About the project
Recent work has highlighted the importance of turbulent mixing in the ocean bottom boundary layer in upwelling the dense waters formed at high latitudes. This project will use cutting-edge sensors, including optical fibres along the seafloor, to provide a new window on near-bottom ocean turbulence.
Since the seminal work of Walter Munk, oceanographers have believed that the upwelling of cold, abyssal waters, that regulates the deep ocean's ability to sequester heat and carbon, is driven by turbulent mixing associated with breaking waves in the ocean interior. Measurements of deep-ocean turbulence starkly contest this scenario, suggesting that breaking waves drive downwelling of abyssal waters.
Inspired by this conundrum, theoretical investigations have developed an alternative view with upwelling driven by turbulence within thin layers near the seafloor, known as the bottom boundary layer. Recent tracer observations have provided initial evidence that boundary driven upwelling occurs in canyons, but the underlying physical processes and wider applicability are unknown due to a lack of deep ocean observations.
This project will assess the nature of the underpinning turbulent processes on sloping bottom boundaries and their role in upwelling. This will be achieved using conventional oceanographic observations and novel distributed optical fibre sensing (DOFS). The conventional observations consist of measurements of turbulent mixing using high resolution temperature and velocity collected in the Rockall Trough.
DOFS senses the physical properties (temperature and strain) of an optical fibre at many positions along its length. The potential of DOFS to observe turbulence has recently been demonstrated. Within this project the properties of DOFS as a turbulence sensor will be characterised utilising existing DOFS datasets and upcoming fieldwork campaigns. This will unlock the significant global legacy infrastructure of seafloor cables to unveil the physics of ocean bottom boundary turbulence and revisit the abyssal ocean circulation.
Supervisors
You will also be supervised by organisations other than the University of Southampton, including Dr Carl Spingys and Dr Mohammad Belal from the National Oceanography Centre.