The Black Sea Palaeoclimate and Environment during the penultimate glacial - reconstructions from lacustrine sediments (BlackPearl)
Final Report Abstract
Within the framework of the DFG-project ‘BlackPearl’, for the first time sediment cores could be investigated for high-resolution multi-proxy reconstructions of the climate and environmental variability in the Black Sea ‘Lake’ during nearly the entire Marine Isotope Stage 6 (MIS 6; 184-130 ka BP), representing the latest period of the penultimate glacial as one of the strongest glaciations during the Quaternary. The age-depth model of a composite core obtained during a cruise with RV Maria S. Merian (MSM33) is mainly based on correlations between the δ18O record of the Black Sea ostracods and well-dated δ18O records from speleothems of Northern Anatolia and Hungary confirmed by three identified tephrochronological markers. The multi-proxy approach comprises organic biomarkers, ostracod geochemistry, and major and trace element geochemistry. Three periods during MIS 6 with pronounced negative excursions in δ18Oostracods coinciding with periods of a reduced Eurasian Ice Sheet (EIS) imply enhanced meltwater discharge into the former isolated Black Sea ‘Lake’. High input of freshwater is compatible with a decreased salinity during these periods as reflected by lower Sr/Caostracods. The resulting lake level potentially caused overflows into the Sea of Marmara. High radiogenic values in the 87Sr/86Srostracods during the two younger meltwater pulses further suggest a freshwater source in the foothills of the Himalayan region in addition to the EIS, because loess and rivers carry a very high radiogenic Sr-isotope signature in that region. The TEX86-based temperature reconstructions imply generally warmer conditions and millennial-scale Dansgaard-Oeschger-like temperature variability during the first part of MIS 6, which is in line with other temperature records across the North Atlantic-Eurasian corridor. The comparison of temperature records during MIS 3 (last glacial) and MIS 6 (penultimate glacial) from the North Atlantic, Mediterranean Sea, and Black Sea, suggests that the strength of the atmospheric teleconnection across the North Atlantic-Eurasian realm was ultimately controlled by the continental extent of the EIS. In comparison to MIS 6, the δ18Oostracods record during MIS 3 fluctuates on a smaller amplitude, but reveals a characteristic pattern with increased/decreased values during smaller/larger EIS extent. The increased δ18Oostracods values during the milder periods are most likely associated with a retreat of the EIS thereby causing a northward migration of the atmospheric polar front and an increased contribution of North Atlantic/Mediterranean moisture sources in the Black Sea region comprising a generally higher δ18O composition in rainfall and runoff. The new studies on the Black Sea sediment cores carried out within the DFG-project ‘BlackPearl’ offered crucial new insights into the dynamics between continental ice sheets and atmospheric circulation over Eurasia during the last two glacials, which strongly controlled the regional climate and hydrological conditions in the former Black Sea ‘Lake’.
Publications
- (2019). Major hydrological shifts in the Black Sea “Lake” in response to ice sheet collapses during MIS 6 (130-184 ka BP). Quaternary Science Reviews 219: 126-144
Wegwerth, A., O. Dellwig, S. Wulf, B. Plessen, I. C. Kleinhanns, N. R. Nowaczyk, L. Jiabo and H. W. Arz
(See online at https://doi.org/10.1016/j.quascirev.2019.07.008) - (2020). Impact of Eurasian Ice Sheet and North Atlantic climate dynamics on Black Sea temperature variability during the penultimate glacial (MIS 6, 130-184 ka BP), Paleoceanography and Paleoclimatology
Wegwerth, A., Kaiser, J., Dellwig, O., Arz, H.W.
(See online at https://doi.org/10.1029/2020PA003882)
