Tracing water availability, organic carbon sources, and life at the dry limit using radiocarbon analysis

Our project is about reconstructing changes in water availability and its effect on organic carbon sources in desert soils. We use the information encoded in the distribution and isotopic composition of molecular fossils, i.e. remnants of plant and microbial life, for the identification of microbial communities as well as of climate variability past and present. A major part of our work is dedicated to technical and methodological developments for radiocarbon dating of very small samples (i.e. extremely low organic carbon content).

The most challenging aspect is to extract traces of plant and microbial life and to get age information by radiocarbon dating from soils located in the hyperarid core of the desert that exposes very low organic carbon contents. For instance, we need to extract about 5 kg of soil to obtain few micrograms of plant-derived organic matter. Therefore, major analytical developments are required to enable the analysis of these samples.

“Exploring life at the dry limit is a very fascinating topic and doing fieldwork in the hyperarid core of the Atacama felt like being on Mars. The project gives us the unique opportunity to study distinct plant and microbial communities which developed a very specific life style to grow and survive at such extreme climatic conditions. We were surprised by the good preservation of organic compounds originating from plant remains, which enabled us to analyze their isotopic composition for paleoclimate reconstruction.”
– Janet Rethemeyer

Publication:

• Rethemeyer, J., Gierga, M., Heinze, S., Stolz, A., Wotte, A., Wischhöfer, P., Berg, S., Melchert, J.O., Dewald, A., 2019. Current sample preparation and analytical capabilities of the radiocarbon laboratory at CologneAMS. Radiocarbon, doi.org/10.1017/RDC.2019.16.
• Stolz, A., Dewald, A., Heinze, S.., Altenkirch, R., Hackenberg, G., Herba, S., Müller-Gatermann, C., Schiffer, M., Zitzer, G., Wotte, A., Rethemeyer, J., Dunai, T., 2019. Improvements in the measurement of small ¹⁴CO₂ samples at CologneAMS. Nuclear Instr. and Methods in Physics Res. B 439, 70-75.
• Stolz, A., Dewald, A., Altenkirch, R., Herb, S., Heinze, S., Schier, M., Feuerstein, K., Müller-Gatermann, C., Wotte, A., Rethemeyer, J., Dunai, T., 2017. Radiocarbon measurement of small gaseous samples at CologneAMS. Nuclear Inst. and Methods in Physics Res. B 406, 283-286.

Contact
Prof. Dr. Janet Rethemeyer
Phone: +49 (0)221 470-7317
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Constraining the Pleistocene environmental history of the Atacama: Extending the age range of luminescence dating

The D05 project uses optically stimulated luminescence (OSL) dating, a technique that informs about the timing of sediment deposition, to provide chronological constraints for landscape and climate evolution of the Atacama Desert. By applying OSL dating, temporal patterns for geomorphologic and climatic changes deduced from sediment records such as alluvial fans, clay pans or hillslope deposits can be established. This includes the application of conventional OSL dating approaches as well as the development of new techniques that enable to target sediments which can as yet not be dated.

Due to the high age of the Atacama Desert many sediment records exceed the age range of conventional OSL dating. Therefore, a special focus of project D05 is the development of new techniques that can extend the conventional age range of OSL dating. The innovative technique investigated in this project is optically stimulated luminescence  dating using violet stimulation (VSL), which will allow to date much older sediments than can be achieved using the techniques available until now.

We are among the first to further advance and apply this specific dating technique (VSL dating). It gives information on geomorphologic structures and climatic events in the Atacama Desert that so far could not be dated by any other approach.

Contact

Prof. Dr. Helmut Brückner
Phone +49 (0)221 470-1724
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Statistical-dynamical modelling of aeolian processes in the Atacama Desert over geological time scales and their implications to life at the dry limit.

In project A03 we study weather types over the Subtropical Southeast Pacific. The focus of our research of these weather types in the Atacama Desert is their impact on climate and aeolian transport which plays a major role in shaping the surface. We study both present-day and paleo-climate conditions, going back from thousands to millions of years. To do this, a regional climate model (Weather Research and Forecasting Model, WRF) is used to simulate climate and surface processes on high spatial resolution to obtain detailed data on the conditions in the Atacama Desert. The overall goal of the project is to better understand the processes important for the geomorphological and biological evolution in this extremely dry region of the Earth, to test various hypotheses and provide paleo-climate and -environment data to other projects of the CRC.

“This is what I find particularly interesting. The CRC brings together researchers from different disciplines to study the extreme environment of the Atacama Desert.”
– Dr. Mark Reyers

For the first time, we have developed an objective classification of weather types for the Atacama region, which can be applied to global paleo-climate simulations and is useful for many other applications, such as the assessment of water resources and renewable energy resources. Further, a set of long-term regional climate simulations for the Atacama Desert under the present-day and paleo-climate conditions has been  established and will be made available for the research community at large.

 Publication:

• Reyers M, Hamidi M, Shao Y (2019): Synoptic analysis and simulation of an unusual dust event over the Atacama Desert. Atmospheric Science Letters. DOI:10.1002/asl.899 (https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/asl.899)
• Reyers M, Shao Y (2019): Cutoff lows off the coast of the Atacama Desert under present day conditions and in the Last Glacial Maximum. Global and Planetary Change 181 (2019) 102983

Contact

Prof. Dr. Yaping Shao
Phone: +49 (0)221 470-3688
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Dr. Mark Reyers
Scientist in A3
Phone: +49 (0)221 470-7302
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