Decadal Cycles in Glacial Wind Dynamics - Reconstruction from annually laminated Eifel maar sediments and comparison to transient model simulations (13,000 – 43,000 yr b2k)

• Applicants: Professor Dr. Gerrit Lohmann; Dr. Klemens Seelos; Professor Dr. Frank Sirocko
• Subject Area: Geology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550972244

Changes in wind systems and atmospheric circulation play a critical role in driving abrupt climate and weather changes, leading to hemispheric-wide teleconnections. Understanding these dynamics is crucial for predicting future climate scenarios and mitigating the impacts of extreme weather events. We will use annually laminated (varved) maar lake sediments from the Dehner Maar in the Eifel/Germany to reconstruct an annual resolution time series of dust deposition for the time 13,000 - 43,000 yr b2k, which covers dust transport during the Last Glacial Maximum and the stadials of MIS3. The sediment cores from Dehner Maar are already dated by single grain quartz OSL, 14C of ostracods, varve counting and ice core tuning. We will use further single grain OSL analysis, and 14C of of spruce needles to increase the robustness of the MIS3 chronology; 10Be analysis is planned to detect the Laschamp interval as a stratigraphical marker also in the Dehner Maar record. Annual resolution grain size analysis of petrographic thin sections will be applied to detect quartz dust particles and separate them from wave induced quartz particles eroded from the lake shore. The grain size of the local eolian carbonate fraction (well rounded and sorted carbonate grains in the coarse silt and fine sand fraction) will be then used to quantify the variability of the annual proportion of dust derived from provenances in the east of the Dehner Maar. Rounded carbonate grains can only be derived from limestone outcrops east of the Dehner Maar lake. The eolian carbonate grains will be separated into the local fraction of saltated grains and the fine grained fraction from long distance dust transport by the annual resolution grain size analysis. It is thus the carbonate fraction of the fine sand and coarse silt, which characterizes the trajectories from the east into the Dehner Maar basin, and which annual resolution proxy time series is the main product of this project. This record is important, because changes in the east wind intensity are an important diagnostic tool for the validation of global circulation models of the last glacial maximum. The already observed multidecadal structure in the annual resolution time series from Dehner Maar can be directly compared to respective time series from time transient model experiments, which are conducted at Bremen University since many years. With this knowledge, upcoming model experiments can be designed to meet the proxy record appropriate. In addition, we will analyze together with our partners the time series of dust activity on a statistical basis to quantify significant decadal and multidecadal structures in the proxy and model records and understand their causal mechanisms.

• DFG Programme: Research Grants
• International Connection: Sweden, Switzerland
• Co-Investigators: Dr. Ronny Friedrich; Dr. Sebastian Kreutzer; Professor Dr. Frank Lehmkuhl; Professor Dr. Stephan Pfahl; Professorin Dr. Antje Schwalb; Dr. Hubert Vonhof
• Cooperation Partners: Dr. Marcus Christl; Professor Dr. Raimund Muscheler