Transport by Intrusions Generated by Boundary Mixing

过去十年的野外观测表明，盆地边界附近的混合比盆地内部的混合多一个数量级或更多，这在很大程度上决定了盆地的平均混合速率。在海洋中，边界混合归因于内波对地形的临界反射和内潮流过粗糙地形所产生的内波。在湖泊中，边界混合是由于临界反射和来自沉积物的底流产生的湍流。尽管最近的许多工作都集中在边界混合过程上，但对混合流体的最终命运的研究却很少。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如何被输送到内部。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。这项工作的目标是：1)根据产生的内波场和平均流的性质对湖泊对强迫的响应进行分类；2)识别入侵并将湍流和混合与强迫联系起来；3)跟踪入侵的演变。湖泊的大小不同，要检验的一个假设是，势能变化的大小和为混合提供的能量取决于湖泊的大小，但这些速率的比率（称为混合效率）在湖泊的倾斜侧面比在平坦的底部大。将进行电流和温度的测量，并计算内波的频谱。将用荧光染料跟踪侵入，并在整个染料斑块上进行微观结构测量。拟议工作的更广泛影响包括研究生和本科生的培训，向爱荷华州立大学附近的一所农村学校推广，以及以爱荷华湖畔实验室为基础的推广。这将在湖滨实验室开设一门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。PI研究小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。PI的研究小组扩大了代表性不足的群体的参与，并通过其过去的活动向公众传播了结果。该项目的研究成果将影响和联系海洋学、湖沼学和工程学；特别是，外联将提高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.