Shear Madness: New Ways to measure Ocean Currents from a Glider

海水流动的速度有多快，是什么引起的，它是如何变化的，我们能预测吗？这些都是海洋科学试图回答的基本问题。传统上，海洋学家使用所谓的地转近似法，从船上的水温和盐度剖面计算切变（水平速度的垂直梯度）。然后，我们必须在已知的深度进行独立的速度测量，以参考这种切变，从而获得总的地转速度。几十年来，我们一直使用船载声学多普勒海流剖面仪（ADP）来参考切变。新的挑战是找出如何最好地测量被称为滑翔机的长航时剖面自动水下航行器的海流。滑翔机测量温度和盐度，因此可以推断出地转切变。根据它们在俯冲过程中的位移，它们还提供了俯冲平均流速，可用于参考地转切变。这个项目将通过探索使用一种新的ADP安装在Seaglider. MethodologyADP已经开始被用于其他滑翔机（如喷雾），以确定流场。通过NERC资助的孟加拉湾边界层实验（BoBBLE）项目，我们最近获得了购买集成Nortek 1 MHz ADP的Seaglider的资金。调试试验定于2017年3月在加那利群岛进行，该试验将比较基于滑翔机的ADP测量与来自更传统平台的测量。学生将评估传感器的性能，并确定利用所得数据集的最佳技术。2012年，UEA在南极洲的一艘海上滑翔机上试用了ADP的早期版本。从中吸取了有益的经验教训，这将使该项目受益。我们预计学生将在2017-2018年与其他资助项目一起设计并部署ADP使能的滑翔机，可能在孟加拉湾。同时，学生将使用UEA滑翔机科学组已经获得的滑翔机数据，将俯冲平均气流应用于参考地转剪切来研究陆架断裂气流（例如）。在伊比利亚半岛和阿曼海。培训：NEXUSS CDT为环境科学提供最先进的、高度体验式的培训，包括应用和开发尖端智能和自主观测系统，以及全面的个人和专业发展。学生将有广泛的机会，通过与学术，研究和工业/政府/政策合作伙伴的广泛网络的互动，扩大他们的多学科视野。该学生将在诺里奇的UEA海洋与大气科学中心（COAS）注册和托管，但将在南安普顿的NOC与MARS工程师合作，分享滑翔机操作的最佳实践。具体培训将包括：- 海洋滑翔机驾驶，操作和数据分析-海洋学，海洋动力学，海洋物理学-声学多普勒剖面仪的原理-潜水平均电流计算和优化的原理-大型数据集的计算和处理-航海和海洋数据收集技能-传感器集成和开发的工程挑战。

Project RationaleHow fast is the seawater flowing, what causes this, how does it vary, and can we predict it? These are the fundamental questions that much of ocean science tries to answer. Traditionally, oceanographers calculate the shear (vertical gradient in horizontal velocity) from ship-based profiles of the temperature and salinity of the water, using what is known as the geostrophic approximation. We then have to make an independent measurement of velocity at a known depth in order to reference this shear, and thus obtain the total geostrophic velocity. For a couple of decades now, we have used ship-based acoustic Doppler current profilers (ADP) to reference the shear. The new challenge is to work out how best to make measurements of currents from long-endurance profiling autonomous underwater vehicles known as gliders. Gliders measure temperature and salinity, so the geostrophic shear can be deduced. From their displacement during a dive, they also provide a dive-average current velocity, which can be used to reference the geostrophic shear. This project will address this challenge by exploring the use of a novel ADP installed in a Seaglider.MethodologyADPs have begun to be used on other gliders (e.g. the Spray) to determine the flow field. Through the NERC-funded Bay of Bengal Boundary Layer Experiment (BoBBLE) project, we have recently been awarded funding to purchase a Seaglider with an integrated Nortek 1 MHz ADP. Commissioning trials are scheduled for March 2017 in the Canary Islands, that will compare glider-based ADP measurements with those from more conventional platforms. The student will evaluate the sensor performance and determine the best techniques for exploiting the resulting data set. In 2012 UEA trialled a previous version of the ADP on a Seaglider in the Antarctic. Useful lessons were learnt that will benefit this project. We anticipate that the student will design and undertake a deployment with the ADP-enabled glider in 2017-2018, in conjunction with other funded projects, possibly in the Bay of Bengal.In parallel, the student will use glider data already obtained by the UEA Glider Science group, applying the dive-average currents to reference geostrophic shear to study shelf-break currents (e.g.) off the Iberian Peninsula and in the Sea of Oman. The science questions to be addressed include quantifying the transport, its variability, and understanding the driving mechanisms.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 and hosted in the Centre for Ocean and Atmospheric Sciences (COAS) at UEA in Norwich but will spend time based at NOC in Southampton working with MARS engineers to share best practice for glider operations. Specific training will include: - ocean glider piloting, operation, and data analysis- oceanography, ocean dynamics, ocean physics- principles of acoustic Doppler profilers- principles of dive-average current calculation and optimisation- computing and processing of large data sets- seagoing and marine data collection skills- engineering challenges for sensor integration and development.