ORCID Profile
0000-0001-7192-5391
Current Organisation
Australian National University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Geomatic Engineering | Geodesy | Geodesy | Geophysics | Geodynamics | Seismology and Seismic Exploration | Natural Hazards | Glaciology | Geophysics Not Elsewhere Classified | Water Resources Engineering | Geochronology | Satellite, Space Vehicle and Missile Design and Testing | Oceanography | Civil Engineering | Gravity | Physical Oceanography | Glaciology | Earthquake Seismology | Geophysical Fluid Dynamics | Geotectonics | Groundwater Hydrology | Climate Change Processes | Oceanography Not Elsewhere Classified | Galactic Astronomy | Cosmology and Extragalactic Astronomy | Geophysics not elsewhere classified
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Earth Sciences | Climate change | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Earth sciences | Environmental and resource evaluation not elsewhere classified | Water Allocation and Quantification | Other | International aid | Land and water management | Climate Variability (excl. Social Impacts) | Natural Hazards not elsewhere classified | Vocational education and training | Marine Oceanic Processes (excl. climate related) | Natural Hazards in Coastal and Estuarine Environments | Natural Hazards in Antarctic and Sub-Antarctic Environments | Natural Hazards in Farmland, Arable Cropland and Permanent Cropland Environments | Expanding Knowledge in the Environmental Sciences | Environmental education and awareness | Expanding Knowledge in the Physical Sciences |
Related Links
Publications
ICESHEET 1.0: A program to produce paleo-ice sheet models with minimal assumptions
Publisher: Copernicus GmbH
Date: 20-01-2016
DOI: 10.5194/GMD-2016-9
Abstract: Abstract. We describe a program that produces paleo-ice sheet models using an assumption of steady state, perfectly plastic ice flow behaviour. It incorporates three input parameters: ice margin, basal shear stress and basal topography. Though it is unlikely that paleo-ice sheets were ever in complete steady-state conditions, this method can produce an ice sheet without relying on complicated and unconstrained parameters such as climate and ice dynamics. This makes it advantageous to use in glacial-isostatic adjustment ice sheet models, which are often used as input parameters in global climate modelling simulations. We test this program by applying it to the modern Greenland Ice Sheet and Last Glacial Maximum Barents Sea ice sheet and demonstrate the optimal parameters that balance computational time and accuracy.
Estimating network effect in geocenter motion: Applications
Publisher: American Geophysical Union (AGU)
Date: 10-2017
DOI: 10.1002/2017JB014247
Estimating network effect in geocenter motion: Theory
Publisher: American Geophysical Union (AGU)
Date: 10-2017
DOI: 10.1002/2017JB014246
Comparison between Laser Ranging Interferometer and K/Ka band Ranging instruments.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-6368
Abstract: & & & & & span& The GRACE Follow-On mission is the first twin-satellite mission& /span& & span& equipped with a laser ranging interferometer (LRI) to measure the inter-satellite distance between the pair of satellites. The LRI operates independently of the K/Ka-band interferometer (KBR& /span& & span& )& and uses& /span& & span& & wavelengths& /span& & span& & & /span& & span& & /span& & sup& & span& & /span& & /sup& & span& & times& /span& & span& & shorter than the K-band& /span& & span& & system.& & & /span& & span& Released at the end of July 2019, the LRI range data is& & /span& & span& therefore& & /span& & span& expected to be of higher accuracy than the KBR and offers the possibility of a better spatial resolution. We compare the LRI and KBR observations of the GRACE-FO mission, from launch to December 2019, to assess the quality of the new LRI system.& /span& & span& & & /span& & span& Spectral analysis of the level1B data shows that the noise level of the LRI is 3& & /span& & span& orders& /span& & span& & of magnitude smaller than the KBR& /span& & span& & and that& & /span& & span& the gravity signal can be detected in the spectral band up to& & /span& & span& mHz in the LRI data& & /span& & span& compared& /span& & span& & to& & /span& & span& mHz& /span& & span& & & /span& & span& i& /span& & span& n& /span& & span& & the& & /span& & span& KBR& /span& & span& & data& /span& & span& .& /span& & span& & & /span& & span& & We compare& /span& & span& & gravity& & /span& & span& fields& /span& & span& & estimated using LRI& & /span& & span& and KBR and show which parts of the spherical harmonic spectrum are affected by the improved accuracy of the LRI observations.& /span& & & & / &
A global water cycle reanalysis (2003-2012) merging satellite gravimetry and altimetry observations with a hydrological multi-model ensemble
Publisher: Copernicus GmbH
Date: 12-08-2014
DOI: 10.5194/HESS-18-2955-2014
Abstract: Abstract. We present a global water cycle reanalysis that merges water balance estimates derived from the Gravity Recovery And Climate Experiment (GRACE) satellite mission, satellite water level altimetry and off-line estimates from several hydrological models. Error estimates for the sequential data assimilation scheme were derived from available uncertainty information and the triple collocation technique. Errors in four GRACE storage products were estimated to be 11–12 mm over land areas, while errors in monthly storage changes derived from five global hydrological models were estimated to be 17–28 mm. Prior and posterior water storage estimates were evaluated against independent observations of river water level and discharge, snow water storage and glacier mass loss. Data assimilation improved or maintained agreement overall, although results varied regionally. Uncertainties were greatest in regions where glacier mass loss and subsurface storage decline are both plausible but poorly constrained. We calculated a global water budget for 2003–2012. The main changes were a net loss of polar ice caps (−342 Gt yr−1) and mountain glaciers (−230 Gt yr−1), with an additional decrease in seasonal snowpack (−18 Gt yr−1). Storage increased due to new impoundments (+16 Gt yr−1), but this was compensated by decreases in other surface water bodies (−10 Gt yr−1). If the effect of groundwater depletion (−92 Gt yr−1) is considered separately, subsurface water storage increased by +202 Gt yr−1 due particularly to increased wetness in northern temperate regions and in the seasonally wet tropics of South America and southern Africa. The reanalysis results are publicly available via ald/.
Absolute Calibration in Bass Strait, Australia: TOPEX, Jason-1 and OSTM/Jason-2
Publisher: Informa UK Limited
Date: 07-2011
An assessment of the ICE6G_C(VM5a) glacial isostatic adjustment model
Publisher: American Geophysical Union (AGU)
Date: 05-2016
DOI: 10.1002/2015JB012742
Supplementary material to "ICESHEET 1.0: A program to produce paleo-ice sheet models with minimal assumptions"
Publisher: Copernicus GmbH
Date: 20-01-2016
Plain Language Summary Required for Submission to Journal of Geophysical Research: Solid Earth
Publisher: American Geophysical Union (AGU)
Date: 05-2021
DOI: 10.1029/2021JB022351
Abstract: The editors of JGR: Solid Earth announce that Plain Language Summaries will be required for all manuscripts.
A statistical fracture model for Antarctic glaciers
Publisher: Copernicus GmbH
Date: 09-06-2017
DOI: 10.5194/TC-2017-98
Abstract: Abstract. Antarctic and Greenland hold more than 99 % of all fresh water on Earth and, therefore, can significantly influence global sea level. Predicting future ice sheet mass balance depends upon ice sheet modelling, but it is limited by knowledge of a number of processes, some of which are still poorly understood. One such process is the calving of the ice shelves, where blocks of ice break off from the ice front. However, large scale ice flow models do not include an accurate representation of this process and the most commonly used damage mechanics and fracture mechanics methods have a large number of uncertainties. Here we present an alternative, statistics-based method to model the most probable zones of nucleation of fractures. We test our theory on all main ice shelf regions in Antarctica, including the Antarctic Peninsula. We can model up to 99 % of observed fractures, with an average rate of 77 % which represents a 50 % improvement over previously used damage-based approaches, thus providing the basis for modelling calving of ice shelves. We found that classifying Antarctic ice shelf regions based on the factors that controlled fracture formation led to grouping of ice shelves/glaciers with similar physical characteristics and geometry.
Analysis of uncertainties in the inference of groundwater dynamics from gravity recovery and climate experiment observations over Australia
Publisher: IEEE
Date: 07-2012
Global joint assimilation of GRACE and SMOS for improved estimation of root-zone soil moisture and vegetation response
Publisher: Copernicus GmbH
Date: 27-08-2018
Abstract: Abstract. The lack of direct measurement of root-zone soil moisture poses a challenge to the large-scale prediction of ecosystem response to variation in soil water. Microwave remote sensing capability is limited to measuring moisture content in the uppermost few centimetres of soil. In contrast, GRACE (Gravity Recovery and Climate Experiment) mission detected the variability in storage within the total water column, which is often dominated by groundwater variation. However, not all vegetation communities can access groundwater. In this study, satellite-derived water content from GRACE and SMOS were jointly assimilated into an ecohydrological model to better predict the impact of changes in root-zone soil moisture on vegetation vigour. Overall, the accuracy of root-zone soil moisture prediction though the joint assimilation of surface soil moisture and total water storage retrievals showed improved consistency with ground-based soil moisture measurements and satellite-observed greenness when compared to open-loop estimates (i.e. without assimilation). For ex le, the correlation between modelled and in-situ measurements of root-zone moisture increased by 0.1 on average over grasslands and croplands. Improved correlations were found between vegetation greenness and soil water storage derived from the joint assimilation with an increase up to 0.47 over grassland compared to open-loop estimates. Joint assimilation results show a more severe deficit in soil water in eastern Australia, western North America and eastern Brazil over the period of 2010 to 2015 than the open-loop, consistent with the satellite-observed vegetation greenness. The assimilation of satellite-observed water content contributes to more accurate knowledge of soil water availability, providing new insights for monitoring hidden water stress and vegetation response.
Estimation of Glacial Isostatic Adjustment uplift rate in the Totten glacier's outlet from GPS and GRACE
Publisher: Copernicus GmbH
Date: 02-10-2020
DOI: 10.5194/GSTM2020-40
Abstract: & & Glacial Isostatic Adjustment (GIA) refers to the gradual response of the solid Earth to the deglaciation of historic ice sheets. & This ongoing rebound is contributing to the measurements of gravity change and land deformation, respectively, by Gravity Recovery And Climate Experiment (GRACE) and Global Positioning System (GPS). & When these space geodetic data are used to quantify the present-day ice mass change, the effect such as GIA must be accounted for. & In this study, we developed a method to estimate GIA and elastic deformation by the present-day ice mass change in the GPS time series with the ex le of Casey station in East Antarctica. & We determined a high-resolution, present-day ice mass change model on the outlet of Totten Glacier and calculated the elastic rebound over the area. & Our high-resolution model indicated a total mass loss of 15.7 & #177 0.5 Gt/yr on the outlet of Totten Glacier from 2002 to 2017 with the accelerated loss in the last half of the period. & We estimated the viscoelastic deformation attributed to GIA by removing the predicted elastic deformation from GPS measurements. & Four different GPS position solutions for the Casey station, the continuously operating GPS station near the area, were examined. & The estimated GIA signal appears to be within 0.3 & #8211 1.3 mm/yr which shows its contribution on the vertical deformation between 30 & #8211 60 % among different GPS solutions. & On the other hand, the vertical elastic deformation trend is predicted to be 0.7 mm/yr from the ice mass change model.& The GPS measured seasonal variation is explained equally by atmospheric-oceanic loading and degree-1 loading with a couple mm litude in vertical time series.& The elastic rebound from the present-day ice mass change also perturbed the horizontal displacement by 0.13 mm/yr in west and 0.21 mm/yr in north directions. & This is in the opposite to the plate motion of the East Antarctica around the Casey station and amounts approximately up to 10 % of the measured tectonic motion.& &
Crustal strain partitioning and the associated earthquake hazard in the eastern Sunda‐Banda Arc
Publisher: American Geophysical Union (AGU)
Date: 11-03-2016
DOI: 10.1002/2016GL067941
Periodontal treatment during pregnancy and birth outcomes: a meta-analysis of randomised trials
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2011
DOI: 10.1111/J.1744-1609.2011.00210.X
Abstract: The objective of this review was to conduct a meta-analysis of all up-to-date randomised control trials to determine whether periodontal treatment during pregnancy has the potential of reducing preterm birth and low birth weight incidence. Bibliographic databases MEDLINE (1966-present), EMBASE (1980-present), CINAHL (1982-present) and the Cochrane library up to and including 2010 Issue 10 were searched. The reference list of included studies and reviews were also searched for additional literature. Eligible studies were, published and ongoing randomised control trials that compared pregnancy outcomes for pregnant women who received periodontal treatment during the prenatal period. Two of the investigators independently assessed the studies and then extracted and summarised data from eligible trials. Extracted data were entered into Review Manager software and analysed. A total of 5645 pregnant women participated in the 10 eligible trials. Meta-analysis found that periodontal treatment significantly lowered preterm birth (odd ratio 0.65 95% confidence interval, 0.45-0.93 P = 0.02) and low birth weight (odd ratio 0.53 95% confidence interval, 0.31-0.92 P = 0.02) rates while no significant difference was found for spontaneous abortion/stillbirth (odd ratio 0.71 95% confidence interval, 0.43-1.16 P = 0.17). Moderate heterogeneity was observed among the studies for preterm birth and low birth weight. Subgroup analysis showed significant effect of periodontal treatment in pregnant women with low rate of previous preterm birth/low birth weight (odd ratio 0.35 95% confidence interval, 017-0.70 P = 0.003) and less severe periodontal disease (odd ratio 0.49 confidence interval, 028-0.87 P = 0.01) as defined by probing depth. The cumulative evidence suggests that periodontal treatment during pregnancy may reduce preterm birth and low birth weight incidence. However, these findings need to be further validated through larger more targeted randomised control trials.
Supplementary material to "A statistical fracture model for Antarctic ice shelves and glaciers"
Publisher: Copernicus GmbH
Date: 20-03-2018
Extracting white noise statistics in GPS coordinate time series
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2013
Global joint assimilation of GRACE and SMOS for improved estimation of root-zone soil moisture and vegetation response
Publisher: Copernicus GmbH
Date: 21-02-2019
DOI: 10.5194/HESS-23-1067-2019
Abstract: Abstract. The lack of direct measurement of root-zone soil moisture poses a challenge to the large-scale prediction of ecosystem response to variation in soil water. Microwave remote sensing capability is limited to measuring moisture content in the uppermost few centimetres of soil. The GRACE (Gravity Recovery and Climate Experiment) mission detected the variability in storage within the total water column. However, root-zone soil moisture cannot be separated from GRACE-observed total water storage anomalies without ancillary information on surface water and groundwater changes. In this study, GRACE total water storage anomalies and SMOS near-surface soil moisture observations were jointly assimilated into a hydrological model globally to better estimate the impact of changes in root-zone soil moisture on vegetation vigour. Overall, the accuracy of root-zone soil moisture estimates through the joint assimilation of surface soil moisture and total water storage retrievals showed improved consistency with ground-based soil moisture measurements and satellite-observed greenness when compared to open-loop estimates (i.e. without assimilation). For ex le, the correlation between modelled and in situ measurements of root-zone moisture increased by 0.1 (from 0.48 to 0.58) and 0.12 (from 0.53 to 0.65) on average for grasslands and croplands, respectively. Improved correlations were found between vegetation greenness and soil water storage on both seasonal variability and anomalies over water-limited regions. Joint assimilation results show a more severe deficit in soil water anomalies in eastern Australia, southern India and eastern Brazil over the period of 2010 to 2016 than the open-loop, consistent with the satellite-observed vegetation greenness anomalies. The assimilation of satellite-observed water content contributes to more accurate knowledge of soil water availability, providing new insights for monitoring hidden water stress and vegetation conditions.
Toward near-real time analysis of gravity change with the examples of flood and flash drought events
Publisher: Copernicus GmbH
Date: 26-09-2022
DOI: 10.5194/GSTM2022-59
Abstract: & & We discuss a methodology of scientifically utilizing high-precision laser ranging measurements (in addition to K-band microwave) for higher temporal s ling of surface mass changes. & The standard spatial analysis (i.e., global gravity field recovery) over a month period such as L2 and L3 data processing would produce a biased estimate when characteristic time scales of mass change processes are shorter than a month. & Our proposed time-domain (along-track) analysis will lead to better quantification of such processes. & Furthermore, we exploit the low-latency (within 1& #8211 days) Quick-Look (QL) L1B data to examine the feasibility of immediate assessment of extreme events such as flood and flash drought. & Such QL data processing can promote timely assessment of severe weather events and natural hazards as important applications of the GRACE-FO mission. & As ex les, we present the data processing results for the 2019 South East US flash drought, the 2020 (unusually large) monsoonal flood in Bangladesh, and the 2021 Eastern Australia flood. & A new streamlined along-track data processing chain is proposed to facilitate utilization of superb laser ranging measurements for advanced quantification of rapid Earth system changes we experience recent years.& &
Shallow intraplate earthquakes in Western Australia observed by Interferometric Synthetic Aperture Radar
Publisher: American Geophysical Union (AGU)
Date: 11-2008
DOI: 10.1029/2008JB005807
Global Mapping Function (GMF): A new empirical mapping function based on numerical weather model data
Publisher: American Geophysical Union (AGU)
Date: 2006
DOI: 10.1029/2005GL025546
New Insights into the present-day kinematics of the central and western Papua New Guinea from GPS
Publisher: Oxford University Press (OUP)
Date: 15-06-2015
DOI: 10.1093/GJI/GGV200
Impact of a priori zenith hydrostatic delay errors on GPS estimates of station heights and zenith total delays
Publisher: American Geophysical Union (AGU)
Date: 05-12-2006
DOI: 10.1029/2006GL027706
Quantifying FES2004 S2 tidal model from multiple space-geodesy techniques, GPS and GRACE, over North West Australia
Publisher: Springer Science and Business Media LLC
Date: 07-03-2009
A new approach to estimate ice dynamic rates using satellite observations in East Antarctica
Publisher: Copernicus GmbH
Date: 09-12-2016
DOI: 10.5194/TC-2016-269
Abstract: Abstract. Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It's often been assumed that changes in ice dynamic rates only need to be considered when assessing long term ice sheet mass balance however, two decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about changes in ice dynamic rates are still limited, especially in East Antarctica. Without understanding ice dynamic rates it is not possible to properly assess changes in ice sheet mass balance, surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice dynamic rates by removing modelled rates of surface mass balance, firn compaction and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of ice dynamic rates by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction and ice dynamic rates can be modelled and correlate with observed elevation changes from satellite altimetry.
Supplementary material to "A statistical fracture model for Antarctic glaciers"
Publisher: Copernicus GmbH
Date: 09-06-2017
Improved water balance component estimates through joint assimilation of GRACE water storage and SMOS soil moisture retrievals
Publisher: American Geophysical Union (AGU)
Date: 03-2017
DOI: 10.1002/2016WR019641
Empirical modelling of site-specific errors in continuous GPS data
Publisher: Springer Science and Business Media LLC
Date: 03-06-2014
A model of the western Laurentide Ice Sheet, using observations of glacial isostatic adjustment
Publisher: Elsevier BV
Date: 05-2016
A decade of horizontal deformation from great earthquakes
Publisher: American Geophysical Union (AGU)
Date: 05-2013
DOI: 10.1002/JGRB.50154
Relationship between glacial isostatic adjustment and gravity perturbations observed by GRACE
Publisher: American Geophysical Union (AGU)
Date: 21-09-2011
DOI: 10.1029/2011GL048624
Forecasting dryland vegetation condition months in advance through satellite data assimilation
Publisher: Springer Science and Business Media LLC
Date: 28-01-2019
DOI: 10.1038/S41467-019-08403-X
Abstract: Dryland ecosystems are characterised by rainfall variability and strong vegetation response to changes in water availability over a range of timescales. Forecasting dryland vegetation condition can be of great value in planning agricultural decisions, drought relief, land management and fire preparedness. At monthly to seasonal time scales, knowledge of water stored in the system contributes more to predictability than knowledge of the climate system state. However, realising forecast skill requires knowledge of the vertical distribution of moisture below the surface and the capacity of the vegetation to access this moisture. Here, we demonstrate that contrasting satellite observations of water presence over different vertical domains can be assimilated into an eco-hydrological model and combined with vegetation observations to infer an apparent vegetation-accessible water storage (hereafter called accessible storage). Provided this variable is considered explicitly, skilful forecasts of vegetation condition are achievable several months in advance for most of the world’s drylands.
Resolving slip-vector azimuths and plate motion along the southern boundary of the South Bismarck Plate, Papua New Guinea
Publisher: Wiley
Date: 10-2001
Thank You to Our 2019 Reviewers
Publisher: American Geophysical Union (AGU)
Date: 05-2020
DOI: 10.1029/2020JB019781
ANU GRACE Data Analysis: Orbit Modeling, Regularization and Inter‐satellite Range Acceleration Observations
Publisher: American Geophysical Union (AGU)
Date: 02-2022
DOI: 10.1029/2021JB022489
Abstract: Several different basis functions have been used to represent the Earth's gravity field in order to generate estimates of mass variations on Earth from the analysis of data of the Gravity Recovery and Climate Experiment ( grace ) and its successor grace Follow‐On missions, including spherical harmonics, mass concentration elements (mascons) and slepian functions. Each approach depends inherently upon accurate modeling of the orbits of the pair of satellites as they revolve around the Earth, so that the observations of inter‐satellite changes in range (or, more specifically, range rate) can be exploited to identify mass variations. We have developed software using a classical orbit modeling approach, mascons and 24‐hr orbit integration, to estimate simultaneously corrections to orbital parameters and the temporal gravity field from grace data. Rather than using the range rate, we use the range acceleration as the inter‐satellite observable as it aids in localizing the mass variations. Level‐1 B range acceleration observations contain high levels of high‐frequency noise that inhibits their usefulness for this purpose. Instead, we generate range acceleration observations by numerical differentiation of the Level‐1B range rate prefit residuals. Simulations show that the gravity signal is not attenuated in this process. Our monthly estimates of mass anomalies from grace data (2003–2016) agree well with previous studies, both spatially and temporally. When converted to spherical harmonics our time series of C 2,0 , derived from grace data alone, are close to the independent estimates from satellite laser ranging, but the overall solution is improved by substituting the SLR C 2,0 .
Atmospheric pressure loading corrections applied to GPS data at the observation level
Publisher: American Geophysical Union (AGU)
Date: 11-2005
DOI: 10.1029/2005GL024104
Tropical cyclones and the ecohydrology of Australia's recent continental-scale drought
Publisher: American Geophysical Union (AGU)
Date: 02-2012
DOI: 10.1029/2011GL050263
Australian sea levels—Trends, regional variability and influencing factors
Publisher: Elsevier BV
Date: 09-2014
Slow slip events and the 2016 Te Araroa Mw 7.1 earthquake interaction: Northern Hikurangi subduction, New Zealand
Publisher: American Geophysical Union (AGU)
Date: 28-08-2017
DOI: 10.1002/2017GL074776
Thank You to Our 2022 Peer Reviewers
Publisher: American Geophysical Union (AGU)
Date: 07-2023
DOI: 10.1029/2023JB026890
Abstract: Editors of JGR‐Solid Earth express their appreciation to those who served as peer reviewers for the journal in 2022.
A statistical fracture model for Antarctic ice shelves and glaciers
Publisher: Copernicus GmbH
Date: 05-10-2018
Abstract: Abstract. Antarctica and Greenland hold enough ice to raise sea level by more than 65 m if both ice sheets were to melt completely. Predicting future ice sheet mass balance depends on our ability to model these ice sheets, which is limited by our current understanding of several key physical processes, such as iceberg calving. Large-scale ice flow models either ignore this process or represent it crudely. To model fractured zones, an important component of many calving models, continuum damage mechanics as well as linear fracture mechanics are commonly used. However, these methods have a large number of uncertainties when applied across the entire Antarctic continent because the models were typically tuned to match processes seen on particular ice shelves. Here we present an alternative, statistics-based method to model the most probable zones of the location of fractures and demonstrate our approach on all main ice shelf regions in Antarctica, including the Antarctic Peninsula. We can predict the location of observed fractures with an average success rate of 84 % for grounded ice and 61 % for floating ice and a mean overestimation error rate of 26 % and 20 %, respectively. We found that Antarctic ice shelves can be classified into groups based on the factors that control fracture location.
Interplay of Altitude, Ground Track Coverage, Noise, and Regularization in the Spatial Resolution of GRACE Gravity Field Models
Publisher: American Geophysical Union (AGU)
Date: 2023
DOI: 10.1029/2022JB024330
Abstract: Models of the temporal gravity field derived from space gravity missions are typically produced with monthly temporal resolution and ∼300‐km spatial resolution. However, variations in instrument performance and altitude of the Gravity Recovery and Climate Experiment (GRACE) mission impact the spatial resolution that can be achieved month‐to‐month. As the altitude of the orbits of the twin spacecraft vary throughout the mission, so does the ability of the observations to recover certain components of the temporal gravity field. The spatial resolution of GRACE observations should increase as the altitude decreases throughout the mission because the reduced altitude intensifies the gravity signals acting on the satellites. Simulations using actual GRACE altitude and ground track coverage and realistic noise levels confirm this predicted influence of the altitude of the satellites on the accuracy of the estimated solutions. Solutions with larger mass concentration elements (mascons) are more numerically stable as the satellite altitude decreases but they suffer from greater error caused by the inability to properly represent spatial variations of signals within mascons, referred to as intramascon variability. Mascons as small as ∼150 × 150 km (i.e., ∼1.5 arc‐degree) reduce the intramascon variability and, with appropriate regularization, yield the most accurate solutions, especially during the low‐altitude periods of the GRACE mission. Importantly, unlike spherical harmonic solutions, regularized mascon solutions are not degraded during resonant orbit months, and are of comparable quality to months with full ground track coverage.
ICESHEET 1.0: a program to produce paleo-ice sheet reconstructions with minimal assumptions
Publisher: Copernicus GmbH
Date: 03-05-2016
Abstract: Abstract. We describe a program that produces paleo-ice sheet reconstructions using an assumption of steady-state, perfectly plastic ice flow behaviour. It incorporates three input parameters: ice margin, basal shear stress and basal topography. Though it is unlikely that paleo-ice sheets were ever in complete steady-state conditions, this method can produce an ice sheet without relying on complicated and unconstrained parameters such as climate and ice dynamics. This makes it advantageous to use in glacial-isostatic adjustment ice sheet modelling, which are often used as input parameters in global climate modelling simulations. We test this program by applying it to the modern Greenland Ice Sheet and Last Glacial Maximum Barents Sea Ice Sheet and demonstrate the optimal parameters that balance computational time and accuracy.
Deformation in the Jura Mountains (France): First results from semi-permanent GPS measurements
Publisher: Elsevier BV
Date: 15-05-2006
Non-linear motions of Australian geodetic stations induced by non-tidal ocean loading and the passage of tropical cyclones
Publisher: Springer Science and Business Media LLC
Date: 12-06-2014
Atmospheric effects and spurious signals in GPS analyses
Publisher: American Geophysical Union (AGU)
Date: 11-09-2009
DOI: 10.1029/2009JB006344
150 km ANU mascon solutions
Publisher: Copernicus GmbH
Date: 26-09-2022
DOI: 10.5194/GSTM2022-32
Abstract: & & We present updated mascon solutions of the temporal gravity field, derived from the analysis of Level-1B GRACE and GRACE-FO data using the range acceleration observable. Our previous solutions contained significant noise in particular regions of high mass loss (e.g. West Antarctica), which was caused by inappropriate levels of regularisation. Here we show a new approach of both iteration and regularisation of the solutions which generates more reliable estimates of the mass variations across the whole Earth, with both temporal and spatial consistency despite not applying any temporal or spatial inter-mascon constraints. We compare mascon solutions at spatial resolutions from 300 km to 100 km, show estimates of ocean mass increase and mass loss in ice-covered regions as well as assess the C20 time series estimated directly from GRACE data alone. Our new mascon estimates, at ~200 km x 200 km spatial resolution, are now publicly available.& &
A new approach to estimate ice dynamic rates using satellite observations in East Antarctica
Publisher: Copernicus GmbH
Date: 17-05-2017
Abstract: Abstract. Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It has often been assumed that changes in ice dynamic rates only need to be considered when assessing long-term ice sheet mass balance however, 2 decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about ice sheet changes due to changes in the ice dynamics are still limited, especially in East Antarctica. Without understanding ice dynamic rates, it is not possible to properly assess changes in ice sheet mass balance and surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice sheet changes due to ice dynamic rates by removing modelled rates of surface mass balance, firn compaction, and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of the rate of change due to ice dynamics by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction, and ice dynamic rates can be modelled and correlated with observed elevation changes from satellite altimetry.
Interplay of altitude, ground track coverage, noise and regularisation in the spatial resolution of GRACE gravity field models
Publisher: Copernicus GmbH
Date: 26-09-2022
DOI: 10.5194/GSTM2022-34
Abstract: & & Models of the temporal gravity field derived from space gravity missions are typically produced with monthly temporal resolution and ~300 km spatial resolution. However, variations in instrument performance and altitude of the GRACE mission impact the spatial resolution that can be achieved month-to-month. As the altitude of the orbits of the twin spacecraft vary throughout the mission, so does the ability of the observations to recover certain components of the temporal gravity field. The spatial resolution of GRACE observations should increase as the altitude decreases throughout the mission because the reduced altitude intensifies the gravity signals acting on the satellites. Simulations using actual GRACE altitude and ground track coverage and realistic noise levels confirm this predicted influence of the altitude of the satellites on the accuracy of the estimated solutions. Solutions with larger mass concentration elements (mascons) are more numerically stable as the satellite altitude decreases but they suffer from greater error caused by the inability to properly represent spatial variations of signals within mascons, referred to as intra-mascon variability. Mascons as small as ~150 x 150 km (i.e. ~1.5 arc-degree) reduce the intra-mascon variability and, with appropriate regularisation, yield the most accurate solutions, especially during the low-altitude periods of the GRACE mission. Importantly, unlike spherical harmonic solutions, regularised mascon solutions are not degraded during resonant orbit months, and are of comparable quality to months with full ground track coverage.& &
Effects of atmospheric pressure loading and seven-parameter transformations on estimates of geocenter motion and station heights from space geodetic observations
Publisher: American Geophysical Union (AGU)
Date: 2005
DOI: 10.1029/2004JB003334
First geodetic measurement of convergence across the Java Trench
Publisher: American Geophysical Union (AGU)
Date: 15-09-1994
DOI: 10.1029/94GL01856
The impact of mapping functions for the neutral atmosphere based on numerical weather models in GPS data analysis
Publisher: Springer Berlin Heidelberg
Date: 2007
ANU GRACE Data Analysis: Characteristics and Benefits of Using Irregularly Shaped Mascons
Publisher: American Geophysical Union (AGU)
Date: 02-2022
DOI: 10.1029/2021JB022412
Abstract: The estimation of mass anomalies using Gravity Recovery and Climate Experiment (GRACE) data involves parameterizing the temporal gravity field using basis functions. In this study, we show that the use of irregularly shaped mass concentration (mascon) tiles that follow land/ocean boundaries reduces the leakage of land signals into ocean regions and vice versa. Leakage of signal from continents to oceans in mascons that cross the coastline affect the integrated mass changes at a regional scale. For ex le, the calculated mass loss in 2016 is ∼5% greater for Greenland when using mascons that follow coastlines. We describe efficient algorithms for computing the accelerations acting on the satellites caused by mass changes on mascons, along with the partial derivatives relating the mass changes to the inter‐satellite observations. Through simulation, we quantify the impact of different mascon geometries, spatial resolution and regularization. The variations of mass change signals within mascons, which we call “intra‐mascon variability,” contribute to errors in estimates of mass variation from GRACE data. While this can be mitigated through the regularization of the inversions, it cannot be removed entirely. The use of irregularly shaped mascons that follow land/ocean boundaries reduces the “intra‐mascon leakage” of land signals into ocean regions and vice versa. This approach can also be applied to hydrological basins for calculating integrated mass changes on catchment scales.
Glacial isostatic adjustment and nonstationary signals observed by GRACE
Publisher: American Geophysical Union (AGU)
Date: 23-06-2009
DOI: 10.1029/2008JB006161
Twentieth century constraints on sea level change and earthquake deformation at Macquarie Island
Publisher: Oxford University Press (OUP)
Date: 06-2010
Tectonic interpretation of aftershock relocations in eastern Papua New Guinea using teleseismic data and the arrival pattern method
Publisher: Oxford University Press (OUP)
Date: 03-2005
Effect of post-seismic deformation on earth orientation parameter estimates from VLBI observations: A case study at Gilcreek, Alaska
Publisher: Springer Science and Business Media LLC
Date: 20-06-2005
Slow slip events in Mexico revised from the processing of 11 year GPS observations
Publisher: American Geophysical Union (AGU)
Date: 07-08-2010
DOI: 10.1029/2009JB006852
Motion of the South Bismark Plate, Papua New Guinea
Publisher: American Geophysical Union (AGU)
Date: 12-1999
DOI: 10.1029/1999GL010840
Reply to Comment by W. R. Peltier, D. F. Argus, and R. Drummond on “An Assessment of the ICE6G_C (VM5a) Glacial Isostatic Adjustment Model”
Publisher: American Geophysical Union (AGU)
Date: 02-2018
DOI: 10.1002/2017JB014930
A directional model of tropospheric horizontal gradients in Global Positioning System and its application for particular weather scenarios
Publisher: American Geophysical Union (AGU)
Date: 18-04-2017
DOI: 10.1002/2016JD026184
Plate kinematics in the western Pacific derived from geodetic observations
Publisher: American Geophysical Union (AGU)
Date: 2002
DOI: 10.1029/2001JB000406
A global water cycle reanalysis (2003–2012) reconciling satellite gravimetry and altimetry observations with a hydrological model ensemble
Publisher: Copernicus GmbH
Date: 18-12-2013
DOI: 10.5194/HESSD-10-15475-2013
Abstract: Abstract. We present a global water cycle reanalysis that reconciles water balance estimates derived from the GRACE satellite mission, satellite water level altimetry and off-line estimates from several hydrological models. Error estimates for the sequential data assimilation scheme were derived from available uncertainty information and the triple collocation technique. Errors in four GRACE storage products were estimated to be 11–12 mm over land areas, while errors in monthly storage changes derived from five global hydrological models were estimated to be 17–28 mm. Prior and posterior estimates were evaluated against independent observations of river water level and discharge, snow water storage and glacier mass loss. Data assimilation improved or maintained agreement overall, although results varied regionally. Uncertainties were greatest in regions where glacier mass loss and sub-surface storage decline are both plausible but poorly constrained. We calculated a global water budget for 2003–2012. The main changes were a net loss of polar ice (−341 Gt yr−1) and mountain glaciers (−185 Gt yr−1), with an additional decrease in seasonal snow pack (−19 Gt yr−1). Storage in lakes increased by +77 Gt yr−1, due to new reservoir impoundments (+87 Gt yr−1), water level change in the Caspian Sea (−27 Gt yr−1) and net increases in the remaining lakes combined (+17 Gt yr−1). There was no change in subsurface storage, because groundwater depletion (−90 Gt yr−1) was offset by increased water storage in the seasonally wet tropics of South America and southern Africa (+87 Gt yr−1), which agrees with observed and predicted changes in the tropical monsoon.
The effect of melting land-based ice masses on sea-level around the Australian coastline
Publisher: Informa UK Limited
Date: 06-2012
GRACE estimates of sea surface height anomalies in the Gulf of Carpentaria, Australia
Publisher: Elsevier BV
Date: 07-2008
Thank You to Our 2018 Peer Reviewers
Publisher: American Geophysical Union (AGU)
Date: 04-2019
DOI: 10.1029/2019JB017745
Evidence for active subduction at the New Guinea Trench
Publisher: American Geophysical Union (AGU)
Date: 07-2004
DOI: 10.1029/2004GL020190
Detecting hydrologic deformation using GRACE and GPS
Publisher: American Geophysical Union (AGU)
Date: 07-08-2009
DOI: 10.1029/2009GL038718
Erratum: Atmospheric effects and spurious signals in GPS analyses (Journal of Geophysical Research B: Solid Earth (2009) 114 (B09403) DOI: 10.1029/2009JB006344)
Publisher: American Geophysical Union (AGU)
Date: 18-02-2011
DOI: 10.1029/2010JB008157
Uncertainty analysis of earthquake source parameters determined from InSAR: A simulation study
Publisher: American Geophysical Union (AGU)
Date: 27-09-2007
DOI: 10.1029/2007JB005209
A statistical fracture model for Antarctic ice shelves and glaciers
Publisher: Copernicus GmbH
Date: 20-03-2018
DOI: 10.5194/TC-2018-5
Abstract: Abstract. Antarctica and Greenland hold enough ice to raise sea level by more than 65 m if they were to melt completely. Predicting future ice sheet mass balance depends on our ability to model these ice sheets, which is limited by our current understanding of several key physical processes, such as iceberg calving. Large-scale ice flow models either ignore this process or represent it crudely. To model fracture formation, which is an important component of many calving models, Continuum Damage Mechanics as well as Linear Fracture Mechanics are commonly used. However, these methods applied across the Antarctic continent have a large number of uncertainties. Here we present an alternative, statistics-based method to model the most probable zones of nucleation of fractures. We test this approach on all main ice shelf regions in Antarctica, including the Antarctic Peninsula. We can model up to 99 % of observed fractures, with an average rate of 84 % for grounded ice and 61 % for floating ice and mean overestimation error of 26 % and 20 %, respectively, thus providing the basis for modelling calving of ice shelves. We find that Antarctic ice shelves can be classified into groups based on the factors that control fracture location. The factors that trigger fracturing as well as sustain existing fractures advected from upstream vary from one ice shelf to another.
Is the Australian Plate deforming? A space geodetic perspective
Publisher: Geological Society of America
Date: 2003
The ANU GRACE visualisation web portal
Publisher: Elsevier BV
Date: 03-2013
Impact of solid Earth tide models on GPS coordinate and tropospheric time series
Publisher: American Geophysical Union (AGU)
Date: 2006
DOI: 10.1029/2005GL025538
Thank You to Our 2020 Peer Reviewers
Publisher: American Geophysical Union (AGU)
Date: 03-2021
DOI: 10.1029/2021JB021896
Abstract: Members of the editorial board of JGR‐Solid Earth express their appreciation to those who served as peer reviewers for the journal in 2020.
Continental breakup and UHP rock exhumation in action: GPS results from the Woodlark Rift, Papua New Guinea
Publisher: American Geophysical Union (AGU)
Date: 11-2014
DOI: 10.1002/2014GC005458
Thank You to Our 2021 Peer Reviewers
Publisher: American Geophysical Union (AGU)
Date: 04-2022
DOI: 10.1029/2022JB024501
Abstract: Editors of JGR‐Solid Earth express their appreciation to those who served as peer reviewers for the journal in 2021.
Quantifying GRACE data contamination effects on hydrological analysis in the Murray-Darling Basin, southeast Australia
Publisher: Informa UK Limited
Date: 04-2010
Characterization of Changes in Groundwater Storage in the Lachlan Catchment, Australia, Derived From Observations of Surface Deformation and Groundwater Level Data
Publisher: American Geophysical Union (AGU)
Date: 12-2022
DOI: 10.1029/2022JB024669
Abstract: Global Positioning System (GPS) deformation measurements were combined with groundwater level data to examine the spatiotemporal variability of groundwater storage in the Lachlan catchment located in central New South Wales (Australia). After correcting for effects of glacial isostatic adjustment, non‐tidal oceanic and atmospheric loading as well as hydrologic loading using existing models, we show that the seasonal and interannual variability of ground deformation and hydraulic head level data, extracted using wavelet time‐frequency analysis, exhibits an in‐phase behavior, indicating that the observed surface deformation is the poroelastic response to groundwater pressure change in aquifer system. Combination of GPS displacement and groundwater level change enables the estimation of elastic skeletal specific storage coefficients, which were then used for estimating groundwater storage changes. The estimated groundwater storage changes clearly reflect the four climate events of the Lachlan catchment since 1996: (a) the Millennium drought over 1996–2009, (b) the 2011–2012 La Nina and two significant floods in 2012 and 2016, (c) the drought conditions from mid‐2017 to late‐2019, and (d) the return of La Nina conditions since early 2020. We also found annual and long‐term groundwater storage variations of respectively and over the period 2012–2021. Moreover, we show that groundwater level fluctuations can be predicted from GPS displacement measurements and storage coefficients with sufficient accuracy (80% correlation and 70% RMS reduction when compared in terms of seasonal cycle). This study provides essential information that can contribute to future groundwater planning, management, and control over the Australian continent.
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