Despite growing concerns about potential enhancement of global warming and slope failure by methane produced by gas hydrate dissociation, much uncertainty surrounds estimates of gas hydrate reservoir sizes, as well as methane fluxes and oxidation rates at the sea floor. For cold seep sediments of the eastern Mediterranean Sea, depth-dependent methane concentrations and rates of anaerobic oxidation of methane (AOM) are constrained by modeling the measured pore-water sulfate profile. The calculated dissolved methane distribution and flux are sensitive to the advective flow velocity, which is estimated from the depth distributions of conservative pore-water constituents (Na, B). Near-complete anaerobic oxidation of the upward methane flux is supported by the depth distributions of indicative biomarkers, and the carbon isotopic compositions of organic matter and dissolved inorganic carbon. Pore-water and solid-phase data are consistent with a narrow depth interval of AOM, 14-18 cm below the sediment-water interface. Based on an isotopic mass balance, the biomass of the microbial population carrying out oxidation of methane coupled to sulfate reduction at the given methane flux represents about 20% of the total organic carbon, which is a significant pool of in situ formed organic matter. Model results indicate that the asymptotic methane concentration is reached a few meters below the sediment surface. The predicted asymptotic concentration is close to the in situ saturation value with respect to gas hydrate, suggesting that the rate of shallow gas hydrate formation is controlled by the ascending methane flux. The proposed model approach can be used to predict the formation of gas hydrate, and to quantify methane fluxes plus transformation rates in surface sediments where fluid advection is an important transport mechanism.

The Fitzoy Estuary is one of several macrotidal estuaries in tropical northern Australia that face ecological change due to agricultural activities in their catchments. The biochemical functioning of such macrotidal estuaries is not well understood in Australia, and there is a pressing need to identify sediment, nutrient and agrochemical pathways, sinks and accumulation rates in these extremely dynamic environments. This is particularly the case in coastal northern Queensland because the impact of water quality changes in rivers resulting from vegetation clearing, changes in land-use and modern agricultural practices are the single greatest threat to the Great Barrier Reef Marine Park. This report includes: 1 Aims and Research questions 2 Study Area 3 Climate and Hydrology 4 Geology 5 Vegetation and land use 6 Methods 7 Sampling strategy 8 Water column observations and samples 9 Bottom sediment properties 10 Core and bottle incubations 11 Data analysis 12 Results 13 Discussion 14 The roll of Keppel Bay in accumulating and redirecting sediment and nutrients from the catchment 15 Sediment biogeochemistry 16 Links between primary production, biogeochemistry and sediment dynamics: A preliminary zonation for Keppel Bay 17 Conclusions

Increasing the knowledge of ocean current patterns in Torres Strait region is of direct interest to indigenous communities and industries such as fisheries and shipping that operate in the region. Ocean circulation in Torres Strait influences nearly all aspects of the ecosystem, including sediment transport and turbidity patterns, primary production in the water column and bottom sediments, and recruitment patterns for organisms with pelagic phases in their life cycles. This study is the first attempt to describe the water circulation and transport patterns across Torres Strait and adjacent gulfs and seas, on time scales from hours to years. It has also provided a framework for an embedded model describing sediment transport processes (described in Margvelashvili and Saint-Cast, 2006). The circulation model incorporated realistic atmospheric and oceanographic forcing, including winds, waves, tides, and large-scale regional circulation taken from global model outputs. Simulations covered a hindcast period of eight years, allowing the tidal, seasonal, and interannual flow characteristics to be investigated. Results demonstrated that instantaneous current patterns were strongly dominated by the barotropic tide and its spring-neap cycle. However, longer-term transport through Torres Strait was mainly controlled by seasonal winds, which switch from north-westerly monsoon winds in summer to south-easterly trades in winter. Model results were shown to be relatively insensitive to internal model parameters. However, model performance was strongly dependent on the quality of the forcing fields. For example, the prediction of low-frequency inner-shelf currents was improved substantially when temperature and salinity forcing based on the average seasonal climatologies was replaced by that from global model outputs. Uncertainties in the tidal component of the forcing also limited model skill, particularly predictions to the west of Cape York which were strongly dependent on the sealevels imposed along the open boundary in Gulf of Carpentaria.

The Paterson National Geoscience Agreement project is using a number of tools to better understand the time-space evolution of the northwest Paterson Orogen in Western Australia. One of these tools, 3D Geomodeller, is an emerging technology that constructs three-dimensional (3D) volumetric models based on a range of geological information. The Paterson project is using 3D Geomodeller to build geologically-constrained 3D models for the northwest Paterson Orogen. This report documents the model building capability and benefits of 3D Geomodeller and highlights some of the geological insights gained from the model building exercise. The principal benefit of 3D Geomodeller is that it provides geoscientists with a rapid tool for testing multiple working hypotheses. The Cottesloe Syncline district was selected as the focus for a trial of the 3D Geomodeller software. The 3D model was built by members of the Paterson Project, as well as model building specialists within Geoscience Australia. The resultant Cottesloe Syncline model including two dimensional sections, maps and images was exported from 3D GeoModeller and transformed into a Virtual Reality Modelling Language (VRML), enabling a wide audience to view the model using readily available software.

Geoscience Australia's Risk & Impact Analysis Group has developed a statistical model of wind hazard utilising the Generalised Pareto Distribution (GPD). The model calculates the return period of severe winds based on daily maximum wind gust observations. The model utilises an automated procedure to partition the data into the hazard constituents (thunderstorms, synoptic winds, tornadoes, etc) based on the World Meteorological Observation Codes 3-hourly coded observations. This observational data set records the archived and present weather at the station site. The model fits the GPD to the station data (daily maximum wind gust) by automating the selection of the appropriate threshold above which data is included in the extreme value distribution. This threshold <em>u</em> is selected as the maximum of all feasible return period values obtained by fitting the GPD. Published comparative findings, including same region results, demonstrate the model can produce similar results in a more efficient, fully computational way. Confidence intervals for return periods are calculated automatically to allow wind analysts to distinguish regions of greater reliability.

Geothermal energy has been harnessed in Australia for several decades for both direct use applications and power generation, but only at very small scale installations. Australia's geothermal resources are amagmatic and unconventional by the accepted definitions in other parts of the world centred on active volcanism or plate margin collision. Worldwide, there is a lack of experience in exploring for and developing unconventional resources, and few "deposit" or resource models to aide exploration. The conceptualisation of a range of geological environments amenable to geothermal resource development will underpin the large scale development of geothermal utilisation in Australia. This will include developing exploration models spanning the range of unconventional geothermal resources; from "EGS" or "Hot (Dry) Rock" where permeability stimulation is a pre-requisite, to "Hot Sedimentary Aquifer" where no permeability stimulation is required.

The MODIS (or Moderate Resolution Imaging Spectroradiometer) 250 m EVI dataset provides a valuable ongoing means of characterising and monitoring changes in land use and resource condition. However the multiple factors that influence a time series of greenness data make the data difficult to analyse and interpret. Without prior knowledge, underlying models for time series in a given remote sensing image are often heterogeneous. So while conventional time series analysis methods such as wavelet transform and Fourier analysis may work well for part of the image, these models are either invalid or must be substantially re-parameterised for other parts of the image. To overcome these challenges we propose a new approach to distil information from earth observation time series. The characteristics of a remote sensing time series are represented by a set of statistics (which we call coefficients) selected to correspond to the dynamics of a natural system. To ensure the coefficients are robust and generic, statistics are calculated independently by applying statistical models with less complexity on shorter segments within the time series. An International Standards Organization (ISO) Land Cover classification was generated for cropping regions in the Gwydir and Namoi catchments, in Australia. Areas identified in the classification as irrigated and rain fed cropping were analysed using a tailored time series analysis tool. The crop analysis tool identifies time series features such as the number and duration of fallow periods, crop timing, presence/absence of a crop during a year for a specific growing season. This information is combined with paddock boundaries derived from Landsat imagery to provide detailed year-by-year insight into cropping practices in the Gwydir and Namoi catchments.

Geoscience Australia is supporting the exploration and development of offshore oil and gas resources and establishment of Australia's national representative system of marine protected areas through provision of spatial information about the physical and biological character of the seabed. Central to this approach is prediction of Australia's seabed biodiversity from spatially continuous data of physical seabed properties. However, information for these properties is usually collected at sparsely-distributed discrete locations, particularly in the deep ocean. Thus, methods for generating spatially continuous information from point samples become essential tools. Such methods are, however, often data- or even variable- specific and it is difficult to select an appropriate method for any given dataset. Improving the accuracy of these physical data for biodiversity prediction, by searching for the most robust spatial interpolation methods to predict physical seabed properties, is essential to better inform resource management practises. In this regard, we conducted a simulation experiment to compare the performance of statistical and mathematical methods for spatial interpolation using samples of seabed mud content across the Australian margin. Five factors that affect the accuracy of spatial interpolation were considered: 1) region; 2) statistical method; 3) sample density; 4) searching neighbourhood; and 5) sample stratification by geomorphic provinces. Bathymetry, distance-to-coast and slope were used as secondary variables. In this study, we only report the results of the comparison of 14 methods (37 sub-methods) using samples of seabed mud content with five levels of sample density across the southwest Australian margin. The results of the simulation experiment can be applied to spatial data modelling of various physical parameters in different disciplines and have application to a variety of resource management applications for Australia's marine region.

Seismic reflection and gravity potential field data acquired during the Geoscience Australia SW Margins Survey 2008-09 was used to investigate the distribution of volcanic facies and large-scale structural architecture of the Mentelle Basin, located on the southwestern margin of Australia. Based on structural differences the basin is subdivided into the Western (WMB) and Eastern (EMB) Mentelle Basins. Isopach and seismic facies maps were used to identify the thickness and distribution of volcanic facies. These maps show that volcanism is generally confined to the Western Mentelle Basin, with two distinct areas of thick volcanic deposits occurring in the central and northern portion. Two and three dimensional gravity forward models were used to investigate the structural architecture of the Mentelle Basin. Two dimensional gravity modelling shows that the crust is extremely thin in the WMB (c.10km), associated with two mantle highs. The crust thickens from the EMB (>20km) towards mainland Australia. The two modelled mantle highs coincide with the two seismically defined areas of thick volcanic deposits. Analogue models indicate that rift related volcanism is generally confined to the locus of extension where crustal thinning and strain are greatest. Thus results of gravity modelling and seismic interpretation have been interpreted to indicate that Jurassic - Cretaceous extension was focussed in the WMB. This thinning of the crust and presence of mantle highs suggests that the WMB is a failed rift formed during the initial breakup between Australia and Greater India and abandoned at the onset of spreading in the Perth Basin.

Nutrients dynamics in estuaries are temporarily variable depending on changing physical-chemical conditions and the response of functional primary producer groups such as phytoplankton, microphytobenthos, seagrass and macroalgae. In order to reveal temporal regime shifts in primary producer groups and associated changes in estuarine nutrient dynamics we developed a box-model coupling the hydrology and nitrogen dynamics in Wilson Inlet, a large, central basin dominated, intermittently closed estuary exposed to Mediterranean climate. The model is calibrated and validated with monitoring data, aquatic plant biomass estimates and biogeochemical rate measurements. Macrophytes and their microalgal epiphytes appear to rapidly assimilate first flush nutrients from the catchment in winter, but this buffer capacity then ceases and a phytoplankton bloom develops in response to subsequent river run-off events in spring. In late spring to autumn high light availability stimulates high primary production by microphytobenthos leading to reduced benthic ammonia fluxes particularly in deep basin areas and contributing about 50% of annual whole-system primary production. Significant amounts of bioavailable nitrogen are flushed out, because phytoplankton predominance occurs concurrently with the opening of the bar.