Mapping ocean mixing using autonomous gliders: Indian Ocean and Antarctic shelf seas

项目基本原理：海洋中发生了多少湍流混合，这种混合发生在哪里，这是物理海洋学中尚未回答的关键问题之一。与基于全球平均层化和全球上升流之间的平流-扩散平衡的间接估计相比，在有限地点对湍流的直接测量似乎低估了混合的背景水平。很明显，混合并不是均匀地发生在整个海洋内陆，但作为一个社区，我们远远不能确定混合的所有全球“热点”。空间分布具有特别重要的意义，因为在大尺度海洋环流和气候模式中，混合和相关的亚网格尺度过程必须被参数化，通常作为空间均匀的扩散系数。然而，已有研究表明，来自这类模型的预测可能对哪里的混合增强很敏感。因此，更好地了解海洋中湍流混合的空间分布(和时间变异性)对于发展现实的混合参数化是至关重要的。本项目将使用自主海洋滑翔机收集的新的和现有的湍流测量数据，以及最近开发和建立的分析方法，来研究全球海洋多个地区湍流混合的空间分布和时间变异性。方法：学生将使用来自微结构滑翔机的高分辨率温度数据，以及这些滑翔机和其他滑翔机收集的标准温度/盐度测量，来估计湍流混合率。作为更广泛项目的一部分，将按照Fer等人的方法，使用微观结构剪切数据对混合速度进行独立估计。(2014)和Palmer等人。(2015)。这些将用于交叉验证。这个博士项目的具体目标是：1)利用Peterson和Fer(2014)的方法和Thorpe尺度分析，从快速响应热敏电阻数据中估计林尼湖、印度洋和南极半岛西部周围的湍动能(TKE)耗散率和赤道涡流扩散率。2)将这些混合率与使用大涡方法的标准温度/盐度测量得出的结果进行比较。3)确定能量混合的区域和周期，然后根据学生的兴趣，研究：(A)驱动混合的动力学过程，例如内波，使用高级分析方法；或(B)利用来自滑翔机上的生物地球化学传感器的额外数据，研究混合对当地海洋化学和浮游植物种群的影响。培训：NEXUSS CDT提供在环境科学中应用和开发尖端智能和自主观测系统的最先进、高度有经验的培训，以及全面的个人和专业发展。通过与学术、研究和产业/政府/政策合作伙伴的广泛网络互动，学生将有广泛的机会扩展他们的多学科视野。这名学生将被东英吉利大学(UEA)注册，并被东英吉利大学环境科学学院接待。该学生将加入UEA滑翔机科学组(www.uaglider.uea.ac.uk)和BAS滑翔机组。具体培训将包括：-自主海洋滑翔机数据处理、质量控制和分析技术-微结构数据处理和分析技术-海洋滑翔机操作，包括准备、部署和驾驶-参与海洋研究巡航-动态海洋过程的数值模拟-在国际会议和研讨会上介绍研究

Project Rationale:How much turbulent mixing occurs in the ocean and where this mixing takes place is one of the key unanswered questions in physical oceanography. Direct measurements of turbulence at a limited number of locations appear to underestimate the background level of mixing relative to indirect estimates based on an advective-diffusive balance between global mean stratification and global upwelling. It is clear that mixing does not occur uniformly throughout the ocean interior, but as a community we are far from identifying all the global "hotspots" of mixing. The spatial distribution is of particular importance because mixing and associated sub-gridscale processes have to be parameterised in large-scale ocean circulation and climate models, typically as a spatially uniform diffusivity. However, it has been shown that predictions from such models can be sensitive to where mixing is enhanced. A better understanding of the spatial distribution (and temporal variability) of turbulent mixing in the ocean is therefore essential for development of realistic mixing parameterisations. This project will use new and existing measurements of turbulence collected using autonomous ocean gliders, along with recently developed and established analysis methods, to investigate the spatial distribution and temporal variability of turbulent mixing in multiple areas of the global ocean.Methodology:The student will use high-resolution temperature data from microstructure gliders, along with standard temperature/salinity measurements collected by these and other gliders, to make estimates of turbulent mixing rate. As part of the wider project, independent estimates of mixing rate will be made using microstructure shear data following the methods of Fer et al. (2014) and Palmer et al. (2015). These will be used for cross-validation. Specific objectives for this PhD project are:1) Make estimates of turbulent kinetic energy (TKE) dissipation rate and diapycnal eddy diffusivity in Loch Linnhe, the Indian Ocean, and around the West Antarctic Peninsula from the fast-response thermistor data using the method of Peterson and Fer (2014) and Thorpe scale analysis.2) Compare these mixing rates with those inferred from the standard temperature/salinity measurements using the large eddy method.3) Identify regions and periods of energetic mixing then, depending on the interests of the student, investigate either: (a) the dynamical processes that drive the mixing, for example internal waves, using advanced analysis methods; or (b) the effect of the mixing on local ocean chemistry and phytoplankton populations using additional data from the biogeochemical sensors on the gliders.Training:The NEXUSS CDT provides state-of-the-art, highly experiential training in the application and development of cutting-edge Smart and Autonomous Observing Systems for the environmental sciences, alongside comprehensive personal and professional development. There will be extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial / government / policy partners. The student will be registered at University of East Anglia (UEA), and hosted at UEA School of Environmental Sciences. The student will join both the UEA Glider Science Group (www.ueaglider.uea.ac.uk) and the BAS Glider Group. Specific training will include: - Autonomous ocean glider data processing, quality control, and analysis techniques - Microstructure data processing and analysis techniques- Ocean glider operations, including preparation, deployment, and piloting- Participation in oceanographic research cruises- Numerical modelling of dynamic ocean processes - Presentation of research at international conferences and workshops