Environmental geodesy

Australia, as part of the global community, is ominously poised in a period of significant environmental change caused by warming of the Earth’s atmosphere. Changing sea-levels and variation in national water storage present significant challenges that are at the forefront of Australian consciousness.

This research program realises the first assembly of national geodetic intellect (Australian National University, University of Tasmania, University of New South Wales and Curtin) to tackle these complex problems through the development and extension of space-geodetic observational techniques, and drawing upon recent and significant cash injections into geospatial infrastructure in Australia. It will provide the first-ever comprehensive indication of the contemporary state of changes in sea-level, Antarctic ice cover and broad-scale water storage in the Australian context.

Relevant current and recent peer-reviewed papers are included in each of the research areas below:

Cryospheric mass transport in the Earth system

We are analysing the impact of changes in the mass balance of the cryosphere (the portions of the Earth’s surface where water is in solid form) on the whole Earth system. Different procedures and software have been developed to model changes in the Earth’s gravity field, centre of mass, rotation and global sea level change based on changes in ice cover. We have shown that the melt of ice-covered areas does not lead to a globally uniform sea level change, but it varies depending on location, which is important when analysing the impact of local, regional and global sea level change (e.g., extents of flooding). GRACE (Gravity Recovery and Climate Experiment) satellite mission data have been analysed and used to assist in both the determination of recent mass changes in the cryosphere and corresponding changes in the Earth’s gravity field and regional sea level.

Spatial variations in sea level

Different data sources such as satellite radar altimetry, tide-gauge records and the GRACE (Gravity Recovery and Climate Experiment) satellite mission are being used to monitor and analyse the most dominant spatial and temporal variations in global sea level and the Earth’s gravity field. In order to do this, different analytical and statistical modelling techniques, such as harmonic analysis and principal component analysis, have been employed. This includes the identification and quantification of spatial and/or temporal biases in global sea level change estimates caused by insufficient sampling of the sea level change signal. Furthermore, recent GRACE-derived gravity changes are being used to derive mass changes in the cryosphere (the portions of the Earth’s surface where water is in solid form) and all major river drainage basins.

Spatial variations in sea level in Australia

Variations of sea level and water storage in the Australian region

Australiais ominously situated in a period of significant environmental change caused bycontinued warming of the Earth. Changing sea-levels and variation in nationalwater storage present challenges that are at the forefront of Australianconsciousness. This research provides the first assembly of national geodeticintellect to tackle these complex problems through the development andextension of space-geodetic observational techniques, and drawing upon recentand significant injections into geospatial infrastructure. It will provide thefirst-ever comprehensive indication of the contemporary state of changes insea-level, Antarctic ice cover and broad-scale national water storage.

  • Awange, J.L., M.A. Sharifi, O. Baur, W. Keller, W.E. Featherstone and M. Kuhn (2009) GRACE hydrological monitoring of Australia: current limitations and future prospects, Journal of Spatial Science 54(1): 23-36

Environmental effects of falling water levels

South-west seismic zone

The southwest seismic zone (SWSZ) in Western Australia is one of few intra-plate tectonic regions in the world where earthquake activity is not associated with the plate boundaries. Importantly, the proximity of the SWSZ zone to Perth presents a significant seismic hazard. However, the magnitude, type and controls deformation of the Earth’s crust in the SWSZ are not fully understood at present. We have therefore used palaeosiesmology (the study of ancient earthquakes) to create a longer time-series of large earthquakes, which will lead to improved risk-mapping techniques in the SWSZ. We have also used a combination of GPS-geodetic and geophysical measurements to place additional controls on the current seismicity in the SWSZ, also with a view to improved risk-mapping.