Abstract
Ice rises situated around the perimeter of Antarctica buttress ice flow
and contain information about the past climate and changes in flow
regime. Moreover, ice rises contain convergent and divergent flow
regimes, and both floating and grounded ice over comparatively small
spatial scales, meaning they are ideal locations to study ice-flow
dynamics. Here, we introduce a new modelling framework that permits the
comparison between modelled and observed stratigraphy. A
thermo-mechanically coupled, isotropic, full Stokes ice flow model with
a dynamic grounding line is used (Elmer/Ice). The result is the
simulated age-depth field of a three-dimensional, steady-state ice rise
which is dynamically coupled to the surrounding ice shelf. Applying the
model to Derwael Ice Rise, results show a good match between observed
and modelled stratigraphy over most of the ice rise and predict
approximately $8000$ year old ice at a depth of $95$
\%. Differences in the prediction of age between
simulations using Glen’s flow law exponents of $n=3$ and $n=4$ are
generally small ($<5$ \% over most areas).
In the ice rise shear zones, large differences in shear strain rates in
the velocity direction are found between the $n=3$ and the $n=4$
simulations. Our simulations indicate that a Glen’s flow law exponent of
$n=4$ may be better suited when modelling ice rises due to a
steady-state geometry which is closer to the observed geometry. Our
three-dimensional modelling framework can easily be transferred to other
ice rises and has relevance for researchers interested in ice core
dating and understanding ice-flow re-organisation.