G012-0006
An Open-source 3D Glacial Isostatic Adjustment Modeling Code using ASPECT
Monday, 14 December 2020
Poster
Maaike F. M. Weerdesteijn1, Clinton P Conrad1, John Naliboff2 and Kate Selway3, (1)University of Oslo, Centre for Earth Evolution and Dynamics, Oslo, Norway, (2)University of California, Davis, Computational Infrastructure for Geodynamics (CIG), Earth and Planetary Sciences Department, Davis, CA, United States, (3)Macquarie University, Department of Earth and Environmental Sciences, Sydney, NSW, Australia
Abstract:
Models of Glacial Isostatic Adjustment (GIA) processes are useful because they help us understand landscape evolution in past and current glaciated regions. Such models are sensitive to ice and ocean loading as well as to Earth material properties, such as viscosity. Many current GIA models assume radially-symmetric (layered) viscosity structures, but viscosity may vary laterally and these variations can have large effects on GIA modeling outputs. Here we present the potential of using ASPECT, an open-source finite element mantle-convection code that can handle lateral viscosity variations, for GIA modeling applications. ASPECT has the advantage of adaptive mesh refinement, making it computationally efficient, especially for problems such as GIA with large variations in strain rates. Furthermore, ASPECT is open-source, as will be the GIA extension, making it a valuable future tool for the GIA community.
Our GIA extension is benchmarked using a similar case as in Martinec et al. (GJI, 2018), such that the performance of our GIA code can be compared to other GIA codes. In this case, a spherically symmetric, five-layer, incompressible, viscoelastic Earth model is used (Spada et al., GJI 2011). The surface load consists of a linearly increasing, then constant, spherical ice cap centered at the North pole. We coupled ASPECT to the sea level equation, and include a time varying ocean geometry. We also implement time-varying distributed surface loads and laterally-varying Earth structures. These capabilities allow for modeling of GIA for realistic ice load scenarios imposed above potentially complex earth structures. Here, we present a preliminary case study for Greenland, where we implement a low-viscosity band extending through central Greenland. Such a low-viscosity feature is possible as a consequence of Greenland having passed above the Iceland plume more than 50 Myr ago. Our new code allows us to evaluate the impact of this viscosity heterogeneity on modern-day GIA uplift rates in Greenland.
