Impact of the Keweenaw Current on Cross-Margin Transport in Lake Superior

9712871布朗研究将响应五大湖海岸研究机会(NSF97-38)的宣布而进行。这是一个由来自五个学术研究机构的11名研究人员参与的合作研究项目。这项研究是在NSF海岸海洋过程(COOP)计划和NOAA海岸海洋计划的赞助下进行的。这项合作的、跨学科的5年研究计划将需要一个综合计划，包括实地和实验室研究以及数学建模，以量化沿海洋流和热锋在调节苏必利尔湖跨边界运输中的作用。苏必利尔湖基韦诺半岛的西岸展示了一股戏剧性的海岸急流，被称为基韦诺洋流。一种强烈的、与海岸平行的密度锋，即热棒，也是该地区的特征，并持续到夏季。这项拟议工作的目标是确定强烈的物理强迫对该系统产生的物理、化学和生物影响，特别是阐明这些影响如何在时间和空间上相互作用，以确定苏必利尔湖不同的近岸和近海环境。该项目是对苏必利尔湖沿岸地区物理、化学和生物耦合过程进行模拟的第一次努力，在那里垂直和水平的热结构和输送过程都很重要。研究团队分为三个小组：物理过程、化学梯度和生物群落。物理过程小组将利用现场观测、数值模拟和卫星观测，审查支配跨边界输送的所有强迫因素(例如，风致变异性、斜压不稳定)的相对重要性。化学梯度小组将表征近岸-近海化学物种分布的差异，评估水和沉积物运动的化学示踪剂，并调查由洋流引起的化学循环的差异(近岸与近海)。生物群落小组将确定初级生产、营养结构和物质转化速度的梯度是如何发展的。这三个小组将在整个项目期间密切互动，以获得和分享互补的数据集，并得出该系统的物理/化学/生物耦合模型。该项目实现的详细的、过程级别的了解将促进我们对调控沿海地区生物、化学和地质重要物质的运输、转化和命运的过程的定量理解，并为未来如何最好地保护苏必利尔湖的原始性质的管理决策提供坚实的基础。根据这项合同，将在整整三年内部署系泊设施，以便可以监测所有季节的情况，包括冰层下的情况。将通过卫星同时测定地表温度来加强地面测量，并将利用存档图像来获得热结构年际变化的记录。还将开展工作，通过对源自研究区的颗粒进行指纹识别，开发水和沉积物运动的化学示踪剂，以便跟踪和量化颗粒从近岸向近海迁移的现代和历史模式。测量近岸区和近海区岩心中颗粒上的放射性核素，将在确定沉积物迁移和沉积路径方面发挥关键作用。

9712871 Brown Research will be undertaken in response to an Announcement of Opportunity (NSF 97-38) for Coastal Studies in the Great Lakes. This is a collaborative research project involving eleven investigators from five academic research institutions. The research is being conducted under the auspices of the NSF Coastal Ocean Processes (CoOP) program and the NOAA Coastal Ocean Program. This collaborative, interdisciplinary 5-year research program will entail an integrated program of field and laboratory studies and mathematical modeling to quantify the role of coastal currents and thermal fronts in mediating cross-margin transport in Lake Superior. The western shore of Lake Superior's Keweenaw Peninsula exhibits a dramatic coastal jet known as the Keweenaw Current. A strong, shore-parallel density front, the thermal bar, also is characteristic of this region and persists long into the summer. The goal of the proposed work is to determine the physical, chemical, and biological effects that arise from the intense physical forcing on this system, and specifically, to elucidate how these effects interact temporally and spatially to define distinct nearshore and offshore environments in Lake Superior. This project represents the first effort to model coupled physical, chemical, and biological processes in the coastal zone of Lake Superior where both vertical and horizontal thermal structure and transport processes are important. The research team is divided into three subgroups: Physical Processes, Chemical Gradients, and Biological Communities. The Physical Processes group will examine the relative importance of all forcing factors (e.g., wind-driven variability, baroclinic instability) that govern cross margin transport using in situ observations, numerical modeling, and satellite observations. The Chemical Gradients group will characterize nearshore-offshore differences in distributions of chemical species, evaluate chemical tracers of wa ter and sediment movement, and investigate differences (inshore vs. offshore) in chemical cycles induced by the current. The Biological Communities group will determine how gradients in primary production, trophic structure, and rates of material transformation develop. All three groups will interact closely throughout the project to obtain and share complementary data sets and to derive a coupled physical/chemical/biological model of the system. The detailed, process-level understanding achieved by this project will advance our quantitative understanding of the processes that regulate the transport, transformation and fate of biologically, chemically and geologically important matter in coastal regions and provide a firm basis for future management decisions on how best to preserve the pristine nature of Lake Superior. Under this award, moorings will be deployed through three full years so that conditions in all seasons, including under the ice, can be monitored. Ground-based measurements will be enhanced by concurrent satellite determination of surface temperature and archived images will be employed to obtain a record of interannual variability in thermal structure. Work will also lead to development of chemical tracers of water and sediment movement by fingerprinting particles originating within the study zone in order to track and quantify present-day and historic patterns of particle transport from nearshore to offshore. Measurement of radionuclides on particles within the nearshore zone and in cores from the offshore zone will play a critical role in identification of sediment transport and deposition pathways.