Researchers from Heidelberg and Mainz precisely date devastating volcanic eruption – It did not cause the sudden-onset cold period 13,000 years ago

The synchronization of data from two natural climate archives – a speleothem from the Herbstlabyrinth Cave in Hesse (Germany) and ice cores from Greenland – offers new insights into the chronology of abrupt climate changes in Central Europe. According to the analysis, the devastating eruption of the Laacher See volcano in what is now Rhineland-Palatinate occurred earlier than previously assumed and hence could not have triggered the sudden-onset cold period of approximately 13,000 years ago. Research by geoscientists from Heidelberg University and Mainz University has confirmed this finding. Along with precisely dating the volcanic eruption, the research team also estimated its climatic impact.

The last eruption of the Laacher See volcano is considered to be one of the most devastating events of the past two million years, with effects that reached as far as northern Italy, Scandinavia, and Russia. Exactly when the eruption occurred and whether it was directly connected to a sudden cold period termed the Younger Dryas has long been a topic of scientific debate. A new temporal classification was undertaken in 2021 using radiocarbon dating of tree trunks. The results suggest that the volcanic eruption must have taken place 130 years earlier than previously assumed. The research team from Heidelberg and Mainz were able to confirm this new date using a speleothem from the Herbstlabyrinth Cave in Breitscheid, Hesse.

Because a volcanic eruption is associated with high sulfur emissions, this volcanic signal would also have to be present in the speleothem. “The high-resolution sulfur and oxygen isotope measurements taken by the ion probe in Heidelberg were pivotal in making this determination,” explains Prof. Dr Axel Schmitt, a researcher at Curtin University in Perth (Australia) and honorary professor at Heidelberg University. With the ion probe, it is possible to measure various isotope ratios and trace elements at micrometer level.

The geochemical data could be synchronized with a heretofore unattributed sulfate peak in Greenland ice cores. The statistical analyses were performed under the direction of Prof. Dr Denis Scholz, an expert in age determination of historical climate fluctuations at the Institute for Geosciences at Mainz University. “This synchronization represents a breakthrough for the dating of climate and environmental archives in that, until now, no absolutely dated time marker before the Younger Dryas cooling was known,” states Dr Sophie Warken, who conducts research into the climatic changes of past millennia at the Institutes of Earth Sciences and Environmental Physics at Heidelberg University.

According to Dr Warken, the new age determination shows that the eruption took place about 150 years prior to the Younger Dryas cold period. “This therefore excludes a causal relationship between the volcanic eruption and the abrupt change in climate,” explains the Heidelberg researcher and first author of the study. Identifying the sulphate spikes in the Greenland ice cores allowed the research team to draw conclusions as to the climatic events at the beginning of the Younger Dryas. Until now, it was unknown whether the climatic changes associated with this approximately 1,000-year cold period arose simultaneously in the North Atlantic region and Europe or whether it spread from Greenland to Central Europe over several decades or even centuries. “Our results lead to the conclusion that a significant drop in temperature occurred simultaneously, indicating that the Central European and Arctic climates were directly linked,” explains Dr Warken.

The geoscientist adds that the research results open up new perspectives for understanding complex climatic relationships of the past. The results also offer a solid basis for more precise predictions of future climate developments, as Sophie Warken emphasizes. The research was part of the collaborative “Terrestrial Magmatic Systems” (TeMaS) project carried out jointly by Heidelberg University, Goethe University Frankfurt (Main) and Mainz University, with funding by the state of Rhineland-Palatine, among others. Additional funding was provided by the German Research Foundation and the European Research Council. The results of the research were published in the journal “Science Advances”.