Summary
Geophysical observables (e.g. surface elevation, gravity anomalies, seismic data, surface heat flow, etc.) are one of the main sources of information used to make inferences about the interior of the Earth. Obtaining consistent models requires combining simultaneously different observable datasets into joint inversions. Among geophysical data, gravity data from ESA’s GOCE satellite mission provides key information in properly constraining the Earth’s density distribution. WINTERCG is a new global thermochemical model of the lithosphere and upper mantle (currently being extended to transition zone) that, among other observables, uses global satellite gravity from GOCE to constrain the model. Its inversion scheme has two main steps. In step 1, 1D inversion is performed using waveform seismic tomographic data and isostasy primarily. Then, in step 2, the output model from step 1 is used as prior information for the inversion of GOCE’s gravity field data for the 3D crustal density and upper mantle composition. As a consequence, the density field changes and modifies the isostatic balance previously achieved in step 1. It originates a residual isostatic topography that can be regarded as a proxy for dynamic topography. However, within a rigorous framework, residual topography and computed dynamic topography (i.e. solving the Stokes equation) should be consistently integrated into a joint inversion with feedback from both the static and dynamic sides. This is currently missing in WINTERC-G and the goal of this project is to add a third step to WINTERC-G global inversion scheme that consistently integrates dynamic topography as an additional model constrain. To do that, we will explicitly compute dynamic topography solving the associated Stokes equation fed by the model 3D distributions of densities and viscosities within the upper mantle and transition zone. Furthermore, the dynamic effects related to mantle convection affect geoid sensitivity kernels; in this project we will also consistently modify the description of the gravity field to include viscosity effects.
