Speleothem sulfur spike confines timing and impact of late Glacial Laacher See eruption

The Laacher See eruption (LSE) deposited a key tephra layer that synchronizes Late Glacial paleoclimate records across Europe, and thus provides the temporal framework to investigate the onset of the Younger Dryas cooling in the North Atlantic region. The absolute timing and climatic consequences of this event remain, however, still debated. Here, we present evidence from a high-resolution speleothem record from Herbstlabyrinth Cave, Central Germany, demonstrating distinct spikes in sulfur, fluorescent organic matter, and ash-leached trace elements assigned to the LSE and dating the event c. 13,047 BP1950, with an uncertainty of about 30–40 years. This age supports the recently published radiocarbon wiggle matching date of 13,006 ± 9 BP1950 (Reinig et al., 2021) and contradicts speculations about potential biases arising from volcanic CO2 emissions. The near-annually resolved speleothem calcite δ18O data further allows to assess the timing of the LSE and its impact on the regional climatology. Our findings exclude the LSE as a possible trigger of the Younger Dryas and indicate a regional climatic and environmental impact restricted to c. 20 years after the eruption. This unprecedented combination of stable isotopes, trace elements, annually resolved fluorescence, and radiometric dates for a single record provides independent evidence for the Late Glacial synchroneity of Atlantic-European climate relationships and opens new pathways toward a precise, absolutely dated time marker between European terrestrial and Greenland ice core records prior to the Holocene. References Reinig F, Wacker L, Jöris O, et al. (2021) Precise date for the Laacher See eruption synchronizes the Younger Dryas. Nature 595(7865): 66-69.