In December 2004 a team of European scientists extracted the first ice core sample from the Antarctic icecap. The sample was 3.2 km deep and contained an archive of information about the climate of the previous 800,000 years. It was the famous EPICA campaign, which allowed scientists to obtain the longest map of temperature fluctuations on Earth during glacial and interglacial periods.
Seventeen years later, those ice core samples continue to contribute to scientific discovery, thanks to sophisticated analyses that are also carried out at Ca’ Foscari. The most recent achievement of an international research team that specialises in the palaeoclimatology of polar regions was published in Nature Geoscience.
The article describes a new curve in the temperature of the past 800,000 years, with a slight update made possible thanks to the new data that has emerged thanks to research on oxygen and hydrogen isotopes.
The research team has analysed approximately 5,800 samples, multiple times. Oxygen analyses were carried out in Ca’ Foscari’s isotope geochemistry library and at the University of Parma. Hydrogen analyses on the same ice core samples were conducted at the Laboratoire des Sciences du Climat et de l’Environnement (LSCE) in France.
These new analyses offer valuable information on the hydrogen isotope, deuterium. In particular, scientists were able to build deuterium excess records compared with recent water vapour conditions.
“The oxygen and hydrogen isotopes that make a water molecule allow us to reconstruct past climate conditions in the areas where Antarctic precipitations form — in our case, in the Indian sector of the Southern Ocean — as well as the ones at Dome C, the Antarctic site where the EPICA ice core was extracted” says Barbara Stenni, professor of geochemistry at Ca’ Foscari and co-author of the study. “These two reconstructions add to our understanding of the past climate of a region of the Southern Ocean which is still largely unexplored, but that nevertheless plays a crucial role in the global carbon cycle and in the absorption of human-related carbon emissions, as highlighted in recent IPCC reports.”
Deuterium excess allows scientists to reconstruct the temperatures of the oceanic area in which the masses of water vapour which subsequently cause precipitation are formed, as well as the temperature in the site where the ice core sample was extracted — i.e., in the Antarctic inland.
“During the past interglacial periods, maximum temperature in the evaporative moisture source regions and at the Antarctic site were not always synchronous,” says Ilaria Crotti, PhD candidate in Science and Management of Climate Change at Ca’ Foscari and Paris-Saclay University and co-author of the study. “The cause of this time discrepancy might be the latitudinal variation of the moisture source regions which reached Antarctica during interglacial periods.”
“This publication,” says Stenni “attests that the record of deuterium excess of the EPICA Dome C ice core sample is not only the longest in terms of time, but it is also the one that allows us to most accurately reconstruct past climate.”
As researchers continue to study the EPICA ice core sample, the Beyond EPICA Oldest Ice challenge continues. The campaign aims to extract a new ice core that can reveal information about the climate of the past 1.5 million years.
The on-site team is working on ice core extraction at the Little Dome C site, an area of 10 km2 that is 40 km southeast of the Italian-French Concordia Station, on the eastern Antarctic plateau. The team’s aim is to gain access to the deep ice of this invaluable archive.
The Beyond EPICA campaign is coordinated by CNR-ISP (the Institute of Polar Sciences of the Italian National Research Council), under the direction of professor Carlo Barbante. Ca’ Foscari is training new ice and climate scientists thanks to the PhD in Polar Sciences and a European PhD project, the Innovative Training Network DEEPICE, which is strongly linked to the Beyond EPICA campaign.