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

在下流条件下，浮力强的海岸水流可以将来自河流的物质沿海岸输送数百公里。这些物质的命运最终取决于与周围沿海水域混合的程度。尽管混合在控制河流源物质沿陆架扩散方面发挥着重要作用，但很少有研究直接测量河流羽流远场的混合。本研究将通过综合现场程序和数值模型相结合，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选择，因为它具有可预测的沿海洋流，并且靠近北卡罗来纳州达克市USACE设施的广泛研究基础设施。这项研究的四个主要目标是：量化在下沉条件下羽流鼻部区域、内部和近海边缘的混合，获得羽流传播速度的详细测量和在下沉有利风的浮力沿海流鼻部后环流结构，确定导致盐混合和夹带到沿海流中的主要机制。并记录主导的动态平衡，控制羽流传播在下降条件下的风强迫范围。这个综合的现场项目将包括系泊、船载和微观结构-水下航行器对羽流内循环和混合的观察。使用ROMS的高分辨率模拟将通过提供更全面的混合估计、诊断羽流动力学以及评估风、波和内部切变在驱动羽流混合中的作用来补充现场程序。沿海困住的河流羽流代表了一种重力流，已经通过数值模型和实验室实验进行了广泛的研究。详细的野外观测结果将为浮力重力流的混合和环流过程提供新的见解。该项目将提供前所未有的测量数据，记录混合和平流应变在改变羽流中的相对作用。分层。在鼻区混合与羽流后面由于风和波的广泛分布混合的相对重要性也将被检查。结果还将阐明，一旦等等线变为垂直，地转动力学在鼻部和沿羽流离岸边缘的作用。现场项目将使用自适应采样，结合船舶调查和auv微观结构观察沿海水流的传播。利用AUV对短暂的海岸特征进行自适应采样有望导致观测海洋学的技术进步。拉格朗日数据将由系泊阵列补充，该阵列将提供前所未有的近地表分层和远场河流羽流剪切分辨率。对湍流的详细近地表观测将有助于确定将周围海水带入羽流的主要混合机制。这个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大学和伍兹霍尔大学本科生研究经验项目参与实地工作。“更广泛的影响”的目标是将本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，鼓励未来的科学家（K-12年级）学习STEM。美国国家科学基金会资助的海洋科学教育卓越网络海洋世界中心和海洋观测倡议的教育和公众参与（OOI EPE）实施组织（IO）的专业知识将被用来为本科生创建一个在线学习模块。这些经验教训将通过OOI EPE在线门户网站和海洋科学会议（例如AGU和ASLO海洋）讲习班广泛传播。这些模块将强调用真实数据教学的好处，重点是让本科生参与科学过程。

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.