Collaborative Research: Nonlinear Wake Observations at a Kuroshio Seamount (NOKS)

本文将分析2021-2022年在日本南部Tokara海峡Hirase海山背风处收集的海洋数据，以研究强烈的非线性黑潮-海山相互作用和相关湍流。数据包括从船舶、系泊处和剖面浮子阵列测量的温度、盐度、速度和湍流耗散的高分辨率观测数据。这些数据将用于识别动量和浮力方程中的主要非线性项，量化潜在涡度异常，并确定导致海底山下游延伸20公里的高能湍流层的垂直和横向不稳定机制。阐明湍流的产生机制，特别是非线性尾迹的产生机制，是改善现有湍流耗散和混合参数化的重要任务，因此对模拟和海洋中的能量级联、质量和营养物质输送以及生物地球化学平衡具有广泛的意义。该项目将为早期职业科学家Anda Vladoiu博士提供支持。所有APL-UW pi都积极参与华盛顿大学和当地科学中心以及西雅图K-12教室的外展活动。Lien还积极支持华盛顿大学本科生的暑期项目。Kunze是西雅图太平洋科学中心的科学传播研究员，每年参与四次志愿者科学聚焦活动，并参加年度太平洋科学中心气候好奇心周末，向公众介绍经向翻转环流和海洋湍流混合。黑潮和平濑海山之间的强烈相互作用产生了独特的非线性和湍流状态，允许在通常的线性内波和平衡动力学之外进行研究。将分析四维精细和微观结构调查，以研究强非线性黑潮-海山相互作用和相关湍流，其中罗斯比数超过1，梯度弗劳德数为𝑂(1)。船上ADCP，正在进行的CTD和VMP散热器测量，以及四个全深度EM-APEX浮动盒阵列，提供水平亚中尺度（~ 1公里）和垂直精细尺度（~ 10米）的流动结构。两个ADCP/CTD系泊提供了6个月的背景流量变异性和剪切不稳定层的时间序列。这些数据将用于(i)确定动量和浮力方程中的主要非线性项，（ii）量化潜在涡量（PV）异常，以及（iii）确定垂直和横向不稳定机制，这些不稳定机制导致具有纵向扩散系数𝐾~ 10−2 m2 s−1的高能湍流层延伸到海底山下游20公里处。在海山的下风处系泊6个月长的时间序列将允许分离亚惯性和内波波动，以解决可能的时空混叠。这些通常会提高对海洋中非线性流动-地形相互作用的理解。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。

Oceanographic data collected in the lee of Hirase Seamount in Tokara Strait, south of Japan, during 2021-2022 will be analyzed to investigate strong nonlinear Kuroshio-seamount interactions and associated turbulence. The data include highly resolved observations of temperature, salinity, velocity, and turbulent dissipation measured from ship, moorings, and profiling float arrays. The data will be used to identify the dominant nonlinear terms in the momentum and buoyancy equations, quantify potential vorticity anomalies, and determine the vertical and lateral instability mechanisms responsible for energetic turbulence layers extending 20 km downstream of the seamount. Elucidating turbulence generation mechanisms, especially in nonlinear wakes, is an essential task to improve existing turbulent dissipation and mixing parameterizations, and therefore has broad implication for the energy cascade, mass and nutrient transports, and biogeochemical budgets in simulations and the ocean. This project will provide support for early-career scientist Dr. Anda Vladoiu. All APL-UW PIs are actively engaged in outreach at UW and local science centers and Seattle K-12 classrooms. Lien also actively supports the summer program for UW undergraduate students. Kunze is a Science Communication Fellow at the Pacific Science Center in Seattle, which involves four volunteer Science Spotlight activities per year, and participation in the annual Pacific Science Center-Climate Curiosity Weekend, to introduce the general public to the meridional overturning circulation and ocean turbulent mixing.Strong interactions between the Kuroshio and Hirase Seamount produce a uniquely nonlinear and turbulent regime that allows study outside the usual linear internal-wave and balanced dynamics. Four-dimensional fine- and microstructure surveys will be analyzed to investigate strong nonlinear Kuroshio-seamount interactions and associated turbulence where Rossby numbers exceed 1 and gradient Froude numbers are 𝑂(1). Shipboard ADCP, underway CTD and underway VMP radiator surveys, as well as four full-depth EM-APEX float box-arrays, provide horizontal submesoscale (~ 1 km) and vertical finescale (~ 10 m) flow structures. Two ADCP/CTD moorings provide 6-month time-series of the background flow variability and shear- unstable layers. These data will be used to (i) identify the dominant nonlinear terms in the momentum and buoyancy equations, (ii) quantify potential vorticity (PV) anomalies and (iii) determine the vertical and lateral instability mechanisms responsible for energetic turbulence layers with diapycnal diffusivities 𝐾 ∼ 10−2 m2 s−1 extending 20 km downstream of the seamount. The six-month long mooring time-series in the lee of the seamount will allow the separation of subinertial and internal-wave fluctuations to resolve possible time-space aliasing. These will generally improve understanding of nonlinear flow-topography interactions in the ocean.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.