| 31 Aug 2026
Stability and basal thermal conditions of East Antarctic divide regions during the last glacial cycle
Abstract. Ice domes and divides of the East Antarctic Ice Sheet (EAIS) are primary targets for deep ice core drilling because of their presumed stability and cold basal conditions. These characteristics are essential for preserving undisturbed and continuous stratigraphy, which is critical for interpreting climate proxies from ice core records. Here, we conduct an ensemble of transient thermomechanical simulations of the Antarctic ice sheet over the last glacial cycle to evaluate the stability of six regions identified as potential candidates for deep ice core drilling. The evolution of the basal thermal regime and its response to climate forcing are also assessed. Results indicate that domes and divides of the EAIS remained relatively stable throughout the last glacial cycle, with displacements occurring primarily within 20 to 40 km of their initial positions and elevation changes ranging from 50 to 150 m between glacial and interglacial periods. Dome migration is primarily driven by changes in local accumulation patterns and large-scale grounding-line migration. Basal temperatures and melt rates exhibit a lagged response to climate forcing of approximately 17 to 35 ka, suggesting that present-day basal thermal conditions still reflect the cooler climate of the Last Glacial Maximum. Finally, we find favourable thermodynamic conditions for the preservation of ancient ice at the base in all but one of the studied regions, and use this information to identify and map potential drilling sites across Antarctica. However, estimates of the thermal state are highly sensitive to geothermal heat flow and even minor inaccuracies in modelled ice thickness, indicating that local constraints are required to better decipher conditions at the ice-bedrock interface.
Summary
This manuscript studies the problem of domes migration, elevation changes and basal thermal state in the East Antarctic ice sheet. This is of primary importance for the definition of potential old ice drilliing sites or for the interpretation of already drilled ice cores such EDC, DF, etc. The tool used is the Kori-ULB model, which is an hybrid SIA-SSA ice sheet model, used at 25 km resolution (although some limited 8 km simulations are used for comparison). The different unknowns of the modeling, such as the GHF or climate forcings, are investigated using an ensemble simulations with a scoring that measures the agreement with present-day or past ice sheet observations.
It is found that domes stayed relatively stable in the past, with movements primarily of 20-40 km from their initial position. Moreover, elevation changes range from 50 to 150 m, in agreement with previous studies such as Ritz et al. (2001). It is also found that basal temperatures and basal melting lag the climate forcing by 17 to 35 kyr. Finally, a updated map of potential drilling sites is given.
This subject is of primary importance for ice core scientists. The study is generally well crafted, the manuscript reads well and the figures are rich (sometimes maybe even too rich!) and well designed. I recommend the publication of the manuscript but I have some minor comments that I hope the authors will find useful.
Important comments:
- the maps of the potential drilling sites are interesting, but they rely heavily on parameters such as the GHF forcing which is poorly known. These maps therefore provide a general overview but of course smaller scale studies are needed, which is clearly stated in the manuscript, so this is ok.
- one limitation is that the study focuses on domes. These are not the only interesting targets for old ice sites. There are interesting locations all along the ridge swith minimal horizontal displacements. I do not ask to redo the study, but maybe this limitation should be stated somewhere.
- regarding the climate forcing, Parrenin, Fujita et al. (JG, 2016) found, from the volcanic synchronisation between EDC and DF, that the SMB_DF/SMB_EDC ratio was strongly varying during the last climatic cycle. Hence, the accumulation pattern is not stable in the past. I am wondering how the precipitation forcing used in the present study agrees with this ice core observation. I think this comparison should be made somewhere in the manuscript because it is an important point.
- Basal melting is quantified at Dome C (see, e.g., Figure 5). We actually have fairly accurate estimates of basal melting at EDC based on the ice core age scale. Parrenin et al. (CP, 2007, "1D ice flow modeling...") found 0.66 ice-mm/yr while the more recent Jeaumot et al. (TC, submitted) study found 0.68 ice-mm/yr. It would be good to cite at least one of these studies for comparison.
- Parrenin et al. (2017) and Chung et al. (PAGES, 2023) found elevated isochrones around North Patch (also called Dome C North by the Australian MYIC project) and made the hypothesis that it could be diluted Raymand arches due to the more Northern dome position during the past. Your reconstruction of the Dome C position during the past seems to confirm this hypothesis. It is an interesting outcome of this study that could be stated.
- p. 19, it is explained that the thermal equation is not solved in the bedrock, neglecting the propagation of thermal waves underneath the ice. I am wondering if this would be a big work to implement this. I am not asking to do it for the current study because this would imply redoing all the simulations. But I do hope this will be implemented for a future study.
More technical points:
- p. 2, l. 46: regarding flow band modeling, note that the Chung et al. (2025) study uses the recently published forward model of Parrenin et al. (2025).
- p. 8, l. 219: "by widespread retreat during _the last_ deglaciation..."
- p. 11, Figure 2: note that Ridge B is now called Dome B (because there is actually a dome here!) and the previous Dome B (which was actually on a ridge!) is now called Old Dome B.
- p. 11, Figure 2 (again): the dome maps with the 3 colors superimposed are really difficult to read.