Joint Inversion for Surface Accumulation and Geothermal Flux from
Ice-Penetrating Radar Observations at Dome A, East Antarctica. Part I:
Model Description, Data Constraints, and Inversion Results
Abstract
Ice-penetrating radar data contain a wealth of information about the bed
and internal structure of the ice sheet. While these data have long been
used to diagnose the presence of basal water or infer attenuation rates,
they have rarely been used in a formal inverse model for the ice sheet
temperature structure. Here, we invert a coupled thermomechanical ice
sheet and basal hydrology model to infer both geothermal flux and
accumulation rate from multiple classes of radar observations in the
area around Dome A, East Antarctica. Our forward model solves for a
coupled steady state between the ice sheet flow field, temperature, and
basal hydrology, including melt, water transport, and freeze-on. We fit
radar observations of basal water, freeze-on, and internal layers, along
with a geothermal flux prior based on aeromagnetic observations (Martos
et al., 2017). We minimize the combined misfit function by first using
an evolutionary algorithm to find the approximate answer in parameter
space, and then optimizing the fit with localized perturbations. In
addition to inferring the spatial distribution of geothermal flux and
accumulation rate, we are also able to estimate the uncertainty and
skewness of their probability distributions, as well as quantify how our
result on each individual data constraint. Our results demonstrate a new
method for combining multiple glaciological constraints into a single
inverse model of the ice sheet, and give us a more rigorous picture of
the information content provided by each dataset. In a companion paper
we analyze and interpret the best-fit model.