Collaborative Research: Lateral mixing and dispersion on the inner shelf

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。该奖项旨在表彰一系列全面的实地观察，以阐明和量化内大陆架的混合过程，并直接研究这些过程对内大陆架生物分布的影响。海岸流的预测建模需要子网格尺度过程的参数化，在水平维度上，子网格尺度过程具有10到1000米的特征长度尺度。这项研究将提供一个全面的图片水平分散在这些尺度上的内大陆架和标量分布的影响。据推测，所施加的垂直边界和分层的物理限制，限制垂直运动和交换过程，导致强烈的各向异性流场和分散在内部货架。以前的工作表明，混合在底部边界层是尺度依赖于在水平方向上的底部边界层的限制作用，尽管。在水柱中，由于波浪、风以及表面加热和冷却的影响，分层可能会产生更大的各向异性和对垂直传输速率的限制，而在表面混合层中，尺度依赖性可能会有所不同。该项目将直接测量在不同强迫条件下的底部混合层，分层的内部和表面混合层的横向扩散率，以量化任何尺度相关的混合，并突出不同深度的横向混合的相似性和差异。一旦分散率和规模的依赖性被确定，他们将被用来检查如何混合的横向速率可能对应于生物薄层的发展，维护和降解。两个，为期两周的实地实验将在北方蒙特雷湾的内大陆架进行，以检查这些问题。在部署了一系列系泊仪器以测量物理、光学和声学特性后，研究小组将在北方加州上升流季节的早期和晚期在底部边界层、分层内部和表面混合层内单独释放示踪染料。染料？的空间和时间分布将使用配备有快速响应荧光计的自主水下航行器以及配备有荧光计和辅助仪器的拖曳体来测量，这些仪器同时测量感兴趣的生物和地球化学特性。染料测量将被用来量化的横向混合，通过拟合的数据规模依赖的法律，并比较和对比相应的速度的分散与不同的气候和水动力学强迫条件（风，表面波，内波，分层，湍流）在这两个测量期间。将横向混合过程和强迫条件与测得的生物分布（薄层）连接起来，将有助于确定水平混合在生物标量的扩散和/或再分布中的作用。更广泛的影响这项工作将提供宝贵的新的见解，在沿海地区的标量的运输和混合，特别是在'中间'尺度的10秒至1000米。它将产生广泛的科学影响，特别是对内大陆架的跨学科建模工作，其中横向混合的估计和/或参数化会导致显着的不确定性。随着沿海人口继续增长，海洋生态系统所受压力继续增加，了解决定近岸环境迁移和/或滞留的基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虫和有害藻华的迁移/滞留，而且对污染物的迁移/滞留具有重要意义。更好地了解这些混合过程最终将有利于沿海社区的环境规划者、决策者和其他利益攸关方。拟议的研究还将支持一名博士后学者和两名博士生。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Intellectual Merit This 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 Impacts This 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.