06/12/2024 – PhD defense of Romilly Harris Stuart directed by Amaëlle Landais and Patricia Martinerie
Gas records from ice cores provide critical insights into atmospheric composition changes over the past 800,000 years, but their interpretation remains challenging. Gas composition is altered in the firn before bubble formation, requiring a deeper understanding of local processes. This thesis explores two main areas to reduce uncertainties in these records.
The first area examines δ15N and δ40Ar isotopes to reconstruct firn column characteristics, such as height and thermal gradients. New measurements at Dome C reveal a seasonal bias in isotopic ratios, affecting the interpretation of ice core data, particularly at EPICA Dome C.
The second area investigates δO2/N2 as a tool for orbital dating. While this method is crucial for projects like Beyond EPICA, factors such as temperature and accumulation rates influence this parameter in addition to insolation. Observations from contrasting sites, D47 and Little Dome C, confirm that local conditions play a key role, supporting further research to refine climate chronologies.
This work highlights fundamental mechanisms of gas dynamics in the firn, paving the way for more accurate reconstructions of past atmospheric conditions.
