Dansgaard/Oeschger Ereignisse während des Marinen Isotopenstadiums 8
Zusammenfassung der Projektergebnisse
Previous studies have shown that speleothem isotope data from the Alps can be strongly affected by in-cave processes. Therefore, part of the work within this project focused on developing an isotope evolution model, which successfully reproduces differences between contemporaneous growing speleothems. For the main part of the project, we produced and analysed oxygen (δ18O) and carbon isotope (δ13C) and Mg/Ca data from speleothems formed mainly below a glacier-covered catchment in the Alps 300,000 to 200,000 years ago. Additional information from isotope-enabled climate model simulations was utilised which revealed that δ18O of precipitation in the Alps was higher by approximately 1 ‰ during interstadials (IS) compared to stadials (S). This agrees with IS-S amplitudes of our new speleothembased estimate but only when considering additional cave-internal effects on the δ18O. Periods of occurrence of S-IS transitions in our new record agree with other regional and more distant records and are ~220-230, 240-255, 260-265 and 280-305 ka. Furthermore, we proposed that the variability of these cave-internal effects offers a unique tool for reconstructing long-term dynamics of warm-based Alpine palaeoglaciers. We found millennial-scale changes in the glacier-related source of the water infiltrating in the karst at Melchsee-Frutt during Marine Isotope Stage (MIS) 8 and 7d and linked them to Northern Hemisphere climate variability. Another part of this project focused on comparison of a compilation of speleothem records from the North and Central European Alps growing during the last glacial with model simulations of glacier evolution. The speleothem growth history and δ13C records are used to infer soil vs. glacier cover and the thermal regime of the glacier over the last glacial cycle. The compatibility with existing glacier evolution models is statistically assessed. A general agreement between speleothem δ13C-derived information on soil vs. glacier presence and modelled glacier coverage is found. However, glacier retreat during MIS 3 seems to be underestimated by the model. Furthermore, speleothem data provides evidence of surface temperature above the freezing point below the ice which is, however, not fully reproduced by the simulations. Finally, the speleothem record produced within this project covering the period between 200,000 to 300,000 years ago was investigated together with the speleothem record from the same cave system produced in the predecessor project (FO 809/4-1) covering the period between 130,000 to 200,000 and another speleothem record from this site (Neotektonik cave and Schratten cave). Using this record of two full glacial cycles, history of glacier cover and the glaciers’ thermal regime was explored for the high-elevation site Melchsee-Frutt in the Swiss Alps. Based on the speleothem δ13C data, warm-based glacier cover is inferred for MIS 8, 7d, 6, and early 2. Also a short period of cold-based ice coverage is found for early MIS 6.
Projektbezogene Publikationen (Auswahl)
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Are oxygen isotope fractionation factors between calcite and water derived from speleothems systematically biased due to prior calcite precipitation (PCP)?. Geochimica et Cosmochimica Acta, 305, 212-227.
Deininger, Michael; Hansen, Maximilian; Fohlmeister, Jens; Schröder-Ritzrau, Andrea; Burstyn, Yuval & Scholz, Denis
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Contemporaneously growing speleothems and their value to decipher in-cave processes – A modelling approach. Geochimica et Cosmochimica Acta, 348, 381-396.
Skiba, V. & Fohlmeister, J.
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Deciphering local and regional hydroclimate resolves contradicting evidence on the Asian monsoon evolution. Nature Communications, 14(1).
Wolf, Annabel; Ersek, Vasile; Braun, Tobias; French, Amanda D.; McGee, David; Bernasconi, Stefano M.; Skiba, Vanessa; Griffiths, Michael L.; Johnson, Kathleen R.; Fohlmeister, Jens; Breitenbach, Sebastian F. M.; Pausata, Francesco S. R.; Tabor, Clay R.; Longman, Jack; Roberts, William H. G.; Chandan, Deepak; Peltier, W. Richard; Salzmann, Ulrich; Limbert, Deborah ... & Trinh, Anh Duc
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Millennial-scale climate variability in the Northern Hemisphere influenced glacier dynamics in the Alps around 250,000 years ago. Communications Earth & Environment, 4(1).
Skiba, Vanessa; Spötl, Christoph; Trüssel, Martin; Schröder-Ritzrau, Andrea; Schröder, Birgit; Frank, Norbert; Eichstädter, René; Tjallingii, Rik; Marwan, Norbert; Zhang, Xu & Fohlmeister, Jens
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Speleothem growth and stable carbon isotopes as proxies of the presence and thermodynamical state of glaciers compared to modelled glacier evolution in the Alps. Quaternary Science Reviews, 322, 108403.
Skiba, Vanessa; Jouvet, Guillaume; Marwan, Norbert; Spötl, Christoph & Fohlmeister, Jens
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The role of Northern Hemisphere summer insolation for millennial-scale climate variability during the penultimate glacial. Communications Earth & Environment, 4(1).
Fohlmeister, Jens; Luetscher, Marc; Spötl, Christoph; Schröder-Ritzrau, Andrea; Schröder, Birgit; Frank, Norbert; Eichstädter, René; Trüssel, Martin; Skiba, Vanessa & Boers, Niklas
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SISALv3: a global speleothem stable isotope and trace element database. Earth System Science Data, 16(4), 1933-1963.
Kaushal, Nikita; Lechleitner, Franziska A.; Wilhelm, Micah; Azennoud, Khalil; Bühler, Janica C.; Braun, Kerstin; Ait, Brahim Yassine; Baker, Andy; Burstyn, Yuval; Comas-Bru, Laia; Fohlmeister, Jens; Goldsmith, Yonaton; Harrison, Sandy P.; Hatvani, István G.; Rehfeld, Kira; Ritzau, Magdalena; Skiba, Vanessa; Stoll, Heather M. ... & Szűcs, József G.
