In January 2025 the drilling team of the Beyond EPICA project reached the depth of 2800 m hence providing an ice core covering the history of climate and atmosphere composition over at least the last 1.5 million years. The Beyond EPICA ice core is the only ice core able to provide a continuous record over such a long time period hence almost doubling the period covered by the EPICA Dome C ice core (800,000 years before present). Its analyses will reveal the dynamics of the succession of glacial – integlacial periods which characterize the climate of the Quaternary (last 2.6 million years) and help understanding the long lasting mystery of the mid pleistocene transition between 1.2 million years and 600,000 years before present when the periodicity of the glacial – interglacial cycles changed from a 40,000 years to a 100,000 years, without any modifications of the external forcing (variations of the seasonal and latitudinal energy received at the Earth surface from the sun and driven by orbital parameters, i.e. eccentricity, obliquity and precession).

The last 1.5 million years are also characterized by different amplitudes of the glacial – interglacial cycles as inferred from marine sediment records. This variability is also expected in the record of Antarctic temperature from the Beyond EPICA ice core. The classical way to reconstruct temperature variations from ice cores is through water isotopic measurements (d18O or dD of water). However, several caveats limit the reconstruction of Antarctic temperature variations from the water isotopic record. Indeed, the isotopic composition of snow is not only affected by local temperature when it snows but also by the processes occuring along the water mass trajectory from the evaporation to the precipitation site. Moreover, after snow has been deposited at the surface, the water isotopic composition can evolve under the influence of the sun and wind. For these reasons, alternative proxies for reconstructing the past temperature were proposed such as the isotopic composition of inert gases in the air bubbles (d15N of N2, d40Ar or Ar) which is directly influenced by the temperature gradient in the top 100 m of the ice sheet above the depth of air bubble formation.

This internship aims at combining several isotopic proxies (water isotopes and isotopes of inert gases in the air bubbles) in the Beyond EPICA ice core to produce the most accurate temperature reconstruction over the last 1.5 million years. The internship includes a part on data acquisition and interpretation using different models (model of moisture trajectory equipped with water isotopes ; model of snow densification with air transport) ; a part on data synthesis based on comparisons to series from other archives (sediment cores in the austral ocean) and a part on valorization (presentation to a conference, possibility of writing a scientific paper).

Reference :

EPICA community members, Eight glacial cycles from an Antarctic ice core. Nature, 2004, vol. 429, no 6992, p. 623-628.

Berends, C. J., Köhler, P., Lourens, L. J., & Van de Wal, R. S. W. (2021). On the cause of the mid‐Pleistocene transition.

Jouzel, J., Masson-Delmotte, V., Cattani, O., Dreyfus, G., Falourd, S., Hoffmann, G., … & Wolff, E. W. (2007). Orbital and millennial Antarctic climate variability over the past 800,000 years. science, 317(5839), 793-796

Landais, A., Dreyfus, G., Capron, E., Jouzel, J., Masson-Delmotte, V., Roche, D. M., … & Teste, G. (2013). Two-phase change in CO2, Antarctic temperature and global climate during Termination II. Nature geoscience, 6(12), 1062-1065.

Landais, A., Stenni, B., Masson-Delmotte, V., Jouzel, J., Cauquoin, A., Fourré, E., … & Grisart, A. (2021). Interglacial Antarctic–Southern Ocean climate decoupling due to moisture source area shifts. Nature Geoscience, 14(12), 918-923.