Lava flows contribute to the surface morphology of large areas of the earth, both on continents and on the seafloor, and other planets. They are also sites for the formation of nickel and platinum ore deposits. They may also be used to make inferences about past volcanic activity.
Staff in Geophysical Fluid Dynamics have been studying the dynamics of lava flows through laboratory fluid dynamics analog modelling and theoretical descriptions. This has proven a powerful approach and has shown that the morphology of lava flows is closely controlled by both the eruption rate and surface cooling. Many different types of lava flows can now be seen as members of a sequence of dynamical regimes. The work has involved some of the first ever studies of cooling and solidifying gravity currents.
There are many outstanding questions concerning both melting of underlying rock, solidification of the flow, and mechanisms controlling the cooling of large channel flows. The work may involve interaction with volcanologists from the USA. Contact: Dr Ross Kerr, Professor Ross Griffiths.

Where waters of different temperature (T) and salinity (S) lie close to each other in the oceans, there is frequently a region of relatively large lateral T and S gradients (a front). Mixing between the two masses of water is found to involve horizontal finger-like intrusions, often with many interleaved intrusions in a vertical stack. Thermohaline convection is a favoured driving mechanism for these intrusions, but the role of low-frequency internal inertia-gravity waves is unclear. The project will involve laboratory experiments designed to explore the possibility that waves may produce the intrusions and to examine the interactions of internal waves and thermohaline convection.

The oceans overturn, with surface waters sinking to deep in the ocean at high latitudes, drawing warm waters and heat poleward from low latitude. This flow and its transport of heat represents an important part of the climate system. The driving forces governing the overturning circulation, and its adjustment to changing boundary conditions associated with global warming, are controversial topics in oceanography and climate science. Global warming will cause more freshwater inflow from the melting of ice-caps at high latitude, and this might slow or even shut-down the ocean overturning. However, fundamentals of the dynamics are not understood. Laboratory experiments are being used to explore the convective circulation in simple cases. CFD simulations are being utilised in parallel with the experiments to further probe the dynamics. A PhD student with a physics or mathematics background will carry out laboratory fluid dynamics experiments or computational work with convection in a long rotating box forced by various distributions of heating and cooling on the base. The work will involve computer data logging, flow visualisation, and the analysis of the experimental data, from which we will learn about the physics underlying global ocean overturning.

Have you ever thought about how the oceans overturn, with surface waters sinking to deep in the ocean at high latitudes, drawing warm waters and heat poleward from low latitude? The driving forces governing this circulation, and the adjustment of the circulation to changing boundary conditions associated with global warming are controversial topics in oceanography and climate science. Global warming will cause more freshwater inflow from the melting of ice-caps at high latitude, and this might slow or even shut-down the ocean overturning. However fundamentals of the dynamics are not understood. Laboratory experiments are being used to explore the convective circulation in simple cases. An Honours or Masters student with a physics or mathematics background will carry out laboratory fluid dynamics experiments with convection in a long rotating box forced by various distributions of heating and cooling on the base. The work will involve computer data logging, flow visualisation, and the analysis of the experimental data, from which we will learn about the physics underlying global ocean overturning.

Have you ever thought about how the oceans overturn, with surface waters sinking to deep in the ocean at high latitudes, drawing warm waters and heat poleward from lowlatitude? Global warming will cause greater freshwater inflow at the sea surface from the melting of ice-caps at high latitude. This might slow, or even shut-down, the ocean overturning. In the geophysical fluid dynamics laboratory we are carrying out experiments with convection and rotation that explore the physics underlying global ocean overturning. A PhB scholar, research Intern, Summer Scholar or a student looking for a Special Research Topic, and who is studying physics or mathematics will assist with the laboratory fluid dynamics experiments, the computer logging of data, and the analysis of the experimental data.

Contact the supervisor directly for more information.

Mantle plumes carry heat upwards from a thermal boundary layer at the bottom of the mantle, and the thermal boundary layer is formed by heat conducting out of the core. Plumes thus help to cool the core. The efficiency with which plumes remove heat is debated and needs to be clarified. The project would be to use an existing numerical code to explore different parameters that control the plume and to compare the resulting plume with observational constraints. Some programming experience would be required.

The so-called maximum entropy production principle is a relatively new idea that may apply to fairly complex dynamical systems. The project would be to test the MEP principle by developing applications to some of Earth's internal processes and comparing its predictions with progressively more sophisticated numerical models. Potential applications are the compositional-dynamical stratification of the mantle and the energy involved with core convection and the dynamo mechanism of Earth's magnetic field. Good computational skills would be required.

The physics of thermal mantle plumes is quite well understood, and they provide a good explanation for volcanic centers like Hawaii and Iceland, and for the chains of extinct volcanos that extend away from these 'hotspot' sites. They also seem to explain gigantic flood basalt eruptions that occur once every 10-20 Ma. However there is a range of other volcanism that doesn't fit the classic pattern of flood basalts and related hotspot tracks. Plumes may entrain some denser material from the bottom of the mantle, and then their dynamics would be more complicated. These dynamics would be explored with numerical models in two and three dimensions. The results would have implications for the tectonic evolution of the continents and for the cooling of the core and the history of the dynamo. Good computational skills would be required.

This project continues numerical modelling of mantle dynamics in two and three dimensions to explore models that can accommodate geophysical, geochemical and tectonic constraints. We have a fairly clear understanding of how plate tectonics, mantle convection and mantle plumes work at present, but we would like to know how the dynamics of the mantle system has changed as Earth has slowly cooled over the past 4.5 Ga. There is geochemical and isotopic information from the mantle that has been difficult to reconcile with dynamical modelling. The chronology and tectonic history of the continental crust also provides important constraints, especially since they indicate the system has had episodes of heightened activity. Good computational skills would be required.

The photo on the right shows two photos of different fluid instability -- the upper one is often called Kelvin-Helmholtz instability, the lower one is called Holmboe's instability. The generation of these two instabilities are both predicted from some simple physics, but as they grow to larger size the physics becomes complicated. These types of instability occur in both the ocean and atmosphere, where they are an important source of turbulence and mixing.

The best way of determining what happens in these instabilities is to isolate them in laboratory. This project will involve a series of laboratory experiments making measurements of the flow speed and the generation of instabilities. The student/intern can expect to conduct a number of experiments, making visual (qualitative) measurements of the flow as well as quantitative measurements of the instabilities as they grow.

Contact the supervisor directly for more information.

Ocean straits are narrow constrictions which separate marginal seas from oceans, such as the straits of Gibraltar, the Indonesian Throughflow and the Heads of Sydney Harbour. Straits therefore restrict the flow of water between different parts off the ocean. It follows that these straits play a key role in regulating flow of water, nutrients and pollutants around the ocean.

This project will exmine the fundamental fluid dynamics of flow through straits, and will apply these results to the ocean. The project may either be based on laboratory experiments, numerical simulation or a combination of the two. The student can expect to develop and implement a program of experiments to learn more about flow through straits, and to develop conceptual understanding of this important aspect of oceanography.

Contact the supervisor directly for more information.

One of the outstanding puzzles in paleoclimatology is to determine the cause of ice ages. Data shows that CO2 (in the red) varies with temperature (black) in the figure, indicating that CO2 plays a significant role in controlling glaciation; but what controls CO2?

This project will use simple models to attack this problem. The student will start from a 2-equation model of the climate system which replicates the major elements of the glacial cycles, and will develop this model into a multi-box model to gain constraints on possible influences on glacial climate dynamics.

The Southern Ocean plays a critical role in the global ocean circulation. It connects all three major ocean basins (the Indian, Atlantic and Pacific) and so helps to control heat transport, climate variability and nutrient balances. Yet, circulation in the Southern ocean is poorly understood - mainly because there is a relatively small amount of observational data.

This project aims to simulate the circulation of the Southern Ocean in a realistic way, and look at ways in which this circulation will vary. The simulations will use existing eddy-resolving ocean models (see figure for the "eddy field", or turbulence which is modelled). The simulations will be performed on the local supercomputer (the AC) and some modification of the models will be required. This project would suit a student with an applied maths or physics background, and in interest in climate dynamics or physical oceanography.

Contact the supervisor directly for more information.