Effects of CMB Topography on Core Flows

Researchers have long assumed that Earth’s core processes occur within a nearly perfect spherical shell and that this condition is sufficient to explain the geodetic and geomagnetic observations. However, seismological and mantle convection studies suggest that the core-mantle boundary (CMB) contains variations in shape and temperature, creating a heterogeneous boundary. Recent models suggest that boundary heterogeneities may control both the large-scale generation of the Earth’s magnetic field and the exchange of angular momentum between the mantle and core. In fact, the effects of heterogeneous boundaries may be one of the most important controlling factors influencing Earth’s core processes. However, we know of only a few laboratory experiments that have been conducted to study the effects of thermal heterogeneity and none that investigate the effects of topographic heterogeneity.
Graduate Student Mike Calkins is leading our project to measure the effects of heterogeneous boundary topography on core flows, using coupled laboratory and numerical experiments. While previous studies of topographic heterogeneity have utilized estimates inferred from seismic studies, the goal of our study is to determine the upper bounds of core-mantle topography for a given imposed core-style flow.
Funding for this project provided by the NSF Geophysics Program.