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An ice core from Mont Blanc’s Dôme du Goûter contains a unique, intact archive of past climatic conditions. An international research team, including scientists from Heidelberg University, has succeeded in comprehensively dating the core collected in 1999. For the first time, the team used radiocarbon dating combined with a quantum-physical process to date the younger layers of ice. The analyses show that the approximately 40-meter-long core also contains glacial ice from the end of the last Ice Age, and with it climate and environmental data from the last 12,000 years.
Press Release
Heidelberg, 14 October 2025
Ice Core from Mont Blanc Massif Holds Intact Climate Archive from the Last 12,000 Years
Glacial ice from the French Alps provides information on climatic changes
An ice core from Mont Blanc’s Dôme du Goûter contains a unique, intact archive of past climatic conditions. An international research team, including scientists from Heidelberg University, has succeeded in comprehensively dating the core collected in 1999. For the first time, the team used radiocarbon dating combined with a quantum-physical process to date the younger layers of ice. The analyses show that the approximately 40-meter-long core also contains glacial ice from the end of the last Ice Age, and with it climate and environmental data from the last 12,000 years. It is the first climate record from ice in the European Alps that reaches so far back into the past.
Glacial ice as well as the polar ice sheets form year after year from deposited snow and hold a variety of information on past environmental conditions. While the climate archive of the polar ice cores extends up to 800,000 years in the past, Alpine glacial ice is usually no older than several thousand years, explains Prof. Dr Werner Aeschbach, a researcher at the Institute of Environmental Physics of Heidelberg University. He reports that the ice core from the French Alps currently under study offers a first uninterrupted chronology from Alpine ice covering the entire Holocene and even the end of the preceding glacial period. The stable isotopes of the water as well as the ice-bound dust particles and aerosols – chemical compounds from natural and human sources transported through the air – provide the information on past climatic conditions.
For the first time researchers used a combination of two methods based on counting radioactive isotopes to comprehensively date the core. Along with the established C-14 method for ice layers older than 1,000 years, they used the quantum-physical method known as Atom Trap Trace Analysis (ATTA) for younger layers of ice. ATTA allows for the detection of the extremely rare Argon-39 isotope. “Only by combining the two methods could the information stored in the ice be reliably placed chronologically and interpreted,” stresses Prof. Aeschbach, who together with Prof. Dr Markus Oberthaler of Heidelberg University’s Kirchhoff Institute for Physics developed ATTA for Ar-39.
The analyses of water isotopes show that the temperature difference between the late last Ice Age and the current Holocene warm period is three degrees Celsius. These findings refer to summer temperatures, because winter snow at Dôme du Goûter is largely lost due to wind erosion. The phosphorous concentrations in the ice, indicative of changes in vegetation, point to the spread of forests facilitated by the warmer climate after the end of the last Ice Age. Unlike the polar ice sheets, the Alps are located near human habitats, and data from the ice core therefore provide insights into the development of modern societies in the late Holocene. For example, the data show the deforestation resulting from land use and industrialization.
The sea salt and dust concentrations deposited in the ice are also of interest to the researchers. These aerosols can absorb and scatter sunlight – and hence significantly influence the regional climate. The analyses reveal that the sea salt content in the ice decreased after the last Ice Age, a sign of slackening winds offshore of Western Europe. In evaluating dust concentrations, the researchers drew different conclusions than from earlier climate models. These concentrations were not only twice as high during the Ice Age but eight times higher than in the Holocene. One reason could be the increased plumes of dust from the Sahara, which remain the main source of dust in Europe today.
Researchers from Mannheim and Tübingen as well as Grenoble (France) and Reno (USA) contributed to the work. The European Community funded the drilling of the ice core from the Dôme du Goûter by researchers from Grenoble in 1999. The U.S. National Science Foundation (NSF) and the German Research Foundation (DFG) financed the recent research work. The research results were published in the journal “PNAS Nexus”.
Contact:
Heidelberg University
Communications and Marketing
Press Office, phone +49 6221 54-2311
presse@rektorat.uni-heidelberg.de
Prof. Dr Werner Aeschbach
Institute of Environmental Physics
Phone +49 6221 54-6331
werner.aeschbach@uni-heidelberg.de
M. Legrand, J. R. McConnell, S. Preunkert, D. Wachs, N. J. Chellman, K. Rehfeld, G. Bergametti, S. M. Wensman, W. Aeschbach, M. K. Oberthaler, and R. Friedrich: Alpine ice core record of large changes in dust, sea-salt, and biogenic aerosol over Europe during deglaciation. PNAS Nexus (6 June 2025), https://doi.org/10.1093/pnasnexus/pgaf186
https://www.iup.uni-heidelberg.de/en/research/aquatic-systems/hydrospheric-trace... – Werner Aeschbach research group
https://www.kip.uni-heidelberg.de/oberthaler – Markus Oberthaler research group
The 1999 expedition team collecting the ice core from Dome du Goûter just below the summit region of ...
Copyright: © LGGE/OSUG, Bruno Jourdain
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The 1999 expedition team collecting the ice core from Dome du Goûter just below the summit region of ...
Copyright: © LGGE/OSUG, Bruno Jourdain
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