The Ice Shelf Lasagne: Understanding the Effects of Differing Rheologies on the Dynamics of an Ice Shelf

Abstract:

Most major ice shelf models use flow laws for ice which are derived from laboratory deformation experiments. However, these experiments are typically performed on ice with no physical or chemical impurities, and often use data from the secondary creep stage rather than the tertiary, meaning they do not properly represent the in situ behaviour of shelf ice. Most models also fail to incorporate zones of differing rheology within the shelf (for example, the presence of a marine ice layer at the base), and their effects on shelf dynamics.

We have performed compressional deformation experiments on samples of both marine and meteoric ice from the Amery Ice Shelf, Antarctica, collecting strain rate data during the experiments, and microstructural data before and after deformation. We compare these to equivalent data from pure laboratory ice, and examine differences in behaviour and the likely impacts of those differences on shelf dynamics. Natural ice samples display significantly larger variability in results than pure laboratory ice, but initial results indicate that tertiary creep strain rates for natural marine and meteoric ice are much more similar to those for laboratory ice than secondary creep strain rates from the same experiments.