Regional patterns of anthropogenic warming in East Antarctica

Global warming driven by human activities has a greater impact on polar regions than the global average, a phenomenon known as polar amplification (Casado et al. 2023; England et al. 2021). Strong warming has been directly observed in West Antarctica and in the Antarctic Peninsula. Yet, evidences in the East Antarctic Plateau region remains anecdotal (Clem et al. 2020), even though this region, characterised by thicker ice sheet, represents the largest potential source of global sea-level rise and plays a key role in understanding climatic feedbacks essential for future projections. The ERA5 reanalysis data suggest a warming trend over the recent 30-year at multiple sites on the plateau. However, the natural variability at decadal scale observed on the plateau complicates the isolation of a multi-decadal forced warming trend. In addition, the reliability of this trend estimation is constrained by the time series’ limited coverage, starting in 1940 and exhibiting a discontinuity around 1980, coinciding with the assimilation of satellite data. To address this, ice core records offer a valuable long-term climatic archive. Water stable isotopes (δ¹⁸O and δD) from ice cores, with their well-establish relationship to local temperature – commonly referred to as “paleo-thermometer” – are crucial for reconstructing past temperature variations.

In this study, we present isotopic records from four firn cores collected at the Paleo site, located in the interior of the East Antarctic Plateau. The 18-meter-deep cores were drilled during the austral summer 2019-2020 as part of the East Antarctic International Ice Sheet Traverse (EAIIST) project. By stacking the four ice cores, we enhance the signal-to-noise ratio, resulting in a record that effectively captures climate information at a scale better than interdecadal. These results are first compared to reanalysis data to evaluate their ability to represent the climatic conditions in this remote area on the plateau, which lacks direct observations. Subsequently, the extended time series is presented, offering valuable insights into climatic variability over the past ~350 years and potentially improving the isolation and quantification of the anthropogenic warming trend in this region.