Modeling upper mantle rheology with numerical experiments and mapping marine gravity with satellite altimetry

This thesis consists of modeling upper mantle rheology with numerical experiments and mapping marine gravity anomalies with satellite altimetry data. Chapter 1 introduces my reasoning for undertaking projects in two distinct fields. Chapters 2 and 3 are numerical modeling projects. Chapters 4 and 5 and the appendix are satellite altimetry projects.; Chapter 2 presents numerical modeling experiments of small-scale convection in the asthenosphere beneath California. Using the timing provided by the tectonic history and knowledge of the current thermal state from seismic tomography, our numerical experiments provide upper and lower bounds on the asthenosphere viscosity, and demonstrate the effects of rheologies that depend on temperature, pressure, and strain rate.; Chapter 3 presents a numerical model to test the asthenosphere flow paradigm in which hotspots feed the low viscosity asthenosphere, and lithosphere consumes the asthenosphere. The model is applied to two distinct regions--the Iceland hotspot centered on the Mid-Atlantic Ridge, and the Kerguelen hotspot located near the Southeast Indian Ridge. The asthenosphere flow paradigm can explain major features of hotspot-ridge interactions for both on-axis and off-axis hotspots.; Chapter 4 presents a resolution analysis of repeat satellite altimeter profiles to compare the along-track resolution capabilities of Geosat, ERS-1 and TOPEX data. On average globally, the along-track resolution (0.5 coherence) of eight-cycle stacks are approximately the same, 28, 29, and 30 km for TOPEX, Geosat, and ERS-1, respectively. TOPEX 31-cycle stacks (22 km) resolve slightly shorter wavelengths than Geosat 31-cycle stacks (24 km).; Chapter 5 presents a method to improve global gravity profiles by iterating on the current grid. We use new repeat cycle data to improve stacks (averages) for ERS-1/2 (43 cycles) and Topex (142 cycles), and then implement the method for improving gravity profiles globally. We demonstrate the maximum accuracy of our new grid by comparing the grid to ship profiles.; The appendix includes an analysis of the environmental corrections supplied with TOPEX data to evaluate which corrections may be important when using sea surface slope data for marine gravity and oceanographic variability studies.