Transport by Intrusions Generated by Boundary Mixing

OCE-0647253过去十年的现场观测表明，盆地边界附近的混合比内陆地区的混合高一个数量级或更多，并在很大程度上决定了盆地平均混合速率。在海洋中，边界混合被归因于内波在地形上的临界反射和内潮在崎岖地形上流动所产生的内波。在湖泊中，边界混合是由于海塘底流产生的临界反射和湍流造成的。虽然最近的许多工作都集中在边界混合过程上，但关于混合流体的最终命运的工作很少。在这项研究中，将进行现场实验，以确定在分层水体边界混合的流体是如何输送到内陆的。实验将在爱荷华州的两个湖泊进行：爱荷华州立大学附近的Ada Hayden湖和更大、更深的West Okoboji湖。这项工作的目的是：1)根据产生的内部波场和平均流的特性对湖泊对强迫的响应进行分类；2)识别侵入体并将湍流和混合与强迫联系起来；3)跟踪侵入体的演化。两个湖泊的大小不同，一个将要检验的假设是，势能变化的大小和为混合提供的能量取决于湖泊的大小，但这些比率(称为混合效率)在湖的斜坡上将比沿平底更大。将对电流和温度进行测量，并计算内波谱。这项拟议工作的广泛影响包括对研究生和本科生的培训，扩展到爱荷华州立大学附近的一所农村学校，以及爱荷华州立实验室的扩展。这将在湖滨实验室开设一个新的夏季物理湖沼学课程，并为当地居民和K-12学校开设非学分课程。国际和平研究所研究组的研究生将为拟议的研究进行实验并参与外展活动。所要求的设备将加强研究的基础设施。国际和平协会的研究小组扩大了代表性不足群体的参与，并通过其过去的活动向公众传播结果。该项目的成果将影响海洋学、湖泊学和工程学，并将其联系起来；特别是，外联活动将提高人们对地方和国家水质问题的认识。

OCE-0647253Field observations over the last decade suggest that mixing near basin boundaries exceeds that in the interior by an order of magnitude or more and largely determines the basin-averaged mixing rate. In the ocean, boundary mixing has been attributed to critical reflection of internal waves on topography and internal waves generated by internal tides flowing over rough topography. In lakes, boundary mixing is due to critical reflection and turbulence generated by bottom currents from seiches. Although much recent work has focused on boundary mixing processes, there has been little work on the ultimate fate of the mixed fluid. In this study, field experiments will be conducted to determine how fluid mixed at the boundary of a stratifiedwater body is transported to the interior. Experiments will be conducted in two lakes in Iowa: Ada Hayden Lake, near Iowa State University and West Okoboji Lake, which is larger and deeper. The objectives of the proposed work are to 1) classify the response of lakes to forcing according to the properties of the resulting internal wave field and mean currents, 2) identify intrusions and relate the turbulence and mixing to the forcing, and 3) to track the intrusions as they evolve. The lakes differ in size and one hypothesis that will be tested is that the magnitudes of potential energy change and energy supplied for mixing depend on the size of the lake but the ratio of these rates (called the mixing efficiency) will be larger on the sloping sides of the lake than along the flat bottom. Measurements of currents and temperature will be made and the spectra of internal waves will be calculated. Intrusions will be tracked with a fluorescent dye and microstructure measurements will be made throughout the dye patch.Broader impacts of the proposed work include the training of graduate and undergraduatestudents, outreach to a rural school near Iowa State University, and outreach based out of the Iowa Lakeside Laboratory. This will a new summer class on physical limnology at the Lakeside Laboratory as well as non-credit courses for local residents and K-12 schools. Graduate students in the PI's research group will both conduct the experiments for the proposed research and participate in the outreach activities. Requested equipment will enhance the infrastructure for research. The PI's research group has broadened participation of underrepresented groups and disseminated results to the public through its past activities. Results from this project will affect and connect oceanography, limnology, and engineering; in particular, the outreach will increase awareness of local and national water quality issues.