Dynamics of rotating convection and the ocean overturning circulationSupervisor: Ross Griffiths (PhD only)
The factors influencing the global deep circulation of oceans are still hotly debated. Even the dominant driving forces are not agreed upon. Yet the circulation and the transport of heat represents an important part of the climate system. At ANU we are examining the fundamentals dynamics of the circulation, using laboratory experiments and computational models to provide tests for theory and to gain new insights into the processes involved. There is an opportunity for a PhD student with a physics or mathematics background to carry out laboratory fluid dynamics experiments and computational work modelling overturning thermal convection in a rotating rectangular basin forced by a horizontal temperature surface temperature gradient. A rich variety of phenomena occur in this system and there is scope to include further complexities.
High-resolution modelling of Antarctic Bottom Water ProcessesSupervisor: Steph Downes, Andy Hogg (PhD, Honours)
Antarctic Bottom Water is the densest water in the ocean, and forms in areas like the Ross Sea or Weddell Sea. This class of water is both saline (through salt excreted from sea ice) and cold; it mixes with various water types on the continental shelf, and is entrained in the Ross or Weddell Gyres (respectively) before sinking to the abyssal ocean. This project will use a combination of existing ocean observations, high resolution ocean models and theory to understand how Bottom Water forms and is distributed throughout the global oceans; the ultimate goal is to be able to predict variations in Bottom Water induced by climate change.
Energetics of turbulent mixing in real fluidsSupervisors: Ross Griffiths, Graham Hughes (PhD, Honours, Internship, PhB)
Turbulent mixing in a density stratification is believed to play an essential role in governing the rate of deep overturning circulation in the oceans, and is a common process in many oceanographic and environmental setting. However, the rate of irreversible mixing achieved for a given rate of energy supply to turbulence is poorly understood, as much of the energy is dissipated. In recent work we have developed a better understanding of mixing in a simple fluid. However, real mixing also involves transfer of energy to and from internal chemical potential energy. Through buoyancy this influences the mechanical energy of the flow. There is an opportunity for a PhD student with a physics, mathematics or chemistry background to carry out novel experiments with turbulence in a stratified flow including significant nonlinear mixing effects and to examine the energetics in a more general case.
Laboratory modelling of the Southern Ocean circulationSupervisors: Ross Griffiths, Andy Hogg (PhD, Honours)
There is an opportunity for a student to join a team investigating the dynamics of the Southern Ocean and to carry out laboratory modelling. In concert with computational modelling we have been using in a sophisticated and complex rotating apparatus to examine the behaviour of a model Antarctic Circumpolar Current and the combined roles of surface wind stress, buoyancy forcing and turbulent eddies in governing the zonal transport. There is much more to be learned, and there is scope to use the laboratory model to investigate the roles of drag from different bottom topography, the Drake Passage, and different forms of buoyancy forcing.
Eddies in the Southern OceanSupervisor: Andy Hogg (PhD, Honours)