTS测量可以为nliw提供一个独特的视角——允许检测内波特征（形式和路径）、可变传播速度、反射、波-波相互作用和“内部潮池”（波跑回斜坡后留下的冷水）。此外，与基于船的测量相反，船的测量必须在物理上跟随波浪穿过大陆架，拟议的测量能够捕获许多波浪的跨大陆架视图，并将有助于理解大陆架上内波“天气”的变化。观测将在两个位置进行，代表不同的大陆架几何形状和特征内波场，并对数据进行分析，以提高我们对大陆架内部NLIW转换，内波能量的命运以及NLIW对质量通量和湍流混合的影响的认识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In a layered fluid like the ocean, waves can occur in the interface between the different density layers of water. These are called internal waves and they have been largely studied in deep ocean basins and mid-to-outer continental shelf regions. However, steep internal waves are common in the inner shelf and can modify turbulent mixing, exchange of materials across the continental shelf, and biological productivity of coastal waters. This research will conduct an intensive field campaign and numerical modeling aiming at resolving the transformation of internal waves across the shelf including breaking and dissipation. Historically, internal waves are detected using observations of subsurface ocean temperature that are made at fixed locations using moorings or vertical profiles of temperature, each with their own limitations in resolution. This research uses a fiber optic distributed temperature sensing (DTS) system, a new method that provides measurement over large areas over the shelf (kilometers), with high spatial (1 meter) and temporal resolutions. These measurements will be combined with more traditional point measurements for hydrographic and turbulence variables. Results from this work will yield insights into benthic ecology, cross-shelf exchange of nutrients and pollutants, turbulent mixing, larval connectivity, coastal hypoxia, and ocean acidification. The educational component of this CAREER project is based on the idea that one of the best ways to help students succeed in the sciences, and to shape the innovators of the next generation is to inspire passion for science. This is achieved through the integration of research and teaching and activities that relate curricular concepts to societal issues that excite the students, and by demonstrating how perseverance is an important part for success. At the university level, courses will be re-designed to include: (i) socio-scientific issues related to ongoing research, and (ii) active learning techniques that encourage risk-taking and perseverance as a constructive path to scientific discovery. At primary and secondary education levels, the investigator will develop a mentor-toolkit to help professionals in STEM careers, who desire to serve as a role model but lack training in elementary education, to most effectively communicate their path to science and the struggles that they faced and overcame along the way.The inner shelf is, in effect, a "swash zone" for nonlinear internal waves (NLIWs) and their intermittency and small spatiotemporal scales pose challenges to observation. Consequently, there are few comprehensive field measurements of NLIWs on the inner shelf to test dynamical theories derived from numerous laboratory and numerical studies. This project will use high resolution DTS measurements, coupled with a dense array of hydrographic instruments and turbulence measurements, to capture a continuous view of the cross-shelf evolution of NLIWs. Results from a pilot study in the South China Sea demonstrate that DTS measurements can provide a unique perspective on NLIWs - allowing for detection of internal wave characteristics (form and path), variable propagation speed, reflection, wave-wave interactions, and "internal tidepools" (cool water left behind after the wave has run back down the slope). Furthermore, as opposed to boat-based measurements, which must physically follow a wave across the shelf, the proposed measurements are capable of capturing a cross-shelf view of many waves and will be useful for understanding variability in internal wave "weather" on the shelf. The observations will be performed at two locations, representing different shelf geometries and characteristic internal wave fields, and the data will be analyzed to advance our knowledge on NLIW transformation over the inner shelf, the fate of internal wave energy, and the effects of NLIWs on mass flux and turbulent mixing.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.