TY - JOUR A1 - Jambrina-Enriquez, Margarita A1 - Sachse, Dirk A1 - Valero-Garces, Blas L. T1 - A deglaciation and Holocene biomarker-based reconstruction of climate and environmental variability in NW Iberian Peninsula: the Sanabria Lake sequence JF - Journal of paleolimnolog N2 - The molecular biomarker composition of two sediment cores from Sanabria Lake (NW Iberian Peninsula) and a survey of modern plants in the watershed provide a reconstruction of past vegetation and landscape dynamics since deglaciation. During a proglacial stage in Lake Sanabria (prior to 14.7 cal ka BP), very low biomarker concentration and carbon preference index (CPI) values similar to 1 suggest that the n-alkanes could have derived from eroded ancient sediment sources or older organic matter with high degree of maturity. During the Late glacial (14.7-11.7 cal ka BP) and the Holocene (last 11.7 cal ka BP) intervals with higher biomarker and triterpenoid concentrations (high %nC(29) , nC(31) alkanes), higher CPI and average carbon length (ACL), and lower P-aq (proportion of aquatic plants) are indicative of major contribution of vascular land plants from a more forested watershed (e.g. Mid Holocene period 7.0-4.0 cal ka BP). Lower biomarker concentrations (high %nC(27) alkanes), CPI and ACL values responded to short phases with decreased allochthonous contribution into the lake that correspond to centennial-scale periods of regional forest decline (e.g. 4-3 ka BP, Roman deforestation after 2.0 ka, and some phases of the LIA, seventeenth-nineteenth centuries). Human activities in the watershed were significant during early medieval times (1.3-1.0 cal ka BP) and since 1960 CE, in both cases associated with relatively higher productivity stages in the lake (lower biomarker and triterpenoid concentrations, high %nC(23) and %nC(31) respectively, lower ACL and CPI values and higher P-aq). The lipid composition of Sanabria Lake sediments indicates a major allochthonous (watershed-derived) contribution to the organic matter budget since deglaciation, and a dominant oligotrophic status during the lake history. The study constrains the climate and anthropogenic forcings and watershed versus lake sources in organic matter accumulation processes and helps to design conservation and management policies in mountain, oligotrophic lakes. KW - Plant n-alkanes KW - Lipid biomarker KW - Sanabria Lake KW - n-Alkanes KW - Holocene KW - Lateglacial KW - Iberian Peninsula Y1 - 2016 U6 - https://doi.org/10.1007/s10933-016-9890-6 SN - 0921-2728 SN - 1573-0417 VL - 56 SP - 49 EP - 66 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Trauth, Martin H. A1 - Foerster, Verena A1 - Junginger, Annett A1 - Asrat, Asfawossen A1 - Lamb, Henry F. A1 - Schäbitz, Frank T1 - Abrupt or gradual? BT - Change point analysis of the late Pleistocene-Holocene climate record from Chew Bahir, southern Ethiopia JF - Quaternary research : an interdisciplinary journal N2 - We used a change point analysis on a late Pleistocene-Holocene lake-sediment record from the Chew Bahir basin in the southern Ethiopian Rift to determine the amplitude and duration of past climate transitions. The most dramatic changes occurred over 240 yr (from similar to 15,700 to 15,460 yr) during the onset of the African Humid Period (AHP), and over 990 yr (from similar to 4875 to 3885 yr) during its protracted termination. The AHP was interrupted by a distinct dry period coinciding with the high-latitude Younger Dryas stadial, which had an abrupt onset (less than similar to 100 yr) at similar to 13,260 yr and lasted until similar to 11,730 yr. Wet-dry-wet transitions prior to the AHP may reflect the high-latitude Dansgaard-Oeschger cycles, as indicated by cross-correlation of the potassium record with the NorthGRIP ice core record between similar to 45-20 ka. These findings may contribute to the debates regarding the amplitude, and duration and mechanisms of past climate transitions, and their possible influence on the development of early modern human cultures. KW - Late Pleistocene KW - Holocene KW - Change point analysis KW - Principal component analysis KW - Paleoclimatology KW - Southern Ethiopian Rift KW - African Humid Period KW - Younger Dryas KW - Dansgaard-Oeschger cycles Y1 - 2018 U6 - https://doi.org/10.1017/qua.2018.30 SN - 0033-5894 SN - 1096-0287 VL - 90 IS - 2 SP - 321 EP - 330 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Ni, Jian A1 - Cao, Xianyong A1 - Jeltsch, Florian A1 - Herzschuh, Ulrike T1 - Biome distribution over the last 22,000 yr in China JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Patterns of past vegetation changes over time and space can help facilitate better understanding of the interactions among climate, ecosystem, and human impact. Biome changes in China over the last 22,000 yr (calibrated radiocarbon date, a BP) were numerically reconstructed by using a standard approach of pollen-plant functional type-biome assignment (biomization). The biomization procedure involves pollen data from 2434 surface sites and 228 fossil sites with a high quality of pollen count and C-14 dating, 51 natural and three anthropogenic plant functional types (PFTs), as well as 19 natural and one anthropogenic biome. Surface pollen-based reconstruction of modern natural biome patterns is in good agreement (74.4%) with actual vegetation distribution in China. However, modem large-scale anthropogenic biome reconstruction has not been successful based on the current setup of three anthropogenic PFTs (plantation, secondary, and disturbed PFT) because of the limitation of non-species level pollen identification and the difficulty in the clear assignment of disturbed PFTs. The non-anthropogenic biome distributions of 44 time slices at 500-year intervals show large-scale discrepant and changed vegetation patterns from the last glacial maximum (LGM) to the Holocene throughout China. From 22 ka BP to 19 ka BP, temperate grassland, xerophytic shrubland, and desert dominated northern China, whereas cold or cool forests flourished in central China. Warm-temperate evergreen forests were restricted to far southern China, and tropical forests were absent During 18.5 ka BP to 12 ka BP, cold, cool, and dry biomes extended to some parts of northern, westem, and eastern China. Warm-temperate evergreen and mixed forests gradually expanded to occupy the whole of southern China. A slight northward shift of forest biomes occurred from 15 ka BP to 12 lea BP. During 11.5 ka BP to 9 ka BP, temperate grassland and shrubland gradually stretched to northern and western China. Cold and cool forests widely expanded into northern and central China, as well as in the northern margin of South China along with temperate deciduous forest. Since the early mid-Holocene (approximately 8.5 ka BP to 5.5 ka BP), all forest biomes shifted northward at the expense of herbaceous and shrubby biomes. Simultaneously, cold and cool forest biomes occupied the marginal areas of the Tibetan Plateau and the high mountains in western China. During the middle to late Holocene, from 5 ka to the present, temperate grassland and xerophytic shrubland expanded to the south and east, whereas temperate deciduous forests slightly shifted southward. After 3 lea BP, forest biomes were absent in western China and on the Tibetan plateau surface. Dramatic biome shifts from the LGM to the Holocene were observed in the forest-grassland ecotone and transitional zones between temperate and subtropical climates, between subtropical and tropical regions, and in the mountainous margins of the eastern Tibetan Plateau. Evidence showed more human disturbances during the late Holocene. More pollen records and historical documents are therefore further needed to understand fully the human disturbance-induced large-scale forest changes. In addition, more classifications of anthropogenic biome or land cover, more distinct assignment of pollen taxa to anthropogenic PFTs, and more effective numerical and/or mechanistic techniques in building large-scale human disturbances are required. (C) 2014 Elsevier B.V. All rights reserved. KW - Anthropogenic biome KW - Biomization KW - Holocene KW - Last glacial maximum KW - Plant functional types KW - Pollen dataset Y1 - 2014 U6 - https://doi.org/10.1016/j.palaeo.2014.04.023 SN - 0031-0182 SN - 1872-616X VL - 409 SP - 33 EP - 47 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mishra, Praveen Kumar A1 - Prasad, Sushma A1 - Anoop, A. A1 - Plessen, Birgit A1 - Jehangir, Arshid A1 - Gaye, Birgit A1 - Menzel, Philip A1 - Weise, Stephan M. A1 - Yousuf, Abdul R. T1 - Carbonate isotopes from high altitude Tso Moriri Lake (NW Himalayas) provide clues to late glacial and Holocene moisture source and atmospheric circulation changes JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - High resolution isotopic (delta O-18 and delta C-13) investigations on endogenic carbonates (calcite/aragonite) from Tso Moriri Lake, NW Himalaya show dramatic fluctuations during the late glacial and the early Holocene, and a persistent enrichment trend during the late Holocene. Changes in this lake are largely governed by the [input (meltwater + monsoon precipitation)/evaporationj (WE) ratio, also reflected in changes in the carbonate mineralogy with aragonite being formed during periods of lowest I/E. Using new isotopic data on endogenic carbonates in combination with the available data on geochemistry, mineralogy, and reconstructed mean annual precipitation, we demonstrate that the late glacial and early Holocene carbonate delta O-18 variability resulted from fluctuating Indian summer monsoon (ISM) precipitation in NW Himalaya. This region experienced increasing ISM precipitation between ca. 13.1 and 11.7 cal ka and highest ISM precipitation during the early Holocene (11.2-8.5 cal ka). However, during the late Holocene, evaporation was the dominant control on the carbonate delta O-18. Regional comparison of reconstructed hydrological changes from Tso Moriri Lake with other archives from the Asian summer monsoon and westerlies domain shows that the intensified westerly influence that resulted in higher lake levels (after 8 cal ka) in central Asia was not strongly felt in NW Himalaya. (C) 2015 Elsevier B.V. All rights reserved. KW - Carbonates KW - Holocene KW - Indian summer monsoon KW - Isotopes KW - Tso Moriri Lake Y1 - 2015 U6 - https://doi.org/10.1016/j.palaeo.2015.02.031 SN - 0031-0182 SN - 1872-616X VL - 425 SP - 76 EP - 83 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Trauth, Martin H. A1 - Asrat, Asfawossen A1 - Düsing, Walter A1 - Foerster, Verena A1 - Krämer, K. Hauke A1 - Marwan, Norbert A1 - Maslin, Mark A. A1 - Schäbitz, Frank T1 - Classifying past climate change in the Chew Bahir basin, southern Ethiopia, using recurrence quantification analysis JF - Climate dynamics : observational, theoretical and computational research on the climate system N2 - The Chew Bahir Drilling Project (CBDP) aims to test possible linkages between climate and evolution in Africa through the analysis of sediment cores that have recorded environmental changes in the Chew Bahir basin. In this statistical project we consider the Chew Bahir palaeolake to be a dynamical system consisting of interactions between its different components, such as the waterbody, the sediment beneath lake, and the organisms living within and around the lake. Recurrence is a common feature of such dynamical systems, with recurring patterns in the state of the system reflecting typical influences. Identifying and defining these influences contributes significantly to our understanding of the dynamics of the system. Different recurring changes in precipitation, evaporation, and wind speed in the Chew Bahir basin could result in similar (but not identical) conditions in the lake (e.g., depth and area of the lake, alkalinity and salinity of the lake water, species assemblages in the water body, and diagenesis in the sediments). Recurrence plots (RPs) are graphic displays of such recurring states within a system. Measures of complexity were subsequently introduced to complement the visual inspection of recurrence plots, and provide quantitative descriptions for use in recurrence quantification analysis (RQA). We present and discuss herein results from an RQA on the environmental record from six short (< 17 m) sediment cores collected during the CBDP, spanning the last 45 kyrs. The different types of variability and transitions in these records were classified to improve our understanding of the response of the biosphere to climate change, and especially the response of humans in the area. KW - Paleoclimate dynamics KW - Eastern Africa KW - Pleistocene KW - Holocene KW - Time-series analysis KW - Recurrence plot Y1 - 2019 U6 - https://doi.org/10.1007/s00382-019-04641-3 SN - 0930-7575 SN - 1432-0894 VL - 53 IS - 5-6 SP - 2557 EP - 2572 PB - Springer CY - New York ER - TY - JOUR A1 - Lauterbach, Stefan A1 - Witt, Roman A1 - Plessen, Birgit A1 - Dulski, Peter A1 - Prasad, Sushma A1 - Mingram, Jens A1 - Gleixner, Gerd A1 - Hettler-Riedel, Sabine A1 - Stebich, Martina A1 - Schnetger, Bernhard A1 - Schwalb, Antje A1 - Schwarz, Anja T1 - Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years JF - The Holocene : an interdisciplinary journal focusing on recent environmental change N2 - In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio) geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100-4350, 3450-2850, and 1900-1500 cal. yr BP. The distinct similar to 1500year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia. KW - Central Asia KW - climate KW - Holocene KW - lake sediments KW - mid-latitude Westerlies KW - NAO Y1 - 2014 U6 - https://doi.org/10.1177/0959683614534741 SN - 0959-6836 SN - 1477-0911 VL - 24 IS - 8 SP - 970 EP - 984 PB - Sage Publ. CY - London ER - TY - JOUR A1 - Wang, Yongbo A1 - Bekeschus, Benjamin A1 - Handorf, Doerthe A1 - Liu, Xingqi A1 - Dallmeyer, Anne A1 - Herzschuh, Ulrike T1 - Coherent tropical-subtropical Holocene see-saw moisture patterns in the Eastern Hemisphere monsoon systems JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - The concept of a Global Monsoon (GM) has been proposed based on modern precipitation observations, but its application over a wide range of temporal scales is still under debate. Here, we present a synthesis of 268 continental paleo-moisture records collected from monsoonal systems in the Eastern Hemisphere, including the East Asian Monsoon (EAsM), the Indian Monsoon (IM), the East African Monsoon (EAfM), and the Australian Monsoon (AuM) covering the last 18,000 years. The overall pattern of late Glacial to Holocene moisture change is consistent with those inferred from ice cores and marine records. With respect to the last 10,000 years (10 ka), i.e. a period that has high spatial coverage, a Fuzzy c-Means clustering analysis of the moisture index records together with "Xie-Beni" index reveals four clusters of our data set. The paleoclimatic meaning of each cluster is interpreted considering the temporal evolution and spatial distribution patterns. The major trend in the tropical AuM, EAfM, and IM regions is a gradual decrease in moisture conditions since the early Holocene. Moisture changes in the EAsM regions show maximum index values between 8 and 6 ka. However, records located in nearby subtropical areas, i.e. in regions not influenced by the intertropical convergence zone, show an opposite trend compared to the tropical monsoon regions (AuM, EAfM and IM), i.e. a gradual increase. Analyses of modern meteorological data reveal the same spatial patterns as in the paleoclimate records such that, in times of overall monsoon strengthening, lower precipitation rates are observed in the nearby subtropical areas. We explain this pattern as the effect of a strong monsoon circulation suppressing air uplift in nearby subtropical areas, and hence hindering precipitation. By analogy to the modern system, this would mean that during the early Holocene strong monsoon period, the intensified ascending airflows within the monsoon domains led to relatively weaker ascending or even descending airflows in the adjacent subtropical regions, resulting in a precipitation deficit compared to the late Holocene. Our conceptual model therefore integrates regionally contrasting moisture changes into the Global Monsoon hypothesis. (C) 2017 Elsevier Ltd. All rights reserved. KW - Global monsoon KW - Holocene KW - Eastern hemisphere KW - Moisture evolution Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2017.06.006 SN - 0277-3791 VL - 169 SP - 231 EP - 242 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Saha, Sourav A1 - Owen, Lewis A. A1 - Orr, Elizabeth N. A1 - Caffee, Marc W. T1 - Cosmogenic Be-10 and equilibrium-line altitude dataset of Holocene glacier advances in the Himalayan-Tibetan orogen JF - Data in brief N2 - A comprehensive analysis of the variable temporal and spatial responses of tropical-subtropical high-altitude glaciers to climate change is critical for successful model predictions and environmental risk assessment in the Himalayan-Tibetan orogen. High-frequency Holocene glacier chronostratigraphies are therefore reconstructed in 79 glaciated valleys across the orogen using 519 published and 16 new terrestrial cosmogenic 10Be exposure age dataset. Published 10Be ages are compiled only for moraine boulders (excluding bedrock ages). These ages are recalculated using the latest ICE-D production rate calibration database and the scaling scheme models. Outliers for the individual moraine are detected using the Chauvenet's criterion. In addition, past equilibrium-line altitudes (ELAs) are determined using the area-altitude (AA), area accumulation ratio (AAR), and toe-headwall accumulation ratio (THAR) methods for each glacier advance. The modern maximum elevations of lateral moraines (MELM) are also used to estimate modern ELAs and as an independent check on mean ELAs derived using the above three methods. These data may serve as an essential archive for future studies focusing on the cryospheric and environmental changes in the Himalayan-Tibetan orogen. A more comprehensive analysis of the published and new 10Be ages and ELA results and a list of references are presented in Saha et al. (2019, High-frequency Holocene glacier fluctuations in the Himalayan-Tibetan orogen. Quaternary Science Reviews, 220, 372–400). KW - Cosmogenic nuclides KW - Equilibrium-line altitudes KW - Holocene KW - Central asia KW - Glaciation Y1 - 2019 U6 - https://doi.org/10.1016/j.dib.2019.104412 SN - 2352-3409 VL - 26 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Herzschuh, Ulrike A1 - Ni, Jian A1 - Birks, H. John B. A1 - Böhner, Jürgen T1 - Driving forces of mid-Holocene vegetation shifts on the upper Tibetan Plateau, with emphasis on changes in atmospheric CO2 concentrations JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Numerous pollen records across the upper Tibetan Plateau indicate that in the early part of the mid-Holocene, Kobresia-rich high-alpine meadows invaded areas formerly dominated by alpine steppe vegetation rich in Artemisia. We examine climate, land-use, and CO2 concentration changes as potential drivers for this marked vegetation change. The climatic implications of these vegetational shifts are explored by applying a newly developed pollen-based moisture-balance transfer-function to fossil pollen spectra from Koucha Lake on the north-eastern Tibetan Plateau (34.0 degrees N; 97.2 degrees E; 4540 m a.s.l.) and Xuguo Lake on the central Tibetan Plateau (31.97 degrees N; 90.3 degrees E; 4595 m a.s.l.), both located in the meadow-steppe transition zone. Reconstructed moisture-balances were markedly reduced (by similar to 150-180 mm) during the early mid-Holocene compared to the late-Holocene. These findings contradict most other records from the Indian monsoonal realm and also most non-pollen records from the Tibetan Plateau that indicate a rather wet early- and mid-Holocene. The extent and timing of anthropogenic land-use involving grazing by large herbivores on the upper Tibetan Plateau and its possible impacts on high-alpine vegetation are still mostly unknown due to the lack of relevant archaeological evidence. Arguments against a mainly anthropogenic origin of Kobresia high-alpine meadows are the discovery of the widespread expansion of obviously 'natural' Kobresia meadows on the south-eastern Tibetan Plateau during the Lateglacial period indicating the natural origin of this vegetation type and the lack of any concurrence between modern human-driven vegetation shifts and the mid-Holocene compositional changes. Vegetation types are known to respond to atmospheric CO2 concentration changes, at least on glacial-interglacial scales. This assumption is confirmed by our sensitivity study where we model Tibetan vegetation at different CO2 concentrations of 375 (present-day), 260 (early Holocene), and 650 ppm (future scenario) using the BIOME4 global vegetation model. Previous experimental studies confirm that vegetation growing on dry and high sites is particularly sensitive to CO2 changes. Here we propose that the replacement of drought-resistant alpine steppes (that are well adapted to low CO2 concentrations) by mesic Kobresia meadows can, at least, be partly interpreted as a response to the increase of CO2 concentration since 7000 years ago due to fertilization and water-saving effects. Our hypothesis is corroborated by former CO2 fertilization experiments performed on various dry grasslands and by the strong recent expansion of high-alpine meadows documented by remote sensing studies in response to recent CO2 increases. KW - Tibetan Plateau KW - Pollen KW - Holocene KW - Transfer function KW - Kobresia meadow KW - Atmospheric CO2 concentration Y1 - 2011 U6 - https://doi.org/10.1016/j.quascirev.2011.03.007 SN - 0277-3791 VL - 30 IS - 15-16 SP - 1907 EP - 1917 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Mischke, Steffen A1 - Zhang, Chengjun A1 - Fan, Rong T1 - Early to mid-Holocene lake high-stand sediments at Lake Donggi Cona, northeastern Tibetan Plateau, China - T2 - Quaternary research : an interdisciplinary journal KW - Microfossils KW - Ostracoda KW - Lake level KW - Wetlands KW - Depositional setting KW - Tibetan Plateau KW - Holocene Y1 - 2015 U6 - https://doi.org/10.1016/j.yqres.2014.06.005 SN - 0033-5894 SN - 1096-0287 VL - 83 IS - 1 SP - 256 EP - 258 PB - Elsevier CY - San Diego ER -