Joint Inversion for Surface Accumulation and Geothermal Flux from
Ice-Penetrating Radar Observations at Dome A, East Antarctica. Part II:
Ice Sheet State and Geophysical Analysis
Abstract
Dome A is the peak of the East Antarctic Ice Sheet (EAIS), underlain by
the rugged Gamburtsev Subglacial Mountains (GSM). The rugged basal
topography produces a complex hydrological system featuring basal melt,
water transport and storage, and freeze-on. In a companion paper, we
used an inverse model to infer the spatial distributions of geothermal
flux and accumulation rate that best fit a vareity of observational
constraints. Here, we present and analyze the best-fit state of the ice
sheet in detail. Our model agrees well with the observed water bodies
and freeze-on structures, while also predicting a significant amount of
unobserved water and suggesting a change in stratigraphic interpretation
that reduces the volume of the freeze-on units. We predict that a weak
Raymond effect underneath the ice divide has been mostly masked by the
high-amplitude variability in the layers produced by draping over
subglacial topography. Our model stratigraphy agrees well with
observations, and we predict- assuming that the ice divide has been
stable over time- that there will be two distinct patches of ice older
than 1 Ma suitable for ice coring underneath the divide. Finally, our
geothermal flux estimate is substantially higher than previous estimates
for this region. Correcting for the bias induced by unresolved narrow
valleys still leaves our result in the high end of past estimates, with
substantial local anomalies that are hotter still. Fundamentally, the
observational evidence of a complex basal hydrological system is
inconsistent with a simple picture of a uniformly cold East Antarctic
craton.