Geo- und Umweltnaturwissenschaften

Isotopes

With aims to understand the paleoclimate, atmospheric dynamics, and geochemical processes in caves we study oxygen isotopes in precipitation, cave dripwater and speleothems; and multiproxies in sediments and secondary carbonates.

Water isotopologues, i.e. the ratio between the more abundant H216O and the heavier H218O, are an important tracer of the hydrological cycle. These ratios change at phase changes along the moisture path of water parcels and can reveal important information on the dynamics of the climate system. One key research in the SPACY group is to decipher the diverse influences on these ratios from climate archives, such as speleothems, ice cores, shelf ice, and wood, but also from precipitation and drip water monitoring.

Main research topics

  • Paleoclimate and paleoenvironmental reconstructions based on speleothems and other cave materials

  • Effects of climate on the isotopic composition of rainwater from Tübingen and other sites in Southern Germany

  • We study the atmospheric dynamics and trace (extreme) weather events by studding isotopic composition in precipitation

  • We monitor the microclimate and geochemical conditions of cave environment and its surroundings

  • We explore worldwide isotope data in databases (SISAL, Iso2k, etc) and comparison with climate models

On-going work and methods

To progress on these research questions, we have two main approaches:

Lab-based (check out our lab):

  • establishing a weather station on the GUZ institute building which allows us to actively monitor weather parameters and events.
  • collecting precipitation in and around Tübingen and analyze the isotopic composition with the aim to set up an official rain water sample station to supply data to the Global Network of Isotopes in Precipitation (GNIP).
  • paleoclimate reconstruction based in stalagmites from mid-western Brazil
  • cave monitoring in tropical caves
  • climate and water isotopic monitoring from the Swabian Alb region and its karst system  
  • analyzing our samples in the laboratory using a large variety of methods and instruments, e.g. a cavity-ring-down-spectrometer

Analysis-based:

  • analyzing large databases of records of oxygen isotopes (e.g. iso2k [1] or SISALv2 [2]) and compare the results to output of isotope-enabled general circulation models. This model-data comparison can reveal discrepancies between model and data [3].
  • using Paleoclimate Data Assimilation with isotopic data from proxy records and isotope-enabled GCMs to infer past (hydro)climate fields.  With this method, we are currently working on a reanalysis of the last millennium comprising both isotope and non-isotope proxy data.

Thesis projects & collaboration

If you are interested in joining our research team, you are invited to contact us as described here.

As part of our research work, we currently offer thesis / HiWi projects on

  • Build an automatic rainwater collector for the GUZ institute: that allows us to probe specific weather events and collect short interval samples with e.g. remote control (B.Sc. or M.Sc. thesis)
  • Implement and improve the IT-interface for the weather station: we want to include an active user interface on the institute’s webpage and stream live-weather data onto the GUZ monitor in the entrance hall (HiWi-project)
  • geochemical analysis on water and modern speleothems obtained from cave monitoring
  • implementation of cave monitoring over the region of the Swabian Alb

 

If you’re interested in other ideas related to water isotopes, check out our team members’ work on modeling climate, who also work on developing and tuning isotope-enabled models or understanding the variability of the hydroclimate and stable water isotopes in the research area climate's variability across time scales.

References

[1] Konecky,  L., et al. "The Iso2k database: a global compilation of paleo-δ18O and δ2H records to aid understanding of Common Era climate." Earth System Science Data 12.3 (2020): 2261-2288, DOI: 10.5194/essd-12-2261-2020

[2] Comas-Bru, L, et al. "SISALv2: a comprehensive speleothem isotope database with multiple age–depth models." Earth System Science Data 12.4 (2020): 2579-2606, DOI: 10.5194/essd-12-2579-202

[3] Bühler, J. C., et al. "Comparison of the oxygen isotope signatures in speleothem records and iHadCM3 model simulations for the last millennium." Climate of the Past 17.3 (2021): 985-1004, DOI: 10.5194/cp-17-985-2021

More

Novello, V. F. et al. “Investigating d13C values in stalagmites from tropical South America for the last two millennia.” Quaternary Science Reviews 255, (2021): 106822, DOI: 9.1016/j.quascirev.2021.106822.

Novello, V. F. et al. “Vegetation and environmental changes in tropical South America from the last glacial to the Holocene documented by multiple cave sediment proxies.” Earth and Planetary Science Letters 524 (2019), 115717, DOI: 10.1016/j.epsl.2019.115717.

Novello, V. F. et al. “A high-resolution history of South American Monsoon from Last Glacial Maximum to the Holocene.” Scientific Reports 7 (2017), 44267, DOI: 10.1038/srep44267.

Sekhon, N. et al. (2020). “Diurnal to seasonal ventilation in Brazilian caves.” Global and Planetary Change 147, (2020), 103378, DOI: 1016/j.gloplacha.2020.103378.

Moquet, J. S. et al. “Calibration of speleothem d18O records against hydroclimate instrumental records in Central Brazil.” Global and Planetary Change 139, (2026) 151-164.

Lachniet, Matthew S. "Climatic and environmental controls on speleothem oxygen-isotope values." Quaternary Science Reviews 28.5-6 (2009): 412-432.

Dansgaard, W. "Stable isotopes in precipitation." tellus 16.4 (1964): 436-468.