CAREER: What’s salt got to do with it? Linking the variability of mixing to exchange flows in real estuaries

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。河口是世界上最具生产力的生态系统和海上商业中心之一。在河口，海洋和河水之间的交换对物理和循环以及生物地球化学过程（如养分通量、缺氧和污染物运输）至关重要。这使得了解混合和交换流对于预测人为变化和气候变化对河口系统及其生态的影响至关重要。关于河口水流交换的文献主要集中在部分混合河口或简化的海岸形态。在广泛的分层条件下，对于地形复杂的河口（不规则的水深、收敛的宽度、岬角和狭窄），还有很多未知的地方。这个CAREER项目提供了一个有组织的途径，以便更全面地了解陆海联系、淡水和盐水的交换以及不同条件下、不同环境下的物质运输。PI将记录和解释智利巴塔哥尼亚的Reloncavi峡湾（分层）、美国东北海岸的Penobscot河口（部分混合到盐楔）和法国西南海岸的吉伦特河口（充分混合到部分混合）混合和交换流的时空变化，使用现场收集的数据和数值模型模拟。这种方法利用了她最近对吉伦特、佩诺布斯考特和巴塔哥尼亚峡湾的研究。来自CAREER项目的新知识是更好地理解陆地淡水流动如何影响交换流、确定污染物、幼虫和有害藻华等水生物质运输的时间尺度的重要组成部分，并将使政策制定者能够利用这些发现做出基于科学的决策。这项研究的结果将与缅因州- edna轨道1 EPSCoR的研究人员分享，以帮助告知他们的主题目标，即在美国东北部沿海水域出现有害或转移的分类群时，改善监测和预警系统。高中公民科学家将帮助测量部分混合的河口，PI将与学生和教师合作，为9-12年级制定应用数学/科学课程计划。这些课程将突出三个河口之间的差异，解释简单的潮汐和体积守恒理论，并介绍数据可视化工具。课程计划将通过社区演讲、三语项目网站和其他外展机制与美国缅因州的高中科学和数学教师分享。通过这些活动，PI将帮助未来的劳动力做好准备，以执行有关河口和沿海环境的明智政策决定。在三大洲战略性地选择研究区域将促进基于地点和全球视角，帮助所有项目参与者接受科学和工程教育中的文化和社会多样性。该倡议建议扩大对妇女STEM素养和兴趣的关注，并在STEM应用研究学科中招聘相关人员，作为扩大河口科学和工程劳动力参与的一种手段。该研究计划将描述不同分层潮汐河口的混合和交换流的沿通道结构。先前的研究表明，驱动交换流和混合的动力学可能具有意想不到的复杂性，潮汐、密度和风的作用力可能是它们发展的核心。然而，这项工作的大部分集中在混合和交换流的体积平均值上，或者只考虑了这些过程在部分混合河口的空间变化。该项目将解决关于混合的空间和时间变化如何改变未部分混合的河口交换流机制的知识空白。由盐度变化耗散定义的淡水和盐水混合的时空变化将与量化为总交换流（TEF）和欧拉交换流（EEF）的交换流在水动力学上联系起来。这种耦合将为河口参数空间的表征提供基础。这将有助于世界各地的河口研究人员更好地规划实地活动，并建立适当的方法来了解河口的混合和交换流，从而了解物质运输。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Estuaries are among the most productive ecosystems and maritime commercial centers in the world. In estuaries, the exchange between the ocean and the river water is fundamentally important to the physics and circulation as well as biogeochemical processes such as nutrient fluxes, hypoxia and contaminant transport. This makes the understanding of mixing and exchange flows vital to predicting the impact of anthropogenic change and climate change on estuarine systems and their ecology. The literature of flow exchange in estuaries focuses on partially mixed estuaries or simplified coastal morphometries. Much remains unknown regarding estuaries with complicated topography (irregular bathymetry, convergent width, headlands, and constrictions) over a wide range of stratification conditions. This CAREER project provides an organized pathway for a more comprehensive understanding of land-sea connections and exchange of fresh and salt water, as well as material transport under varied conditions, in varied settings. The PI will document and interpret spatial and temporal variations in mixing and exchange flows in Reloncavi Fjord in Chilean Patagonia (stratified), the Penobscot Estuary on the northeast coast of the USA (partially-mixed to salt-wedge) and the Gironde Estuary on the southwest coast of France (well-mixed to partially-mixed) using in-situ collected data and numerical model simulations. This approach leverages her recent research on the Gironde, Penobscot, and Patagonian Fjords. New knowledge from this CAREER project is an essential building block for better understanding how land-based freshwater flows affect exchange flows, determining timescales for transport of water borne materials such as pollutants, larvae and harmful algal blooms, and will allow for policy makers to use these findings to make science-based decisions. The results of this research will be shared with Maine-eDNA Track 1 EPSCoR researchers to help inform their Thematic Goal of improving surveillance and early warning systems for harmful or shifting taxa as they emerge in coastal waters in the northeast USA. High school citizen scientists will help measure partially mixed estuaries and the PI will work with students and teachers to develop applied mathematics/science lesson plans for grades 9-12. These lessons will highlight differences among the three estuaries, explain simple tidal and volume conservation theory, and introduce data visualization tools. Lesson plans will be shared with high school science and mathematics teachers in Maine, the US and internationally through community presentations, a tri-lingual project website and other outreach mechanisms. Through these activities, the PI will help prepare the future workforce to execute informed policy decisions regarding estuarine and coastal environments. The strategic selection of study areas on three continents will promote place-based and global perspectives, helping all project participants embrace cultural and social diversity in science and engineering education. The PI proposes to amplify a focus on STEM literacy and interest of women, and related recruitment in STEM applied research disciplines as a means of broadening participation in the estuarine science and engineering workforce.The research plan will characterize the along-channel structure of mixing and exchange flows in tidal estuaries of varying stratification. Previous work has shown that the dynamics driving exchange flows and mixing can have unexpected complexity and that tidal, density and wind forcing can be central to their development. However, much of this work has focused on volume averages of mixing and exchange flows or has considered spatial variations of these processes only in partially mixed estuaries. This project will address the gap in knowledge of how spatial and temporal variations in mixing alters exchange flow regimes in estuaries that are not partially-mixed. Spatial and temporal variations of fresh and saltwater mixing defined by the dissipation of salinity variance will be hydrodynamically linked to exchange flows quantified as total exchange flow (TEF) and Eulerian exchange flow (EEF). This coupling will provide a basis for characterization of the estuarine parameter space. This will help estuarine researchers around the world better plan field campaigns and establish appropriate methodologies for understanding mixing and exchange flows in estuaries, and thus material transport.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.