Implementation and performance of adaptive mesh refinement in the Ice Sheet System Model (ISSM v4.14)

• Published in: Geoscientific Model Development Vol. 12; no. 1; pp. 215 - 232
• Main Authors: dos Santos, Thiago Dias, Morlighem, Mathieu, Seroussi, Helene, Devloo, Philippe Remy Bernard, Simoes, Jefferson Cardia
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 14-01-2019; Copernicus Publications
• Subjects: Accuracy; Adaptive systems; Analysis; Arctic research; Bedrock; Benchmarks; Climate change; Climate models; Computational efficiency; Computer applications; Computer simulation; Computing time; Control stability; Dynamics; Errors; Evolution; Finite element method; Glaciation; Glaciers; Grid refinement (mathematics); Ice; Ice sheet dynamics; Ice sheet models; Ice sheets; Mathematical models; Modelling; Nonlinear programming; Resolution
• ISSN: 1991-9603; 1991-959X; 1991-962X; 1991-9603; 1991-962X
• DOI: 10.5194/gmd-12-215-2019

Accurate projections of the evolution of ice sheets in a changing climate
require a fine mesh/grid resolution in ice sheet models to correctly capture
fundamental physical processes, such as the evolution of the grounding line,
the region where grounded ice starts to float. The evolution of the grounding
line indeed plays a major role in ice sheet dynamics, as it is a fundamental
control on marine ice sheet stability. Numerical modeling of a grounding line
requires significant computational resources since the accuracy of its
position depends on grid or mesh resolution. A technique that improves
accuracy with reduced computational cost is the adaptive mesh refinement
(AMR) approach. We present here the implementation of the AMR technique in
the finite element Ice Sheet System Model (ISSM) to simulate grounding line
dynamics under two different benchmarks: MISMIP3d and MISMIP+. We test
different refinement criteria: (a) distance around the grounding line, (b) a
posteriori error estimator, the Zienkiewicz–Zhu (ZZ) error estimator, and
(c) different combinations of (a) and (b). In both benchmarks, the ZZ error
estimator presents high values around the grounding line. In the MISMIP+ setup,
this estimator also presents high values in the grounded
part of the ice sheet, following the complex shape of the bedrock geometry.
The ZZ estimator helps guide the refinement procedure such that AMR
performance is improved. Our results show that computational time with AMR
depends on the required accuracy, but in all cases, it is significantly
shorter than for uniformly refined meshes. We conclude that AMR without an
associated error estimator should be avoided, especially for real glaciers
that have a complex bed geometry.