The influence of climate,hydrology and permafrost on Holocene peat accumulation at 3500 m on the eastern Qinghai–Tibetan Plateau

Peatland of the eastern Qinghai–Tibetan Plateau lies at the convergence of the East Asian and Indian monsoon systems in eastern Asia. To understand the evolution of this peatland and its potential to provide new insights into the Holocene evolution of the East Asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near Hongyuan. The age-depth profile was determined using 16 ¹⁴C-AMS age dates, the peat analysed for a range of environmental variables including carbon, nitrogen and hydrogen concentration, bulk density, δ¹³C and the associated spring water analysed for hydrogen and oxygen isotopes. The age-depth profile of the recovered peat sequence covers the period from 9.6 to 0.3 kyr BP and is linear indicating that the conditions governing productivity and decay varied little over the Holocene. Using changes in carbon density, organic carbon content and its δ¹³C, cold dry periods of permafrost characterised by low density and impeded surface drainage were identified. The low δ¹⁸O and δD values of the spring water emanating around the peat deposit, down to ?13.8 and ?102‰ (VSMOW), respectively, with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day. In view of the current annual mean air temperature of 1 °C this suggests conditions in the past have been conducive to permafrost. Inferred periods of permafrost correspond to independently recognised cold periods in other Holocene records from across China at 8.6, 8.2–7.8, 5.6–4.2, 3.1 and 1.8–1.5 kyr BP. The transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at Hongyuan are of longer duration than equivalent cold dry periods over central and eastern China. Light–dark banding peat on a scale of 15–30 years from 9.6 to 5.5 kyr BP may indicate a strong influence of decadal oscillations possibly the Pacific Decadal Oscillation and a potential link between near simultaneous climatic changes in the northwest Pacific, ENSO, movement of the Intertropical Convergence Zone and the East Asian Monsoon.     

Altitude Effects of Climatic Variation on Tibetan Plateau and Its Vicinities

High topographies,such as the Tibetan plateau(TP) in China,have been considered as the sensitive areas in response to global climate change.By analyzing the relationship between warming structure and altitude(1000-5000m) in the TP and its vicinities using the 46-year January mean observed temperature data,we found that there was a significant altitude effect of temperature warming onset time(mutation time) on the plateau and the neighboring regions:the higher the altitude,the later the climate warming happe...     

川西高原黄土记录的末次冰期气候变化

川西高原位于高原气候区和季风气候区的过渡位置,该地区的气候特征对于认识青藏高原对周边气候的影响具有重要意义。通过对漳腊黄土剖面的¹⁴C年代测试、地层对比,结合粒度-年龄模型建立了剖面的年代序列。测试了粒度、色度、磁化率和碳酸盐等指标,建立了剖面的气候演化序列。结果表明,剖面记录了104 ka以来的气候变化过程。漳腊黄土粒度在MIS（深海氧同位素阶段）3和MIS4阶段的中值粒径接近,分别为17.6 μm和17.7 μm,反映了期间有一次高原隆升。漳腊黄土粒度曲线记录了多个粒度变粗和变细事件,粒度在H（海因里希）2时明显粗于H1,表明受到了高纬气候系统的影响。另外还存在2个明显的粒度变细事件,分别发生在处于MIS3的28~31 ka和42~45 ka,是低纬气候系统影响的结果。漳腊黄土研究结果表明川西高原气候系统影响因素的复杂性。     

青藏高原南部枪勇错冰前湖泊沉积记录的近千年来冰川与气候变化

以钻取自青藏高原南部大枪勇错冰前湖中的1．06m湖芯为研究对象,对沉积物样品进行了粒度、磁化率、元素含量、碳酸盐和总有机碳含量等多项指标的分析测定;在明确了沉积物来源的基础上,分析讨论了各指标变化的影响因素及其具体气候环境指示意义;结合沉积序列放射性同位素定年结果,对湖芯中各指标进行了综合对比分析,恢复了青藏高原南部枪勇错地区近千年来的冰川与气候变化。结果表明：1．06m沉积序列年代跨度为自公元11世纪前后至今的逾千年时间;沉积物主要来源于枪勇冰川融水对冰川上部沉降粉尘颗粒的携带,而沉积物的粒度、磁化率及各组分含量与区域气候条件下枪勇冰川融化强度有密切关系;自公元11世纪至今,青藏高原南部地区环境温度总体呈现波动中逐渐升高的趋势,枪勇冰川随之逐渐融化退缩。具体来说,公元11世纪初,该地区环境温度较低,枪勇冰川融化较弱;公元11世纪中叶至13世纪初,该地区气候温暖,枪勇冰川融化较强;公元14世纪开始至18世纪中叶,该地区进入小冰期,枪勇冰川融化强度显著降低;自公元18世纪中后叶至今,该地区环境温度急剧升高,枪勇冰川呈加剧融化退缩趋势。     

青藏高原中东部最大冰期时代高度与气候环境探讨

本文应用不同来源的各种资料，经逐步综合推导，认为最大冰期出现时间相当于深海氧同位素１８－１６阶段（０．７２－０．５２ＭａＢＰ）。当时青藏高原低于现代１０００Ｍ左右。高原中，东部唐古拉山，阿尼玛卿山、果洛山与稻城海子山４个山区的冰川面积达４００００ＫＭ＾２，为现代冰川面积的１８倍，平衡线高度为３４５０－４２５０Ｍ，６－８月平均温度为２．３－３．４℃，年降水量为１２６０－１９６０ＭＭ，是现代平衡线上降     

青藏高原冰川氮记录研究进展

近年来,青藏高原冰川持续退缩,显著影响区域气候与生物地球化学循环.作为重要的营养元素,氮在生态系统中的循环备受关注.冰川中含氮化合物的迁移转化是冰冻圈地区氮循环的重要环节.基于青藏高原地区冰川氮记录研究,综述了近年来冰芯氮记录的历史变化,指出不同区域的变化趋势存在差异,认为一定程度上受亚洲地区人类活动排放污染物的影响....     

藏北高原环纳木错首次发现晚更新世湖滩岩

200-2001年夏,在开展藏北高原"纳木错第四纪环境演变调查研究"与"1:25万当雄幅"区域地质填图工作中,笔者首次在环纳木错湖岸阶地上发现了一种与湖泊演化有关的湖相沉积岩石--湖滩岩.目前,国际上只有海滩岩一说,湖滩岩尚罕见正式报道.     

青藏高原冷湿地生态系统CH4排放量估算

The areal extent of cold freshwater wetlands on the Tibetan Plateau is estimated to be 0.133×10 6 km 2, suggesting a significant methane potential. Methane fluxes from wet alpine meadows, peatlands, Hippuris vulgaris mires and secondary marshes were 43.18,12.96,-0.28 and 45.90 mg·m -2 ·d -1 , respectively, based on the transection studies at the Huashixia Permafrost Station from July to August 1996. Average CH 4 flux in the thaw season was extrapolated to be 5.68 g·m -2 according to the areal percentage of wetland areas in the Huashixia region. CH 4 fluxes at four fixed sites, representative of similar ecosystems, ranged from -19.384 to 347.15 mg·m -2 ·d -1 , and the average CH 4 fluxes varied from 6.54 to 71.97 mg·m -2 ·d -1 at each site from April to September 1997. CH 4 emissions at each site during the entire thaw season was estimated from 1.21 to 10.65 g·m -2 , displaying strong spatial variations. Seasonal variations of CH 4 fluxes were also observed at the four sites. It is found that CH 4 bursted in the early thaw season, and increased afterwards with rising soil temperatures. Episodic fluxes were observed in summer, which influenced the average CH 4 flux considerably. Annual CH 4 emissions from cold wetlands on the plateau were estimated at about 0.7～0.9 Tg based on the distribution of wetlands, representative CH 4 fluxes, and number of thaw days. The centers of CH 4 releasing are located in the sources of the Yangtze and Yellow Rivers, and Zoige Peatlands.     

Isotopic characteristics of river sediments on the Tibetan Plateau

We systematically collected 40 modern clastic sediment samples from rivers in different tectonic units of the Tibetan Plateau and measured their Sr–Nd isotopic compositions. The isotopic characteristics provide insight into the controversial paleo-tectonic affinity of terranes of the Tibetan Plateau and the provenance of Songpan–Ganzi flysch complex. The Qilian Terrane and Himalaya Terrane have more negative ε_Nd(0) values (from ? 14.3 to ? 11.8 and from ? 20.64 to ? 13.26, respectively) and high ⁸⁷Sr/⁸⁶Sr values (from 0.719674 to 0.738818 and from 0.721020 to 0.824959, respectively), reflecting old and mature continental crust origin of these two terranes. The southern Lhasa Terrane is more radiogenic in ε_Nd(0) values (from ? 8.82 to ? 3.8) and low in ⁸⁷Sr/⁸⁶Sr values (from 0.711504 to 0.719489), implying the combined impact of the Neo-Tethys mantle and Himalaya old continental crust. Sr–Nd isotopic compositions of the Qilian Terrane are similar to those in the Yangtze Craton, indicating that the Qilian Terrane was probably separated from the Yangtze Craton. Sr–Nd isotopic characteristics of the Songpan–Ganzi Terrane are similar to the Yangtze Craton and are remarkably different to those in the North China Craton, eastern Kunlun–Qaidam and the central Qiangtang metamorphic belt, implying that the widely distributed flysch complex of the Songpan–Ganzi Terrane was sourced from the Yangtze Craton.     

1901~2010年青藏高原土壤温度变化的模拟研究

冻土变化是气候变化研究领域的热点问题之一,而土壤温度是冻土变化研究的重要参量。但目前对百年尺度土壤温度,特别是深层土壤温度变化的认识还存在不足。本研究利用CRUNCEP大气强迫资料驱动最新版本的通用陆面模式（CLM4.5）对过去百年的青藏高原土壤温度变化进行了模拟研究。利用来自气象站和野外钻孔监测站的土壤温度观测资料对模拟结果进行了验证,结果显示：1）通用陆面模式能合理地模拟出观测的青藏高原土壤温度变化,模拟和观测结果的相关系数为0.92,纳什效率系数为0.82,趋势分别为0.27℃/10年和0.28℃/10年。模拟结果明显优于再分析资料;2）1901~2010（1979~2010）年青藏高原15m土壤温度增加率为0.05（0.27）℃/10年,冬季增温高于夏季,土壤增温随深度增加而减弱、随经度增加而减小、随纬度的增加呈先增加后略减小的变化;3）青藏高原土壤温度变化主要受气温控制,1m（15m）深度土壤温度对气温变化的敏感性为0.79（0.37）℃/℃,浅层土壤温度对气候变化较深层敏感,多年冻土温度对气候变化较季节冻土敏感。这些结果从百年时间尺度上深化了对青藏高原土壤温度变化的认识。

     

青藏高原东部和湄公河盆地晚第四纪风化剥蚀与东亚季风演化在南海中的记录

通过南海西南部湄公河口MD01—2393孔和MD97—2150孔的高分辨率粘土矿物和粒度分析,及铷、锶、钕同位素分析,揭示出青藏高原东部和湄公河盆地晚第四纪190ka以来的风化剥蚀和东亚季风演化历史。铷、锶、钕同位素研究证实这两个孔的陆源碎屑物质主要来源于湄公河流域的直接输入。蒙脱石／(伊利石 绿泥石)值和蒙脱石／高岭石值指示了化学风化历史,而陆源碎屑颗粒的粒径比值2．5～6．5μm／15～55μm则指示了湄公河沉积物的供给能力。相对高的比值发生在间冰期,表明强盛的夏季风降雨和减弱的冬季风环流;相对低的比值对应于冰期,表明强盛的冬季风和减弱的夏季风,揭示出东亚季风气候驱动的风化剥蚀演化历史。东亚季风演化的强弱与北半球夏季日射量基本呈线性关系,表明东亚季风演化的天文驱动机制。     

保温法保护多年冻土的长期效果分析

通过分析青藏公路昆仑山越岭地段保温材料(EPS)试验段的地温观测资料发现:结果表明:路基中的保温板近8 a来工作正常,大大减小了保温板下土体温度较差.试验段施工完成12 a来EPS保温板的导热系数没有发生大的改变,车辆荷载、水分和冻融循环等对其影响较小.保温路基段天然孔的年平均温度升温速率比对比段天然孔大,但保温路基下多年冻土近7 a来的升温速率均小于对比段.计算结果证明,路基中铺设的保温材料,可以使进入路基的热交换量大为下降,并使进入路基活动层的热量每年减少近3/4.最后,基于年平均气温,用有限元方法给出了青藏公路多年冻土地区保温法的适用范围.     

Study on the Seismic Source Mechanisms of the Tibetan Plateau

STUDY ON THE SEISMIC SOURCE MECHANISMS OF THE TIBETAN PLATEAU     

3500 m钻机移摆管设计及动力学仿真研究

随着我国探矿深度不断增加,钻探设备的尺寸不断加大,操作人员的劳动强度也在增加。基于此,3500 m液压岩心钻机需要适配一套移摆管装置,以实现快速、安全地运移钻杆,降低工人的劳动强度。对移摆管机构的设计进行了简单介绍,并利用ADAMS动力学仿真软件对移摆管机构进行运动仿真,找出设计的不足之处,给出优化建议。     

Simulation Study on Precipitation Recycling Ratio in the Tibetan Plateau from 1982 to 2005

A dynamical downscaling approach using a regional climate model WRF (Weather Research and Forecasting Model Vision 3.5) driven by a global climate model CCSM4 (The Community Climate System Model Version 4) was adopted, and the downscaling results for the historical period (1982-2005) were evaluated for annual mean precipitation rate and evaporation rate over the Tibetan Plateau (TP). Furthermore, the spatial distribution and seasonal variation characteristics of Precipitation Recycling Ratio (PRR) simulated by CCSM4 and WRF were analyzed with the QIBT (Quasi-isentropic Back-trajectory method). The results show that the historical spatial distributions of annual mean precipitation rate and evaporation rate over the TP were found to better reproduce in the dynamical downscaling modeling compared to its coarse-resolution forcing. The PRR of the TP is 32% simulated by WRF, with a higher PRR in the wet season and a lower PRR in the dry season for the river basins in the northern TP, but the opposite seasonal variation was found for the river basins in the southern TP. In addition, the different land covers over the TP are more precisely represented in the WRF model, the PRR of grassland, shrubland and sparsely vegetation is higher than that of other land cover types.     

基于微观结构的青藏高原风积沙导热系数变化机理研究

风积沙作为青藏高原一种重要的局地因素, 改变了多年冻土的赋存条件. 风积沙的导热系数特征对预报分析其对冻土赋存有利或者不利具有重要作用. 采用非稳态法对青藏高原红梁河风积沙进行了导热系数测试, 并结合电镜扫描/能谱分析, 从微观结构的角度探讨了风积沙的导热系数变化机理. 结果表明: 研究区风积沙平均粒度为242.427 μm; 标准偏差值为0.125, 分选极好; 偏度为0.359, 接近对称; 峰度值为1.086, 峰态中等; 颗粒粒径主要分布在75～500 μm之间, 沙粒均匀, 不含黏土及砾石成分, 自然堆积状态下其孔隙率为0.391. 天然状态下的风积沙颗粒呈类球形, 颗粒磨圆度高, 点与点接触, 颗粒间孔隙较大; 表面有明显撞击坑和擦痕, 这导致颗粒的比表面积增大, 连通性增强, 孔隙率增加. 干燥状态下风积沙颗粒的相互接触面积较小, 孔隙由空气填充, 导热系数较低; 而在湿润状态下, 正温时孔隙中的水间接增大了风积沙的接触面积, 导致其导热系数增大; 负温时, 孔隙内的水变成冰, 从而导致导热系数进一步增大. 天然状态下, 暖季地表风积沙含水量较低, 导热系数较低, 而冷季地表风积沙含水量较大, 导热系数较大. 此外, 风积沙为颗粒物质, 表面光滑, 颗粒之间粘性小, 孔隙未被填堵, 结构松散, 这些因素导致自然堆积状态下其渗透系数较一般细砂大, 透水性良好, 保水性差, 是防冻胀较好的换填材料.     

青藏高原积雪异常的持续性研究

选取青海省和西藏自治区境内的72个气象站，自建站至1999年12月逐日观观测的积雪深度资料，规定观测到地面有0．5cm以上积雪深度的日子作为积雪日，分别统计了月、冬春、年的积雪日数，通过对积雪日数的分析，确定出高原冬春积雪的异常年份。分析了这些异常年份高原积雪的持续特征，结果表明，高原冬春总体积雪的异常主要是由11月至翌年3月的积雪异常决定的，高原冬春的积雪异常和春末夏初的积雪异常是不相一致的；一般来讲，高原积雪负异常至少持续4个月，大多数般到3月份就结束了；高原冬春总体积雪的正负异常都很难持续到春末夏初，高原冬春异常多积雪的大规模消融期在2月末到3月初。