Abstract. Water stable isotopes (δ18O and δD) from ice cores are widely used to reconstruct past temperature variations through their well-established relationship with local air temperature, commonly referred to as “isotopic paleothermometer”. However, depositional and post-depositional effects lead to large uncertainties in the use this proxy in Antarctica. The magnitude of these uncertainties strongly depends on site location, with larger impacts in low-accumulation regions of East Antarctic Plateau. Depositional effects include origin of moisture, which exhibits asymmetries shaped by the continent's geographical and topographical features, as well as precipitation intermittency, which introduces aliasing in the archived signal. Post-depositional processes, such as sublimation and firn-atmosphere exchange, further alter the isotopic composition of snow before its transformation into ice, thereby modifying the correlation between δ18O and temperature. Here, we present new water isotope measurements from surface snow collected during the East Antarctic International Ice Sheet Traverse (EAIIST), across a remote region of the East Antarctic Plateau. The traverse – crossing a transitional zone between predominately Indian and Pacific moisture sources – provides unique insights into the key role of air mass origin in shaping the isotopic composition of snow. Comparison with LMDZ6iso simulations indicates that the model successfully captures the spatial variability of δ18O-temperature relationship between different basins, with statistically significant correlations (p < 0.05) when the analysis is extended to the Antarctic dataset. This agreement further suggests the model's ability to predict the temporal slope required for calibrating isotopic ice-core records used for temperature reconstructions, even in regions influenced by multiple moisture sources. Temporal slopes based on monthly precipitation values range from 0.4 ‰ °C−1 to 0.5 ‰ °C−1 for the EAIIST drilling sites. Finally, we quantify the impact of sublimation on isotopic composition of surface snow. Including sublimation in the modelling of surface snow reduces the discrepancy between observed and modelled values, compared to simulations accounting precipitation, from 1.9 ‰ to 1.3 ‰ for δ18O and from 6.6 ‰ to 2.9 ‰ for d-excess. These results highlighting the key role of this post-depositional process on the Antarctic Plateau.
Petteni et al. (Tue,) studied this question.