A New Method for the Estimation of Profiles of Diffusivity in the Stratified Marine Environment

大部分海洋都稳定地分层，较轻的水覆盖在较重的水上，在湍流混合的推动下，营养物质、盐、热量和污染物在分层中垂直移动。因此，负责这些垂直通量的过程的性质和强度对海洋系统的形成起着重要作用。例如，营养物质的垂直通量将黑暗、营养丰富的深水与上层阳光充足的水柱连接起来，从而促进支持海洋生态系统的初级生产力。垂直混合也是大尺度海洋环流背后的主要机制之一，因此对我们星球的气候具有极其重要的意义。已经开发了一些技术来估计海洋环境中的垂直混合率。这些措施包括使用自由落体剖面仪直接测量湍流，这是一项非常耗时和劳动密集型的技术，需要专业科学家团队。其他方法使用声学海流计，可以部署在海洋环境中，然后放置一段时间。然而，这种方法的垂直范围有限，到目前为止，在垂直分层或从移动平台部署的环境中还不能很好地工作。我们在这里的建议是将我们开发的用于测量海洋湍流的声学技术扩展到分层的海洋环境中，使用相对便宜的现成仪器。我们的目标是开发一种操作简单且有效的附加系统，该系统可用于传统的剖面测量平台(即CTD)，用于测量分层海洋环境中的剖面湍流。这样的系统将大大简化海洋湍流的测量，促进更多的湍流测量，并使人们能够更好地理解这一重要过程。

Much of the ocean is stably stratified with lighter water overlying heavier water, with the vertical movement of nutrients, salt, heat, and pollutants across stratification driven by turbulent mixing. The nature and strength of the processes which are responsible for these vertical fluxes therefore play a major role in shaping the marine system. For example, vertical fluxes of nutrients link the dark, nutrient-rich, deep waters with the upper, sunlit, part of the water column promoting the primary productivity which supports the marine ecosystem. Vertical mixing is also one of the main mechanisms behind the large scale ocean circulation, and therefore of immense importance for the climate of our planet. A number of techniques have been developed for the estimation of vertical mixing rates in the marine environment. These include direct measurements of the turbulence using a freefalling profiler, which is a very time consuming and labour intensive technique requiring teams of specialist scientists. Other methods use acoustic current meters, which can be deployed in the marine environment and then left for a period of time. However, this method has a limited vertical range, and up until now has not worked well in environments with vertical stratification or when deployed from moving platforms. Our proposal here is to extend an acoustic technique, which we have developed, for measuring marine turbulence, using relatively cheap, off-the-shelf instruments, to the stratified marine environment. Our aim is to develop a simple to operate and effective add-on system that can be used on conventional profiling platforms (i.e. CTDs), for the measurement of profiles turbulence in a stratified marine environment. Such a system would significantly simplify measuring oceanic turbulence, facilitating more turbulence measurements and enabling an improved understanding of this important process.