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估计海洋中混合和扩散综合参数的一种优雅而准确的方法。在这个项目中，提出了一个示踪剂释放实验，以调查在波罗的海中部的深水混合。与来自美国、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长效示踪剂，并将在2007年和2008年的一系列后续巡航中观察其扩散情况。该实验将伴随着停泊的仪器阵列，大规模的水文调查和详细的湍流测量，旨在提高对一些长期存在的研究问题的理解：什么是有效的溶解物质之间的垂直运输通常脱氧深层和上层的波罗的海中部停滞期间？哪些混合机制（内波混合、边界混合、重力流卷吸等）可以确定，以解释示踪剂的有效混合，以及它们的相对重要性是什么？在2006年8月提交给设计小组的另一项提案中，由三个德国研究所组成的科学财团建议购置海洋示踪剂注入系统（奥蒂斯），这是任何示踪剂释放实验的关键组成部分。在OTIS提案中，已经概述了一系列即将进行的示踪剂释放实验，其中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.