Our monthly spotlight on the work and lives of the researchers from the Leeds Institute for Fluid Dynamics
This month: Joseph Elmes
Thesis title: Internal Tide Generation along Continental Margins
School/ Faculty: School of Mathematics
Supervisors: Dr Stephen Griffiths and Prof Onno Bokhove
Tell us a bit about yourself:
I am a fourth year PhD researcher in the School of Mathematics, and am part of the NERC SPHERES DTP. I moved to Leeds from Northampton in 2014 to complete a joint honours undergraduate degree in French and Mathematics. After my year abroad in Lille, I was successfully granted a research scholarship from the London Mathematical Society, working alongside my current supervisor, Dr Stephen Griffiths, on Self-Gravitating Waves on Rotating Elastic Spheres. From this moment, I was convinced that pursuing a PhD at Leeds in Fluid Dynamics would allow me to flourish, building on the mathematical and computational skills I already possessed. When I am not working, you may find me running the streets of Leeds with the local Hyde Park Harriers running club, or drinking coffee in one of the many fantastic cafes around Leeds.
What is your research about?
My research considers the modelling of internal wave generation by the surface tide. These internal waves are referred to in the field of physical oceanography as internal tides. Internal waves exist within a fluid medium, and are typically much greater in amplitude than the surface waves you are perhaps more familiar with. In some places, the amplitude of internal waves can reach up to several hundred metres, and can leave small signatures on the surface of the ocean. These waves exist because of the variation in fluid density, particularly with respect to depth. In the world’s ocean, the change in density occurs due to the variability in salt concentration and temperature. As the tides force the entire fluid column up and down continental margins, internal waves are generated which propagate both off-shore and on-shore. What makes internal waves so interesting to the research community is that they take energy from the surface tide and transfer it to the ocean interior. Moreover, when these internal waves eventually break, they create vertical mixing. This vertical mixing is crucial in the supply of nutrients to the upper oceans which are rich in biological productivity.
A particular focus of my research is to understand how canyon geometry affects the tides in coastal waters. These canyons typically intercept the along-shore flow of the surface tide at the shelf break. Attached is a contour plot of the time-averaged energy flux magnitudes (W/m) with its corresponding vector field overlaid (see key). Here, energy fluxes radiate away from the generation sources: the continental slope and the canyon. It was observed that for a sufficiently wide canyon, there are strong asymmetric energy flux beams, leaving a shadow on the shelf beyond the head of the canyon. A key question my thesis considers, is how does the geometry of the slope-canyon topography affect the generation and propagation of internal waves?
What did you wish you knew before starting a PhD?
Before starting my PhD, I wish I understood the importance of a good work-life balance. A PhD is much like a marathon. You really have to pace yourself, and not exert all your energy right at the beginning. You should also try to enjoy the scenery – by this, I mean, try to make the most of everything which is around you: conferences, social activities, research development and so on. It will certainly make your PhD life more enjoyable by offering variability. Lastly, it is okay to make mistakes. I am constantly looking back at past mistakes, and remarking how silly I had been. However, it is important to remember that each mistake provides you with a new learning opportunity. These mistakes will make you more resilient going forward.
What are your plans for the future?
I plan to submit my thesis in the coming months. I have already secured a position at an engineering company working as a mathematical modelling consultant. I look forward to starting a new chapter of my life, utilising the many skills I have enjoyed developing during my time at Leeds.