ALBERT

Description: Considerable efforts have been devoted to decipher the late Quaternary moisture and thermal evolution of arid central Asia. However, disparate interpretations still exist concerning different proxies. The spatial and temporal heterogeneities have inhibited a holistic understanding of general patterns and underlying mechanisms. To address these issues, two parallel cores (ONW I, 6.00 m; ONW II, 13.35 m) were retrieved in the Gobi Desert of Mongolia from lake Orog Nuur. Multidisciplinary investigations including geomorphological mapping, radiocarbon dating, sedimentological, palynological and ostracod analyses enabled us to gain a comprehensive dataset for vegetation development and hydrological variability over the last ~45 kyr. Higher lake levels during the Marine Isotope Stage (MIS) 3 and early MIS 2 (~35–~24 kyr) were probably caused by increased precipitation. The sharp transition of Termination I (~11 kyr) is indicated by sedimentological, palynological, and ostracod data. During the late Pleistocene, the lower area of the Orog Nuur catchment was dominated by Artemisia steppe and gradually altered to Chenopodiaceae desert steppe in the Holocene. The early Holocene is also characterized by a relatively humid environment. The humid pulses during the MIS 3 and the early Holocene were also recorded in other archives and are possibly the trait of a larger scale phenomenon in arid central Asia. Four major harsh climatic periods were documented in the core at ~43 kyr, ~36 kyr, during the global Last Glacial Maximum, and the Younger Dryas as playa phases. Reduced westerlies' moisture transport and a retreated East Asian Summer Monsoon influence probably caused those dry phases in the Gobi Desert of Mongolia.

Description: Situated in the Yana-Highlands, the Batagai profile is one of the few inland permafrost outcrops in Yakutia and, for the time being, the biggest and most active thermoerosional cirque worldwide. With Yerkhoyansk recorded as place of the pole of cold, the Yana Highlands represent the region with the most severe climatic continentality in the northern hemisphere. In contrast to the numerous sequences in today’s coastal lowlands, the Batagai sequence was always unaffected by maritime climate influence during its formation and thus better indicates the macro-climate evolution in NE-Siberia. As result of intense thermal degradation, the outcrop formed within 30 years only and cut deep into ice-rich permafrost deposits. The 60 m deep outcrop is now about 850 m in diameter, but erosion rates as high as 15 m/year are changing the dimensions continuously. The Batagai profile thus represents a unique window into the past (and future) of ice-rich permafrost deposits in Yakutia. Field based observations have shown that the permafrost sequence consists of 4 distinct units: below a thin Holocene surface cover, a 30 meter thick Ice Complex with characteristic thick ice wedges has formed. At the base of the Ice Complex, there is an up to 2 m thick layer of plant material including large woody remains. Subjacent to this organic layer of supposedly Eemian origin, there is a horizontally stratified unit composed of silty-sand and without thick syngenetic ice wedges presumably deposited during the Middle Pleistocene. At the very base of the sequence, there appears to emerge another unit including syngenetic ice wedges. This unit was not accessible for sampling. The accessible upper about 45 meter of the sequence were sampled from top to bottom in one meter steps using, due to the difficult accessibility of the permafrost wall, thermokarst mounds in the less steep part of the outcrop. The samples were taken for sedimentological analyses and especially for plant macrofossil and other palaeoecological studies. Whereas sediments give insight into the genesis of the sequence, fossil plant macroremains provide information on local vegetation patterns and habitats at the time of deposition; while palynological analyses reflect the regional vegetation and climate history. First palaeobotanical results will be represented in Session 13: Palaeoenvironments in permafrost affected areas. The sedimentological analyses revealed that, despite clearly delimitable bedding units visible at the outcrop, there is no distinct litho-stratigraphical differentiation recognizable in the grain size distribution or other sedimentological parameters. Accordingly, the sequence is characterized by a grain size signature typical for Ice Complex deposits. In comparison to other Yakutian ice-rich permafrost sequences, e.g. in the coastal lowlands, the Batagai profile is however distinguished by a higher fraction of fine sand over the whole recorded sequence. This might be due to increased aeolian deposition from local sources, e.g. from barren ridges in the highlands uncovered by vegetation. The assumption that aeolian deposition played a substantial role in the formation of the sequence is also suggested by impressive dunes in the immediate vicinity of the profile at the boundary of Batagai city.

Description: Clay-mineral fingerprints from modern and fossil lake sediments from Lake Donggi Cona, situated on the northeastern Tibetan Plateauwere studied to determine changes in sediment provenance and environmental development since the late Glacial. To infer the source areas of the lake sediments, characteristic facies units (cover sediments and soils) from the catchment of the lake were studied concerning their clay-mineral compositions and through statistical analyses using the Fuzzy C-Means algorithm. Sediment contributions from the various geological provinces in the catchment of the lake are reflected in a systematic spatial pattern of variable clay-mineral assemblages, which is most pronounced in modern fluvial and lake sediments. Downcore changes in the clay-mineral fingerprints of lake sediments provide information on the spatio-temporal variability of detrital sediment supplies, related to climate-influenced changes in environmental boundary conditions. Since the late Glacial, water-level fluctuations driven by glacier melt appear to have exerted the greatest control over the transport paths of detrital sediments. Probably glacial melt-waters carried mainly illitic rich pre-Cenozoic debris into the lake fromthe northern and north-western catchment areas. During the Holocene the detrital clay mineral supply was mainly controlled from pre-Cenozoic and Neogene sources. However, because of the increased summer monsoon precipitation the lake level rose dramatically to at least modern levels, resulting in a relative increase in the supply frompedogenic karsticweathering sources mainly fromthe east,which during the Holocene was possibly flooded morewidely than today. During the late Holocene a decreasing input of smectite suggests a relative reduction in the supply of far-traveled aquatic suspensions into the lake. In contrast, during the sameinterval kaolinite concentrations increased,which suggests a relatively strong sediment supply from the east, possibly triggered by a current flowing from east to west.

Description: We investigated a well-dated sediment section of a palaeolake situated in the coastal zone of Shikotan Island (Lesser Kurils) for organic sediment-geochemistry and biotic components (diatoms, chironomids, pollen) inorder to provide a reconstruction of the palaeoenvironmental changes and palaeo-events (tsunamis, sea-level fluctuations and landslides) in Holocene. During the ca 8000 years of sedimentation the changes in organic sediment-geochemistry and in composition of the diatoms and chironomids as well as the shifts in composition of terrestrial vegetation suggest that the period until ca 5800 cal yr BP was characterized by a warm and humid climate (corresponds to middle Holocene optimum) with climate cooling thereafter. A warm period reconstructed from ca 900 to at least ca 580 cal yr BP corresponds to a transition to a Nara-Heian-Kamakura warm stage and can be correlated to a Medieval Warm Period. After 580 cal yr PB, the lake gradually dried out and climatic signals could not be obtained from the declining lacustrine biological communities, but the increasing role of spruce and disappearance of the oak from the vegetation give evidences of the climate cooling that can be correlated with the LIA. The marine regression stages at the investigated site are identified for ca 6200–5900 (at the end of the middle Holocene transgression), ca 5500–5100 (Middle Jomon regression or Kemigawa regression), and ca 1070–360 cal yr BP (at the end of Heian transgression). The lithological structure of sediments and the diatom compositions give evidences for the multiple tsunami events of different strengths in the Island. Most remarkable of them can be dated at around ca 7000, 6460, 5750, 4800, 950 cal yr BP. The new results help to understand the Holocene environmental history of the Southern Kurils as a part of the Kuril-Kamchatka and Aleutian Marginal Sea-Island Arc Systems in the North-Western Pacific region.

Description: We present a synthesis of the results of a multiproxy, multisite, palaeoecological study of Holocene environmental change in Kamchatka, Far East Russia, details of which are presented elsewhere in the volume. We summarise the results of the analyses of pollen, diatom, chironomid, and testate amoebae assemblages, together with stable isotopes of oxygen and carbon, and sediment characteristics from the sediments of five lakes and a peat succession on a latitudinal gradient of the Kamchatka Peninsula, to infer environmental change and establish the major climate forcers and climatic teleconnections. There are synchronous shifts in the assemblage composition of most of the biota and across most sites at 6.5–6.2 ka BP, 5.2 ka BP, 4.0 ka BP, and 3.5 ka BP, suggesting a response to strong regional climate forcing at these times. These dates correspond to the warmest part of the Holocene Thermal Maximum(HTM) (6.5–6.2 ka BP), the beginning of theNeoglacial cooling (5.2 ka BP), the coolest and wettest part of the Neoglacial (4.0 ka BP), and a switch to warmer and drier conditions at 3.5 ka BP. Our results provide evidence for the penetration and domination of different air masses at different periods during the Holocene. Cool and dry periods in winter (e.g., at 6.0 ka BP) were driven by a relatively weak pressure gradient between the Siberian High and the Aleutian Low, whereas cool, wet periods in winter (e.g., the Neoglacial and during the LIA) developed when these two systems increased in strength. Warm, dry, continental periods in summer (e.g., at 2.5 ka BP) were driven by a weakening of the Siberian High. We find that the timing of the HTM in Kamchatka is later than in the Eurasian arctic but similar to northern Europe and the sub-arctic part of eastern Siberia. This progressive onset of the HTM was due to the effects of postglacial ice-sheet decay that modulated the routes of westerly storm tracks in Eurasia. A major ecosystem driver was the Siberian dwarf pine Pinus pumila, which spread northward during the Holocene in response to increasing winter snow, and caused water chemistry changes on arrival in the catchments of our study lakes and a response in diatom and chironomid assemblages. We also detect shortterm responses, especially in diatom assemblages, to water chemistry changes following volcanic ash deposits.

Description: Sea-surface temperatures (SSTs) based on radiolarian assemblage changes are estimated for the last 160 kyr, from a sediment core (Y9) recovered fromPukaki Saddle, northeast of Campbell Plateau. Site Y9 lies beneath Subantarctic Surface Water (SAW) immediately to the north of the Subantarctic Front (SAF), which in this region is bathymetrically constrained by the edges of Campbell Plateau and defines the northern boundary of the Antarctic Circumpolar Current (ACC). Radiolarian assemblages are characterised by an exceptionally high abundance of the Antarctic to subantarctic species Antarctissa spp. (up to 68%), especially during glacial intervals. SST estimates are derived using Factor Analysis and the Modern Analog Technique. Both methods capture the glacial-interglacial (G-I) pattern. The SST reconstructions show the changing relative influence of distinct water masses during the past G-I cycle, with major temperature variations of the order of 7–9 °C at glacial Terminations. Glacials (marine isotope stages (MIS) 6 and 2) are associated with particularly cool SSTs that are indicative of a more vigorous SAF/ACC and an enhancement of the inflow through Pukaki Saddle and/or frequent development of cold-core eddies at the SAF. By contrast, the influence of warmer waters and relaxation of the ACC during interglacials can be inferred from temperatures slightly warmer (e.g., mid-Holocene) and/or comparable to present day (e.g., MIS 5e). During these intervals, relatively warmer temperatures most likely indicate a higher warmcore eddy activity due to a strengthened Subtropical Front and/or a weakened inflow of cool water through Pukaki Saddle and/or an increased stratification in the Campbell Plateau region. Furthermore, the SST record is characterised by an abrupt warming at ca. 10 kyr (i.e., Termination I), the occurrence of a reversal at Termination I, and awarming event at the end of MIS 4, coincidingwith the A4 event in the Byrd ice core. These characteristics, together with the pronounced G-I cycle shown by the SST estimates, suggest that Site Y9 is influenced by major oceanographic changes in the SW Pacific and responds to thermal changes at high southern latitudes.

Description: Unmixing of grain-size distributionswithmultivariate statistical analysis gives indications of themain sediment transport processes and related environmental conditions in an area. We performed end-member mixing analysis (EMMA) of sedimentological data from 912 terrestrial sediment samples collected in the Donggi Cona catchment, north-eastern Tibetan Plateau. Up to the present, this is the largest sedimentological dataset on the Tibetan Plateau. EMMA resulted in the characterisation of three end-members that explain 88% of the variance within the dataset. The end-members all represent aeolian deposits. The first end-member EM 1 represents very fine dune sediments that were deflated from a former lake system. EM 2 represents medium sand deposits that were blown out from playa and alluvial fan sediments. EM 3 represents fine loess(−like) sediments mainly found at higher elevations. Different transformations, adding of a fourth end-member and adding of up to 200 loess samples do not change the composition of the end-members, demonstrating the robustness of themodel. EMMA allows the synchronous interpretation of very large datasets, resulting in a general characterisation of sediment transport in a particular area. Performing EMMA on the dataset demonstrates the importance of aeolian transport in this part of the world.