Teachers notes
Professor Stewart Turner
Geophysicist
Contents
Introduction
Summary of career
Extract from interview and focus questions
Activities
Keywords
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Professor Stewart Turner was interviewed in 2004 for for the Interviews with Australian scientists series. By viewing the interviews in this series, or reading the transcripts and extracts, your students can begin to appreciate Australia's contribution to the growth of scientific knowledge.
The following summary of Turner's career sets the context for the extract chosen for these teachers notes. The extract discusses research achievements from his time at the Research School of Earth Sciences at the Australian National University. Use the focus questions that accompany the extract to promote discussion among your students.
John Stewart Turner was born in Sydney in1930. He entered university as an engineering student but later changed to science. He received a BSc in 1952 and an MSc in 1953 from the University of Sydney for his research into theoretical nuclear physics.
Turner joined the CSIRO Division of Radiophysics in 1953, where he began investigating cloud physics. His initial project was to study how raindrops form on salt nuclei. After eighteen months with the CSIRO, he was awarded an1851 Exhibition Overseas Scholarship to study in Great Britain. He worked in the Fluid Dynamics group at Cambridge University and in 1957 was awarded a PhD for his thesis entitled 'Dynamical aspects of cloud physics'. He returned to the CSIRO Division of Radiophysics in 1960, where he worked on various laboratory-based convection problems.
From 1962 to 1966 Turner was employed as an associate scientist at the Woods Hole Oceanographic Institute in the USA. While there he worked on a number of different problems involving clouds including a model for evaporation and condensation, a laboratory model of a tornado vortex and a theoretical and experimental model of the seasonal thermocline.
Turner returned to Cambridge University in 1966 where he stayed until 1975, working first as assistant director of research and then as a reader in the Department of Applied Mathematics and Theoretical Physics. His investigations during these years centred on the dynamics of the upper ocean.
In 1975 Turner was appointed Foundation Professor of Geophysical Fluid Dynamics in the Research School of Earth Sciences at the Australian National University. He established the connection between the physical processes in the ocean and liquid rocks (lava and magma), and wrote the influential book, Buoyancy Effects in Fluids. He retired from RSES in 1995.
He was elected a Fellow of the Australian Academy of Science in 1979 and became a Fellow of the Royal Society in 1982.
Achievements at the Research School of Earth Sciences
What would you regard as the most important research achievements of the GFD group that you led at RSES?
Most important to me is the interdisciplinary research, establishing the connection between the processes in the ocean and in liquid rocks. The experiments with Lew Gustafson demonstrated that you can produce density differences near boundaries due to crystallisation, and that can stratify the surroundings.
Also there were earlier experiments that I did with Herbert Huppert, a former colleague in Cambridge who came for many periods of sabbatical leave in Canberra. During his first sabbatical we did experiments on melting ice in stratified surroundings – spurred, actually, by a suggestion that you might tow icebergs from the Antarctic to arid coastlines. We showed that in fact the meltwater would not just rise to the surface where it could be scooped or pumped off; there would instead be considerable mixing with the surroundings, and in a stratified ocean none of the water would get to the surface at all. It would spread out in layers in the interior.
We later realised that the crystallisation or melting were essentially the same dynamical process. If you looked outside the boundary at the environment, then in each case you were producing a boundary layer of different composition: in one case with the solid boundary extending by crystallisation, in the other case with the boundary receding, but in both cases with dynamics of the flow outside that were exactly the same. That and some later experiments prompted Herbert and me to write a review article comparing the different processes in geological contexts and oceanographic ones in which double-diffusive convection was important. It appeared in an issue of the Journal of Fluid Mechanics which was the Editors' Volume – after 25 years of the journal, all editors were asked to write unrefereed papers.
But at the end of this review we asked ourselves: is it possible to deliberately organise crossover of information from one field to another? Is it likely that a geologist would read a paper on melting icebergs and draw the right conclusions about the importance in his field? We had to concede that, unfortunately, you can't organise such crossover. Really, that depends on individuals, on people with different perspectives on a common physical problem getting together. It helps if people work in multidisciplinary institutions like the Research School of Earth Sciences and others which have interests across the boundaries of the two fields, but I believe that you really can't organise such interactions from the top down. The boss can't say, 'Let's do this together,' and put people to do it. It has got to come from individuals.
What other interdisciplinary or multidisciplinary collaborations would you say were important to you?
One of the most rewarding collaborations I have had was again a very multidisciplinary one. Herbert Huppert, a mathematician, and Stephen Sparks, a perceptive field geologist, came for six months to Canberra and we worked in the laboratory together on problems of mixing in magma chambers. Each of us brought to the subject something that the others didn't have. We couldn't expect to become an expert in anybody else's field but we needed to understand enough of what they were talking about to be plausible collaborators.
Another important collaborator, Ian Campbell, at first was a visitor from Toronto and then came on the RSES staff. He was interested in replenished magma chambers – magma of different composition coming in to the bottom of the chamber and mixing with the surroundings in a way that caused the precipitation of ore. Particularly, platinum ores can be formed if you have enough mixing between the incoming magma and the resident magma.
A very unlikely interdisciplinary project arose out of that. At the same time Doug Baines – another person who had been a visitor to Cambridge and was on sabbatical in Canberra – had come with an interesting problem of heating large buildings such as aircraft hangars from the top, where you pump in hot air and form a layer which extends down towards the floor without obstructing the floor. We realised that these two problems are physically and dynamically exactly the same, except one is turned upside down. The mixing in magma chambers with a 'fountain' of dense fluid coming in from the bottom and the aircraft hangar with hot air coming from the top could both be studied by doing experiments in salt and fresh water. So we published a paper together which was applicable to both these rather unlikely different problems. (Ian Campbell later left the GFD group and went on to be head of the Ore Genesis group in RSES.)
An edited transcript of the full interview can be found at http://www.science.org.au/scientists/interviews/st.
Focus questions
- Turner talks about the suggestion of towing icebergs from the Antarctic as a source of freshwater for arid coastlines. When he investigated this idea, what problems did he identify?
- What are some advantages of multidisciplinary research as described by Turner?
Select activities that are most appropriate for your lesson plan or add your own. You can also encourage students to identify key issues in the preceding extract and devise their own questions or topics for discussion.
- Physics curriculum: Geoscience enrichment (University of Washington and the Northwest School)
A series of additions to the regular physics curriculum which present applications for oceanography and earth science. Specific activities and examples include the effect of gravitation, heat transfer, convection and heat stratification on oceans. - Geophysics I: The physical earth (NSW HSC Online)
Students learn to describe the properties of earth materials that are studied in geophysics, identify the principal methods used in geophysics and describe the type of information that these methods can provide. - Understanding oceans (Discovery School, USA)
Students investigate how the rising and sinking of warmer and colder water produces ocean currents and how these currents affect weather and life globally. - Magma mixing (Earth and Ocean Sciences, University of British Columbia)
Includes information and a movie on how magmas can mix in a magma chamber to form a new hybrid magma. Students view the movie, read the information and then view the movie again. Students then write a short report on what they have learned. - The ocean in motion II: The causes and study of ocean currents (University of South Florida)
Student activities that investigate ocean movements in relation to a number of factors including temperature, density, salinity and wind. - Water density and stability (Naval Meteorology and Oceanography Command, USA)
Student activity to show how salinity affects the density of water. In addition, students will better understand how pure and salt water systems work together. Includes student worksheet and teachers' answer sheet.
crystallisation
density differences
fluid dynamics
geophysical processes
magma
stratification