TY - JOUR A1 - Tian, Fang A1 - Herzschuh, Ulrike A1 - Dallmeyer, Anne A1 - Xu, Qinghai A1 - Mischke, Steffen A1 - Biskaborn, Boris T1 - Environmental variability in the monsoon-westerlies transition zone during the last 1200 years - lake sediment analyses from central Mongolia and supra-regional synthesis JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - A high resolution multi proxy (pollen, grain size, total organic carbon) record from a small mountain lake (Lake Khuisiin; 46.6 degrees N, 101.8 degrees E; 2270 m a.s.l.) in the south eastern Khangai Mountains of central Mongolia has been used to explore changes in vegetation and climate over the last 1200 years. The pollen data indicates that the vegetation changed from dry steppe dominated by Poaceae and Artemisia (ca AD 760-950), to Larix forest steppe (ca AD 950-1170), Larix Betula forest steppe (ca AD 1170-1380), meadow dominated by Cyperaceae and Poaceae (ca AD 1380-1830), and Larix Betula forest steppe (after similar to AD 1830). The cold-wet period between AD 1380 and 1830 may relate to the Little Ice Age. Environmental changes were generally subtle and climate change seems to have been the major driver of variations in vegetation until at least the early part of the 20th century, suggesting that either the level of human activity was generally low, or the relationship between human activity and vegetation did not alter substantially between AD 760 and 1830. A review of centennial scale moisture records from China and Mongolia revealed that most areas experienced major changes at ca AD 1500 and AD 1900. However, the moisture availability since AD 1500 varied between sites, with no clear regional pattern or relationship to present day conditions. Both the reconstructions and the moisture levels simulation on a millennium scale performed in the MPI Earth System Model indicate that the monsoon-westerlies transition area shows a greater climate variability than those areas influenced by the westerlies, or by the summer monsoon only. KW - Pollen KW - Grain size KW - TOC KW - Asian monsoon KW - Westerlies KW - Late Holocene KW - Vegetation change KW - Mongolia Y1 - 2013 U6 - https://doi.org/10.1016/j.quascirev.2013.05.005 SN - 0277-3791 VL - 73 IS - 2 SP - 31 EP - 47 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Taft, Linda A1 - Mischke, Steffen A1 - Wiechert, Uwe A1 - Leipe, Christian A1 - Rajabov, Ilhomjon A1 - Riedel, Frank T1 - Sclerochronological oxygen and carbon isotope ratios in Radix (Gastropoda) shells indicate changes of glacial meltwater flux and temperature since 4,200 cal yr BP at Lake Karakul, eastern Pamirs (Tajikistan) JF - Journal of paleolimnolog N2 - We report delta O-18 and delta C-13 values of 21 fossil shells from the aquatic gastropod Radix from a sediment core taken in the eastern basin of Lake Karakul, Tajikistan (38.86-39.16A degrees N, 73.26-73.56A degrees E, 3,928 m above sea level) and covering the last 4,200 cal yr BP. The lake is surrounded by many palaeoshorelines evidencing former lake-level changes, most likely triggered by changes in meltwater flux. This hypothesis was tested by interpreting the isotope ratios of Radix shells together with delta O-18 values of Ostracoda and of authigenic aragonite. The mean delta O-18 values of Radix and Ostracoda fall along the same long-term trend indicating a change in the isotopic composition of precipitation, which contributed to the glaciers in the catchment as snow and finally as melt water to the lake. The sclerochronological delta O-18 and delta C-13 patterns in Radix shells provide seasonal weather information, which is discussed in context with previously proposed climatic changes during the last 4,200 cal yr BP. The period between similar to 4,200 and 3,000 cal yr BP was characterized by stepwise glacier advance in the catchment most likely due to a precipitation surplus. Subsequently the climate remained relatively cold but the lake level fluctuated, as indicated by ostracod shell isotope data. From similar to 1,800 cal yr BP the sclerochronological patterns provide evidence for increasing melt water flux and transport of allochthonous carbon into the lake, most likely due to an accelerated glacier retreat. The period around 1,500 cal yr BP was characterized by strong warming, increasing meltwater flux, glacier retreat and an increasing lake level. Warm conditions continued until similar to 500 cal yr I'P probably representing the end of the Medieval Warm Period. A short relatively cold (dry?) period and a lower lake level are assumed for similar to 350 cal yr BP, possibly an analogue to the Maunder Minimum cooling in the North Atlantic region. Our results show that the lake system is complex, and that changes were triggered by external forcing and feedbacks. The similarity of delta O-18 values in Radix and ostracod shells demonstrates that both archives provide complementary information. KW - Palaeolimnology KW - Stable isotopes KW - Gastropods KW - Sclerochronology KW - Late Holocene KW - Central Asia Y1 - 2014 U6 - https://doi.org/10.1007/s10933-014-9776-4 SN - 0921-2728 SN - 1573-0417 VL - 52 IS - 1-2 SP - 27 EP - 41 PB - Springer CY - Dordrecht ER -