Promising Oldest Ice sites in East Antarctica based on thermodynamical modelling

Abstract

Abstract. 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.

Heat Flow in Southern Australia and Connections With East Antarctica

“…Four geophysically derived geothermal heat flux models for continental Antarctica, modified from Van Liefferinge et al (). The models of (a) Shapiro and Ritzwoller (), (b) Fox Maule et al (), (c) An et al (), and (d) Martos et al () are plotted using the same color scale, truncated at 30 and 80 mW/m 2 ; purple dashed line indicates the boundary of the Totten glacier catchment.…”

Modelling the Antarctic Ice Sheet across the mid-Pleistocene transition – implications for Oldest Ice

“…The climate snapshots are based on Pliocene (Stepanek and Lohmann, 2012), LIG (Pfeiffer and Lohmann, 2016), LGM and preindustrial orbital, atmospheric and topographic conditions. For each climate snapshot, anomaly fields with respect to the pre-industrial control run are calculated and added to a mean Antarctic climatology , derived from the regional climate model RACMO (van Wessem et al, 2014), or the extrapolated World Ocean Atlas 2009 (Locarnini et al, 2010) to provide the climate forcing for the individual climate epoch. The intermediate climate states between the snapshots are calculated by interpolating the anomaly fields with a climate index approach, utilising either of two climate indices derived from the Dome C deuterium record from Jouzel et al (2007) which is expanded to the last 2 Myr by a transfer function (Michel et al, 2016) using the benthic oxygen isotope stack from Lisiecki and Raymo (2005) (LR04) or the global surface temperature data set from Snyder (2016).…”

Age stratigraphy in the East Antarctic Ice Sheet inferred from radio-echo sounding horizons

“…The normalized depths show smooth lateral variations and a broad pattern of deepening IRHs (smaller ice faction older than 161 ka) towards the ice-sheet margins and towards the South Pole. Veres et al, 2013). The age uncertainties are separated in contributions from depth uncertainties a( d) and age-scale uncertainties a(core).…”

“…In the DML region we use z f = 13 m, derived from the measurements of the complex permittivity of five ice cores, down to depths of 100-150 m . We use the DFO-2006(Kawamura et al, 2007 and Antarctic Ice Core Chronology 2012 (AICC2012, EDML) Veres et al, 2013) age scales to assign ages to the IRHs. We use the mean age from the DF and EDML age scales for the respective IRH.…”

“…We use the mean age from the DF and EDML age scales for the respective IRH. At Vostok, we use the same method of TWT-to-depth conversion, a firn correction of z f = 13 m (Cavitte et al, 2016) and the AICC2012(Vostok) age scale Veres et al, 2013). Uncertainties in IRH depths are a combination of the vertical accuracy of the radar system and the uncertainty in the TWT-to-depth conversion.…”