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

9712871布朗研究将根据五大湖海岸研究机会公告（NSF 97-38）进行。这是一个由来自5个学术研究机构的11位研究者参与的合作研究项目。这项研究是在美国国家科学基金会沿海海洋过程（CoOP）计划和美国国家海洋和大气管理局沿海海洋计划的支持下进行的。这一跨学科合作的5年研究项目将包括实地和实验室研究以及数学建模的综合项目，以量化沿海洋流和热锋在调解苏必利尔湖跨边缘运输中的作用。苏必利尔湖的基威诺半岛的西海岸展示了一个引人注目的海岸射流，被称为基威诺流。一个强大的、与海岸平行的密度锋，即热柱，也是该地区的特征，并持续到夏季。这项工作的目标是确定该系统上强烈的物理强迫所产生的物理、化学和生物效应，特别是阐明这些效应如何在时间和空间上相互作用，以定义苏必利尔湖不同的近岸和近海环境。该项目首次对苏必利尔湖海岸带的物理、化学和生物耦合过程进行了建模，其中垂直和水平的热结构和输送过程都很重要。研究小组分为三个小组：物理过程、化学梯度和生物群落。物理过程组将利用现场观测、数值模拟和卫星观测，研究控制跨缘运输的所有强迫因子（例如，风驱动的变率、斜压不稳定性）的相对重要性。化学梯度组将描述近岸和近海化学物质分布的差异，评估水和沉积物运动的化学示踪剂，并研究洋流引起的化学循环的差异（近岸和近海）。生物群落小组将确定初级生产、营养结构和物质转化速率的梯度如何发展。所有三个小组将在整个项目中密切互动，以获得和共享互补的数据集，并得出系统的耦合物理/化学/生物模型。该项目所获得的详细的、过程级的理解将促进我们对沿海地区重要生物、化学和地质物质的运输、转化和命运的定量理解，并为未来如何最好地保护苏必利尔湖原始自然的管理决策提供坚实的基础。根据该合同，系泊将部署整整三年，以便监测包括冰下在内的所有季节的情况。地面测量将通过同步卫星对地表温度的测定得到加强，存档的图像将用于获得热结构的年际变化记录。工作还将导致开发水和沉积物运动的化学示踪剂，通过对研究区内的颗粒进行指纹识别，以跟踪和量化颗粒从近岸到近海的当今和历史模式。测量近岸带和近海带岩心中颗粒的放射性核素将在确定沉积物运输和沉积途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.