HALL_UENV18NEX - Novel current meters on ocean gliders: using electromagnetic induction to measure flow and subsurface glider motion
Novel current meters on ocean gliders: using electromagnetic induction to measure flow and subsurface glider motion
Ocean gliders are rapidly becoming an essential component of coastal and deep sea oceanographic experiments. These autonomous vehicles ‘fly’ between the surface to the seabed in a sawtooth pattern by changing their density relative to the surrounding water. GPS is used to determine their location and average horizontal velocity, however, their movement underwater is uncertain because GPS can only operate at the surface. This uncertainty in subsurface motion is problematic for both navigation and for calculating key oceanographic variables such as salinity, current velocity, and turbulent mixing.
One solution to the problem subsurface motion is to equip the glider with a current meter to measure its speed relative to the surrounding water. however, traditional current meters tend to be both heavy and power hungry. Fortunately, a new type of current meter has recently been developed for use with gliders and other autonomous underwater vehicles (AUVs) that is small, light and power efficient. These new current meters work on the principles of electromagnetic (EM) induction, rather than acoustic scattering or a mechanical impeller. This PhD project will investigate the capabilities of EM current meters on gliders and improve measurements turbulent kinetic energy (TKE) dissipation rate from glider-collected shear microstructure data.
The student will use an EM current meter (provided by Rockland Scientific), integrated with the microstructure sensor system of a Kongsberg Seaglider. The current meter will be aligned so that it measures the along-axis (axial) speed of the glider through the water. Accurate axial speeds are required to convert glider timeseries data into a spatial field and to process shear microstructure data. Although axial speed can be estimated using hydrodynamic models, at present these models cannot be ground truthed. EM current meters provide an exciting opportunity to directly measure the axial speed of a microstructure glider, allowing improved measurement of TKE dissipation rate and validation of glider flight models. Specific objectives for this PhD project are:
- Test a Seaglider with EM current meter in a recirculating flume and compare measured speeds to acoustic Doppler velocimeter derived free flow velocities.
- Process and quality control EM current meter data from microstructure Seaglider trials and science missions.
- Direct measurements of axial speed will be used to:
- Calculate TKE dissipation rate from shear microstructure without resorting to estimates from the Seaglider flight model.
- Constrain the flight model to improve the quality of the salinity data and dive-average current velocities.
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 the University of East Anglia (UEA), and hosted by UEA in the School of Environmental Sciences with periods of training at the University of Southampton. The student will join the UEA Glider Science 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
This project has been shortlisted for funding by the NEXUSS Centre for Doctoral Training. Undertaking a PhD with the NEXUSS CDT will involve attendance at mandatory training events throughout the course of the PhD.
Selected candidates who meet RCUK’s eligibility criteria will be awarded a NERC/EPSRC studentship - in 2017/18, the stipend is £14,553.
In most cases, UK and EU nationals who have been resident in the UK for 3 years are eligible for a stipend. For non-UK EU-resident applicants NERC/EPSRC funding can be used to cover tuition fees, RTSG and training costs, but not any part of the stipend. Individual institutes may, however, elect to provide a stipend from their own resources.
This PhD studentship is expected to begin in September/October 2018. Both full-time and part-time study are possible (those planning to study part-time may wish to discuss this with the supervisor before applying).
Fer, I., A. K. Peterson, and J. E. Ullgren, 2014: Microstructure measurements from an underwater glider in the turbulent Faroe Bank Channel overflow. Journal of Atmospheric and Oceanic Technology, 31, 1128–1150, doi:10.1175/JTECH–D–13–00221.1.
Palmer, M. R., G. R Stephenson, M. E. Inall, C. Balfour, A. Dusterhus, and J. A. M. Green, 2015: Turbulence and mixing by internal waves in the Celtic Sea determined from ocean glider microstructure measurements, Journal of Marine Systems, 144, 57-69, doi:10.1016/j.jmarsys.2014.11.005.
Dr Bastien Queste (UEA, Environmental Sciences)
Dr Eleanor Frajka-Williams (University of Southampton, Ocean and Earth Science)Dr Rolf Lueck (Rockland Scientific and University of Victoria, Canada)
- Start date October 2018
- Studentship Length 3 years 8 months
- Acceptable First Degree a numerate discipline, e.g. Engineering, Geophysics, Mathematics, Oceanography or Marine Science, or Physics.
- Minimum Entry Standard 2:1 or equivalent