Effects of Using the Consistent Boundary Flux Method on Dynamic Topography Estimates

Abstract

Dynamic topography is defined as the deflection of Earth's surface due to the convecting mantle. ASPECT (Advanced Solver for Planetary Evolution, Convection, and Tectonics) is a continually evolving, finite element code that uses modern numerical methods to investigate problems in mantle convection. With ASPECT version 2.0.0 a consistent boundary flux (CBF) algorithm, used to calculate radial stresses at the model boundaries, was implemented into the released version of ASPECT. It has been shown that the CBF algorithm improves the accuracy of dynamic topography calculations by approximately one order of magnitude. We aim to evaluate the influence of the CBF algorithm and explore the geophysical implications of these improved estimates of dynamic topography changes along the East Coast of the United States. We constrain our initial temperature conditions using the tomography models SAVANI, S40RTS and TX2008, and combine them with a corresponding radial viscosity profile (2 for TX2008) and two different boundary conditions for a total of eight experiments. We perform simulations with and without the CBF method, which takes place during post-processing and does not affect the velocity solution. Our dynamic topography calculations are spatially consistent in both approaches, but generally indicate an increase in magnitude using the CBF method (on average ∼15 and ∼76 per cent absolute change in present-day instantaneous and rate of change of dynamic topography, respectively). This enhanced accuracy in dynamic topography calculations can be used to better evaluate the effects of mantle convection on surface processes including vertical land motions, sea level changes, and sedimentation and erosion. We explore results along the US East Coast, where a Pliocene shoreline has been deformed by dynamic topography change. An increased accuracy in estimates of dynamic topography can improve Pleistocene and Pliocene sea level reconstructions, which allow for a better understanding of past sea level changes and ice sheet stability.