Lily Yu, 2012, English
Time-varying gravity models of the earth are useful for understanding climate change, providing, among other results, insights on drought and ice-melt processes. For my summer internship, I used the gravity field models developed by GRGS (Groupe de Recherche en Géodesie Spatiale) from GRACE (Gravity Recovery and Climate Experiment) satellite data to graph the change in gravity signal over Australia from 2002 to the present in order to investigate a large negative gravity signal over the sparsely populated northwest of Australia. It is the largest gravity signal in Australia, larger even than the ongoing drought in the Murray-Darling Basin, and its causes are poorly understood. Possible geophysical causes include underground aquifer depletion or seismic activity/postglacial rebound. Possible non-geophysical causes include instrument error, analysis error, or contamination of the signal from other processes. Although I was not able to find a definitive cause, I did find that the current hydrological model (GLDAS) and the atmospheric-pressure dealiasing product used by GRGS were unlikely to be significant contributors to the gravity signal.