Speleothem Science News
September 2026
ERC Starting Grant for Sophie Warken
The European Research Council (ERC) has awarded Sophie Warken an ERC Starting Grant worth approximately 1.5 million euros! Over the next five years, the group will use the “PaleoTraCeS” project to reconstruct the activity of tropical cyclones in the past based on stalactites, in order to understand the underlying driving processes and derive a basis for modeling future extreme weather events.
June 2026
New publication in Ocean Science
The natural 234U/238U ratio of seawater contains information about the influx of freshwater from rivers and groundwater. In a recent publication in the journal Ocean Science, Sahra Greve and her co-authors demonstrated that the annual variation in the 234U/238U ratios of a tropical coral sampled off the coast of Cuba indicates significantly stronger freshwater influences on the Caribbean during the Little Ice Age. With the end of the Little Ice Age approximately 150 years ago, the variability of the 234U/238U isotope ratio in seawater has decreased and subsequently shows a qualitative correlation with local precipitation in Cuba. This research was part of Sahra Greve’s doctoral dissertation within the framework of a project on tropical climate variability funded by the DFG under SPP2299. (NF)
New Publication on the Heterogeneous Climate System of the Black Sea
During the last glacial period, abrupt climate changes originated in the far north and spread globally through interactions with the ocean and atmosphere. The region around the Black Sea is particularly interesting in this context. Not only does it connect several climate systems, but it is also especially sensitive to changes in atmospheric circulation. Gaining a better understanding of how this sensitive region has responded to external climate drivers in the past is important for future climate predictions. The new study by Yidong Li et al. shows that the region did not respond uniformly to changes, but behaved differently in the north than in the south. This finding is based on new stalagmite data from Crimea spanning the last 52,000 years. Several climate proxies were measured, and the trace elements were analyzed at the Institute of Environmental Physics in Heidelberg. A comparison with data from the Sofular Cave in Turkey revealed that the stalagmites in the north primarily recorded atmospheric changes and the continental climate. In the south, however, the climate archives were strongly influenced by the composition of the Black Sea, which varied due to freshwater and meltwater. Thanks to the high resolution of their data, the authors were also able to demonstrate that the region responded not only to transitions from warm to cold periods, but also to abrupt climate changes in the North Atlantic. The full article can be read in the journal Quaternary Science Reviews. (FL)
May 2026
EGU General Assembly 2026 in Vienna
This year, the Speleothems Group was well represented at the annual meeting of the European Geosciences Union (EGU) in Vienna. Dr. Sophie Warken served as convener of the session on climate reconstruction based on speleothems and karst archives, and she herself contributed a poster on climate variability on the Yucatán Peninsula. During this session, Prof. Norbert Frank gave a presentation on the growth of speleothems in Yucatán, in which he discussed the pitfalls of combining different dating methods. Aaron Mielke presented a poster outlining his analyses of the resolution limit of trace element measurements using laser ablation. Carmen Schöfer gave a talk on her previous Bachelor's research, in which she had identified external influences on neodymium in cold-water corals near the Azores. Francisca Lövenich presented a poster illustrating how the Caribbean climate can be linked to influencing factors across different time scales. In addition to the presentations, there were also many opportunities to interact with alumni and other researchers, such as at the Speleo dinner following the session. (FL)
April 2026
Master's Thesis Successfully Completed
Francisca Lövenich has successfully completed her master's thesis on the Caribbean climate over the past 200,000 years. On orbital timescales, tropical precipitation is conventionally linked to solar variability, with higher summer solar irradiance associated with increased precipitation. However, previous δ18O data from the Caribbean show the opposite trend and point to other climate drivers. The new speleothem dataset from Puerto Rico, which extends the regional record by an entire orbital cycle, confirms this pattern. Comparisons with isotope-calibrated model data suggest that the early seasonal rainy season may play a significantly greater role than previously assumed. Using δ18O values from the southern end of the Intertropical Convergence Zone, climate indices were also calculated to characterize the width and position of the tropical rain belt. Furthermore, the distinct millennial cycles in the dataset suggest a persistent sensitivity to the strength of the Atlantic Overturning Circulation. Thank you very much, Francisca!
January 2026
Lea Marie Hansen accomplished her Bachelor thesis
December 2025
New Publication on the NASH as a Climate Driver in the Caribbean
The Caribbean climate is still not fully understood. In particular, climate archives from Mesoamerica have shown that the region behaves in a manner unusual for a monsoon region. Instead of stronger summer solar radiation leading to more precipitation, the Caribbean tends to experience drier conditions during these periods. In this context, the new paper by Hanying Li et al. highlights the North Atlantic Subtropical High (NASH), an anticyclone over the North Atlantic, also known as the Azores High. To this end, the authors combined the previously published dataset by Warken et al. from the Santo Tomás cave system in Cuba with their own new speleothem data. As a result, the new data series covers the last 129,000 years. A comparison with a climate model simulation revealed that, over the course of Earth’s precession, increased temperature differences between land and sea amplify the NASH and lead to dry periods in the Caribbean. Until now, this process had been considered relevant only for the annual climate. The study shows that subtropical atmospheric processes can influence rainfall not only over the course of a year, but also on orbital timescales. This finding is particularly important for climate forecasts, as temperature differences between land and sea are expected to continue to increase. The full article can be read in the journal Science Advances. (FL)
News archive
All earlier news can be found in the news archive (currently only in German)
