ALBERT

Description: This study presents a multi-proxy record from Lake Kotokel in the Baikal region at decadal-to-multidecadal resolution and provides a reconstruction of terrestrial and aquatic environments in the area during a 2000-year interval of globally harsh climate often referred to as the Last Glacial Maximum (LGM). The studied lake is situated near the eastern shoreline of Lake Baikal, in a climatically sensitive zone that hosts boreal taiga and cold deciduous forests, coldsteppe associationstypical for northern Mongolia, and mountain tundravegetation.The results provide a detailed picture of the period in focus, indicating (i) a driest phase (c. 24.0–23.4 cal. ka BP) with low precipitation, high summer evaporation, and low lake levels, (ii) a transitional interval of unstable conditions (c. 23.4–22.6 cal. ka BP), and (iii) a phase ( c. 22.6–22.0 cal. ka BP) of relatively high precipitation (and moisture availability) and relatively high lake levels. One hotly debated issue in late Quaternary research is regional summer thermal conditions during the LGM. Our chironomid-based reconstruction suggests at least 3.5 °C higher than present summer temperatures between c. 22.6 and 22.0 cal. ka BP, which are well in line with warmer and wetter conditions in the North Atlantic region inferred from Greenland ice-cores. Overall, it appears that environments in central Eurasia during the LGM were affected by much colder than present winter temperatures and higher than present summer temperatures, although the effects of temperature oscillations were strongly influenced by changes in humidity.

Description: Radiocarbon-dated pollen, rhizopod, chironomid and total organic carbon records from NikolayLake (73°20'N, 124°12'E), Arga Island, Russia reflect mid- to late Holocene vegetation andclimate changes in the Lena Delta area. Shrubby Alnus fruticosa and Betula nana tundra existedon Arga Island during 6000-4200 14C yr BP, and gradually disappeared after that time. Pollen-based climate reconstructions suggest that climate was relatively warm during 6000-5300 14C yrBP, and rather unstable between ca 5100-3500 14C yr BP. Both qualitative interpretation of pollendata and results of quantitative reconstruction imply that climate and vegetation became similarto modern-day conditions after ca 3400 14C yr BP.

Description: Chironomid, pollen, and rhizopod records from a permafrost sequence at the Bolshoy Lyakhovsky Island (New Siberian Archipelago) document the evolution of a thermokarst palaeo-lake and environmental conditions in the region during the Last Interglacial (MIS 5e, ca. 130120 ka). Open Poaceae and Artemisia associations dominated vegetation at the beginning of the interglacial period, ca. 130 ka. Rare shrub thickets (Salix, Betula nana, Alnus fruticosa) grew in more protected and wetter places as well. Saalian ice wedges started to melt during this time, resulting in the formation of an initial thermokarst water body. The high percentage of semi-aquatic chironomids suggests that a peatland-pool palaeo-biotope existed at the site, when initial water body started to form. A distinct decrease in semi-aquatic chironomid taxa and an increase in lacustrine ones point to a gradual pooling of water in basin, which could in turn create thaw a permanent pond during the subsequent period. The highest relative abundance of Chironomus and Procladius reflects an existence of unfrozen water remaining under the ice throughout the ice-covered period during the later stage of palaeo-lake development. Chironomid record points to three successive stages during the water body evolution: (1) a peatland pool; (2) a pond (i.e., less deep than the maximum ice-cover thickness); and (3) a shallow lake (i.e., more deep than the maximum ice-cover thickness). The evolutionary trend of palaeo-lake points to intensive thermokarst processes occurring in the region during the Last Interglacial. Shrub tundra communities with Alnus fruticosa, Betula nana dominated the vegetation during the interglacial optimum that is evidenced by pollen record. The climate was relatively moist and warm. The results of this study suggest that quantitative chironomid-based temperature reconstructions from the Arctic thermokarst ponds/lakes may be problematic owing to other key environmental factors, such as prolonged periods of winter anoxia and local hydrological/geomorphological processes, controlling the chironomid assemblages

Description: An 1180-cm long core recovered in Lake Lyadhej-To (68°15'N, 65°45'E, 150 m a.s.l.) at the NW rim of the Polar Urals Mountains reflects the Holocene environmental history from c. 11,000 cal. yr BP. Pollen assemblages from the diamicton (c. 11,000-10,700 cal. yr BP) are dominated by Pre-Quaternary spores and redeposited Pinaceae pollen, pointing to a high terrestrial input. Turbid and nutrient-poor lake conditions existed in the lake c. 10,700-10,550 cal. yr BP. The chironomid-inferred reconstructions suggest that mean July temperature increased rapidly from 10.0 to 11.8°C during this period. Sparse, treeless vegetation dominated on the disturbed and denudated soils in the catchment area. The period c. 10,550-8800 cal. yr BP is noticeable for the lowest lake-ice coverage and the highest bioproductivity during the lake history. Birch forest with some shrub alder grew around the lake reflecting the warmest environmental conditions during the Holocene. Mean July temperature was likely 11-13°C and annual precipitation - 400-500 mm. The period c. 8800-5500 cal. yr BP is characterised by gradual deterioration of environmental conditions in the lake and lake vicinity. The pollen- and chironomid-inferred temperatures reflect a warm period (c. 6500-6000 cal. BP) with mean July temperature at least 1-2°C higher than today. Birch forests disappeared from the lake vicinity after 6000 cal. yr BP. The vegetation in the Lyadhej-To region became similar to the modern. Shrub (Betula nana, Salix) and herb tundra dominated around the lake since c. 5500 cal. yr BP. All proxies are pointing to rather harsh environmental conditions. Diatom assemblages reflect relatively short growing seasons and longer persistence of ice on the lake c. 5500-2500 cal. yr BP. Pollen-based reconstruction suggest significant cooling between c. 5500 and 3500 cal. yr BP with mean July temperature 7-10°C and annual precipitation - 100-300 mm. The bioproductivity in the lake remained low after 2500 cal. yr BP, but biogeochemical proxies reflect a higher terrestrial influx. Changes in diatom content may indicate warmer water temperatures and reduced ice cover on the lake; however, chironomid-based reconstructions reflect a period with minimal temperatures during the lake history