We here estimate past temperature and hydroclimate variations in eastern Anatolia for marine isotope stages 4 to 1 (MIS4 to MIS1) respectively using branched glycerol dialkyl glycerol tetraethers (brGDGTs) and the hydrogen isotopic composition of n-C 29 leaf-wax n-alkanes (δ 2H wax) stored in the sedimentary record of Lake Van (Turkey). Our millennial-scale lipid biomarker records reflect warm and wet conditions during interstadials/interglacials and colder and dryer periods with increased evapotranspiration and aridity during stadials/glacials. The degree of methylation of the 5-methyl brGDGTs (MBT´ 5me) indicates increasing mean annual air temperatures (MAT) during stadial/interstadial transitions, that characterize Dansgaard-Oeschger events, and during the last glacial termination. Based on the effects of changes in precipitation amount on apparent enrichment factors between the δ 2H of the C 29 n-alkanes and δ 2H of precipitation, a total increase in annual precipitation of about 200 mm during transitions from stadials to interstadials, and of 300–350 mm during glacial-interglacial transitions can be determined, in line with previous paleoclimate reconstructions for the Eastern Mediterranean. High sterol concentrations in sediments deposited during warm and humid interstadials reflect increases in lake level, vegetation density and algal blooms, whereas lower values of the branched versus isoprenoid tetraethers ratio (BIT) likely reflects the increased niche of Thaumarchaeota resulting from enhanced windiness and mixing of the water column during colder periods. This quantitative hydroclimate reconstruction from Lake Van (Turkey), as it is optimally situated to respond to North Atlantic climate change via changes in the large-scale wind fields shed light into millennial-scale global climate variability.
Bibliographische NotizFunding Information:
We thank two anonymous reviewers for constructive comments that helped to improve the manuscript. We also thank the PALEOVAN team for support during collection and sharing of data. The authors acknowledge funding of the Swiss National Science Foundation (SNF) 200021_124981 , 200020_143330 , P300P2-158501 200020_143340 , 20FI21_124972 , 200021_124981 , and 200020L_156110/1 the PALEOVAN drilling campaign by the International Continental Scientific Drilling Program (ICDP), the Deutsche Forschungsgemeinschaft (DFG) LI 582/20-1 , the Scientific and Technological Research Council of Turkey (Tübitak) and the Austrian Science Foundation (FWF Project No. I 2068-N29 ). Serge Robert is thanked for the help in the laboratory. FP acknowledges financial support from NWO-Vidi grant #192.074 .
© 2021 The Authors