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High-resolution precipitation variations in the Northeast Tibetan Plateau over the last 800 years documented by sediment cores of Qinghai Lake

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Chinese Science Bulletin 2003年第14期48卷 1451-1456页

作者： ZHANGJiawu JINMing CHENFahu R.W.Battarbee A.CoG.Henderson CenterforAddEnvironmentandPaleoclimateResearch NationalLab.ofWesternChina'sEnvironmentalSystemLanzhouUniversityLanzhou730000China DesertandDesertificationLab. ColdandAridRegionsEnviron-mentalandEngineeringResearchInstituteChineseAcademyofSci-encesLanzhou730000China EnvironmentalChangeResearchCenter DepartmentofGeographyUniversityCollegeLondon26BedfordWayWC1H0APUK

Short cores of about 80-cm retrieved from three main basins of the deepwater areas in Qinghai Lake, the largest inland enclosed lake in China, were studied. Stable isotopes of authigenic carbonates, grain-size, carbonate and organic matter content at 5-year resolution are used to reconstruct the climatic history over the last 800 years in the Northeastern Tibetan Plateau. Chronology was established according to 210Pb dating and 137Cs methods and the core correlation. It is found that cores from different deep basins of the lake can be well correlated. The sedimentary rate is highest in the western basin of the lake and lowest in the east. In the southern basin of the lake where the short core Qing-6 is located, the recent average sedimentation rate is 0.1004 cm/yr. Variations in effective precipitation recorded by the oxygen isotopes and grain size data during the last 800 years are consistent with the glacial accumulation record form the Dunde and Guliya ice cores. A dry climate lasted for 300 years from 1200 AD to 1500 AD, followed by a wet period from 1500 to 1560 AD. The two dry periods, 1560 to 1650 AD and 1780 to 1850 AD, were the results of southwest monsoon weakening. The effective precipitation generally increased since 1650 AD due to the strengthening of the Asian Southwest Monsoon, resulting in a wet period until the 1950s. Except the early stage, the Little Ice Age on the Plateau is characterized by increased effective moisture. Organic mat- ter content, with nearly 200-year cycles, shows similar trend with the atmospheric delta carbon-14 before the 1850s, indicating that the bioproductivity responds to solar activity.

关键词：中国西藏东北部青海湖沉积岩心古气候碳酸盐氧同位素有效降水量

A carbon- and oxygen-isotope record of recent environ- mental change from Qinghai Lake, NE Tibetan Plateau

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Chinese Science Bulletin 2003年第14期48卷 1463-1468页

作者： A.C.G.Henderson J.A.Holmes ZHANGJiawu M.J.Leng L.R.Carvalho EnvironmentalChangeResearchCentre(ECRC) DepartmentofGeographyUniversityCollegeLondon26BedfordWayLondonWC1H0APUK CenterforAridEnvironmentandPaleoclimateResearch NationalLaboratoryofWesternChina'sEnvironmentalSystemsLanzhouUniversityLanzhou730000China NERCIsotopeGeosciencesLaboratory(NIGL) BritishGeologicalSurveyKeyworthNottingham.NG125GGUK Presentaddress:CentreforEcologyandHydrology(CEH) EdinburghBushEstatePenicuikMidlothianEH260OB.UK

A c. 300-year oxygen and carbon isotope record derived from fine-grained and ostracod carbonate from Qinghai Lake testifies to dramatic interannual tointerdecadal limnological change. Fine-grained carbonates, which are mainly authigenic, are likely to have formed in the epilimnion of the lake and their isotopic composition reflects the summer temperature and, more importantly, the isotopic composition of the near-surface waters, which is mainly a function of evaporative concentration. Ostracod shells are secreted in the benthos of the lake, and their isotopic composition reflects summer bottom-water conditions, together with fractionation effects, which may differ between species. Differences betweencontemporaneous values from authigenic carbonates and ostracod shells may provide an indication of stratification within the lake and variations in effective precipitation over the northeast part of the Tibetan Plateau over the past 300 years. A period of moderate evaporative concentration, from about 300 to 100 yr BP, was interrupted by a marked wet phase from ～100 to 40 yr BP, which was in turnfollowed by a return to drier conditions in the most recent part of the *** increase in ? 18O values in the latter part of the record accords well withinstrumental records of lake-level lowering and salinity increase since about 1955 AD.

关键词：中国西藏东北部环境变化碳同位素氧同位素季风古气候青海湖

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类乌齐县农业生产现状及发展初探

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西藏农业科技 2007年第3期29卷 28-30页

作者：赖乾优类乌齐县农技推广站西藏昌都855600

一、类乌齐县基本情况1.地理位置及区域范围类乌齐县位于西藏东北部,昌都地区西北部,地理坐标北纬30°55'-31°58′东径95°49'- 96°58′.地处国道317线和214线交汇处,北与青海省囊谦县交界,西与昌都地区丁青县相邻,东南与八宿、洛隆... 详细信息

一、类乌齐县基本情况1.地理位置及区域范围类乌齐县位于西藏东北部,昌都地区西北部,地理坐标北纬30°55'-31°58′东径95°49'- 96°58′.地处国道317线和214线交汇处,北与青海省囊谦县交界,西与昌都地区丁青县相邻,东南与八宿、洛隆、昌都县相邻.

关键词：农业生产现状昌都地区西藏东北部区域范围地理位置地理坐标西北部交汇处