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

A c. 300-year oxygen and carbon isotope record derived from fine-grained and ostracod carbonate from Qinghai Lake testifies to dramatic interannual to illterde-cadal linmologicai change. Fine-grained carbonates, whichare mainly authigenic, are likely to have formed in the epillmnion 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 afunction of evapor ative concentration. Ostracod shells aresecreted in the benthos of the lake, and their isotopic compo-sition reflects summer bottom-water conditions, together with fractionation effects, which may differ between species.Differences between contemporaneous values from authi-genic carbonates and ostracod shells may provide an indica-tion of stratification within the lake and variations in effec-tive precip itation over the northeast part of the Tibetan Pla-tcau over the past 300 years. A period of moderate evapora-tive concentration, from about 300 to 100 yr BP, was inter-rupted by a marked wet phase from-100 to 40 vr BP. which was in turn followed by a return to drier conditions in the most recent part of the record. The increase in δ^18O values in the latter part of the record accords well with instrumental records of lake-level lowering and salinity increase since about 1955 AD.     

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

Short cores of about 80-cm retrieved from three main basins of th e deepwater areas in Qinghai Lake,the largest inland enclosed lake in China, were studied. Sta-ble isotopes of authigenlc 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 210^pb dating and 137^Cs methods and the core corrdation. 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-6is located, the recent average sedimentation rate is 0.1004cm/yr. Variations in effective precipitation recorded by the oxygen isotopes and grain size data durine 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 South-west Monsoon, resulting in a wet period until the 1950s. Ex-cept the early stage, the Little Ice Age on the Plateau is characterized b y increased effective moisture. Organic mat-ter content, with nearly 200-year cycles, shows similar trend with the atmospheric delta earbon-14 before the 1850s, indi-eating that the bioproductivity responds to solar activity.     

Uplift of the Tibetan Plateau and environmental changes

Major progress, problems, and challenges of recent investigation of the Tibetan Plateau uplift processes and resulting environmental changes are reviewed and summarized briefly, which especially covers the National Tibetan Research Projects of the Chinese Eighth (1992-1996) and Ninth (1997-2001) "Five-Year Projects". The Tibetan Plateau uplift is a complicated multiple cyclic process. The Gangdise and Himalayas began to uplift in the Middle Eocene and Early Miocene respectively, while the main part of the Plateau merely underwent corresponding passive deformation and secular denudation, resulting in two planation surfaces. The third and also the strongest uplift involved the whole Plateau and its marginal mountains commenced at 3.6 Ma. Successive Kunlun-Huanghe movement at 1.1-0.6 Ma and Gonghe movement at 0.15 Ma raised the Plateau to its present height. The Asian monsoonal system and Asian natural environment formed in response to these tectonic uplifts.     

Thermal Stratification in Lake Zige Tangco, Central Tibetan Plateau

Lake Zige Tangco is an endorheic saline lake in central Tibetan Plateau. Investigations of 1998 and 1999 revealed that is was a typical stratified lake. The characteristics of thermal stratification of the lake have been extensively discussed from 4 aspects, i.e. thermocline, hydrochemistry and dissolved oxygen, stable isotope oxygen, and stability. The thermocline coupled with chemocline was further analyzed.     

A 16000-year pollen record of Qinghai Lake and its paleo-climate and paleoenvironment

The paleoclimate and paleoenvironment of Qinghai Lake indicated by a 16000-year pollen record are as follows. It was very cold and dry before 15200 years. During the Late Glacial, the climate varied from colder and semiarid to cool and semi-humid and fluctuated frequently but with little amplitude. Three cold events in the periods of 13400–13000, 11600–12000, and 11000–10400 aBP respectively correspond to the Oldest Dryas, Older Dryas and Younger Dryas events, whereas the two warm periods between them, 12000–13000 and 11600–11000 aBP, respectively correspond to Bölling and Alleröd periods. The temperature increased abruptly after the Younger Dryas event, and then the climate gradually turned to be warm and wet from warm and semiarid. In the Holocene, the largest amplitude of cold event that occurred at ca. 8200 aBP is quite prominent. The Holocene climatic optimum culminated at 6700 aBP. After 2100 aBP, the climate tended to be cold and dry, keeping on up to now. Palaeoclimatic evolution and events of Qinghai Lake based on pollen assemblage and concentrations can be well parallel with the global climatic events.     

青藏高原的神山类型及其信仰意义

神山是藏族民众对青藏高原高山环境的一种精神创造和象征性符号。藏族宗教从地域权限和文化影响范围将神山分为世界宗教神山、区域族群神山、部落社会神山与民众个人魂山四种层次,将每个区域内的一座或一组高山奉为神山而崇拜,并做为禁忌之地而加以保护,它在历史上强化了族群的团结整合,同时通过崇拜活动使神山呈现自然景观与人文景观的高度和谐,具有了审美价值,保护了高原山系生态环境;在整个青藏高原,高高矗立的神山是人类社会的一种精神寄托,是人与自然和谐的象征。     

Climatic significance of n-alkanes and their compound-specific dD values from lake surface sediments on the Southwestern Tibetan Plateau

The content and hydrogen isotope ratios of n-alkanes extracted from recent lake surface sediments sampled from nine lakes in three different climate zones on the Southwestern Tibetan Plateau were analyzed.Values were compared with n-alkanes in plants from lake drainages,and dD values of meteoric water,lake water,and mean annual precipitation.The results showed that n-C23was predominantly derived from aquatic plants,and n-C27–n-C33from terrestrial higher plants.The average carbon chain length of n-C27–n-C33(ACL27–33)was positively correlated with the mean annual precipitation.dD values of the long-chain n-alkanes n-C29and n-C31of terrestrial origin(varying between-214%and-169%,and-226%and-185%,respectively)were inversely correlated with mean annual precipitation;but in accordance with the average annual variations in dD(OIPC),dD values of n-C31were strongly related to the dD values of growing season meteoric water(R2=0.74).The large difference between dD values of n-C23of aquatic origin and n-C31(an average of about 27%)demonstrates the enrichment of the lake water dD compared to precipitation,caused by strong evaporation in the semiarid–arid areas of the southwestern Tibetan Plateau.Average value of en C25 31=p(-95%)is evidently higher than the value observed in European wet regions(-128%);besides,en C31(about-116%)is constant along the study transect(SD=9),which indicates that n-C31is a useful proxy for the environment.     

青海湖面积动态监测系统的设计与实现

文中以遥感影像为依托,根据历史及现有的遥感影像数据生成各时期青海湖范围水涯线,结合其他矢量数据以及统计数据,设计并实现了“青海湖面积动态监测系统”.系统能够将青海湖面积变化以多种方式客观、科学的展现出来,为青海湖流域生态环境保护和综合治理提供了数据参考.     

Millennial-scale climate change since the last glaciation recorded by grain sizes of loess deposits on the northeastern Tibetan Plateau

Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still not solved but of great significance. The 22-m high-resolution Ioess-paleosol sequence in the Hezuo Basin on the northeastern Tibetan Plateau demonstrates that the Plateau winter monsoon experienced a millennial variation similar to high latitude Northern Hemisphere, with cold events clearly correlated with Heinrich events but less for the warm events (Dansgarrd-Oeschger events). It may indicate that the climate system at high latitudes in the Northern Hemisphere had played an important role in both the Plateau monsoon and the high-level westerlies. On 10^4 year scale, there are two distinct anomalous changes, which are not found in the records from high latitude northern hemisphere, revealed by the loess grain size in the Hezuo Basin. One is that there was a considerable grain size increase at -36 kaBP, suggesting an abrupt enhancement of the Plateau winter monsoon at that time; the other is that, during 43--36 kaBP, the grain size decreased distinctly, indicating a notable weakening of the Plateau winter monsoon around that period. Both of the two anomalies suggest that the Tibetan climate may have been controlled by some other factors, besides the high latitude climatic changes in the Northern Hemisphere.     

Millennial-scale monsoonal climatic change from paleosol sequences on the Chinese western Loess Plateau and Tibetan Plateau: a brief summary and review

This paper summarizes the work from the INQUA 1997 Project "Response of soil formation to short-warm-episodes of Asian summer monsoon" and its seeded related international and domestic grants. It reviews the effects of the millennial monsoonal changes on the loess- paleosols of the Chinese Loess and Tibetan Plateaus. High-resolution proxy records of pedogenesis and monsoons demonstrate that both Asian winter and summer monsoons were unstable and synchronously and inversely coupled during the last glaciation. During that time rapid episodic cycles of cold surges and warm enhancements spanned only ca. 1-2 ka in high- frequency domain. Sub-Milankovitch cycles (6-8 ka) of progressive cooling or weakening in low- frequency domain generally resembled the pattern of the North Atlantic climatic change. However, during the last interglacial, Asian winter and summer monsoons seemed to vary independently, the former being stable and the later unstable. Soil formation seems to occur in surprisingly fast response to the summer monsoon warm enhancements, resulting in weakly or moderately developed paleosol sequences. North Atlantic and polar cold air surges though the westerlies and other paths, and the north-south swing of the westerlies beside the Tibetan Plateau, may be the alternative mechanisms for the rapid monsoonal changes during the last glacial. But in the last interglacial, the summer monsoons worked largely independently.     

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

Lake Sugan at the northern edge of the Qaidam Basin was selected as the research object. The temporal sequence 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 isotopes of carbonate in the fine-grained lake sediments were analysed. Combined with the changes of 8180 values of surface water and air temperature observation data in the study area, it might be thought that the δ^18O value of the carbonate indicates effective moisture, and the changes in δ^13C values 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 climate 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.     

Characteristics of recent temperate glacier fluctuations in the Parlung Zangbo River basin,southeast Tibetan Plateau

Little is known about recent variation of temperate glaciers on the Tibetan Plateau, although they are of particular theoretical and practical interests in terms of climate change and water supply. The study of glacier mass balance and terminus variation for six temperate glaciers in the Parlung Zangbo River basin, southeast Tibetan Plateau, shows the facts of the overall negative mass balance and the continued terminus retreat from 2005/2006 to 2007/2008. The mass balances of smaller glaciers were more negative compared to larger glaciers. Referring the trend of glacier mass balance in the Hengduan Mountains, the Himalayas and glacier shrinkage in southeast Tibetan Plateau, the mass loss and recession of temperate glacier in this region are expected if the current climate condition continues.     

Formate and acetate records in the Muztagata ice core, Northwest Tibetan Plateau

Formic and acetic acids (HCOOH, CH3COOH), originating mainly from biosphere (release by plants, combustion of biomass, motor exhaust and oxidation of organism, etc.), are two simple organic chemical com- pounds in troposphere. Though the concentration of these two organic acids is low in atmosphere, they are the main [1] sources of free acidity in precipitation of remote regions , and contribute minor chemical constituents to the balance between anions and cations, especially to some atm…     

青藏高原中西部湖泊生物标志物记录的过去两千年气候变化

以青藏高原中西部湖泊达则错和阿翁错为研究对象,通过分析湖泊沉积物岩芯中GDGTs、长链不饱和烯酮与叶蜡化合物单体氢同位素等生物分子标志物获得过去2000 a以来青藏高原中西部定量的温度与降水同位素记录,以期探讨晚全新世以来不同时段青藏高原气候变化区域特征,并揭示过去2000 a季风与西风对青藏高原影响范围的变化.结果表明:(1)青藏高原气候变化存在强烈的区域性特征,两个湖泊均存在中世纪暖期(MWP),但是暖期持续的时间有所不同,高原西部(阿翁错) MWP持续时间明显长于高原中部(达则错);达则错有明显的小冰期(LIA)降温,阿翁错没有发现明显的LIA,可能受样品分辨率低的影响;过去200 a达则错温度有缓慢降低趋势,可能是冰融水补给湖泊温度变化滞后于气候变化的表现.(2)过去2000 a印度夏季风在青藏高原的最北界线可能发生了北移,在距今1000～2000 a,夏季风边界线位于阿翁错以北、达则错以南;但在过去1000 a印度季风边界线移动到阿翁错和达则错以北.     

青海湖水位下降的生态环境效应

本文主要分析了青海湖水位下降所导致的湖区生态环境变化,指出青海湖流域的生态环境保护与综合治理任重道远.     

Dust storms and loess accumulation on the Tibetan Plateau：A case study of dust event on 4 March 2003 in Lhasa

Whether the Tibetan Plateau is a significant dust source area is of great importance, because this is related to the understanding of sources, accumulation and environmental effects of dusts on the Tibetan Plateau and inthe Far East-Pacific Ocean regions as well as to the evointion of coupling of the Tibetan Plateau and atmaspbere-oeean-continent exchange. Synoptic dynamics and remote sensing tracing of a dust storm on 3 to 5 March, 2003 in Lhasa onSouth Tibet demonstrate that the Tibetan Plateau possessesall factors and conditions of generating dust storms. Accompanied with this dust storm is a strong ascending stream onthe Plateau which has raised various sizes of durst particlesinto different levels. The lifted coarse particles were largelyfallen down and accumulated as loess on the eastern TibetanPlateau, and the fine particles were translated by the westerly jet and subsided in the northern Pacific Ocean. The spa-tial-temporal distribution of dust-storms between years 1961and 2000 ou the Plateau shows that duststorms mainly occurin winter and early spring with high frequency, and tile pathof dust storm moves gradually from south to north, which isclosely coupled with the northward moving of the westerlyjet from winter to spring over the Tibetan Plateau. Com-pared with other twelve dust source areas in China. the Ti-betan Plateau is one of the key dust souree areas for thelong-distance transport because its high occurring frequencyand elevation cause fine particles easily to be lifted into thezone of the westerly jet.     

Aepyosciurinae——a new subfamily of Sciuridae(Rodentia, Mammalia)from basal loess deposits at the northeastern border of Tibetan Plateau

Aepyosciurinae,a new subfamily of Sciurldae,were found at the base of the early Pleistocene loess deposits in dongxiang County,Gansu Province.Its umilaterally hyp-sodont and lophodont cheek teeth are unique among the sciurids so far known all over the world.Certain degree of similarity can be observed between the cheek teeth of the new subfamily and the Anomalurinae living in tropical and subtropical forests in central and western Africa.Aepyosci-uris orientalis gen.et sp.nov.might have lived in montaneous woodland or grassland and lived on harder leaves,harks,or even grass.This tends to show that the northeastern border area of the Tibetan Plateau had been lifted considerably high in early Pleistocene(ca.2 Ma),with drier climate,becoming a suitable habitat for Aepyosciurus orientalis.     

TRMM/PR在青藏高原土壤水分变化研究中的应用

针对热带降雨观测计划(TRMM)上搭载的降雨雷达(PR)参数情况发展了基于积分方程模型与一阶植被散射模型的青藏高原地区的土壤水分变化反演模型.利用AVHRR/NDVI产品以及PR数据,用上述模型对青藏高原3个试验区1998年4～9月的土壤水分变化情况进行了反演,结果显示模型反演结果与实测结果吻合较好,3个站点的均方根误差分别为0.045,0.069和0.056.