Quaternary environmental changes in central Chukotka (NE Siberia, Russia) inferred from Lake El’gygytgyn pollen record and biome reconstruction

• Main Author: Wenwei, Zhao
• Format: Doctoral or Postdoctoral Thesis
• Language: German; English
• Published: 2017
• Subjects: ddc:550; Arctic; Chukotka; Tundra; Siberia
• Online Access: https://kups.ub.uni-koeln.de/7876/; https://kups.ub.uni-koeln.de/7876/1/Dissertation.pdf

The thesis aims to reconstruct the Arctic vegetation during the Quaternary and to provide insights into the orbital and internal forcings of the regional climate changes. The sedimentary record of the Lake El’gygytgyn is vital for understanding the response of the vulnerable ecosystems in the Northeast Siberia to climate variations. With the successful recovery of the deep-drilled ICDP 5011-1 sediment cores, high-resolution palynological analysis and biome reconstruction are applied to the time intervals of ~2150 to 2100 ka (MIS 82-79, including the Réunion Subchron polarity reversal event), ~1091 to 715 ka (MIS 31-18, encompassing the Mid-Pleistocene Transition), and ~240.5 to 181.5 ka (MIS 7.5-6.6; mainly the penultimate interglacial). For the interval of 2150-2100 ka (MIS 82-79) during the early Quaternary, the tundra (TUND) biome generally has higher affinity scores as compared to cold steppe (STEP) or cold deciduous forest (CLDE). An exception is a climatic optimum between ~2139-2131 ka, coinciding with MIS 81 (approximately the Réunion Subchron) when the CLDE biome has the highest scores. The coeval pollen spectra indicate that deciduous forest and shrubs expanded in the regional vegetation and the climate was relatively warm and wet. Over the Mid-Pleistocene Transition (1091-715 ka), the pollen spectra reveal seven vegetation successions that have clearly distinguishable glacial-interglacial cycles. Comparing the interglacials during the course of the Mid-Pleistocene Transition, a tendency of a gradual replacement of trees and shrubs by open herbaceous communities can be observed. Since the first large glaciation (MIS 24-22), the long-term tendency of decreasing CLDE biome scores and landscape openness index indicates a prominent aridification in the Northeast Siberia. During the late Quaternary at 240.5-181.5 ka (MIS 7.5-6.6), mixed herbs and shrubs (mainly alder and birch) dominated the regional vegetation. The high-affinity scores of the TUND biome show that the vegetation landscape was generally open. ...