Investigation of deep-water mixing in the Baltic Sea with the help of a tracer release experiment

有目的地释放长寿命示踪剂是一种优雅而准确的方法，可以估计海洋中混合和扩散的综合参数。在这个项目中，为了研究波罗的海中部的深水混合，提出了一个示踪剂释放实验。与美国、瑞典和波兰的合作伙伴合作，将于2007年8月在东哥特兰盆地的深水中注入一种长效示踪剂，并将在2007年和2008年的一系列巡航中观察其传播情况。该实验将伴随着系泊仪器阵列、大规模水文测量和详细的湍流测量，目的是更好地了解一些长期存在的研究问题：在停滞期，通常脱氧的深层和波罗的海中部上层之间的溶解物质的有效垂直输送是什么？哪种混合机制(内波混合、边界混合、重力流卷吸等)是否可以确定以解释示踪剂的有效混合，它们的相对重要性是什么？在2006年8月提交给DFG的另一份提案中，一个由三个德国研究所组成的科学联盟建议购买海洋示踪器注入系统，这是任何示踪剂释放实验的关键组成部分。在奥的斯的提案中，概述了即将进行的一系列示踪剂释放实验，第一个实验将在下文中详细描述。

The purposeful release of a long-lived tracer is an elegant and accurate method to estimate integrated parameters of mixing and dispersal in the ocean. In this project, a tracer release experiment is proposed in order to investigate deep-water mixing in the central Baltic Sea. In collaboration with partners from the US, Sweden, and Poland, a long-lived tracer will be injected in August 2007 in the deep water of the Eastern Gotland Basin, and its spreading will be observed during a series of subsequent cruises in 2007 and 2008. The experiment will be accompanied by moored instrument arrays, large-scale hydrographic surveys, and detailed turbulence measurements aimed at an improved understanding of a number of long-standing research questions: What is the effective vertical transport of dissolved substances between the usually deoxygenated deep layers and the upper layers of the central Baltic during stagnation periods? Which mixing mechanisms (internal-wave mixing, boundary mixing, gravity current entrainment, etc.) can be identified in order to explain the effective mixing of the tracer, and what is their relative importance? In a separate proposal, submitted to the DFG in August 2006, a scientific consortium of three German institutes has suggested the acquisition of an Ocean Tracer Injection System (OTIS), which is the key component of any tracer release experiment. In the OTIS-proposal, a series of upcoming tracer release experiments has been sketched, the first of which is described in detail in the following.