Description: The northeastern part of Eurasia represents one of Earth‟s most extreme periglacial climate regions, characterized by the strongest seasonal temperature amplitudes on the northern hemisphere. The region is occupied by deep-reaching permafrost and covered by widespread taiga and tundra vegetation (Müller et al., 2010). Paleoenvironmental studies have been conducted close to the northern polar cycle in the Verkhoyansk Mountain Range and its western foreland to infer periglacial landscape dynamics in response to late Quaternary climate change. The distribution of preserved terminal moraines reveal several mountain glacier advances in the past (Stauch and Lehmkuhl, 2010). According to luminescence dating, the widest geologically documented glacial advence took place during the Saalian stage around 135 ka. Less extended glaciations to the foreland appeared during the early Weichselian at 100-120 ka and at 85-90 ka, while the youngest glaciation (〉50 ka) was confined to the mountain area. No regional glacial advance is evident for the late Weichselian and the last glacial maximum, a time which was characterized by aeolian loess formation (Stauch et al., 2007, Popp et al., 2007). Sediment cores from the 25 m deep Lake Billyakh (340 m a.s.l.), a former proglacial basin, document environmental changes of the last 50 kyr (Diekmann et al., 2007). Pollen records indicate a dry climate for the late Weichselian, indicated by a change from tundra towards cold steppe vegetation after 32 ka until 13.5 ka BP (Müller et al., 2009, 2010). For the same time, sedimentological and diatom data indicate a lake level drop. Modelling experiments with a general circulation model suggest that the consecutive decline in the extent of mountain glaciers and increase in dryness through the Weichselian was dictated by the growing shielding effect of the western Eurasian ice sheets that prevented the supply of moist Atlantic air masses to eastern Siberia (Krinner et al., 2011). In addition, enhanced deposition of dust reduced the albedo and promoted ice and snow melting during summer (Krinner et al., 2011). Environmental changes towards interglacial conditions of the Holocene are documented in the Lake Billyakh deposits (Müller et al., 2009) as well as in a peat section at Dyanushka River (Werner et al., 2009). Both records show that climate amelioration started after 13.5 ka BP with the quick return of larch trees that also persisted during the Younger Dryas cold spell, suggesting that the Verkhoyansk Mountain area possibly represented a plant refugium during the climate extremes of the last ice age (Tarasov et al., 2009). Reforestation continued since 11.4 ka BP with the spread of boreal cold deciduous and taiga forests and reached a maximum extent after 7 ka BP. Limnological conditions of Lake Billyakh changed to a higher lake-level and increased biological productivity consistent with climate warming and increased humidity. Mean July air temperatures reconstructed by fossil aquatic chironomids, using a regional inference model (Nazarova et al., 2011), indicate warmest summer temperatures between roughly 9.0 and 6.6 ka BP. The stable-isotope composition of ice wedges in permafrost soils point to warmer winters during the early Holocene compared to the late Holocene (Popp et al, 2006). The recognition of a regional early Holocene climate optimum is consistent with long-term Holocene climate development in wide parts of northern Eurasia. References Diekmann, B., Andreev, A.A., Müller, G., Lüpfert, H., Pestryakova, L., Subetto, D., 2007. Expedition 'Verkhoyansk 2005' - Limnogeological studies at Lake Billyakh, Verkhoyansk Mountains, Yakutia. In: Schirrmeister, L. (ed.): Expeditions in Sibiria in 2005, Reports on Polar and Marine Research, 550: 247-258. Krinner, G., Diekmann, B., Colleoni, F., Stauch, G., 2011. Global, regional and local scale factors determining glaciation. Quaternary Science Reviews, 30: 821-831. Müller, S., Tarasov, P. E., Andreev, A., Diekmann, B., 2009. Late Glacial to Holocene environments in the present-day coldest region of the Northern Hemisphere inferred from a pollen record of Lake Billyakh, Verkhoyansk Mts ., NE Siberia. Climate of the Past 5: 73-84. Müller, S., Tarasov, P.E., Andreev, A.A., Tuetken, T., Gartz, S., Diekmann, B., 2010. Late Quaternary vegetation and environments in the Verkhoyansk Mountains region (NE Asia) reconstructed from a 50-kyr fossil pollen record from Lake Billyakh. Quaternary Science Reviews, 29: 2071-2086. Nazarova, L., Herzschuh, U., Wetterich, S., Kumke, T., Pestryakova, L., 2011. Chironomid-based inference models for estimating mean July air temperature and water depth from lakes in Yakutia, northeastern Russia. Journal of Paleolimnology, 45(1): 57-71. Popp, S., Belolyubsky, I., Lehmkuhl, F., Prokopiev, A., Siegert, C., Spektor, V., Stauch, G., Diekmann, B. (2007): Sediment provenance of late Quaternary morainic, fluvial and loess-like deposits in the southwestern Verkhoyansk Mountains (eastern Siberia) and implications for regional palaeoenvironmental reconstructions. Geological Journal, 42: 477-497. Popp, S., Diekmann, B., Meyer, H., Siegert, C., Syromyatnikov, I., Hubberten, H. W., 2006. Palaeoclimate signals as inferred from stable-isotope composition of ground ice in the Verkhoyansk foreland, Central Yakutia. Permafrost and Periglacial Processes, 17: 119-132. Stauch, G., Lehmkuhl, F., 2010. Quaternary glaciations in the Verkhoyansk Mountains, Northeast Siberia. Quaternary Research, 74: 145-155. Stauch, G., Lehmkuhl, F., Frechen, M., 2007. Luminescence chronology from the Verkhoyansk Mountains (North-Eastern Siberia). Quaternary Geochronology, 2: 255-259. Tarasov, P., Müller, S., Andreev, A., Werner, K., Diekmann, B., 2009. Younger Dryas Larix in eastern Siberia: A migrant or survivor? PAGES News, 17(3): 122-123. Werner, K., Tarasov, P.E., Andreev, A.A., Müller, S., Kienast, F., Zech, M., Zech, W., Diekmann, B., 2009. A 12.5-kyr history of vegetation dynamics and mire development with evidence of Younger Dryas larch presence in the Verkhoyansk Mountains, East Siberia, Russia. Boreas, 39(1): 56-68.

Description: Fossil diatom assemblages in a sediment core from a small lake in Central Kamchatka (Russia) were used to reconstruct palaeoenvironmental conditions of the late Holocene. The waterbody may be a kettle lake that formed on a moraine of the Two-Yurts Lake Valley, located on the eastern slope of the Central Kamchatka Mountain Chain. At present, it is a seepage lake with no surficial outflow. Fossil diatom assemblages show an almost constant ratio between planktonic and periphytic forms throughout the record. Downcore variations in the relative abundances of diatom species enabled division of the core into four diatom assemblage zones, mainly related to changes in abundances of Aulacoseira subarctica, Stephanodiscus minutulus, and Discostella pseudostelligera and several benthic species. Associated variations in the composition and content of organic matter are consistent with the diatom stratigraphy. The oldest recovered sediments date to about 3220 BC. They lie below a sedimentation hiatus and likely include reworked deposits from nearby Two-Yurts Lake. The initial lake stage between 870 and 400 BC was characterized by acidic shallow-water conditions. Between 400 BC and AD 1400, lacustrine conditions were established, with highest contributions from planktonic diatoms. The interval between AD 1400 and 1900 might reflect summer cooling during the Little Ice Age, indicated by diatoms that prefer strong turbulence, nutrient recycling and cooler summer conditions. The timing of palaeolimnological changes generally fits the pattern of neoglacial cooling during the late Holocene on Kamchatka and in the neighbouring Sea of Okhotsk, mainly driven by the prevailing modes of regional atmospheric circulation.

Description: A 415 cm thick permafrost peat section from the Verkhoyansk Mountains was radiocarbon-dated and studied using palaeobotanical and sedimentological approaches. Accumulation of organic-rich sediment commenced in a former oxbow lake, detached from a Dyanushka River meander during the Younger Dryas stadial, at ∼12.5 kyr BP. Pollen data indicate that larch trees, shrub alder and dwarf birch were abundant in the vegetation at that time. Local presence of larch during the Younger Dryas is documented by well-preserved and radiocarbon-dated needles and cones. The early Holocene pollen assemblages reveal high percentages of Artemisia pollen, suggesting the presence of steppe-like communities around the site, possibly in response to a relatively warm and dry climate ∼11.4–11.2 kyr BP. Both pollen and plant macrofossil data demonstrate that larch woods were common in the river valley. Remains of charcoal and pollen of Epilobium indicate fire events and mark a hiatus ∼11.0–8.7 kyr BP. Changes in peat properties, C31/C27 alkane ratios and radiocarbon dates suggest that two other hiatuses occurred ∼8.2–6.9 and ∼6.7–0.6 kyr BP. Prior to 0.6 kyr BP, a major fire destroyed the mire surface. The upper 60 cm of the studied section is composed of aeolian sands modified in the uppermost part by the modern soil formation. For the first time, local growth of larch during the Younger Dryas has been verified in the western foreland of the Verkhoyansk Mountains (∼170 km south of the Arctic Circle), thus increasing our understanding of the quick reforestation of northern Eurasia by the early Holocene.

Description: The Antarctic Circumpolar Current (ACC) plays a crucial role in global ocean circulation by fostering deep-water upwelling and formation of new water masses. On geological time-scales, ACC variations are poorly constrained beyond the last glacial. Here, we reconstruct changes in ACC strength in the central Drake Passage in vicinity of the modern Polar Front over a complete glacial-interglacial cycle (i.e., the past 140,000 years), based on sediment grain-size and geochemical characteristics. We found significant glacial-interglacial changes of ACC flow speed, with weakened current strength during glacials and a stronger circulation in interglacials. Superimposed on these orbital-scale changes are high-amplitude millennial-scale fluctuations, with ACC strength maxima correlating with diatom-based Antarctic winter sea-ice minima, particularly during full glacial conditions. We infer that the ACC is closely linked to Southern Hemisphere millennial-scale climate oscillations, amplified through Antarctic sea ice extent changes. These strong ACC variations modulated Pacific-Atlantic water exchange via the “cold water route” and potentially affected the Atlantic Meridional Overturning Circulation and marine carbon storage.

Description: A marine sediment record from the central Bering Sea, spanning the last 20 thousand years (ka), was studied to unravel the depositional history with regard to terrigenous sediment supply and biogenic sedimentation. Methodic approaches comprised the inference of accumulation rates of siliciclastic and biogenic components, grain-size analysis, and (clay) mineralogy, as well as paleoclimatic modelling. Changes in the depositional history provides insight into land-ocean linkages of paleoenvironmental changes. During the finale of the Last Glacial Maximum, the depositional environment was characterized by hemipelagic background sedimentation. A marked change in the terrigenous sediment provenance during the late Heinrich 1 Stadial (15.7–14.5 ka), indicated by increases in kaolinite and a high glaciofluvial influx of clay, gives evidence of the deglaciation of the Brooks Range in the hinterland of Alaska. This meltwater pulse also stimulated the postglacial onset of biological productivity. Glacial melt implies regional climate warming during a time of widespread cooling on the northern hemisphere. Our simulation experiment with a coupled climate model suggests atmospheric teleconnections to the North Atlantic, with impacts on the dynamics of the Aleutian Low system that gave rise to warmer winters and an early onset of spring during that time. The late deglacial period between 14.5 and 11.0 ka was characterized by enhanced fluvial runoff and biological productivity in the course of climate amelioration, sea-level rise, seasonal sea-ice retreat, and permafrost thaw in the hinterland. The latter processes temporarily stalled during the Younger Dryas stadial (12.9-11.7 ka) and commenced again during the Preboreal (earliest Holocene), after 11.7 ka. High river runoff might have fertilized the Bering Sea and contributed to enhanced upper ocean stratification. Since 11.0 ka, advanced transgression has shifted the coast line and fluvial influence of the Yukon River away from the study site. The opening of the Bering Strait strengthened contour currents along the continental slope, leaving behind winnowed sand-rich sediments through the early to mid-Holocene, with non-deposition occurring since about 6.0 ka.

Description: Extra-tropical circulation systems impede poleward moisture advection by the Indian Summer Monsoon. In this context, the Himalayan range is believed to insulate the south Asian circulation from extra-tropical influences and to delineate the northern extent of the Indian Summer Monsoon in central Asia. Paleoclimatic evidence, however, suggests increased moisture availability in the Early Holocene north of the Himalayan range which is attributed to an intensification of the Indian Summer Monsoon. Nevertheless, mechanisms leading to a surpassing of the Himalayan range and the northern maximum extent of summer monsoonal influence remain unknown. Here we show that the Kunlun barrier on the northern Tibetan Plateau [~36°N] delimits Indian Summer Monsoon precipitation during the Holocene. The presence of the barrier relocates the insulation effect 1,000 km further north, allowing a continental low intensity branch of the Indian Summer Monsoon which is persistent throughout the Holocene. Precipitation intensities at its northern extent seem to be driven by differentiated solar heating of the Northern Hemisphere indicating dependency on energy-gradients rather than absolute radiation intensities. The identified spatial constraints of monsoonal precipitation will facilitate the prediction of future monsoonal precipitation patterns in Central Asia under varying climatic conditions.