Exploring the impact of anisotropic viscosity on the interplay between ice and mantle dynamics

Introduction

The loss of ice mass from polar and high-elevation regions is a significant contributor to global sea level rise and affects climate and biosphere changes. Due to its importance, a better understanding of the dynamics of ice sheets is considered a priority for scientific advancement by the Intergovernmental Panel on Climate Change.

Project Goals

DYNAMICE aims to enhance our understanding of ice sheet dynamics and ice mass loss by investigating the coupled flow dynamics of polar ice and the deforming mantle below, with a focus on the role of anisotropic viscosity for determining deformation rates.

Anisotropic Crystals

Ice and olivine, the main building crystals of ice sheets and the mantle, respectively, are two of the most anisotropic crystals on Earth. This means that individual crystals have preferred slip systems, along which it is easier to deform them.

Variability in Viscosity

Depending on the deformation direction with respect to the mean orientation of crystals in both ice and mantle rock, the bulk viscosity can vary by a few orders of magnitude. Such variations in viscosity can greatly affect:

1. The flow of ice from ice divides to the sea.
2. The mantle’s viscous response to the unloading of deglaciated ice.

As a result, spatial differences in ice texture can locally enhance or slow down ice flow, leading to some areas with faster than average ice loss and others where ice is stabilized.

Interaction Between Ice and Mantle

Moreover, in locations where ice loss is fast, and where mantle textures are favorably oriented, the viscous response of the mantle can be fast enough to uplift the ice and slow further ice loss, potentially stabilizing the ice sheet. Hence, anisotropic viscosity might play a critical role in the interplay between ice and mantle dynamics.

Methodology

In DYNAMICE, I will implement a framework to infer anisotropic viscosity from both ice and mantle textures in a numerical flow model. This will open new avenues for understanding solid earth and cryospheric dynamics, and their critical interactions that affect the future of Earth’s ice sheets.