Gravity studies over West Antarctica

This thesis describes the results of new analysis of gravity studies over West Antarctica. Set on the Siple Coast, an airborne geophysical survey was flown between 1994 and 1997 that covered the trunk of Bindschadler Ice Stream and the up-stream areas, including Whitmore Accommodation Zone and Byrd Subglacial Basin. The new gravity reduction methodology removed vertical and horizontal accelerations, the Eötvös effect, and the theoretical gravity; unlike previous analyses, this reduction did not level individual lines, preserving the high frequency data and avoiding introduction of new errors. This reduction provided the free-air gravity disturbance over the area, which was then leveled and registered by the more regional extensive GOCE satellite gravity. The processing and reduction of the data improved the high frequency signal over previous work on the data, giving better definition of small scale, short wavelength features, which works well with satellite gravity data that emphasizes the large scale, long wavelength features. The leveled free-air gravity was then processed with a FORTRAN 90 program that calculates the Bouguer disturbance based on the free-air gravity and the topography. The topography was gathered concurrently with the gravity with ice penetrating radar during the airborne survey. The Bouguer disturbances provide a crustal model of the area. The final Bouguer disturbance was also corrected for the ice above sea level, which was calculated with a simple Bouguer slab correction. Finally, a power spectrum analysis was run on a profile in the Bouguer gravity disturbance in order to complete a spectral analysis. The spectral analysis provides crustal density boundaries for a density anomaly near the surface, a mid-crustal anomaly, and the Moho boundary. The improved the high frequency content of the data allows spectral analysis down to 4 km. The differing crustal thickness from spectral analysis also shows the character and extent of the West Antarctic Rift System, the northern flank of which extends out from Marie Byrd Land and into the survey area. Bindschadler Ice Stream is located on the WARS rift floor and MacAyeal Ice Stream sits on the rift flank.