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| CSIRO | SOLVE | Issue 12 | Aug 07 | |
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ARTICLE
ENVIRONMENT:
Research in Depth By Toby Hemming
Researchers analysing corals using mining industry technology are throwing light on climate change.By applying techniques traditionally used in the mining industry, scientists from the Wealth from Oceans Flagship are creating a picture of life underwater dating back some 400 years. Employing electron-probe microanalysis to study deep-sea corals, the scientists have uncovered the most detailed historical record so far of past ocean conditions in the southern hemisphere. Of particular technical interest is the way the team – led by CSIRO’s Dr Ron Thresher and comprising scientists from CSIRO, the Antarctic Climate and Ecosystems Cooperative Research Centre, the Woods Hole Oceanographic Institute and the California Institute of Technology – went about its work.
Drawing on microanalysis capability at CSIRO Minerals, Dr Thresher’s team applied The work has its genesis in the development of electron-probe microanalysis in the 1950s, which provided scientists with a highly accurate way of measuring the quantity of specified elements within a mineral or material. Used to characterise samples so small they can be studied virtually no other way, the technology has advanced considerably in recent years. CSIRO electron microscopist Colin MacRae says current instruments can measure features less than 100 nanometres in length, offering new insight into a range of processes. (One nanometre is one-billionth of a metre.) Mr MacRae says the technology has predominantly been used by CSIRO in the mining industry, helping in exploration and in the extraction and processing of mineral deposits. He says the use of the devices for this sort of work has had a profound impact on the industry – improving efficiency, lowering costs and increasing yields. Outside of the mining industry, Mr MacRae says the technology is also used to help develop new metal alloys, which has been especially useful in the aircraft industry where engineers are continually pushing materials to their limits. And it is a crucial tool in other scientific fields, including thin-films analysis, the study of sediments and research on ceramics and composites. Dr Thresher started his microanalysis work in marine applications about 15 years ago in response to what he says was a dearth of historical information about the deep ocean. He could see the potential of microanalysis in helping create a picture of deep-water conditions going back centuries. One of the objectives of Dr Thresher’s deep-sea coral research was simply to help ‘calibrate’ existing climate change models. “People were building all sorts of complicated models showing how water mass distribution was going to vary as a result of climate change, but there was very little information to tell us whether these models were ‘real’ or accurate,” Dr Thresher says. “Without this sort of work, it’s extremely difficult to tell whether the information we currently have relates to natural (climate) cycles, or whether it’s the result of other factors.” By studying growth rings on coral collected off the south-east coast of Tasmania, the team was able to unlock details of water temperature and salinity level variations over the course of the corals’ lifetime. The corals were, in a sense, living time capsules, revealing to the team secrets from centuries past. The first thing Dr Thresher’s work showed was that the corals were much longer-lived than previously thought, with some predating European settlement. He says this discovery has a bearing on the management of the coral reefs themselves: “Given its age, the coral isn’t going to come back quickly if there’s any damage done to it.” Perhaps more significantly, the work also shows there has been a one to one-and-a-half degree temperature change deep in the Southern Ocean over the past 400 years. “This might not sound like much,” Dr Thresher says, “but when you consider that the temperature range at these depths (about 1000 metres) is only very small (from four to six degrees), what we’re looking at is a very major change.” So, what does this tell us about global warming? “Well we’re still working on that,” Dr Thresher says. “But what it does tell us is that there’s some large-scale variability in the (global) system that needs to be taken into account if we’re to make any sense of what’s happening with climate change.” A finding such as this is, of course, a catalyst for further work. And that’s what Dr Thresher, in cooperation with Mr MacRae, intends to do. Dr Thresher believes that studying corals from other parts of the world will give him a much clearer picture of what’s going on. Meanwhile, the potential applications for microanalysis technology continue to advance – from studying paint fragments on precious art works, to analysing extra-terrestrial materials such as meteorites, and studying early steel-making techniques. And as the technology is refined even further, giving scientists the ability to look for smaller and smaller volumes of material, the possibilities seem endless.APPLICATION Electron-probe microanalysis was used to examine growth rings on deep-sea corals, revealing water temperature and salinity level variations over the corals’ lifespans. BENEFIT A detailed record of ocean conditions in the southern hemisphere over the past 400 years, which will contribute to understanding of present-day global warming and climate change. For further information contact: |
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