Wave processes along 26N

尽管我们从理论和数值研究中对海洋中的大尺度和长周期波有了坚定的理解，但由于缺乏适当的数据来解决所涉及的长时间和大空间尺度，许多行星传播范式尚未在真实海洋中进行测试。理论和数值处理所需的简化假设(例如，垂直侧壁、理想化分层和受限的时间响应)都缩小了允许的运动范围，因此对真实海洋的不完整描述也是如此。然而，现在几乎可以使用位于26°N的大西洋子午线翻转环流系泊阵列(MOCHA/WBTS/RAPID项目)的广泛和长期测量来检查副热带环流的几乎整个波谱。七年的AMOC阵列数据扩展了之前在地表以下和长时间内的卫星观测基础，并允许测试关于亚热带盆地中的波信号和路径的假设。通过对地下观测的分析，这项研究将在较宽的频率范围内调查波的能量和波型。将特别注意行星波(开尔文和罗斯比)和内波(潮汐和惯性)，利用对盆地8个系泊处的动态高度和底部压力以及西部4个系泊处的水平速度进行再处理的高频全深度测量，解析周期为2小时至2年的波动。通过对位能(动高)和动能(速度)的诊断，能量方程可以部分地诊断为西边界频率的函数。可以通过检查深度和模式空间中的频谱斜率来推断频率之间和系泊之间的能量转移。通过将压力和速度分解到模式空间中，可以计算能量通量，阵列的线性几何结构可以对能量通量发散进行二维估计，从而深入了解这些波的传播和可能的消散。能量通量分解的一个特别突出的方面是能够检查风和潮汐内波的低频变异性，由于缺乏长期的地下数据，这一点还没有得到很好的理解。虽然已经有明确的观测到跨盆地的罗斯比波在公海传播，但它们到达西部边界后的命运仍然不明朗。这些命运可能包括局部消散、反射，甚至转化为沿着西部边界向南辐射的开尔文波。由于时间长、空间尺度大，以往的观测研究没有解决这些过程。利用阵列的时间和空间分辨率并应用理论关系(动能与势能之比、极化关系和色散方程)，将有助于识别这些信号所包含的方差，并量化西部边界上这些类别波的能量路径。为了补充地下采样，将合作研究一种高频卫星测高产品，以检查水平尺度和传播。在任何频率下，大尺度波动的来源、路径和汇在很大程度上都是未知的，这项研究是量化它们在西副热带大西洋中作用的第一步。智力上的好处：这个项目将描述广泛的波动谱并阐明波的路径，增加我们对大尺度、低频行星波以及潮汐和风生内波的理解。这些分析为AMOC阵列已经收集的数据提供了额外的好处。广泛的影响：该项目支持两名初级科学家建立他们的研究生涯。科学成果将发展研究大尺度波浪的方法，并将极大地扩展参与子午线相干、海洋可预报性和海洋-大气反馈模式的波浪的观测基础。教育部分包括对本科生的培训和通过基于网络的推广方案传播成果。

Despite our firm understanding of large-scale and long-period waves in the ocean from theoretical and numerical studies, many paradigms of planetary propagation have not yet been tested in the real ocean for lack of suitable data that resolve the long temporal and large spatial scales involved. The simplifying assumptions necessary for theoretical and numerical treatment (e.g. vertical side-walls, idealized stratification, and constrained temporal responses) all reduce the range of allowable motion and so are incomplete descriptions of the real ocean. However, nearly the entire wave spectrum across a subtropical gyre can now be examined using extensive and prolonged measurements from the Atlantic Meridional Overturning Circulation (AMOC) moored array located at 26°N (the MOCHA/WBTS/RAPID project). Seven years of AMOC array data extend the previous satellite observational basis below the surface and over long periods and allows testing of hypotheses about wave signals and pathways in a subtropical basin. Through the analysis of subsurface observations, this study will investigate wave energies and wave patterns over a broad frequency range. Particular attention will be given to planetary waves (Kelvin and Rossby) and internal waves (tidal and inertial), resolving waves with periods ranging from 2 hours to 2 years using reprocessed high-frequency full-depth measurements of dynamic height and bottom pressure at 8 moorings across the basin and horizontal velocity at the 4 western moorings. With diagnosis of potential energy (dynamic height) and kinetic energy (velocity), the energy equation can be partially diagnosed as a function of frequency at the western boundary. Inferences about energy transfer between frequencies and between moorings can be made by examining spectral slopes in depth- and mode-space. Decomposition of pressure and velocity into mode-space allows the calculation of energy flux and the array's linear geometry enables a 2D estimate of energy flux divergence, lending insight into the propagation and possible dissipation of these waves. A particularly salient aspect of the energy flux decomposition is the ability to examine the low-frequency variability of wind and tidal internal waves, which is not well understood due to a lack of long term subsurface data. Though there have been clear observations of cross-basin Rossby wave propagation in the open ocean, their fate upon reaching the western boundaries remains unclear. These fates might include local dissipation, reflection or even transformation to Kelvin waves that radiate southward along the western boundary. Due to the long time and large spatial scales, previous observational studies have not resolved these processes. Utilizing the temporal and spatial resolution of the array and applying theoretical relations (ratios of kinetic to potential energy, polarization relations and dispersion equations), will help identify the variance contained by these signals, and quantify the energy pathways for these classes of waves at the western boundary. To complement the subsurface sampling, a high frequency satellite altimetry product will be investigated in collaboration to examine horizontal scales and propagation. At any frequency the sources, pathways, and sinks of large-scale waves are largely unknown, and this study is a first step toward quantifying their roles in the western subtropical Atlantic.Intellectual Merit: This project will characterize a broad spectrum of wave motion and elucidate pathways of waves, increasing our understanding of both large-scale, low-frequency planetary waves and tidal and wind-generated internal waves. These analyses provide added benefit to the data already collected by the AMOC array.Broader Impacts: This project supports two junior scientists in establishing their research careers. Scientific results will develop methods for investigating large-scale waves and will greatly extend the observational basis of waves that participate in meridional coherence, ocean predictability, and ocean-atmosphere feedback patterns. Educational components consist of training an undergraduate student and of disseminating results through a web-based outreach program.