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  • Grzybowski Foundation  (1)
  • Molecular Diversity Preservation International  (1)
  • Nature Research  (1)
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  • 1
    Publication Date: 2021-04-06
    Description: The Late Holocene was characterized by several centennial-scale climate oscillations including the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age. The detection and investigation of such climate anomalies requires paleoclimate archives with an accurate chronology as well as a high temporal resolution. Here, we present 230Th/U-dated high-resolution multi-proxy records (δ13C, δ18O and trace elements) for the last 2500 years of four speleothems from Bunker Cave and the Herbstlabyrinth cave system in Germany. The multi-proxy data of all four speleothems show evidence of two warm and two cold phases during the last 2500 years, which coincide with the Roman Warm Period and the Medieval Warm Period, as well as the Dark Ages Cold Period and the Little Ice Age, respectively. During these four cold and warm periods, the δ18O and δ13C records of all four speleothems and the Mg concentration of the speleothems Bu4 (Bunker Cave) and TV1 (Herbstlabyrinth cave system) show common features and are thus interpreted to be related to past climate variability. Comparison with other paleoclimate records suggests a strong influence of the North Atlantic Oscillation at the two caves sites, which is reflected by warm and humid conditions during the Roman Warm Period and the Medieval Warm Period, and cold and dry climate during the Dark Ages Cold period and the Little Ice Age. The Mg records of speleothems Bu1 (Bunker Cave) and NG01 (Herbstlabyrinth) as well as the inconsistent patterns of Sr, Ba and P suggests that the processes controlling the abundance of these trace elements are dominated by site-specific effects rather than being related to supra-regional climate variability.
    Electronic ISSN: 2076-3263
    Topics: Geosciences
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  • 2
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    Grzybowski Foundation
    In:  In: Contributions to the micropaleontology and paleoceanography of the northern North Atlantic (collected results from the GEOMAR Bungalow Working Group). , ed. by Hass, H. C. and Kaminski, M. A. Grzybowski Foundation, Krakow, pp. 227-243.
    Publication Date: 2016-01-19
    Description: The present investigation was initiated to report on species compositions and dynamics in the Norwegian-Greenland Sea during low production phases in spring and early summer. Thus, the distribution patterns of living coccolithophores during June to July, 1990, February and May, 1991, and March to April, 1995 were investigated. In general, the seasonal development of the phytoplankton started after the yearly dark period and coccolithophores increased in abundance when the water column was more stratified and both temperatures and insolation increased. Cell densities reached a maximum of 207x10~c occospheres/l in the southeastern part of the studied area. However, these high cell densities probably resulted from ,,old" populations, drifted to the Norwegian-Greenland Sea from the North Atlantic. Some of the collected samples did not contain any coccolithophores. In total, 15 coccolithophore species were identified. The diversity was generally higher in the eastern part of the Norwegian-Greenland Sea and to the west the coccolithophore communities often were monospecific. Emiliania huxleyi is the dominant species, but Calciopappus caudatus and Algirosphaera robusta also considerably contribute to the communities. High cell densities of C. caudatus were interpreted as the result of a bloom or more probably close to bloom conditions during the general low productive period. In addition, many of the E. huxleyi coccolith from the surface waters of the southeastern Norwegian-Greenland Sea were heavily corroded. These specimens may have drifted within the Atlantic water for a longer time.
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 3
    Publication Date: 2024-03-15
    Description: Variations of atmospheric CO 2 during the Pleistocene ice-ages have been associated with changes in the drawdown of carbon into the deep-sea. Modelling studies suggest that about one third of the glacial carbon drawdown may not be associated to the deep ocean, but to the thermocline or intermediate ocean. However, the carbon storage capacity of thermocline waters is still poorly constrained. Here we present paired 230 Th/U and 14 C measurements on scleractinian cold-water corals retrieved from ~ 450 m water depth off the Maldives in the Indian Ocean. Based on these measurements we calculate ∆ 14 C, ∆∆ 14 C and Benthic-Atmosphere (B atm ) ages in order to understand the ventilation dynamics of the equatorial Indian Ocean thermocline during the Last Glacial Maximum (LGM). Our results demonstrate a radiocarbon depleted thermocline as low as -250 to -345‰ (∆∆ 14 C), corresponding to ~ 500–2100 years (B atm ) old waters at the LGM compared to ~ 380 years today. More broadly, we show that thermocline ventilation ages are one order of magnitude more variable than previously thought. Such a radiocarbon depleted thermocline can at least partly be explained by variable abyssal upwelling of deep-water masses with elevated respired carbon concentrations. Our results therefore have implications for radiocarbon-only based age models and imply that upper thermocline waters as shallow as 400 m depth can also contribute to some of the glacial carbon drawdown.
    Type: Article , PeerReviewed
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