Spatial variability of climate change signature in Antarctica revealed by ice cores

Polar amplification leads to a larger warming in polar regions compared to the global average [1]. While an overall warming is observed in West Antarctica and Antarctic Peninsula, the temperature signal in East Antarctica remains uncertain [2]. In Antarctica, atmospheric weather stations are sparse and mainly located near the coast. While state-of-the-art atmospheric reanalysis are available from 1940, the historical climate variability at the Southern Hemisphere high latitudes are mostly based on the teleconnections with low-latitude regions, as almost no high-latitude observations are available before the satellite era (i.e., 1979). This therefore introduces a discontinuity in around 1980 associated with the incorporation of satellite observations in reanalysis.

To address these limitations, ice core records provide a valuable long-term archive of past climatic conditions through the well-established relationship between water isotopes (δ¹⁸O and δ²H) and local temperature. This relationship – commonly referred to as “paleothermometer” – is widely used for reconstructing past temperature variations.

Within the framework of the East Antarctic International Ice Sheet Traverse (EAIIST, 2019–2020), a set of shallow ice cores was recovered between Concordia Station and the South Pole. Here, we present isotope records from firn cores collected at Paleo (79°38′47″S; 126°08′15″E) that we combine to the water isotopic record obtained on the 85 m firn core at Little Dome C within the Ice CORe Dating project (ICORDA, 2019–2025, see poster by Minster, Samin et al.) providing climatic information at decadal resolution in this region of the interior of the East Antarctic Plateau. By comparing these records with atmospheric reanalyses and temperature reconstructions, we observe a strong spatial contrast between the interior and the coastal region over the past few decades. This dipole pattern is characterized by a surface warming in the interior of the continent and surface cooling along the coast of Adélie Land. To isolate the local signal of anthropogenic warming, we account for the influence of large-scale atmospheric dynamics, such as the Southern Annular Mode. Furthermore, ice core evidences, combined with climate model outputs, provide a context of the current warming over the last two centuries. This permits to assess whether climate models can correctly reproduce the spatial contrast between the interior and the coastal region in terms of surface temperature multi-decadal variability, essential for reliable future projections.

Italian partners received funding from the PNRA through “EAIIST” (PNRA16_00049-B) and “EAIIST-phase2” (PNRA19_00093) projects.

 

[1] Casado M., et al. (2023), Nat. Clim. Change 13. https://doi.org/10.1038/s41558-023-01791-5

[2] Clem KR., et al. (2020), Nat. Clim. Change 10. https://doi.org/10.1038/s41558-020-0815-z