Collaborative Research: Kelvin-Helmholtz Instabilities at a Kuroshio Seamount (KHIKS)

合作研究：黑潮海山的开尔文-亥姆霍兹不稳定性 (KHIKS)

• 批准号: 2048764
• 负责人: Anda Vladoiu
• 金额: $ 150.41万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2048764&HistoricalAwards=false
• 关键词: Collaborative; Research; Kelvin; Helmholtz; Instabilities

Wind-driven western boundary currents, such as the Kuroshio in the western Pacific, transport large amounts of heat, salt and momentum northward, contributing to the ocean overturning circulation and the climate system heat balance. How western boundary currents vary in time and space, and how they lose energy to their surroundings, are long-standing questions. Unlike the Gulf Stream in the Atlantic where topographic features are rare, the Kuroshio frequently interacts with ridges, islands and seamounts. Energy is thus extracted from the large-scale flow through turbulent mixing, particularly in settings with large shear in horizontal velocities. These are known to support a variety of shear instabilities, such as Kelvin-Helmholtz (KH) or Holmboe, whereby small perturbations in the flow amplify, to become important mechanisms for turbulence generation. Although KH shear instability has been widely studied in idealized laboratory experiments and numerical simulations, direct observations in the ocean are rare and mostly confined to estuaries and sills. Consequently, the generation, evolution and decay of KH-like billows in high-Reynolds-number oceanic flows, their modulation by background flow and decay into turbulence are under-observed in the open ocean. The project is a collaboration with Taiwanese scientists, using their available ship-time, to measure high-resolution temperature, salinity and velocity finestructure of primary KH-like billows and evolution in the lee of a seamount in the path of the Kuroshio. Several moorings will also be deployed to gain longer-term spatial assessment of variability in the seamount vicinity. Turbulent dissipation and mixing within the observed KH-like billows will be assessed, to determine their roles in turbulent fluxes of heat, salinity, mass, and nutrients, modification of Kuroshio and local water-masses, and energy dissipation in the Kuroshio, of relevance to the gyre-scale circulation. This project supports two early-career scientists in their transition to observational oceanographers. International collaborations will provide shiptime and access to Kuroshio waters of global scientific importance. Activities within the summer program for UW undergraduate students are included, along with educational visits to K-12 classrooms, and outreach at UW and local science centers. Shear instabilities with Kelvin-Helmholtz (KH)-like characteristics will be measured in the lee of a seamount in the path of the Kuroshio east of Taiwan. The finescale 3-D (vertical, along- and across-stream) density structure will be resolved to 10-m horizontally and 1-m vertically using towed CTD chain surveys, augmented with shipboard ADCP and echosounder. Such detailed measurements in such high-Reynolds-number oceanic flows are unprecedented, and will elucidate their kinematic structure, dynamic evolution and associated turbulence, to offer guidance for realistic numerical model simulations and laboratory experiments. A moored array of ADCPs and temperature sensors will provide additional time-series profiles of (i) shear and stratification upstream of the seamount, (ii) high temporal and vertical resolution of 3-D velocity and echosounder images on the seamount summit, and (iii) 3-D along- and across-stream time- series profiles of velocity fields in the lee of the seamount. Turbulent dissipation and mixing from multiple estimation methods and direct microstructure measurements will help determine the role of these flow/topography interactions on water-mass transformation and dissipation of a western boundary current. Scientifically, understanding the dissipation of the balanced circulation and the sources of diapycnal mixing in the ocean remain among the most pressing challenges in physical oceanography.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.

风向的西部边界电流，例如西太平洋的黑发，向北运输大量热量，盐和动量，导致海洋推翻循环和气候系统的热平衡。西方边界电流在时间和空间上如何变化，以及它们如何失去周围环境的能量，这是长期存在的问题。与地形特征很少见的大西洋的海湾流不同，黑发经常与山脊，岛屿和海拔相互作用。因此，从大规模流过湍流混合的大规模流中提取了能量，尤其是在水平速度较大的剪切速度的设置中。已知这些支持各种剪切不稳定性，例如Kelvin-Helmholtz（KH）或Holmboe，因此流动放大的小扰动可以成为湍流产生的重要机制。尽管在理想化的实验室实验和数值模拟中已经广泛研究了KH剪切不稳定性，但在海洋中进行直接观察很少见，并且大部分局限于河口和窗台。因此，在高雷诺（Reynolds-number）海洋流中，kH样浪费的产生，进化和衰变，在开阔的海洋中，它们通过背景流量和腐烂的调节不足。该项目是与台湾科学家的合作，利用其可用的船舶时间来衡量原代kh样毛笔的高分辨率温度，盐度和速度罚款，以及在kuroshio路径中的封口中的lee中的进化。还将部署几个系泊设备，以获得对海山附近变异性的长期空间评估。将评估观测到的KH样浪费和混合的湍流耗散和混合，以确定它们在热，盐度，质量和营养素的湍流中的作用，黑鲁希奥和局部水质的修饰以及在黑素中的能量耗散，以及与Gyre Scale循环相关的kuroshio。该项目支持两位早期职业科学家向观察海洋学家过渡。国际合作将为全球科学重要性提供奇特赛和进入黑鲁西奥水域。包括西澳大学本科生的夏季计划中的活动，以及对K-12教室的教育访问，以及UW和当地科学中心的宣传活动。将在台湾以东的黑鲁希奥（Kuroshio）路径的lee中测量Kelvin-Helmholtz（KH）类似特征的剪切不稳定性。罚款3-D（垂直，沿着流）密度结构将使用拖曳的CTD链调查垂直分配至10米，并用船舶ADCP和Echosounder增强。这样的高元素数量的海洋流中的这种详细测量是前所未有的，并将阐明其运动学结构，动态进化和相关的湍流，以为现实的数值模型模拟和实验室实验提供指导。 A moored array of ADCPs and temperature sensors will provide additional time-series profiles of (i) shear and stratification upstream of the seamount, (ii) high temporal and vertical resolution of 3-D velocity and echosounder images on the seamount summit, and (iii) 3-D along- and across-stream time- series profiles of velocity fields in the lee of the seamount.来自多种估计方法和直接微观结构测量的湍流耗散和混合将有助于确定这些流/地形相互作用在水质量转化和西部边界电流的耗散方面的作用。从科学上讲，了解海洋平衡循环的耗散和二元混合的来源仍然是物理海洋学中最紧迫的挑战之一。该奖项反映了NSF的法定任务，并被认为值得通过基金会的知识分子优点和更广泛的影响标准通过评估来进行评估。