Modelling Simulation of climate archives and climate signals from the past
For the past two decades, studies on cave interiors such as speleothems have become increasingly important in reconstructing the climate of the past. Stalagmites are formed from CaCO3-saturated drip water. Thanks to 230Th/U dating, a precise chronology can be established and a wealth of geochemical trace elements and isotopes can be analysed to determine the climate of the past.
However, only a few proxies provide quantitative climate reconstructions, and the form that actually developed cannot be included in the interpretation today. Modelling remains a rare goal. We focus on chronology and the use of radiocarbon (14C) as a tool to calibrate atmospheric 14C content and to identify past vegetation changes in relation to soil carbon cycle dynamics. In recent years, we have moved to coupling climate model outputs with a geochemical groundwater model (CaveCalc by Owen et al. 2018) to simulate the composition and even the shape of such deposits as a function of changing environmental conditions. Finally, the isotopic composition of past dripping waters can be reconstructed based on the fluids trapped in the speleothems. The research has so far been funded by the DFG and we hope to see more stones grow in the future. As part of a collaboration with the Climate Computing Centre in Hamburg and colleagues at the University of Potsdam, we have already achieved initial success in simulating the shape of stalagmites and their isotopic composition. A first bachelor's thesis on this was published in the journal Frontiers of Science in 2022 (Merz et al. 2022). Numerous master's theses followed or preceded the publication. We are steadily approaching a better understanding of the prediction of stalagmite climate signals. Further projects related to the simulation of cold-water coral reefs in natural climate change are still future plans.