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Different climatic controls of soil δ^(13)C_(org) in three mid-latitude regions of the Northern Hemisphere since the Last Glacial period

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Chinese Science Bulletin 2007年第2期52卷 259-266页

作者： RAO ZhiGuo ZHU ZhaoYu zhang jiawu Key Laboratory of Marginal Sea Geology Guangzhou Institute of Geochemistry Chinese 510640 China Center for Arid Environment and Paleoclimate Research (CAEP) Key Laboratory of Westem China's Environmental System ofo Ministry of Education Lanzhou University Lanzhou 730000 China Graduate University of Chinese Academy of Sciences Beijing 100039 China

Paleoecological records of soil δ13Corg from three regions in the middle latitudes of the Northern Hemisphere, including the Chinese Loess Plateau (CLP), the Great Plains and adjacent areas of North America and northwestern Europe, showed different variations since the Last Glacial period. An at-tempt was made to evaluate the causes for the difference in δ13Corg on the basis of the modern climatic data collected in these regions and of the modern C3 and C4 plant distributions. The analysis indicates that temperature, especially the growing season temperature, has a dominant control on the growth of C4 plants. When the mean annual or growing season temperatures are below the "threshold value" , the growth of C4 plants is limited. When the temperature is above the "threshold value" , C4 plants can grow under a wide range of precipitation. However, when the precipitation is high enough to favor the growth of trees, the proportions of C4 plants in local biomass will decline. The implicit control factor recovered by sedimentary records is consistent with the control factor on modern C3/C4 distribution. Pure C3 plants have been dominating the local biomass since the Last Glacial period in European loess region, mainly owing to the low local temperature. The increases in C4 plants from the late Pleistocene to the Holocene in the Chinese Loess Plateau, the Great Plains and adjacent areas, mainly reflect the influ-ence of increasing temperature.

关键词：冰河时代大气污染二氧化碳温度气候变化

Paleohydrological Changes in the Western Tibetan Plateau over the Past 16,000 years Based on Sedimentary Records of n-Alkanes and Grain Size

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Acta Geologica Sinica(English Edition) 2020年第3期94卷 707-716页

作者： WANG Mingda YANG Yaping zhang jiawu HOU Juzhi Key Laboratory of Alpine Ecology Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China Key Laboratory of Western China’s Environmental System(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China CAS Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China

Both monsoons and westerlies have exerted influence on climate dynamics over the Tibetan Plateau(TP) since the last deglaciation, producing complex patterns of paleohydroclimatic conditions. Diverse proxy records are essential to forge a robust understanding of the climate system on the TP. Currently, there is a general lack of understanding of the response of inland lakes over the TP to climate change, especially glacier-fed lakes. Paleohydrological reconstructions of such lakes could deepen our understanding of the history of lake systems and their relationship to regional climate variability. Here we use records of n-alkanes and grain size from the sediments of Bangong Co in the western TP to reconstruct paleohydrological changes over the past 16,000 years. The Paq record(the ratio of non-emergent aquatic macrophytes versus emergent aquatic macrophytes and terrestrial plants) is generally consistent with the variations in summer temperature and precipitation isotopes. The changes in grain-size distributions show a similar trend to Paq but with less pronounced fluctuations in the early-middle Holocene. The new data combined with previous results from the site demonstrate that: 1) Bangong Co experienced relatively large water-level fluctuations during the last deglaciation, with a steadily high lake-level during the early-middle Holocene and a decreasing lake-level in the late Holocene;2) The lake level fluctuations were driven by both high summer temperatures via the melting water and monsoon precipitation. However, the dominant factor controlling lake level changed over time. The lake-level history at Bangong Co deduced from the n-alkanes and grain-size records reveals the past hydrological changes in the catchment area, and stimulates more discussion about the future of glacier-fed lakes under the conditions of unprecedented warming in the region.

关键词： lake level n-alkane Paq grain size Bangong Co Tibetan Plateau

The discovery of annually laminated sediments (varves) from shallow Sugan Lake in inland arid China and their paleoclimatic significance

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Science China Earth Sciences 2007年第8期50卷 1218-1224页

作者： ZHOU AiFeng CHEN FaHu QIANG MingRui YANG MeiLin zhang jiawu CAEP Key Laboratory of West China’s Environmental System(Ministry of Education)Lanzhou UniversityLanzhou 730000China

Detailed examination of sedimentary cores retrieved from Sugan Lake in the northern Qaidam Basin of northwest China’s Tibetan Plateau reveal that fine laminated beddings form in the sediments where water depth exceeds 3 m. Seasonal surface sediments trapped at the bottom of the lake suggest that sediments deposited during summer and autumn are mainly light colored monohydrocalcites, while those deposited in winter are dark organic matter, indicating that varve layers form under modern limnological conditions. Continuous varve sediments comprising four types have accumulated in the upper 5.5 m of Core SG03I from the center of the lake. All types exhibit clear seasonality indicative of annual deposition. Varve counts correspondence with 210Pb dates on recent sediments in the upper core suggest the continuous varves of the upper 5.5 m of the core formed in the late Holocene (2670 a BP). The Sugan Lake varve sequence is the first demonstration of annually laminated sediments re-ported in arid western China.

关键词： Sugan Lake varve Tibetan Plateau arid China

Effects of climate change and human activity on lake shrinkage in Gonghe Basin of northeastern Tibetan Plateau during the past 60 years

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Journal of Arid Land 2016年第4期8卷 479-491页

作者： WU Duo CHEN Fahu LI Kai XIE Yaowen zhang jiawu ZHOU Aifeng College of Earth and Environmental Sciences MOE Key Laboratory of Western China's Environmental SystemsLanzhou University

Changes in the status of freshwater resources are a topic of major global, regional and local concern. This is especially so in the arid and semi-arid regions of China, where shortage of water resources plays a crucial role in limiting sustainable socioeconomic development, as well as in sustaining natural ecosystems. Recent climate change, as well as the effects of localized human activity, such as the use of water for irrigation agriculture, may have significant effects on the status of the water resources in the region. Here, we report the results of a study of changes in the areas of lakes in Gonghe Basin, northeastern Tibetan Plateau of China, over the last 60 years. The data were acquired from optical satellite images and demonstrate that the total water area of lakes in Gonghe Basin decreased significantly from the 1950s to 1980s. The cause is ascribed mainly to human activity including exploitation of farmland, against a background of increasing population; in addition, climatic data for the region demonstrate a minor drying trend during this period as the temperature increased slightly. After the construction of several reservoirs, significant amounts of water were redistributed to promote irrigation agriculture and we conclude that this caused a significant shrinkage of the natural lakes. However, both the area of farmland and the population size remained approximately constant after 1990. We conclude that the variation of the total area of lakes during the second period was mainly controlled by climatic factors （precipitation and temperature）. As the regional temperature reached a new high, the area of some of the lakes decreased sharply before finally maintaining a relatively steady state. We emphasize that anthropogenic climate change and human activity have both significantly influenced the status of water resources in the arid and semi-arid regions of China.

关键词： Gonghe Basin lake shrinkage climate change human activity

Extension of drylands in northern China around 250 kaBP linked with the uplift of the southeast margin of Tibetan Plateau

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Chinese Science Bulletin 2002年第20期47卷 1739-1745页

作者： WU Haibin GUO Zhengtang FANG Xiaomin zhang jiawu CHEN Fahu Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China Department of Geography Lanzhou UniversityLanzhou 730000China Institute of Earth Environment Chinese Academy of SciencesXi'an 710075China

Study on two loess sections, one located at Wu-wei near the Tengger Desert in northwestern China, another located near Ganzi at the southeast margin of the Tibetan Plateau in southwest China, reveals a coeval drying step occurred at -250 kaBP. It is expressed by the increase in eolian grain-size at Wuwei, and by a drastic extension of C4 plants and a decrease of loess chemical weathering intensity at Ganzi. Examination of the available eolian data indicates that the event has also been clearly documented in the loess sections near the deserts in northern China, and in the eolian records from the North Pacific. On the contrary, the signal is rather weak for the central and southern Loess Plateau regions as well as for Central Asia, where the climates are influenced by the southeast Asian monsoon and the westerlies, respectively. Since the climate at Ganzi is under strong control of the southwest Asian monsoon, we interpret this drying step as a result of decreased influence of the southwest summer

关键词： aridification loess-paleosol sequences organic carbon isotope chemical weathering intensity Tibetan Plateau.

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一种面向配网设备的在线红外测温系统设计

电工技术 2024年第3期 139-142,146页

作者：张光儒张家午赵军马振祺陈杰国网甘肃省电力公司电力科学研究院甘肃兰州730070 国网甘肃省电力公司甘肃兰州730000

设计了一种面向配网设备的在线红外测温系统,阐述了该系统的设计思路及工作原理,介绍了系统工作流程;利用该系统对一台标准热源进行温度测量,验证其测量重复性;同时,与目前电力系统现场设备红外测温领域广泛应用的红外测温仪进行对比分... 详细信息

设计了一种面向配网设备的在线红外测温系统,阐述了该系统的设计思路及工作原理,介绍了系统工作流程;利用该系统对一台标准热源进行温度测量,验证其测量重复性;同时,与目前电力系统现场设备红外测温领域广泛应用的红外测温仪进行对比分析,验证该红外测温系统的测量有效性及优势,为系统后续深化应用提供参考。

关键词：配网设备红外测温系统重复性验证

Climatic changes documented by stable isotopes of sedimentary carbonate in Lake Sugan,northeastern Tibetan Plateau of China,since 2 kaBP

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Chinese Science Bulletin 2005年第17期50卷 1930-1939页

作者： QIANG Mingrui CHEN Fahu zhang jiawu GAO Shang-yu ZHOU Aifeng China Center of Desert Research at Beijing Normal University and Key Laboratory of Environmental Changes and Natural Disaster Ministry of Education of China Beijing Normal University Beijing 100875 China Center for Arid Environment and Paleoclimate Research (CAEP) Natiunal Laboratory of Western China's Environmental System Ministry of Education of China Lanzhou University Lanzhou 730000 China

Lake Sugan at the northern edge of the Qaidam Basin was selected as the research object. The temporal se-quence of sedimentary cores retrieved from Lake Sugan since 2 kaBP was reconstructed using the 210Pb, AMS 14C and conventional 14C dating methods. Carbon and oxygen iso-topes of carbonate in the fine-grained lake sediments were analysed. Combined with the changes of δ 18O values of sur-face water and air temperature observation data in the study area, it might be thought that the δ 18O value of the carbon-ate indicates effective moisture, and the changes in δ 13C val-ues are related to annual freeze-up duration of the lake and indirectly indicate air temperature changes in winter half year. From the above, the sequence of climatic changes in the region since 2 kaBP was established. The climatic changes experienced five stages: Warm-dry climate during 0-190 AD; cold-dry climate during 190-580 AD; warm-dry cli-mate during 580-1200 AD (MWP); cold-wet climate during 1200-1880 AD (LIA); cold-dry climate during 1880-1950 AD; and climate warming since 1950s. The air temperature changes in winter half year reflected by carbon isotope since 2 kaBP are in good agreement with the historical literature records and other geologic records, which shows that the climate changes recorded by the stable isotopes from Lake Sugan since 2 kaBP are of universal significance.

关键词：气候变化同位素稳定性碳酸盐沉积作用青藏高原

Variations of organic carbon isotopic composition and its environmental significance during the last glacial on western Chinese Loess Plateau

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Chinese Science Bulletin 2006年第13期51卷 1593-1602页

作者： CHEN Fahu RAO Zhiguo zhang jiawu JIN Ming MA Jianying Center for Arid Environment and Paleoclimate Research (CAEP) Key Laboratory of Western China's Environmental System of Ministry of Education Lanzhou University Lanzhou 730000 China Key Laboratory of Marginal Sea Geology Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China Graduate School of Chinese Academy of Sciences Beijing 100039 China

A high-resolution loess section in the western Chinese Loess Plateau, Yuanbao Section, was sampled for organic carbon isotopic analyses. The soil organic carbon isotope (δ13Corg) varied be- tween ?22.6‰ and ?27.5‰ during the last glacial at the section. During the last interstadial, the δ 13Corg values were more negative than those in both early and late periods of the last glacial by 4‰. The iso- topic composition indicates a coupled response of the pure C3 plants to the temperature, precipitation and the concentration of atmospheric CO2. Decrease in temperature and the atmospheric CO2 concentration from the last interstadial to Last Glaicial Maximum (LGM) caused the organic carbon isotopes to be- come positive by 1.5‰―2.0‰. The amplitude of 4‰ in the δ 13Corg variation during the last glacial should be mainly caused by the precipitation change. Therefore, the δ 13Corg variations of the Yuanbao Section during the last glacial period documented the large-amplitude fluctuation of the monsoon precipita- tion, which is estimated to be 250―310 mm more during the last interstadial than that in the LGM, and 100 mm more than that during early last glacial. The rapid changes of the monsoon precipitation on mil-lennial scale during the last glacial have also been recorded in the isotopic variations in Yuanbao loess section. As the isotopic composition varies compli- catedly as shown in the loess-paleosol sequence, it cannot be simply attributed to the abundances of C3 and C4 plants or be used as an indicator of the summer monsoon variations.

关键词：有机碳同位素成品冰黄土高原华西地区

A 1000-year chironomid-based salinity reconstruction from varved sediments of Sugan Lake,Qaidam Basin,arid Northwest China,and its palaeoclimatic significance

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Chinese Science Bulletin 2009年第20期54卷 3749-3759页

作者： CHEN JianHui CHEN FaHu zhang EnLou BROOKS Stephen J ZHOU AiFeng zhang jiawu MOE Key Laboratory of Western China's Environmental Systems Lanzhou University Lanzhou 730000 China State Key Laboratory of Lake Science and Environment Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China Department of Entomology Natural History Museum London SW7 5BD UK

A 1000-year high-resolution(～10 years) chironomid record from varved sediments of Sugan Lake,Qaidam Basin on the northern Tibetan Plateau,is *** chironomid assemblages are mainly composed of the relatively high-saline-water taxa Psectrocladius barbimanus-type and Orthocladius/Cricotopus,and the relatively low-saline-water taxa Procladius and Psectrocladius *** in the chironomid fauna and inferred salinities suggest that over the last millennium,the Sugan Lake catchment has alternated between contrasting climatic conditions,having a dry climate during the period 990―1550 AD,a relatively humid climate during the Little Ice Age(LIA)(1550―1840 AD),and a dry climate again from 1840 AD *** the decadal to centennial scale,a wet event around 1200―1230 AD,interrupting the generally arid period(990―1550 AD),and a dry event around 1590―1700 AD,punctuating the generally humid period(1550―1840 AD),are clearly *** in the chironomid-based salinity time series indicate a highly unstable climate during the LIA when salinity fluctuations were of greater magnitude and higher *** effective moisture evolution in the Sugan Lake catchment during the last millennium reconstructed by chironomid analysis is in broad agreement with previous palaeo-moisture data derived from other sites in arid Northwest China(ANC).The LIA,characterized by generally humid conditions over the west-erly-dominated ANC was distinctly different from that in monsoonal China,implying an "out-of-phase" relationship between moisture evolution in these two regions during the past 1000 years.

关键词：西北干旱地区柴达木盆地古气候意义沉积物中国盐度纹层