Collaborative Research: Lateral mixing and dispersion on the inner shelf

合作研究：内架横向混合与分散

• 批准号: 0926340
• 负责人: Stephen Monismith
• 金额: $ 59.74万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0926340&HistoricalAwards=false
• 关键词: Collaborative; Research; Lateral; mixing; dispersion

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Intellectual MeritThis award is for a suite of comprehensive field observations to elucidate and quantify the mixing processes in the inner shelf and to directly examine the impact of these processes on inner shelf biological distributions. Predictive modeling of coastal flows requires parameterizations of sub-gridscale processes, which, in the horizontal dimension have characteristic length-scales of 10s to 1000s of meters. This study will provide a comprehensive picture of horizontal dispersion on the inner shelf at these scales and its implications for scalar distributions. It is hypothesized that the physical limitations imposed by vertical boundaries and stratification restrict vertical motions and exchange processes leading to strong anisotropies in the flow field and dispersion in the inner shelf. Previous work has shown that mixing in the bottom boundary layer is scale-dependent in the horizontal direction in spite of the limiting effects of the bottom boundary. It is likely that scale-dependency may be different higher in the water column where stratification may create even greater anisotropies and restrictions on vertical transfer rates, and in the surface mixed layer due to the influence of waves, winds, as well as surface heating and cooling. This project will directly measure lateral dispersion rates in the bottom mixed layer, stratified interior, and surface mixed layer on the inner shelf under different forcing conditions in order to quantify any scale-dependent mixing and highlight the similarities and differences in lateral mixing at different depths. Once the dispersion rates and scale dependencies are determined, they will be used to examine how the lateral rates of mixing may correspond with biological thin layer development, maintenance and degradation. Two, two-week long field experiments will be conducted on the inner shelf of northern Monterey Bay to examine these issues. After deploying an array of moored instruments to measure physical, optical and acoustical properties, the research team will release a tracer dye, in separate releases, within the bottom boundary layer, stratified interior, and surface mixed layer during both the early and late portions of the upwelling season in northern California. The dye?s spatial and temporal distribution will be measured using an autonomous underwater vehicle equipped with a fast response fluorometer, as well as a tow body equipped with a fluorometer and ancilliary instrumentation that measure concurrently biological and geochemical properties of interest. The dye measurements will be used to quantify the lateral mixing by fitting the data to scale dependent laws, and comparing and contrasting the corresponding rates of dispersion with different climatological and hydrodynamics forcing conditions (winds, surface waves, internal wave, stratification, and turbulence) during these two measurement periods. Connecting the lateral mixing processes and forcing conditions with measured biological distributions (thin layers) will help determine the role of horizontal mixing in homogenizing and/or redistributing biological scalars.Broader ImpactsThis work will provide valuable new insights into the transport and mixing of scalars in the coastal region, particularly at the 'intermediate' scales of 10s to 1000s of meters. It will have a broad scientific impact, especially on interdisciplinary modeling efforts of the inner shelf where estimates and/or parameterizations of lateral mixing cause significant uncertainty.As coastal populations continue to grow, and pressure on marine ecosystems continues to increase, it will be increasingly important to understand the underlying mechanisms determining transport and/or retention in the nearshore environment. Understanding lateral dispersion in the coastal environment has significant implications not only for the transport/retention of marine larvae, and harmful algal blooms but also for the transport/retention of pollutants. Better understanding of these mixing processes will ultimately be of interest to environmental planners, policy makers and other stakeholders in coastal communities. The proposed research will also support one postdoctoral scholar and two PhD students.

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)资助的。智力价值该奖项是为了表彰一系列全面的现场观察，以阐明和量化内陆架中的混合过程，并直接检查这些过程对内陆架生物分布的影响。沿海水流的预测建模需要亚格子尺度过程的参数化，这些过程在水平维度上具有10到1000米的特征长度尺度。这项研究将提供内陆架在这些尺度上的水平扩散的全面图景及其对标量分布的影响。假设垂直边界和层结施加的物理限制限制了垂直运动和交换过程，导致了流场的强烈各向异性和内陆架的弥散。前人的工作表明，尽管底边界有一定的限制作用，但底边界层中的混合在水平方向上是尺度相关的。由于波浪、风以及地表加热和冷却的影响，在水柱中，层化可能会造成更大的各向异性和对垂直传输速率的限制，而在地表混合层中，尺度依赖性可能会有所不同。该项目将直接测量不同强迫条件下内陆架底层混合层、分层内部混合层和表层混合层的横向弥散率，以量化任何尺度相关的混合，并突出不同深度横向混合的异同。一旦确定了扩散速率和尺度依赖关系，它们将被用来检查横向混合速率如何与生物薄层的发展、维持和降解相对应。将在蒙特利湾北部的内陆架进行为期两周的现场实验，以检查这些问题。在部署了一系列系泊仪器来测量物理、光学和声学特性后，研究小组将在加利福尼亚州北部上升季的早期和后期分别在底部边界层、分层内部和表面混合层中释放示踪剂染料。染料S的空间和时间分布将使用配备快速响应荧光仪的自主水下机器人以及配备荧光仪和辅助仪器的拖体来测量，这些仪器可以同时测量感兴趣的生物和地球化学性质。染料测量将被用来量化横向混合，方法是将数据与尺度相关的定律进行拟合，并比较和对比这两个测量期内不同气候和水动力强迫条件(风、表面波、内波、层结和湍流)下相应的弥散率。将横向混合过程和强迫条件与测量的生物分布(薄层)联系起来，将有助于确定水平混合在均匀和/或重新分布生物标量中的作用。广泛影响这项工作将为沿海地区标量的输送和混合提供有价值的新见解，特别是在10到1000米的“中间”尺度上。这将产生广泛的科学影响，特别是对内陆架的跨学科建模工作，横向混合的估计和/或参数会造成很大的不确定性。随着沿海人口继续增长，海洋生态系统的压力继续增加，了解决定近岸环境中迁移和/或滞留的根本机制将变得越来越重要。了解沿海环境中的横向扩散不仅对海洋幼体和有害藻华的运输/保留有重大影响，而且对污染物的运输/保留也有重大影响。更好地了解这些混合过程最终将引起环境规划者、政策制定者和沿海社区其他利益攸关方的兴趣。拟议的研究还将支持一名博士后学者和两名博士后学生。