Project (DFG - Funded):
Reconstruction of decadal to orbital-scale climate variability during Marine Isotope Stage 9 using precisely dated multi-proxy speleothem records from Central Europe
Reconstruction of climate variability during previous interglacials as well as precise determination of their timing and duration provides important information about our climate system. Marine Isotope Stage (MIS) 9 (340,000-280,000 years BP) is a particularly important interglacial in this context because it shows the highest preindustrial atmospheric CO2 and CH4 concentrations of the last 800,000 years. Therefore, MIS 9 provides insights for a period with strong greenhouse gas forcing, which can be considered as an analogue for postindustrial times.
The majority of palaeoclimate reconstructions for MIS 9 are based on ice cores from Antarctica, marine records, and lake sediments. These climate archives cannot be absolutely dated beyond the 14C-dating range, and their chronology must be established by orbital tuning or wiggle matching with other records. Speleothems can be dated back to 600,000 years BP with exceptional precision by the 230Th/U-method. This is a large advantage of this climate archive and gives us the unique opportunity to obtain independently dated palaeoclimate records.
In the framework of the proposed project, we will precisely date up to seven stalagmites from Dechen Cave (western Germany), which were preliminarily dated to MIS 9. Dechen Cave is located in a region with permafrost during glacial times. Thus, speleothem growth within the cave is very sensitive to warmer and wetter climate conditions. Precise dating of the growth phases of the speleothems will thus enable precise determination of the timing and duration of MIS 9 and its sub-stages. In addition, we will obtain decadal-resolution d13C and d18O values as well as trace element records, which will result in a replicated, precisely dated multi-proxy record completely covering MIS 9.
The generated proxy records will be compared to both regional and global climate records, which will enable us to disentangle local from global climate variability, establish large-scale tele-connections, and to identify the dominant climate forcings for MIS 9. Furthermore, we will compare the reconstructed natural climate variability in central Europe with the present-day trends in order to determine how extraordinary they are. This is particularly important because MIS 9 is the interglacial with the highest preindustrial atmospheric CO2 and CH4 concentrations during the last 800,000 years, which are comparable to AD 1900.