Quantification of shear-induced convection and bottom-boundary mixing in natural waters

天然水中剪切引起的对流和底部边界混合的量化

基本信息

批准号：
27686141
负责人：
Professor Dr. Andreas Lorke
金额：
--
依托单位：
Leibniz-Institut für Ostseeforschung Warnemünde (IOW)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2006
资助国家：
德国
起止时间：
2005-12-31 至 2010-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/27686141?language=en
关键词：
Quantification shear induced convection bottom

项目摘要

It has been pointed out by numerous authors that estimates of the vertical mixing obtained by microstructure profiling techniques in lakes and the ocean can, in general, not explain the total mixing suggested by the global budgets of matter and heat. Searching for additional mixing mechanisms, boundary mixing has been identified as a key process. In this study, a boundary mixing process driven by a gravitationally unstable bottom boundary layer (BBL) is investigated. Such unstable BBLs in stably stratified basins are the result of strong up-slope currents, typically caused by internal seiching in lakes or by long internal-inertial waves in the coastal ocean. Due to the fact that in a turbulent BBL, the up-slope speed increases with increasing distance from the sediment, heavy (i.e. cold or salty) water in the BBL may be advected above lighter (i.e. warmer or fresher) water, leading to convective mixing. Inversely, down-slope currents lead to a suppression of mixing. We plan to investigate this process with an interdisciplinary approach: our primary study site will be Lake Constance, where the BBL dynamics and turbulence will be studied in detail for a limnological set-up. Our oceanographic study site will be the Baltic Sea, where a similar mixing process takes place. A numerical turbulence model will be used to analyze this process at the measuring sites, study the basin-wide effect, and construct a general theory.

众多作者指出，通过湖泊和海洋中的微观结构分析技术获得的垂直混合估计，通常不能解释全球物质和热量预算所建议的总混合。搜索其他混合机制，已经将边界混合确定为关键过程。在这项研究中，研究了由重力不稳定的底部边界层（BBL）驱动的边界混合过程。稳定分层的盆地中这种不稳定的bbl是强大的上坡电流的结果，通常是由于湖泊内部清理或沿海海洋中长的内部惯性波引起的。由于在湍流的BBL中，上坡速度随着与沉积物的距离的增加而增加，因此BBL中的重量（即冷或咸）可以被推入更轻的（即温暖或更新鲜的水）上方，从而导致对流混合。相反，下坡电流导致混合抑制。我们计划采用跨学科方法调查这一过程：我们的主要研究地点将是康斯坦斯湖，在该湖中，将详细研究BBL动力学和湍流以进行林长学设置。我们的海洋学研究地点将是波罗的海，那里发生了类似的混合过程。数值湍流模型将用于在测量位点分析此过程，研究盆地范围的效果并构建一般理论。