2015: Year in review

In 2015 the Geodynamics and Geodesy group comprised 6 academics, one senior manager, 6 PhD students and one M. Phil. student. The research undertaken predominantly uses satellite observations to study changes on Earth, as well as using ground-based geomorphological observations to construct models of ice sheets to represent the deglaciation cycles of the Earth.

The group saw the departure of Dr Lydie Lescarmontier who returned to France after several years in Australia. Two PhD students, Michael Moore and Bianca Kallenberg, submitted their PhD theses during 2015. Michael has returned to the Geodesy group at Geoscience Australia, while Bianca is still at RSES working on firn compaction modelling for mass balance studies of East Antarctica. Both Veronika Emetc and Siyuan Tian successfully passed their mid-term PhD examinations during 2015.

Siyuan and Veronika have made significant progress in their studies. Siyuan presented results of her assimilation of soil moisture observations (from the SMOS mission) and total water storage (from the GRACE mission) into hydrological modelling at the 21st International Congress on Modelling and Simulation at the Gold Coast in December 2015. Veronika presented results of her modelling of fracture processes in glaciers at the 2nd National Geodesy Workshop held at RSES in December. Salim Masoumi (PhD student) also presented his results on modelling of atmospheric gradients using GPS observations at the National Geodesy Workshop.

Crustal deformation studies using GPS focused on Eastern Indonesia in 2015, with Simon McClusky and Achraf Koulali participating in one of several field campaigns during the year. We derived a new block model for the deformation of eastern Indonesia (Koulali et al., GRL, in revision). Several active zones were identified, including the Semau Fault (west of Timor) and the transfer of convergence from the subduction zone south of Indonesia to the back-arc thrust system spanning over 2000 km from north of Java through to the Wetar Thrust in the east (Figure 1). The results highlight a significant seismic threat for eastern Java as well as demonstrating the risk of major earthquakes – and associated tsunamis – for Bali, Lombok and other coasts along the Flores Sea.

Progress in cryospheric studies included further development of a monthly firn compaction model (Figure 2) and refinements of the North American Ice Sheet to account properly for realistic ice sheet topography and the presence of melt lakes. An assessment of the most recent global glacial isostatic adjustment (GIA) model, ICE-6G_C (VM5), has shown significant issues remain in regions of marine-grounded ice sheets. A new model to remove GIA from space gravity estimates of mass balance change will be made publicly available (Purcell et al., 2015).

The in-house software to analyse the GRACE observations has continued to advance. Several improvements were made in the parameterization of the mascon elements used to describe the gravity field on the surface of the Earth. A solar radiation pressure model for the satellites (including thermal re-radiation effects) was developed to aid in the calibration of the onboard accelerometers. Dr Sebastien Allgeyer joined GRACE team in the latter half of the year as part of the current ARC Discovery project funding this research.

Dr Simon McClusky successfully raised funds to acquire a fixed-wing drone to provide a new capability of deriving local digital elevation models (DEMs). After appropriate training, Simon and Dr Herb McQueen have now used the drone to provide information on palaeo-lake shorelines of Lake George and also in the Lake Mungo area (western NSW) to support an ongoing ARC archaeology and geomorphology project (see Figure 3).

Figure 1. The kinematic block model of Koulali et al. (2015) for eastern Indonesia. Blue dots show the locations of earthquakes, black lines represent the locations of block boundaries. The arrows show the predicted relative motions on the block boundaries.

Figure 2. Rate of reduction of ice surface height over Antarctica due to firn compaction. This effect must be accounted for when using satellite altimetry estimates of rates of change of ice heights to calculate mass balance changes in Antarctica.

Figure 3. Dr Herb McQueen launching the new fixed-wing drone for a flight over Lake Mungo. The data collected allows a DEM of the area to be generated with a height accuracy of ~1 cm.

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