Quaternary environmental changes in central Chukotka (NE Russia) inferred from the Lake El'gygytgyn pollen records

The 3.6-Myr sedimentary record of Lake El'gygytgyn is crucial for understanding the response of the sensitive ecosystems in the Arctic to Quaternary climate variations at orbital timescales. In this study, we synthesize previously published pollen records and biome reconstructions and perform pollen diversity analysis of the deep-drilling core ICDP 5011-1 from Lake El'gygytgyn for periods during the Early Pleistocene (MIS 82 - MIS 79), Early-Middle Pleistocene (MIS 31 - MIS 18) and late Middle Pleistocene (MIS 7e - MIS 6f). The results indicate that the predominance of herb tundra in the regional vegetation was most characteristic during glacials/stadials. Interglacials, in contrast, can be distinguished by the expansion of shrub communities mainly composed of birch, alder and willow. The expansion of forest biomes in the region was influenced by peaks in obliquity values, which led to increases in daylight length, which was essential for plant growth in high latitudes. An apparent long-term decreasing trend in the tree and shrub population, accompanied by a reduction in floristic richness, was induced by stepwise cooling and drying since the Mid-Pleistocene Transition (MPT), which is linked to the modulation of extended global ice volume during the MPT via strong snow- and ice-albedo feedback effects.