Collaborative Research: Circulation and mixing in a coastally trapped river plume

合作研究：沿海滞留河流羽流的循环和混合

• 批准号: 1745258
• 负责人: Nicholas Nidzieko
• 金额: $ 1.17万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1745258&HistoricalAwards=false
• 关键词: Collaborative; Research; Circulation; mixing; coastally

Under downwelling conditions, buoyant coastal currents can transport river-derived material hundreds of kilometers down the coast. The fate of this material is ultimately determined by the extent of mixing with the ambient coastal waters. Despite the importance that mixing plays in controlling the along-shelf dispersal of river-derived materials, few studies have directly measured mixing in the far-field of river plume. This study will quantify mixing and circulation in the Chesapeake Bay by combining a comprehensive field program with numerical models. The Chesapeake is ideal for this study because of its predictable coastal current and its proximity to extensive research infrastructure at the USACE facility in Duck, NC. The four primary objectives of the study are: to quantify mixing within the nose region, the interior, and the offshore edge of the plume during downwelling conditions, to obtain detailed measurements of plume propagation speeds and the structure of the circulation behind the nose in a buoyant coastal current under downwelling favorable winds, to identify the dominant mechanisms responsible for mixing and entrainment of salt into the coastal current, and to document the dominant dynamic balances that govern plume propagation during downwelling conditions under a range of wind forcing. This comprehensive field program will consist of moored, shipboard, and microstructure-AUV observations of circulation and mixing within the plume. High resolution simulations using ROMS will complement the field program by providing more comprehensive estimates of mixing, diagnose the dynamics of the plume, and assess the role of wind, waves and internal shear in driving plume mixing.Coastally-trapped river plumes represent a class of gravity currents that have been extensively studied using numerical models and laboratory experiments. Detailed field observations resulting from this study will provide new insights into mixing and circulation processes in a buoyant gravity current. This project will provide unprecedented measurement documenting the relative roles of mixing and advective straining in modifying the plume?s stratification. The relative importance of mixing in the nose region versus broadly distributed mixing behind the plume due to winds and waves will also be examined. Results will also elucidate the role of ageostrophic dynamics in the nose region and along the off-shore edge of the plume, once isopycnals become vertical. The field program will use adaptive sampling that combines both ship-based surveys and AUV-microstructure observations of a propagating coastal current. Utilizing the AUV to adaptively sample an ephemeral coastal feature is expected to lead to technological advances in observational oceanography. Lagrangian data will be complemented by a mooring array that will provide unprecedented near-surface resolution of stratification and shear in the far field of a river plume. Detailed near surface observations of turbulence will help to identify the dominant mixing mechanisms responsible for entraining ambient sea water into the plume.This project will serve as the basis for one graduate student's thesis at Rutgers. Several undergraduate students will also be included in the field effort through the NSF-funded Research Experience for Undergraduates at Rutgers and Woods Hole. The objectives for Broader Impacts are to translate the science themes and data sets from this study into innovative undergraduate teaching materials and to encourage STEM learning for future scientists (grades K-12) through hands-on activities related to the research. The expertise of the NSF-funded Centers for Ocean Science Education Excellence Networked Ocean World and the Ocean Observing Initiative's Education and Public Engagement (OOI EPE) Implementing Organization (IO) will be leveraged to create an online learning module for undergraduates. These lessons will be disseminated broadly through an OOI EPE online portal and workshops at ocean science meetings (e.g., AGU and ASLO Oceans). The modules will highlight the benefits of teaching with authentic data with the focus of engaging undergraduates in the scientific process.

在下流条件下，漂浮的海岸洋流可以将从河流中提取的物质沿着海岸输送数百公里。这种物质的命运最终取决于与周围沿海水域的混合程度。尽管混合在控制河流衍生物质沿陆架扩散方面发挥了重要作用，但很少有研究直接测量河流羽流远场的混合。这项研究将通过一个综合的现场计划和数值模式相结合来量化切萨皮克湾的混合和环流。切萨皮克是这项研究的理想之选，因为它的海岸水流是可预测的，而且它靠近位于北卡罗来纳州达克的USACE设施的广泛研究基础设施。这项研究的四个主要目标是：量化下行条件下羽流的鼻区、内部和近海边缘内的混合，详细测量下行有利风下的浮力沿岸流中羽流的传播速度和鼻子后面的环流结构，找出导致盐分混合和夹带到沿海流中的主要机制，以及记录在一定范围的风强迫下的下行条件下控制羽流传播的主要动态平衡。这一全面的现场计划将包括系泊、船上和微结构-AUV对羽流内环流和混合的观测。使用ROMS的高分辨率模拟将补充现场程序，提供更全面的混合估计，诊断羽流的动力学，并评估风、波和内部切变在驱动羽流混合中的作用。海岸捕获的河流羽流代表了一类重力流，已通过数值模型和实验室实验进行了广泛的研究。这项研究产生的详细的现场观测将为在浮力流中的混合和循环过程提供新的见解。这个项目将提供史无前例的测量，记录混合和平流应变在修正羽流--S层结中的相对作用。此外，还将研究由于风和海浪引起的鼻区混合与羽流后面广泛分布的混合的相对重要性。结果还将阐明，一旦等径线变得垂直，非地转动力在鼻区和羽流离岸边缘所起的作用。现场计划将使用自适应采样，结合基于船舶的调查和对传播的沿海洋流的AUV微观结构观测。利用AUV自适应地对短暂的海岸地物进行采样，预计将导致观测海洋学方面的技术进步。拉格朗日数据将得到一个系泊阵列的补充，该阵列将提供前所未有的近地表分辨率，了解河流羽流远场的分层和剪切。对湍流的详细近地表观测将有助于确定导致周围海水进入垂直管道的主要混合机制。该项目将作为罗格斯大学一名研究生论文的基础。几名本科生也将通过美国国家科学基金会资助的罗格斯和伍兹霍尔本科生研究体验项目参与实地考察。更广泛影响的目标是将这项研究的科学主题和数据集转化为创新的本科教材，并通过与研究相关的实践活动鼓励未来科学家(K-12年级)学习STEM。将利用NSF资助的海洋科学教育卓越中心、网络化海洋世界和海洋观测倡议的教育和公众参与(OOI EPE)执行组织的专业知识，为本科生创建在线学习模块。这些经验教训将通过海洋科学会议(如AGU和ASLO Ocean)的OOI EPE在线门户网站和讲习班广泛传播。这些单元将突出使用真实数据进行教学的好处，重点是让本科生参与科学过程。