EEPS Colloquium: Meghana Ranganathan

The role of rheology in governing ice sheet dynamics 

Abstract:
Mass loss from the Antarctic Ice Sheet largely occurs due to the viscous ice flow of glaciers from the interior of ice sheets towards the ocean. The rate of flow to the ocean is governed by ice viscosity, which in turn depends on microphysical and macrophysical processes. While increasing amounts of evidence suggest that ice viscosity varies significantly in space and time in the Antarctic Ice Sheet, current ice sheet models treat ice viscosity as a fixed, empirically-derived value. In this talk, I first explore the implications of neglecting this complexity in ice viscosity. I demonstrate using simple, theoretical models that ice rheology may play a significant role in governing transient ice sheet dynamics and may alter the stability portrait of marine ice sheets. I further show that in the current configuration of the Antarctic Ice Sheet, rheology likely plays a substantial role in governing the force balance, thereby setting the flow speed. I then present a bulk parameterization method for incorporating ice crystal-scale processes into a model for ice viscosity and demonstrate that this provides a way of parameterizing the effect of varying flow conditions on future ice sheet behavior. Finally, I then show first steps towards a formal multi-scale ice viscosity model implemented using a neural emulator of an ice microphysics model, which provides a path forward for formally representing crystal-scale variability in ice viscosity in large-scale ice sheet models.

Host: Dougal Hansen

EEPS Colloquia are made possible by the William C. Ferguson Fund