Collaborative Research: The Role of Canyons in Boundary Mixing and Exchange with the Ocean Interior

本文提出了一个实地项目，通过测量蒙特雷海底峡谷和其他几个峡谷的湍流、内波和云状层，来研究混合边界流体与分层内部的交换。将解决几个问题：1。陆坡内波驱动的边界混合对海洋内部分层的净效应是什么？2.细尺度参数化湍流混合下降短的一个因素5 - 6在峡谷，因为（一）一个更连贯的内部波场比发现在公海或（二）与地形的相互作用？测量将包括用XCP进行全深度速度-温度剖面测量，用配备透射计的LADCP/CTD进行海流和水特性的时间序列测量，用微结构剖面仪进行湍流混合的时间序列测量，以及用配备ADCP和热敏电阻链的系泊设备进行底部120米的速度和温度剖面时间序列测量。这些数据将用于（i）通过确定进出边界的内波能量通量以及边界层湍流耗散率来量化BBL能量预算，以及（ii）表征云状层的分布。能量通量发散将被用来确定内部波源和峡谷内的汇，而潜在的外部源将被确定从深水通量。此外，还将探索新的分析技术，包括：（一）利用能量-通量共谱诊断近临界底坡的内波反射;（二）利用双相干性评估高低垂直波数之间的关系;（三）利用动量-通量评估底形阻力;（iv）分层通量和沉积物通量，以确定混合边界水与分层内部的交换。这项工作是与维多利亚大学的Eric Kunze合作进行的，他将进行微观结构测量，并参与整个数据集的分析和解释。在ONR的2006年AESOP计划期间，它将受益于最近在蒙特雷湾南部斜坡上的建模工作和测量结果。我们的动机是基本的问题，涉及（i）交换的流体混合的边界上，在分层的内部和它的作用，在全球混合和温盐环流，以及（ii）如何更好地参数化地形附近内波驱动的湍流混合。调查计划将空间覆盖和高频时间序列相结合，以进行严格的显著性测试。核心XCP模式跨越一个完整的周期的半日潮将提供更好的分辨率的相干内波场的空间和时间比迄今为止实现的实验室外，以更好地了解通过内部波场附近的斜坡地形的能量级联。此外，在其他大陆坡峡谷的探索性测量将有助于扩大适用性，以全球scenery.Broader影响：多机构的合作将促进蒙特雷峡谷和其他大陆坡峡谷的混合过程的跨学科的理解，一个重要方面的营养物质，沉积物和化学示踪剂的地方预算。通过精细尺度混合参数化的完善，它还将有助于大尺度混合预算，并可能有助于气候模型预测。将通过支持研究生和参加外联活动来促进教育。

A field program is proposed to examine exchange of mixed boundary fluid with the stratified interior by measuring turbulence, internal waves and nepheloid layers in Monterey SubmarineCanyon and in several other canyons. Several questions will be addressed:1. What are the net effects of continental-slope internal-wave-driven boundary mixing on theinterior stratification of the ocean?2. Do finescale parameterizations for turbulent mixing fall short by a factor of 5 6 in canyons because of (i) a more coherent internal wave field than found in the open ocean or (ii) interactions with topography?Measurements will include full-depth velocity-temperature profile surveys with XCPs, time seriesof currents and water properties with transmissometer-equipped LADCP/CTD, time-series of turbulent mixing with a microstructure profiler, and a velocity and temperature profile time series of the bottom 120 m with a mooring equipped with ADCP and thermistor chain. These data will be used (i) to quantify the BBL energy budget by determining internal wave energy fluxes into and out of the boundary along with boundary-layer turbulent dissipation rates, and (ii) to characterize the distribution of nepheloid layers. Energy-flux divergence will be used to identify internal wave sources and sinks within the canyon while potential external sources will be identified from deep-water fluxes. In addition, new analysis techniques will be explored, including (i) the use of energy-flux co-spectra to diagnose internal wave reflection from the near-critical bottom slope, (ii) bi-coherence to evaluate relationships between high and low vertical wavenumbers, (iii) momentum-fluxes to evaluate bottom form drag, and (iv) stratification flux and sediment flux to determine the exchange of mixed boundary water with the stratified interior. This work is in collaboration with Eric Kunze at the University of Victoria, who will make the microstructure measurements and participate in analysis and interpretation of the whole data set. It will benefit from recent modeling efforts and measurements on the slope south of Monterey Bay during ONR's 2006 AESOP program.Intellectual Merit: We are motivated by fundamental questions concerning (i) the exchange of fluid mixed on the boundary with that in the stratified interior and its role in global mixing and the thermohaline circulation, and (ii) how to better parameterize internal-wave-driven turbulent mixing near topography. The survey plan combines spatial coverage and high-frequency timeseries to allow rigorous testing of significance. The core XCP pattern spanning a full cycle of the semidiurnal tide will provide better resolution of a coherent internal wavefield in space and time than hitherto achieved outside the laboratory in order to better understand the cascade of energy through the internal wave field near sloping topography. In addition, exploratory measurements in other continental slope canyons will aid in expanding applicability to a global scope.Broader Impacts: The multi-institutional collaboration will advance interdisciplinary understanding of mixing processes in Monterey Canyon and other continental slope canyons, an important facet for local budgets of nutrients, sediment, and chemical tracers. Through the refinement of finescale mixing parameterizations, it will also aid large-scale mixing budgets and,potentially, climate model predictions. Education will be advanced through the support of graduate students and participation in outreach activities.