Scientists have discovered an ice core in the Mont Blanc massif (Dôme du Goûter) that dates back to the last Ice Age — the oldest known glacier ice core from the Alps to date. The 40-meter-long core provides detailed information about the chemical composition of the atmosphere and the climate over the past 12,000 years.
Thanks to radiocarbon dating, it was found that aerosols such as desert dust, sea salt, volcanic ash, and human pollutants have been preserved in this ice core since the last Ice Age. This makes it a unique source for reconstructing past environmental conditions and climate changes in Europe.
The ice remained well-preserved despite the warming of the 20th century, as it was stored at an altitude of over 4,000 meters. Previous drillings in the immediate vicinity contained only a few hundred years old ice — a surprising result for the researchers.
The analysis reveals, among other things:
- A temperature drop of around 3°C during the last Ice Age compared to today’s warm period (Holocene).
- Strong fluctuations in dust, salt, and phosphorus deposits, indicating changes in vegetation, wind patterns, and human activities.
- Around eight times more dust during the Ice Age, exceeding previous climate models and pointing to increased Saharan dust.
In the future, the researchers aim to further analyze the data to better understand the connections between environmental changes and historical human activities — such as mining or industrialization. The findings are also expected to help improve climate models for both the past and the future.
Challenging Measurements at CEZA
The age of the ice core was determined using a combination of different dating methods. On the one hand, argon gas (specifically 39Ar) trapped in the ice bubbles was dated using a newly developed method based on laser cooling (Atom Trap Trace Analysis). On the other hand, the age of tiny amounts of organic material was determined via radiocarbon dating and correlated with historically known lead pollution (e.g., from Roman times).
CEZA, in collaboration with its international partners, is one of the few laboratories equipped with the technology and expertise required to conduct these investigations. In particular, CEZA possesses state-of-the-art equipment for extracting minute amounts of organic material from ice cores, which is essential for dating the highly rare argon isotope using radiocarbon accelerators. The specific demands of this type of research are extremely challenging, which is why we are pleased to have contributed our expertise to this study.