GRAVitational field modelling of Earth’s topography For GEOdetic and GEOphysical applications (GRAV4GEO)

• Applicant: E. Sinem Ince, Ph.D.
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Geophysics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 505165206

The gravity field plays a crucial role in Earth system sciences. Access to the entire field globally and at any time is only possible via mathematical modelling. The heterogeneous gravity field shapes the mean sea level surface and can be used e.g., to determine ocean surface currents, to unify height systems globally, and to complement studies on mapping mass distributions that mirror the processes in Earth’s interior, such as plate tectonics, mantle convection, seafloor spreading and volcanic eruption. Currently available static global gravity field models are limited in resolution due to the band-limited spectral content of the input data from satellite observations and gravity measurements on the Earth’s surface. Digital elevation models (DEMs) with global coverage and high spatial resolution can be used together with laterally varying density estimates to complement the existing gravity field models beyond their current limits. The proposed project aims to compute a very high-resolution topographic gravity field model in terms of harmonic coefficients via direct numerical integration of Newton’s law of gravitation using very high resolution DEMs and recently developed laterally varying density models. The outcomes of the project will be 1) reduction of the omission error and enhancement of the spectral and spatial resolution of global gravity field models with their uncertainty estimation provided, 2) delivery of topography/density-based gravity information particularly in hard-to reach areas which are the least known but yet have crucial roles in the Earth system, 3) improved reduction of the gravity measurements for the topographic effect to investigate the residual signal of deeper Earth layers. This should help in the 3D crustal and lithospheric modelling especially in geologically complex areas, 4) significant improvement in gravity modelling accuracy from using laterally varying density content instead of the commonly used averaged density values, 5) an algorithm that overcomes the approximation and instability issues existing in the beta version. With the high-resolution topographic gravity field model delivered at the end of the project, the spatial resolution of recent global gravity field models will be increased from ~9 km up to ~2 km. The omission error will be reduced drastically, especially in mountainous regions. Uncertainty estimates, which have not been presented in current topographic gravity field models, will be provided. Our project will lead to an improved global gravity field which delivers a more accurate reference surface for international height reference system and basis for better geophysical modelling especially in the regions of density discontinuities. In which ways and to what extend such an improved gravity field can contribute to Earth System research in Geodesy and Geophysics remains underexplored and will be the key question in this project.

• DFG Programme: Research Grants