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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.

许多作者指出，通过湖泊和海洋的微观结构分析技术获得的垂直混合的估计通常不能解释全球物质和热量预算所建议的总混合。在寻找额外的混合机制时，边界混合已被确定为关键过程。在这项研究中，研究了由重力不稳定底部边界层（BBL）驱动的边界混合过程。稳定分层盆地中的这种不稳定的 BBL 是强大的上坡流的结果，通常是由湖泊中的内部淤塞或沿海海洋中的长内惯性波引起的。由于在湍流 BBL 中，上坡速度随着距沉积物距离的增加而增加，BBL 中的重水（即冷水或咸水）可能会在轻水（即较温暖或较新鲜的水）上方平流流动，从而导致对流混合。相反，下坡电流会抑制混合。我们计划采用跨学科方法研究这一过程：我们的主要研究地点将是博登湖，在那里将详细研究 BBL 动力学和湍流，以建立湖泊学设置。我们的海洋学研究地点将是波罗的海，那里发生类似的混合过程。将使用数值湍流模型来分析测量点的这一过程，研究全盆地效应，并构建通用理论。