To resolve the mechanisms behind the major climate
reorganisation, which occurred between 0.9 and 1.2 Ma, the recovery of a suitable 1.5
million-year-old ice core is fundamental. The quest for an Oldest Ice
core requires a number of key boundary conditions, of which the poorly known
basal geothermal heat flux (GHF) is lacking. We use a transient
thermodynamical 1-D vertical model that solves for the rate of change of
temperature in the vertical, with surface temperature and modelled GHF as
boundary conditions. For each point on the ice sheet, the model is forced
with variations in atmospheric conditions over the last 2 Ma and modelled
ice-thickness variations. The process is repeated for a range of GHF values
to determine the value of GHF that marks the limit between frozen and melting
conditions over the whole ice sheet, taking into account 2 Ma of climate
history. These threshold values of GHF are statistically compared to existing
GHF data sets. The new probabilistic GHF fields obtained for the ice sheet
thus provide the missing boundary conditions in the search for Oldest Ice.
High spatial resolution radar data are examined locally in the Dome Fuji and
Dome C regions, as these represent the ice core community's primary drilling
sites. GHF, bedrock variability, ice thickness and other essential criteria
combined highlight a dozen major potential Oldest Ice sites in the vicinity
of Dome Fuji and Dome C, where GHF could allow for Oldest Ice.</p