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: Four retrogressive thaw slumps (RTS) located on Herschel Island and the Yukon coast (King Point) in the western Canadian Arctic were investigated to compare the environmental, sedimentological and geochemical setting and characteristics of zones in active and stabilised slumps and at undisturbed sites. In general, the slope, sedimentology and biogeochemistry of stabilised and undisturbed zones differ, independent of their age or location. Organic carbon contents were lower in slumps than in the surrounding tundra, and the density and compaction of slump sediments were much greater. Radiocarbon dating showed that RTS were likely to have been active around 300 a BP and are undergoing a similar period of increased activity now. This cycle is thought to be controlled more by local geometry, cryostratigraphy and the rate of coastal erosion than by variation in summer temperatures.

Description: The major objective of this presentation to summarize new regional datasets on the quality and quantity of fossil organic matter (OM) in permafrost sequences of NE Siberia, in order to show the permafrost carbon pool heterogeneity related to paleoenvironmental dynamics, and the improved estimation of permafrost organic carbon stocks. OM stored in Quaternary permafrost grew, accumulated, froze, partly decomposed, and refroze under different environmental condition, reflected in specific biogeochemical and cryolithological features. OM in permafrost is mainly represented by twigs, leaves, peat, grass roots, and plant detritus.

Description: In the exploration of the Russian Arctic German-spelling names of scientists occurred since the 18th century. Geographers and geologists like Alexander von Middendorff, Ernst von Bär, Alexander Bunge, Eduard von Toll studied the frozen ground in Siberia and established by doing so permafrost research. Today joint Russian-German research continues in Siberia, mainly hosted by the Mel’nikov Permafrost Institute (Yakutsk), the faculties of Geology, of Geography and of Soil Science of the Moscow State University (Moscow), the Arctic and Antarctic Research Institute (St. Petersburg), the Institute of Physicochemical and Biological Problems in Soil Science (Pushchino), and the Alfred Wegener Institute (Potsdam), the Institute of Soil Science (Hamburg University). The major scientific topics of this long-term research are permafrost archives, paleoclimate and landscape dynamics; coastal dynamics and subsea permafrost; permafrost degradation and modern changes of permafrost landscapes. More than 30 joint expeditions since 1993 took Russian and German scientists to Central and East Siberia.

Description: The Arctic became a region of growing interest for (paleo)climate researchers within the last decade (IPCC, 2007). However, continuous paleo-climate records in the continental Arctic region are rare, especially beyond the Last Glacial Maximum (LGM). At Lake El’gygytgyn, NE Siberia sediment cores were retrieved in an area, which has not been glaciated since the Pliocene. Here, inside a crater structure formed by a meteorite impact circa 3.6 Ma ago (Layer, 2000), a continuous sediment record was deposited. Lake El’gygytgyn is of circular shape, about 12 km in diameter and 170 m deep. This cold-monomictic and ultra-oligotrophic lake has a small catchment (293 km2) and only one outflow. Due to the absence of carbonates in the lake, we used the oxygen isotopic composition of biogenic silica (diatoms) for paleoclimate reconstruction. The usefulness of diatoms and their δ18O values as a proxy for reconstructing air temperatures and/or the isotope composition of precipitation has been widely demonstrated (e.g. Leng & Barker, 2006). Preliminary studies have shown that mainly two diatom species are present in the lake: Cyclotella ocellata which occurs throughout the whole core and Pliocaenicus costatus mainly existing in the Holocene. Various preparation steps (H2O2/HCl treatment, sieving, heavy liquid separation) have been performed in order to gain a clean diatom sample from the original sediment. The 〈10μm fraction was used showing mostly a mono-specific diatom assemblage of Cyclotella ocellata. More than 95% of the samples showed a degree of purity of SiO2 〉 97 %. In a first step, we have analysed δ18O diatom of 96 samples (N=2-4) from shallow sediment core Lz1024 (16.5 m long) dating back to app. 250 ka. Special emphasis was laid on the time periods between 0-20ka BP (resolution ~ 1k) and 120-250ka BP (resolution ~ 3k). The standard deviation between the repetitions was 1σ 〈 ±0.3 ‰. The downcore variations of the δ18O values show that glacial-interglacial cycles are present throughout the whole core. The δ18O values range from δ18O = +19.1‰ to +24.4‰ and reflect the Holocene Thermal Maximum (HTM; δ18O = +23‰; 8.9 ka), the Last Glacial Maximum (LGM; δ18O = +19.1‰; 23.1 ka), the Eemian interglacial period (δ18O = +24.4 ‰; 127.2 ka), the interval corresponding to MIS 7.1, 7.3 (plateau around +23.0‰, ~209-203 ka) and MIS 7.5 (+23.6‰; 243.9 ka). A peak-to-peak amplitude of 5.3‰ between the MIS 5.5 absolute maximum and the LGM absolute minimum was detected, most likely controlled by the δ18O signal of precipitation. This is the longest continuous terrestrial δ18O record from the Arctic directly reflecting paleo precipitation signals. Correlations of the δ18O record with the benthic stack LR04 (Lisiecki and Raymo, 2005; r=0.58) and EPICA Dome-C δD record (EPICA members, 2004; r=0.69) are significant and show the sensitivity of Lake El’gygytgyn and the wider Arctic climate system to global climate change. By the time of the conference, this work will be expanded to the long lake sediment core 5011-1 (dating back to about 3.6 Ma), which was drilled within the ICDP programme at Lake El’gygytgyn in early 2009. EPICA members: Eight glacial cycles from an Arctic ice core, Nature, 429, 623-628, 2004. Layer, P. W.: Argon-40/argon-39 age of the El'gygytgyn impact event, Chukotka, Russia, Meteoritics & Planetary Science, 35, 591-599, 2000. Leng, M. J., and Barker, P. A.: A review of the oxygen isotope composition of lacustrine diatom silica for palaeoclimate reconstruction, Earth-Science Reviews, 75, 5-27, 2006

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.