Geoid and topographic swells over temperature‐dependent thermal plumes in spherical‐axisymmetric geometry

Abstract

Geoid and topographic profiles over constant‐viscosity thermal plumes in spherical‐axisymmetric geometry at moderate Rayleigh numbers are compared with results from previous studies in other geometries. Plumes in spherical‐axisymmetric models produce larger geoid anomalies than plumes in either Cartesian or cylindrical‐axisymmetric geometries; however, the topographic anomalies over the plumes are smaller than the corresponding anomalies in a cylindrical‐axisymmetric geometry but larger than those in a Cartesian geometry. For plumes in a temperature‐dependent viscosity fluid, the geoid and topographic profiles are reduced by a factor of two when compared to a constant viscosity fluid with the same background viscosity profile. In this case, the radially‐averaged temperature profile around the plume creates a low‐viscosity ‘layer’ beneath the lithosphere.