Browsing by Author "Henderson-Sellers, A"

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    Amazonian climatic change: water isotope detection of deforestation and greenhouse impacts
    (International Atomic Energy Agency, 2004-10-25) Henderson-Sellers, A; McGuffie, K
    Land use change in the Amazon basin, the largest and most biologically diverse river system in the world, has the potential to cause significant disruption to hydrological, biogeochemical and human systems. The naturally occurring isotopologues of water, commonly, but incorrectly, termed ‘isotopes’, of interest as possible tracing and validation tools in hydrological simulations are 1H2 18O and 1H2H16O. Large catchment simulations of water resources where isotopes could be applicable include water re-cycling as a function of precipitation type and variability [1, 2]; evaporation sourcing (i.e. whether water vapour comes from transpiration or from evaporation from rivers, lakes, soil water or the vegetation canopy) [3]; ice and snow temperature deposition determination; and aquifer and soil processes including those dependent upon precipitation intensity and melt-water contributions [4]. coupled with measurement of isotopes in water sources, SWI characteristics in river discharge now provide insight into basin- integrated hydro-climates [3, 5]. New data from the Global Network for Isotopes in Precipitation (GNIP) database, and previously published data now fully analysed, reveal significant changes in seasonal isotopic characteristics in the upper reaches of the Amazon basin underlining the use of stable water isotopes as a means of validating and improving numerical models. Despite observational limitations, which make determination of correctness difficult, some global models are shown here to be too poor to be of value in the Amazon. For example, isotopic depletions, a strong function of rainfall amount, are incorrect when precipitation is inadequately predicted seasonally or following ENSO circulation shifts. Isotopic enrichments of d18O and dD exhibit systematic variations in the Amazonian water cycle as a result of forest and flooding changes. We find signatures of both circulation and land-use change impacts in the isotopic record: ENSO events cause decreased depletion in the dry season, due to a decreased emphasis on convective precipitation, while increases in upper basin isotope depletions in the wet season result from relatively less non-fractionating recycling (i.e. less transpiration and full canopy evaporation) because there are fewer trees. Prediction of d18O and dD depletions by an isotope AGCM, while being adequate when averaged over the whole 17-year AMIP II period, are found to be less plausible for shorter periods. An isotope LSS is shown to be very sensitive to the prescription of boundary layer atmospheric water vapour isotopic depletion. We conclude that efforts to evaluate model simulations of the Amazon against isotopic data are currently seriously hampered by: (i) poor simulation of the gross water budget (e.g. lack of surface water conservation in models); (ii) considerable model differences in surface water distribution (i.e. between evaporation and runoff); (iii) wide ranging characterization of other possible causes of water isotopic fluctuations, such as El Niño and La Niña events; and (iv) significantly different characterization by current land-surface schemes of the partition of evaporation between fractionating and non- fractionating processes. While our results show great promise for isotopic evaluation of near-surface continental water cycle impacts in the Amazon, they also underline the need to address existing shortcomings in both atmospheric and land-surface models before isotopic finger-printing can be fully achieved.
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    Atmospheric isotopes: evolution of stable water isotopologues as an applicable data source
    (Australian Institute of Physics, 2005-01-31) Henderson-Sellers, A; McGuffie, K
    Stable water isotopes have been employed as a means of challenging, validating and improving numerical models of basin-scale water processes since the 1980s. Two rare but naturally occurring isotopologues of water, 1H218O and 1H2H16O, are coming to be of practical use in diagnosis of water cycle system changes. Recent developments have served to illustrate how detection and attribution of both human impacts and natural variations in surface-atmosphere water exchanges can beneficially exploit stable water isotope observations and simulations. The promise for isotopic finger-printing of near-surface water cycle changes is illustrated here for three important basins. © 2005 AIP
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    Building a future on knowledge from the past: what paleo-science can reveal about climate change and its potential impacts in Australia
    (Commonwealth Scientific and Industrial Research Organisation, 2005-06) Harle, KJ; Etheridge, DM; Whetton, P; Jones, R; Hennessy, K; Goodwin, ID; Brooke, BP; van Ommen, TD; Barbetti, M; Barrows, TT; Chappell, J; De Deckker, P; Fink, D; Gagan, MK; Haberle, SG; Heijnis, H; Henderson-Sellers, A; Hesse, PP; Hope, GS; Kershaw, P; Nicholls, N
    In Australia, high quality instrumental climate records only extend back to the late 19th century and therefore only provide us with a brief snapshot of our climate, its mean state and its short-term variability. Palaeo-records extend our knowledge of climate back beyond the instrumental record, providing us with the means of testing and improving our understanding of the nature and impacts of climate change and variability in Australia. There is a vast body of palaeo-records available for the Australian region (including Antarctica), ranging from continuous records of sub-decadal up to millennial scale (such as those derived from tree rings, speleothems, corals, ice cores, and lake and marine sediments) through to discontinuous records representing key periods in time (such as coastal deposits, palaeo-channels, glacial deposits and dunes). These records provide a large array of evidence of past atmospheric, terrestrial and marine environments and their varying interactions through time. There are a number of key ways in which this evidence can, in turn, be used to constrain uncertainties about climate change and its potential impacts in Australia.
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    Determination of mid-latitude radon-222 flux from the Southern Ocean using atmospheric radon-222 concentration measurements at an island ground station
    (International Atomic Energy Agency, 2004-10-24) Zahorowski, W; Chambers, SD; Henderson-Sellers, A
    Terrestrial radon (radon-222) fluxes typically exceed oceanic fluxes by 2-3 orders of magnitude [1]. This sometimes leads to the oceanic flux being neglected in atmospheric models [2, 3]. However, direct comparisons between observed and simulated atmospheric radon concentration at remote sites with extended oceanic fetch would benefit from the inclusion of a realistic oceanic radon flux within models [4]. Existing estimates of oceanic radon fluxes are not well constrained, with values ranging over two orders of magnitude (0.0011 - 0.15 atoms cm-2s-1) [1, 5]. At present, the primary factors contributing to the poor characterisation of oceanic radon fluxes are the limited number of observations, and the representativeness of the published results. Previous studies have employed either the accumulation [1] or gradient methods [5]. Both methods are based on spot measurements and as such, are subject to local conditions. More importantly, it would be difficult, if not impossible, to relate such results to a wider range of environmental parameters such as wind speed and sea state, which have a significant effect on ocean-atmosphere exchange. We present a method for the determination of regional oceanic radon fluxes. The method is applied to a subset of high sensitivity hourly atmospheric radon concentration observations from 1999 to 2003 made at Cape Grim, Tasmania (40°41’S, 144°41’E), a World Meteorological Organisation Global Atmosphere Watch (WMO GAW) station. A simple expression for an average oceanic radon flux is derived and applied using a subset of the observations considered to be representative of air parcels with an extended oceanic fetch. We discuss the dataset using the notion of an ‘oceanic event’, which is defined here as any set of consecutive hourly observations coming from the oceanic sector. Typically, the duration of a single oceanic event will vary from a few hours to a few days. The intermittent nature of boundary layer wind fields can result in short-term transitions across the oceanic sector boundaries when the air mass has mixed origins. Since the terrestrial radon source is much stronger than the oceanic source, only oceanic events that persist on synoptic time-scales are likely to include hourly observations that are representative of a minimally perturbed oceanic fetch. The evolution of radon concentration in the composite oceanic event was examined. It was found that radon concentrations in the first 20-30 hours after change to the oceanic sector are strongly perturbed from oceanic values. After the initial 20-30 hours, mean radon concentrations in the composite oceanic event are within the 95% confidence interval. This suggests that radon concentrations from this portion of the composite oceanic event are minimally perturbed from typical oceanic values. The lowest value in the range of estimated mean radon flux from the region of the Southern Ocean within the Cape Grim radon measurement fetch is about 0.0026 atoms cm-2s-1. This value is thought to constitute a lower limit estimate since it was obtained assuming negligible loss of radon from the marine boundary layer to the free troposphere. Taking into account the entrainment of radon from the marine boundary layer to the lowest layer within the free troposphere, derived from airborne measurements of mixing of dimethyl sulphide and aerosol particles over the Southern Ocean, leads to an upper limit estimate of about 0.006 atoms cm- 2s-1. Based on the 10 and 90 percentile radon concentration and wind speed observations, and assuming a mechanically driven mixing height, the regional oceanic radon flux may vary from 0.0014 to 0.008 atoms cm-2s-1 with changes in the sea state induced by wind and other environmental parameters. Our findings support the common assumption that oceanic radon fluxes are 2-3 orders of magnitude lower than terrestrial radon fluxes, which are typically within the range 0.5-2 atoms cm-2s-1. Our values are lower than some experimental spot estimates of oceanic radon flux rates made in the seventies [1, 5]. However, they are in close agreement with more recent estimates of the flux derived from model evaluation studies and also with radon flux values assumed in an intercomparison of the convective and synoptic processes of 20 global atmospheric transport models sponsored by the World Climate Research Program [4]. The new method of oceanic radon flux derivation can be applied to other sites around the world where ‘clean’ ocean air can be clearly identified. The method offers an alternative to experimental local/spot estimates of oceanic radon flux such as the accumulation method and gradient methods. More importantly, it is representative of a large region and allows results to be related to a wider range of environmental parameters that influence sea state (e.g. wind speed), which have a significant effect on ocean-atmosphere exchange.
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    Human activity and climate variability project: annual report 2001.
    (Australian Nuclear Science and Technology Organisation, 2002-01) Harle, KJ; Heijnis, H; Henderson-Sellers, A; Sharmeen, S; Zahorowski, W
    Knowledge of the state of the Australian environment including natural climate variability prior to colonial settlement is vital if we are to define and understand the impact of over two hundred years of post-industrial human activity on our landscape. ANSTO in conjunction with university partners is leading a major research effort to provide natural archives of human activity and climate variability over the last 500 years in Australia utilising a variety of techniques including lead-210 and radiocarbon dating and analyses of proxy indicators (such as microfossils) as well as direct evidence (such as trace elements) of human activity and climate variability. The other major project objectives were to contribute to the understanding of the impact of human induced and natural aerosols in the East Asian region on climate through analysis and sourcing of fine particles and characterisation of air samples using radon concentrations and to contribute to the improvement of land surface parameterisation schemes and investigate the potential to use stable isotopes to improve global climate models and thus improve our understanding of future climate.
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    Human activity and climate variability project: annual report 2002.
    (Australian Nuclear Science and Technology Organisation, 2002-11) Chambers, SD; Harle, KJ; Sharmeen, S; Zahorowski, W; Cohen, DD; Heijnis, H; Henderson-Sellers, A
    This project aims to utilise nuclear techniques to investigate evidence of human activity and climate variability in the Asia Australasian regions. It was originally designed to run over three years, commencing July 1999, with three parallel research tasks: Task 1: Past -- Natural archives of human activity and climate variability; Task 2: Present -- Characterisation of the global atmosphere using radon and fine particles; Task 3: Future -- Climate modelling: evaluation and improvement; Main project objectives -- To determine what proportions of changes in natural archives are due to human activity and climate variability; -- To contribute to the understanding of the impact of human induced and natural aerosols in the East Asian region on climate through analysis and sourcing of fine particles and characterisation of air samples using radon concentrations; -- To contribute to the improvement of land surface parameterisation schemes and investigate the potential to use isotopes to improve global climate models and thus improve our understanding of future climate. Significant project outcomes -- An improved understanding of natural and anthropogenic factors influencing change in our environment; -- A better understanding of the role of aerosols in climate forcing in the Asian region, leading to improved ability to predict climate change; -- An improved understanding of long term changes in the concentrations of trace species in the atmosphere on a regional and a global basis and their use in model evaluation; -- Improved understanding of the impact of different land-surface schemes on simulations by atmospheric models. The next two years of the project Our new and extended projects efforts include: 1) Aligning ourselves with the recently developed mission of the IGBP/PAGES research program 'Human Interactions on Terrestrial Ecosystems' and co-ordinating the Australasian research effort. Further research will focus on: (1) How widespread and reliable are evidence of major climatic events, such as storms and El Nino/La Nina cycles, in natural archives? This would require more natural archives to be examined from northern Australia and also records to be obtained from southern Australia. (2) The spatial extent of mining related pollutants, in the form of aerosol particles, which is of importance to managing the waste in the future. A combination of aerosol and archival studies will address this issue. In Summary: To achieve these extended goals we successfully gained another two years of further support for our project.
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    ISO 9001 accreditation in an R&D environment - is it possible?
    (International Atomic Energy Agency, 2006) Szymczak, R; Henderson-Sellers, A; Lowson, RT; Chisari, R
    The Australian Nuclear Science and Technology Organisation (ANSTO) is Australia's national nuclear organisation and its centre of Australian nuclear expertise. ANSTO is in the process of replacing its 1950’s, 15 MW, high flux (up to 1015 n cm-2 s-1) reactor with a new reactor which will allow it to continue its cutting edge nuclear science and radiopharmaceutical production well into the 21st century. A ministerial requirement for licensing the facility is ISO 9001 accreditation of its quality management system. The accreditation process has been staggered at ANSTO. Individual divisions are attaining ISO 9001 accreditation separately, leading up to site-wide accreditation of an overarching ANSTO Business Management System. ANSTO Environment is the largest multidisciplinary environmental research group in Australia and the largest R & D unit at ANSTO, comprising around 150 biologists, chemists, engineers, geophysicists, meteorologists, microbiologists, oceanographers, physicists, and technicians (Fig. 1). ANSTO Environment operates and maintains a wide range of advanced nuclear and analytical facilities including three particle accelerators, a 10 MV Tandem accelerator, a 3 MV Van de Graaff accelerator and a newly acquired 2MV HVEE tandetron; a high current 50 kV Metal Vapour Vacuum Arc Ion Implantation (MEVVA) Facility; a Secondary Ion Mass Spectrometer (SIMS); and many other laboratory and field-based facilities. The objective of ANSTO Environment is to carry out a problem-focused, balanced program of strategic and applied research and development, using its nuclear science-based core expertise and closely-related techniques, to: · assist the Commonwealth Government to further its national and international initiatives, and to protect and conserve the natural environment through sustainable development; · assist industry in advancing Australia's competitive position in the world economy; · ensure that environmental monitoring of nuclear facilities is effective in assuring operational adherence to sound environmental protection principles. “Make everything as simple as possible, but not simpler” Albert Einstein In February 2000 ANSTO Environment successfully acquired ISO 9001:2000 accreditation of its quality management system and was amongst the first organisations to adopt the new 2000 revision of the international ISO 9001 standard. The new standard allows a much more flexible and less prescriptive format for quality management systems however, in the absence of examples of accreditation in the R & D area, presented a challenge in concept, definition of process, buy-in by staff and subsequent maintenance of the successful certification. The ANSTO Environment Manual of Good Management Practice [1] outlines our identity, our vision, our core values, our responsibilities, our operational processes and our commitment to continual improvement via internal and external review. This paper is a description and discussion of the elements, concepts and process for achieving staff buy-in in the face of initial opposition. This included identifying those necessary elements of a good management system, rejection of pejorative dogma associated with ‘Quality’ and ownership of the process by all the staff.
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    ISO 9001 accreditation in an R&D environment - is it possible?
    (International Atomic Energy Agency, 2004-10-24) Szymczak, R; Henderson-Sellers, A; Lowson, RT; Chisari, R
    The Australian Nuclear Science and Technology Organisation (ANSTO) is Australia's national nuclear organisation and its centre of Australian nuclear expertise. ANSTO is in the process of replacing its 1950’s, 15 MW, high flux (up to 1015 n cm-2 s-1) reactor with a new reactor which will allow it to continue its cutting edge nuclear science and radiopharmaceutical production well into the 21st century. A ministerial requirement for licensing the facility is ISO 9001 accreditation of its quality management system. The accreditation process has been staggered at ANSTO. Individual divisions are attaining ISO 9001 accreditation separately, leading up to site-wide accreditation of an overarching ANSTO Business Management System. ANSTO Environment is the largest multidisciplinary environmental research group in Australia and the largest R & D unit at ANSTO, comprising around 150 biologists, chemists, engineers, geophysicists, meteorologists, microbiologists, oceanographers, physicists, and technicians (Fig. 1). ANSTO Environment operates and maintains a wide range of advanced nuclear and analytical facilities including three particle accelerators, a 10 MV Tandem accelerator, a 3 MV Van de Graaff accelerator and a newly acquired 2MV HVEE tandetron; a high current 50 kV Metal Vapour Vacuum Arc Ion Implantation (MEVVA) Facility; a Secondary Ion Mass Spectrometer (SIMS); and many other laboratory and field-based facilities. The objective of ANSTO Environment is to carry out a problem-focused, balanced program of strategic and applied research and development, using its nuclear science-based core expertise and closely-related techniques, to: assist the Commonwealth Government to further its national and international initiatives, and to protect and conserve the natural environment through sustainable development; · assist industry in advancing Australia's competitive position in the world economy; · ensure that environmental monitoring of nuclear facilities is effective in assuring operational adherence to sound environmental protection principles. “Make everything as simple as possible, but not simpler” Albert Einstein In February 2000 ANSTO Environment successfully acquired ISO 9001:2000 accreditation of its quality management system and was amongst the first organisations to adopt the new 2000 revision of the international ISO 9001 standard. The new standard allows a much more flexible and less prescriptive format for quality management systems however, in the absence of examples of accreditation in the R & D area, presented a challenge in concept, definition of process, buy-in by staff and subsequent maintenance of the successful certification. The ANSTO Environment Manual of Good Management Practice [1] outlines our identity, our vision, our core values, our responsibilities, our operational processes and our commitment to continual improvement via internal and external review. This paper is a description and discussion of the elements, concepts and process for achieving staff buy-in in the face of initial opposition. This included identifying those necessary elements of a good management system, rejection of pejorative dogma associated with ‘Quality’ and ownership of the process by all the staff.
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    Isotopes in Australian environmental analysis
    (International Atomic Energy Agency, 2004-10-24) Henderson-Sellers, A; Stone, DJM; Hollins, SE; Hotchkis, MAC; Fink, D
    ANSTO Environment is playing a pioneering role in developing new methods for monitoring adherence to the Nuclear Non-proliferation Treaty. Working with the IAEA Department of Safeguards, new analytical procedures have been developed to assist with their environmental monitoring programme. Signatures of nuclear activities, in the form of trace amounts of radioisotopes in environmental samples, can be used to identify undeclared nuclear facilities or undeclared activities at declared facilities. At ANSTO we have developed the use of Accelerator Mass Spectrometry (AMS) for analysis of 236U in environmental samples. 236U is a sensitive indicator of irradiated uranium. AMS is also used to detect the long- lived fission product 129I at extremely low levels. The presence of 129I can be a signature of reprocessing. ANSTO performs analyses of these radioisotopes as an accredited member of the IAEA Safeguards network of analytical laboratories. Australian soldiers on duty in the Gulf risk possible exposure to depleted uranium. Depleted uranium is the uranium that is left after most of the radioactive isotopes are removed for nuclear fuel. Due to its high density, it is the ideal material for use in armour-piercing ammunition and in armour for fighting vehicles. However, like any heavy metal, it is toxic in high doses. Depleted uranium enters the body through inhalation of the dust- like particles, ingestion of contaminated food or through wounds. At ANSTO, a sensitive analytical technique based on isotope dilution and inductively coupled plasma mass spectrometry (ICPMS) was used to detect depleted uranium in urine samples. By addition of known quantities of 236U (isotope dilution) to the urine samples and measuring the relative abundances of different isotopes (236U, 235U and 238U) of uranium by ICP-MS, we are able to quantify (quantification limit of 20 ng/L) and distinguish between natural and depleted uranium. In Australia, there are legislative limits on the amount of surface water that can be utilised in a particular catchment, but that is not the case for groundwater, leading to tension amongst users in connected systems. Isotopes such as the stable and radioactive isotopes of water and carbon are particularly appropriate for the study of our dry landscape in its connected water systems, providing a clear method of determining the source of groundwater, and hence the extent of mixing of nearby surface water and the time frame for the mixing process. In particular, the stable isotopes 2H, 18O, and 13C provide a robust end-member analysis for the hydrographical separation of regional groundwater and any amount of river water which was replenished at a remote location; while the radioactive isotopes 3H and 14C are used to confirm the presence in groundwater of (isotopically modern) surface water, but also accurately determine the apparent rate of mixing at particular distances from the river. Isotope tracer techniques have been applied to study the fate, pathways and risks associated with contaminants and particulates in coastal aquatic systems. Examples include: (i) sand and sediment tracing in coasts and estuaries using radiotracers such as 192Ir labelled sand (MacMasters Beach, NSW) or neutron activatable tracers such as 115In (Homebush Bay, Sydney); (ii) biokinetics of environmental contaminants in aquatic and terrestrial systems have been investigated using radionuclides such as 109Cd, 65Zn and 210Pb; (iii) tracing of sewage effluent from Australian coastal outfalls undertaken using radioisotope tracers such as 198Au and tritiated water; and (iv) groundwater dynamics under tidal forcing using a shortlived radioisotope tracer 82Br to track groundwater movement in three dimensions (Hat Head, NSW). Accelerator Mass Spectrometry is still the only technique able to determine extremely low concentrations (<10-12) of long- lived radioisotopes in small (mg) environmental samples. In Australia, radiocarbon dating is used for the study of paleo environments, climate studies, atmospheric studies and hydrology. Atmospheric studies including the high resolution radiocarbon dating of tropical and Southern Hemisphere tree rings provide data for studying the temporal variations of atmospheric radiocarbon and its inter-hemispheric gradient; and analysis of radio-methane trapped in Antarctic ice cores, a direct method of studying past atmospheric composition. It is also a means of studying palaeo-climate change. Exposure dating has been applied to glacial studies and landscape evolution studies. Using AMS measurement of beryllium-10 and aluminium-26 we have been able to determine Southern Hemisphere glacial chronology in Tasmania and the geomorphic evolution of Australian stony deserts. We apply the in-situ method to evaluate long-term average erosion rates, sand or sediment transport, accumulation and burial stages.
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    Moisture isotopes in the biosphere and atmosphere (MIBA) in Australia: a priori estimates and preliminary observations of stable water isotopes in soil, plant and vapour for the Tumbarumba field campaign
    (Elsevier, 2006-05) Twining, JR; Stone, DJM; Tadros, CV; Henderson-Sellers, A; Williams, AG
    An integral part of isotopes in the Program for Intercomparison of Land-surface Parameterisation Schemes (iPILPS) [Henderson-Sellers, A., in press. Improving land-surface parameterization schemes using stable water isotopes; introducing the iPILPS initiative. Global and Planetary Change, in press] is that the models' outputs be evaluated against measured values of δ2H and δ18O in the various simulated environmental compartments. This paper outlines the steps taken in Australia to initiate measurement of these stable water isotopes (SWIs) in the field, at a cool-temperate forest site in S.E. Australia near Tumbarumba, specifically to facilitate the model evaluation process. The selected sampling methodologies are detailed within the context of a conceptual model developed to describe the land-atmosphere exchange systems. This model has also been used to make a priori estimations of the isotopic values to be expected in each measured sub-system. As the data resulting from the Tumbarumba field campaign emerge, they will be compared with these working hypotheses to evaluate and, where necessary, amend the conceptual model. Initial comparisons based on preliminary data are presented here. The new observations derived in March 2005 should allow the land surface schemes used in weather forecast and climate change models to better reflect the environments for which they are attempting to make predictions. © 2006 Elsevier B.V.
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    Nuclear geophysiology: isotopes in Australian environmental analysis
    (International Atomic Energy Agency, 2004-10-28) Henderson-Sellers, A; Stone, DJM; Hollins, SE; Hotchkis, MAC; Fink, D
    Lovelock [1] introduced the term ‘geophysiology’ to describe the holistic study of the Earth systems. By analogy with medicine, and the corresponding field of nuclear medicine, ‘nuclear geophysiology’ describes the application of nuclear techniques to Earth system science. Injections of radioisotopes into the Earth's systems occur naturally and continuously, while artificial radionuclides have been injected at times as a result of human activities. Here, we provide some examples of Australian investigations into the physiology of the Earth derived from the study of these isotopes.
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    Nuclear geophysiology: stable water isotopes as evaluators of hydroclimate predictions in the Murray-Darling basin
    (Australian Institute of Physics, 2005-01-31) Henderson-Sellers, A; Airey, PL; McGuffie, K
    Isotopic data from two end-range and one central aquifer in the Murray Darling Basin are used to determine precipitation intensity thresholds for evaluation of GCM predictions. Applying these to ‘good’ and ‘poor’ Atmospheric Model Intercomparison Project (AMIP) simulations of the Murray Darling gives rise to large differences in rainfall amount (30% to 62%). Selecting only ‘good’ models shows a >150mm annual groundwater recharge loss in El Niño cf. La Niña climates. These isotopic techniques are applicable to future model scenarios of basin-scale hydrology, especially in difficult to simulate semi-arid basins.
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    Shift in stable water isotopes in precipitation in the Andean Amazon: Implications of deforestation or greenhouse impacts?
    (Elsevier Ltd, 2006) Henderson-Sellers, A; McGuffie, K
    Changes in the O and H isotopes in precipitation have been linked to greenhouse warming, but no signal attributable to Amazonian deforestation has been reported. Recent data from the Andes exhibit a seasonally contrasting signal which is consistent with large-area removal of forest. Specifically, at Izobamba, in the far west of the basin, the seasonality in isotopic depletions has become enhanced between 1972 and 2000. The observed more negative isotopic ratios in the wet season are consistent with increases in runoff fraction and/or reductions in recycling through non-fractionating processes. The dry season result (statistically significant less negative isotopic ratios) is harder to explain and could be due to a decrease in fractionating recycling (i.e. partial evaporation from water bodies). Application of a simple isotopic catchment model suggests that these isotopic changes in precipitation may be the result of large-scale deforestation in the Amazon Basin. Isotopically-enabled numerical models are needed to establish regional validity. © 2006 Elsevier B.V.
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    Stable water isotopes as tools for basin-scale water cycle: diagnosis of the Murray–Darling
    (Elsevier Ltd, 2006) Henderson-Sellers, A; Airey, PL; McGuffie, K; Stone, DJM
    We examine the hypothesis that isotopic techniques are applicable to hydrological predictions in difficult-to-simulate semi-arid basins, using the Murray–Darling Basin as an example. Isotopic data from three aquifers in the Murray–Darling characterize precipitation intensity for evaluation of GCMs. Applying these to ‘good’ (water conserving) and ‘poor’ (non-water-conserving) climate model simulations of the Murray–Darling gives rise to large differences in rainfall amount (30–62%). Selecting only ‘good’ models shows a greater than 150 mm annual groundwater recharge loss in El Niño cf. La Niña climates. 2002–2003 El Niño drought data are used to refine isotopic calculation of water lost in evaporation from rivers and irrigation, giving a cumulative loss of 64% of river water during 2002 (cf. 80% using a previous method). This substantiates recent identification of this El Niño drought as evaporatively most extreme and we conclude that stable water isotopes, used synergistically with hydro-climate models, have great potential in future water resource predictions. © 2006 Elsevier B.V.
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    Stable water isotopes: revolutionary tools for global water cycle disturbance diagnosis
    (International Atomic Energy Agency, 2004-10-25) Henderson-Sellers, A; McGuffie, K
    Here we assess the simulation of isotopic fluxes in basin-scale hydrology, focusing on the ‘big leaf’ representation of land surfaces in numerical models as the current mechanism for incorporating water isotopes. Applications of the simulation of stable isotopic behaviour simulated by global climate or earth system models, including river isotopic characterization of basin changes and plant-respired oxygen isotope ‘tagging’, to resolving uncertainty are limited until more basic criteria such as conservation, current mean climate and capture of observed variability are demonstrated. We find that surface water budgets are still rather poorly simulated and inadequately constrained at the scale of large basins; yet surface energy partition can be apparently well captured by models with inadequate land-surface parameterization.
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    Sustainability of groundwater under climate change
    (International Atomic Energy Agency, 2003-05-19) Airey, PL; Henderson-Sellers, A; Bradd, J; Chambers, SD; Hughes, CE; Habermehl, MA
    One of the key commitments from the plan of implementation of the World Summit on Sustainable Development Johannesburg 2002 was to 'develop integrated water resources management and water efficiency plans by 2005'. In this paper, a detailed concept will be presented for assessing the sustainability of groundwater in warm arid and semi-arid areas challenged by climate change. The IAEA Global Network of Isotope Precipitation (GNIP) database is fundamental to the development of the concept which will be extended to the evaluation of climate change models. The concept will be evaluated with data from three recharge areas in the Great Artesian Basin, as well as aquifers in Central Australia, in the far north of the country and in Victoria. Experimental work is currently being extended to the Murray-Darling Basin. The role of the GNIP in the evaluation of climate change models is illustrated with data from the Amazon. Groundwater sustainability is achieved through balancing exploitation of the resource with recharge. As groundwater exploitation raises issues of demand management beyond the scope of this paper, the focus will be on recharge. Surface water infiltration is dependent on total rainfall within the intake areas, the seasonal distribution of rainfall, the rainfall intensity and the antecedent landscape conditions. Variation in total rainfall can be predicted without recourse to isotope data. However, effective recharge will only occur if the total monthly rainfall exceeds a threshold value. The above-mentioned concept involves predicting these threshold values from GNIP and groundwater isotope data. The evaluation of the concept with field data, and its incorporation into a predictive tool are the central themes of this paper. Four stages are involved: Stage 1: Correlating isotope depletion and the total monthly rainfall Analysis of the GNIP data from continental stations shows a widespread trend towards increasing stable isotope depletion with increasing monthly average rainfall. Stage 2: Matching stable isotope levels in groundwater with those in rainfall with monthly totals exceeding a threshold value The stable isotope levels in groundwater is generally depleted relative to that in mean average rainfall at recharge. The groundwater levels match those in rainfall provided the monthly intensity reaches a threshold value. This value, which may be expressed as a percentile of all monthly data for the GNIP station, is interpreted as the threshold value for effective recharge. The difference between the stable isotope ratios in groundwater and in the mean rainfall is called the 'groundwater depletion'. Stage 3: Correlating the 'groundwater depletion' with aridity. It will be shown with reference to data from Australian aquifers that the 'groundwater depletion' correlates with a defined 'aridity index'. Stage 4: Development of the predictive tool: The above mentioned correlation is the basis of a tool which may be applied to a) assessing groundwater sustainability, b) predicting soil moisture in the root zone and thus contribute to agricultural sustainability and c) evaluating climate change models. a) Groundwater sustainability: Climate change leads to variations in the 'aridity index' and hence to variations in the threshold intensity for effective recharge (Stage 3 above). Climate changes may be modelled numerically, assessed through correlations with sub-global parameters such as ENSO (El Nino Southern Oscillation) Index or simply postulated as scenarios. Reliable knowledge of predicted changes to effective recharge, would provide decision makers with additional time to adjust the groundwater exploitation rate consistent with the long term sustainability of the resource. b) Sustainability of the agricultural and pastoral industries: Variations in soil productivity depend on a number of factors including moisture levels in the root zone. Predictions of the soil moisture levels will depend on the temporal variation of the effective recharge (above), the water balance and the residence time distribution of the water. The use of isotopes to establish a water balance at a site in the Darling basin has been demonstrated. c) Evaluation of climate models: The use of isotopes to evaluate climate change models has been demonstrated in the Amazon basin. The principles will be extended to arid and semi arid areas using isotopic data in age dated groundwater as a probe for variations in effective recharge and therefore in the aridity index. The concept will be illustrated with data from the Great Artesian Basin and the Mereenie Sandstone aquifer in Central Australia. On-going project work will be focussed on ANSTO's contribution to the Murray-Darling Water Basin Study through the GEWEX (Global Energy and Water Cycle Experiment) Hydrometeorological Panel and the IAEA Coordinated Research Program Isotope Tracing of Hydrological Processes in Large River Basins, 2002-2004. The Organisation is also contributing to the Integrated Climate System Study (ICSYS) initiative of the IAEA/WCRP (World Climate Research Programme). © The authors.
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    Temporal analysis of stable water isotopic characteristics in the Murray Darling Basin
    (International Atomic Energy Agency, 2004-10-24) Henderson-Sellers, A; Airey, PL; Stone, DJM; Bradd, J; McGuffie, K
    “Water shortages, especially in tropical countries, are the climate challenge for this century” [1]. The isotopic composition of water and carbon in e.g. ice cores, ground water and biomass has been recognized as relevant to hydro-climates on timescales from glacial [2] to extreme weather [3]. We present Australian stable water isotope (SWI) research capability and exploit it in novel ways in order to establish objective validation of and improvement in existing water resource models ultimately reducing uncertainty in predictions. The use of stable water isotopes in hydro-climate modelling is refined on three timescales for the Murray Darling Basin. Isotopes demonstrate that in semi-arid regions, groundwater recharge occurs when the rainfall intensities exceed a threshold suggesting improvement of aquifer predictions over tens to thousands of years using isotopic threshold estimates. A range of atmospheric global circulation models ’ simulations of key hydrological parameters over years to decades reveals poor results for the majority (13 in 20) and underlines the value of isotopic constraints on basin hydrology. Modelling minute to monthly isotope fluxes using land surface schemes and a steady state (phenomenological) model of river hydrology allows comparison of the partitions of precipitation between transpiration, run-off and ‘lake’ evaporation with isotope observations from June 2002 to January 2003. These results will have the greatest importance if combined to improve the dynamics of simulations of regional water cycles [4]. Three timescales have been used here to explore the role of stable water isotopes in refining climate and hydrological models of the Murray Darling Basin. Firstly, over tens to thousands of years, we have examined the processes leading to the effective recharge of groundwater. The isotope data clearly indicate that in the warm arid/semi-arid regions, in contrast to the behaviour in cool temperate zones, effective recharge only occurs when the rainfall intensities exceed a threshold value. Isotopic estimates of this recharge threshold rainfall intensity could be applied to predictions of future groundwater resources. Secondly, over years to decades, we have assessed the success of a range of atmospheric global circulation models in simulating key hydrological parameters over the AMIP II period including El Niño and La Niña forcing. The results are rather poor for the majority (13 out of 20) GCMs suggesting that further constraints on the basin’s hydrology, such as from isotopes, may be valuable. In our third approach, we have modelled minute to monthly isotope fluxes using (a) land surface schemes (LSSs) at particular grid points within the Murray Darling Basin and (b) a steady state (phenomenological) model of river hydrology. Model conservation, climatic variations and ‘plausibility’, all pre-requisites for good simulations, have been investigated here for the Murray Darling. Models’ partitions of precipitation between transpiration, run-off and ‘lake’ evaporation are compared with isotope observations from the Darling River between June 2002 and January 2003. We find that: (i) more work is needed on gross water fluxes first; (ii) simple isotopic models generate plausible values but more complex ones, as yet, do not; and (iii) isotopes have potential for evaluation of whether LSSs are (in)correctly recharging and accessing groundwater reservoirs and for evaluation of the partitioning of water into runoff cf. re-evaporation. Tests based around these concepts offer a novel addition to the traditional methods of validating climate models and their sub-components.