Ice Modeling Indicates Formation Mechanisms of Large-scale Folding in
Greenland's Ice Sheet
Abstract
Radio-echo sounding (RES) has shown that large-scale folds in the
englacial stratigraphy is ubiquitous in Greenland’s ice sheet. However,
there is no consensus yet on how these folds form. Here, we use the
full-Stokes code Underworld2 to simulate ice movements in
three-dimensional convergent flow, mainly investigating the effect of
ice anisotropy due to a crystallographic preferred orientation, vertical
viscosity and density contrasts in ice layers, and bedrock topography.
Our simulated folds show complex patterns and are classified into three
types: large-scale folds, small-scale folds and basal-shear folds. The
amplitudes of large-scale folds tend to be at their maximum in middle
ice layers and decrease towards the surface, in accordance with
observations in RES data. We conclude that bedrock topography
contributes to perturbations in ice layers, and that ice anisotropy
amplifies these into large-scale folds, while vertical viscosity
contrasts in ice layers are insufficient for large-scale fold
amplification.