Brice Van Liefferinge1, Frank Pattyn1, Marie Cavitte2, Nanna Karlsson3,4, Duncan Young2, Johannes Sutter4,5, Olaf Eisen4,6
1Université Libre De Bruxelles, Brussels, Belgium, 2University of Texas at Austin, Austin, USA, 3Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark, 4Alfred Wegener Institute, Bremerhaven, Germany, 5University of Bern, Bern, Switzerland, 6University of Bremen, , Germany
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 such 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 1D 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 (Shapiro and Ritzwoller, 2004; Fox-Maule et al., 2005; Puruker, 2013; An et al., 2015). 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 (Karlson et al., in prep; Young et al., 2017), 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.