巴汗淖孢粉记录的全新世环境变化

利用AMS14C测年,分析了鄂尔多斯高原中部巴汗淖湖泊沉积物孢粉,揭示了鄂尔多斯高原全新世植被和气候演化历史:8.696～7.847 kaBP植被以荒漠草原主导,气候寒冷干旱;7.847～7.130 kaBP植被转变为禾草草原,温湿条件得到改善,但区域气候很不稳定;7.130～4.780 kaBP植被演化为疏林草原,气候温暖湿润且稳定;4.780～4.207 kaBP为松-栎混交林,为温暖湿润且稳定的气候最宜期;4.207～3.622 kaBP植被退化为松属一禾草森林草原,气候向十旱化方向发展;3.622 kaBP以来,植被进一步退化为荒漠草原,气候进一步变干.     

Holocene abrupt climate shifts recorded in Gun Nuur lake core, northern Mongolia

A continuous 7.44 m lake core was successfully drilled at Gun Nuur Lake, northern Mongolia, and analyses on environment magnetic parameters, organic matter content and organic δ^13C were conducted in an attempt to retrieve the Holocene chronosequence of climatic changes based on 6 AMS ^14C dates. We found that the Holocene climate in northern Mongolia has been alternating between cold (or cool)/wet conditions and warm/arid conditions, and also punctuated with a series of abrupt climate shifts. The abrupt climate shifts occurred around 1750, 2800, 4000, 5200, 7200, and 9200 aBP (^14C age), being chronologically correlative to those abrupt climatic events recorded in the high-latitude North Atlantic Ocean. The correlation indicates that the climatic changes in northern Mongolia were linked with those in the North Atlantic Ocean probably via the North Atlantic Oscillation-affected westerly winds. The strength and position of westerly winds might have modulated the Siberian-Mongolian high pressure system (winter monsoon), directly influencing the climate in China.     

Holocene lake deposits of Bosten Lake, southern Xinjiang, China

A 9.25-m-long sediment core from Bosten Lake,Xinjiang, provides detailed information about changes in the water budget and biological acticity over the last 8400 cal-endar years. The chronology is constructed from six AMS radiocarbon dates on the terrestrial plant remains. Based onanalyses of TOC, CO3, detrital compounds and biogenic SiO2,lake level fluctuations and periods of remarkably-negative water budget appeared at 8.4-8.2 cal ka, 7.38-7.25 cal ka,5.7-5.5 cal ka, 3.7-3.4 cal ka and 3.3-2.9 cal ka, respec-tively. As they are in-phase with low lake levels at Sumxl Co and Bangong Co in western Tibet Plateau and with paleo-lakes in Inner Mongolia, a climate-induced change to some-what drier and warmer conditions is inferred. A further drop in lake level after 1320 AD of about 200 yr duration may heattributed to a negative water balance prior to the main phase of the Little Ice Age. Deep and stable lake phases of 1500 yr and 1800 yr duration at 7.2-5.7 cal ka and 5.5-3.7cal ka coincide with maximum moisture during the Holocene Megathermai in China. The long term trend towards aridity since about 4.3 cal ka can dearly be recognised. The reduced water budget of Bosten Lake from 640-1200 AD may be attributed to local effects.     

Vegetation and climate changes during the last 8660 cal. a BP in central Mongolia, based on a high-resolution pollen record from Lake Ugii Nuur

Based on modern pollen studies and reliable chronology of nine AMS 14C dates, a detailed history of vegetation and climate changes during the past 8660 cal. a BP was reconstructed by a high-resolution pollen record from Ugii Nuur in central Mongolia. Poaceae-steppe dominated the study area and the climate was mild and semi-humid before 7800 cal. a BP with a noticeable cool and humid interval at 8350―8250 cal. a BP. Xerophytic plant increased and the climate became warm and dry gradually since 7800 cal. a BP...     

青藏高原东北部西宁盆地中始新世-渐新世沉积物颜色与气候变化

始新世-渐新世是古近纪气候变化中最显著的时期.通过对西宁盆地42.5～26.0 Ma沉积物颜色指标的详细分析,发现颜色参数L*,a*,b*曲线明显以32.8 Ma为界分为上下两段.其中:L*值在下段(42.5～32.8 Ma)波动剧烈并呈缓慢降低趋势,至32.8 Ma左右大幅度降低,此后(32.8～26.0 Ma)波动变小、稍有回升;a*,b*值则与L*值的变化趋势相反,在下段(42.5～32.8 Ma)呈逐渐增大趋势,剧烈波动,在32.8 Ma左右时突然大幅度升高.至上段波动变小.结合西宁盆地孢粉、有机质及CaCO3质量分数变化的特征分析,该区域在32.8 Ma时可能发生大幅度的降温事件(对应于海洋记录所揭示的Oi-1事件),此事件之前气候干旱程度相对较弱、氧化作用逐渐增强、气候波动剧烈.在Oi-1事件之后大陆性干旱程度增强、氧化强烈、气候波动幅度较小.这是在该区高分辨率获得Oi-1事件前后气候变化的记录.它对始新世-渐新世全球气候变冷背景下陆地系统响应研究具有重要意义.     

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.     

A mid－Holocene drought interval as evidenced by lake desiccation in the Alashan Plateau,Inner Mongolia,China

The mid-Holocene in China is traditionally thought to be a warm and humid period with a strong sum-mer monsoon, and is often termed the Holocene Climatic Optimum or Megathermal Period. Here we present lakegeomorphologic and lithologicai evidence from the Alashan Plateau, part of the Mongolian Plateau, that indicates stronglake desiccation during the mid-Holocene. High resolution pollen data from Zhuyeze Lake, at the present summermonsoon margin, is also presented. These data show that present lakes and wetlands in the Juyanze Lake basin west of the Badain Jaran desert, in the Zhuyeze Lake basin between the Badain Jaran and Tengger deserts, and in lakes in the eastern Tengger desert, dried or experienced low lake levelsin the mid-Holocene around 5000-7000 cal yr BP. Pollen data further indicate that the vegetation cover declined in both the local areas and in the Qilian Mountains, suggesting the climate was drier than that associated with the presentAsian summer monsoon. This mid-Holocene drought interval was present throughout a quite large region of the south In-ner Mongolian Plateau. The period was also probably colder,at least in the high Asian plateaus and mountains.     

A mid-Holocene drought interval as evidenced by lake desiccation in the Alashan Plateau, Inner Mongolia, China

A warm and stable mid-Holocene climate has been considered to be the typical interglacial situation, in contrast to the last glacial period, and has commonly been used in global climatic modeling[1]. A recent study, however, has proposed that the mid-Holocene was possibly a period of particularly profound change in low latitudes, with land air temperature apparently declining across much of the globe, and with regional differences in precipitation[2]. Traditionally, the mid-Holocene in most p…     

萨拉乌苏河流域全新世气候变化的元素地球化学记录

通过对萨拉乌苏河流域滴哨沟湾左岸沉积剖面常量元素Si、Al、Fe、Ca、Mg、K、Na含量及其比值变化的分析,结合~(14)C测年结果及粒度、有机质指标,并综合已有研究,探讨了该地区全新世以来的气候变化.研究表明,9.6ka BP前气候干冷,沉积相为风成沉积;9.6~8.4ka BP气候由干冷向暖湿转变,期间存在干冷波动;8.4~4.0ka BP进入全新世大暖期,其中,8.4~6.5ka BP为全新世大暖期的鼎盛时期,降水增加,积水成湖,湖泊水位高且稳定;6.5ka BP气候发生明显转变;6.5~4.0ka BP湖泊水位逐步下降形成富含螺壳的浅水环境,但气候整体仍较为湿润;4.0~1.2ka BP气候变干冷,发育沼泽;1.2~0.7ka BP气候转暖湿,沉积相由沼泽相转变为湖泊相;0.7~0.5ka BP为河流相沉积,气候较为干冷.剖面记录的气候变化可与东亚季风变化、温度变化、太阳辐射进行对比,反映了该区域气候变化与全球气候变化的一致性.     

Evidence for cold events in the early Holocene from the Guliya ice core, Tibetan Plateau, China

Evidence for the “8.2 ka cold event” has been provided mostly from the circum-North Atlantic area. However, whether this cold event occurred in other places is a key to understanding its cause. Here, we provide the evidence for the “8.2 ka cold event” from the Guliya ice core in the northwest Tibetan Plateau, and it was found that the peak cooling (~8.3—8.2 ka) in this ice core was about 7.8—10℃, which was larger than the cooling in the North Atlantic region. The primary causes for this episode were diminished solar activity and weakened thermohaline circulation. Moreover, another weak cold event, centered about 9.4 ka, was also recorded in the Guliya ice core record. These two cold events were concurrent with the ice-rafting episodes in the North Atlantic during the early Holocene, which implies that the millennial-scale climatic cyclicity might exist in the Tibetan Plateau as well as in the North Atlantic.     

Environmental changes and lake level fluctuation recorded by lakes on the plain in northern Xinjiang during the late Holocene

Xinjiang Autonomous Region is located in the arid area of westerly of China and there are many arguments about the changes of past temperature and moisture. Most of the lakes on the plain in northern Xinjiang are sealed lakes and terminal lakes. They can evidently reflect the changes in palaeoclimate. The palaeoenvironmental changes of some plain lakes in northern Xinjiang during the late Holocene will be analysed mainly based on the data of pollen, sedimentary facies, loss on ignition （LOI）, susceptibility and grain size from the Sichang Lake, Dongdaohaizi Lake and Aibi Lake. Results reveal an assembled pattern of temperature and moisture dominated by cold-wet and warm-dry. In addition, the impact factor will be discussed.     

New progress of lake sediments and environmental changes research in China

Environmental change recorded by lake sediments is one of the important branches of the past global changes study. The new progress of lake sediments and environmental changes in China since the late 1980s has been comprehensively discussed. The highlights emphasized are Asian paleomonsoon migration reflected by lake level fluctuation, uplift of the Qinghai-Xizang Plateau recorded by lacustrine sediments, saltlake sediments and environmental evolution, lake response to the natural-human interaction and modern lake biogeochemical process. Meanwhile important suggestions for the lake sediments and environmental research in the future are proposed, which include studies on the quantitative relationship between lake environment proxies and climate factors, high-resolution evolutionary sequence and spatial differentiation of environments, modern lake dynamic process and environment, Quaternary Chinese lake database and global changes.     

青藏高原湖泊沉积记录与环境变化研究

 过去全球变化研究是人类认识气候与环境变化事实与规律,客观评价现代环境在气候与环境发展历史中位置的重要手段,能够为未来气候与环境变化的预测提供科学的检验工具。介绍了湖泊沉积物环境代用指标与气候要素关系定量化的研究,简要回顾利用湖泊沉积物重建高原最近2万年环境变化历史研究成果,阐述高原湖泊沉积对气候变化的敏感响应。     

Late Pleistocene／Holocene wetland events recorded in southeast Tengger Desert lake sediments, NW China

The area along the eastern and southeastern margins of the Tengger Desert, NW China, which is sensitive to the summer monsoon variations, was selected for studying the environmental conditions surrounding the transition between Paleolithic foragers and Neolithic farmer/pastoral-ists. Short cores were obtained from four lake basins in the southwestern Tengger using a hand-driven piston coringdevice. Proxies from these cores were supplemented by ra-diocarbon ages obtained from lake sediment cores, shoreline features and spring mound deposits. Together these records provide evidence of millennial-scale climate change eventsfrom the Pleistocene-Holocene transition to the present.Lake/wetland events, representing periods of more intensive summer monsoon, occur in the records at-12.7-11.6,-10.1, -9.3, -8.0, -5.4, -1.5, and -0.8 ka BP. They do suggest that century- to miliennial-seale climatic cycles are characteristic of the Holocene in the southeastern Tengger Desert although the chronology must be considered extremely tentative.     

Palynological records of environmental changes in the middle part of Inner Mongolia,China

Today, the central part of Inner Mongolia has a continental climate, with cold winters, hot summers, and approximately 70% of the precipitation falling in the summer months. Vegetation is dominated by steppe vegetation with Stipa bungeana and Stipa breviflora. Scattered individuals of Quercus liaotungensis, Populus davidiana, Betula platyplylla are distributed in the mountains, with some Pinus tabluaoformis, near Miaoyu, and with fragmentary Picea above 1700—1800 m a.s.l. The Huitenglian…     

Diatom-based reconstruction of Holocene environmental changes in Angren Lake, Southern Tibet

Based on the diatom analysis the climatic sequence between 11 000 and 6 000 aBP in Angren, southern Tibet is established, i.e. cold period (11 095-9 970 aBP)→temperate period (9 970-9 870 aBP)→Anathermal (9 870-9 770 aBP)→cool-dry period (9 770-8 740 aBP) →super-megathermal (8 740-8 590 aBP)→Megathermal (8 590-5 970 aBP). And the opinion that the reaction of diatom to temperature change is more sensitive than to other ecological factors has been pointed out and certified.     

渭北旱塬黄土记录的晚冰期以来短尺度气候变化

通过对长武下孟村黄土剖面的野外考察和磁化率，粒度，吸湿水含量分析，探讨了该地区晚冰期以来气候变化规律，研究结果表明，该剖面较好地记录了新仙女木期（YD）和博令－阿勒罗德事件（BL＋AL）短尺度较小幅度气候变化事件，对应全新世气候最适宜期（8500－3100a.BP)，该地为黑垆土成壤期，从3100a.BP开始，季风气候格局快速转变，气候干旱化，土壤和土地资源退化，所以3100年来该地区形成了弱成壤的土壤层和黄土层。     

Recent climate changes recorded by sediment grain sizes and isotopes in Erhai Lake

By careful sampling and accurate analysis of recent sediments, the time series of sediment grain sizes and 6" 1B0, S 13C of carbonates in recent 700 years are successfully established, based on which the evolutionary history of the regional climate and environment in Erhai Lake is reconstructed. The results show that the climatic succession type in the region of Erhai Lake is warm-dry and cold-humid alternatively, and there exist 200 and 400 years of quasi-periodical changes in temperature and 100, 200 and 400 years of quasi-periodical changes in aridity/humidity regime. The two coldest periods in recent 700 years occurred in the 14th century and the duration of 1550—1800 AD. The latter period may be the imprint left of the Little Ice Age.     

Pollen-inferred Holocene vegetation and climate histories in Taro Co,southwestern Tibetan Plateau

A 310-cm-long sediment core, covering the last 10,200 years, was collected from Taro Co on the south- western Tibetan Plateau and analyzed for pollen, grain size and total inorganic carbon content. The pollen data showed that vegetation changed from alpine steppe to alpine meadow during 10,200-8,900 cal a BP, to alpine steppe dominated by Artemisia during 8,900-7,400 cal a BP, to alpine meadow during 7,400-3,300 cal a BP and to alpine steppe after 3,300 cal a BP. Correspondingly, the pollen, grain size and total inorganic carbon content results revealed climatic change in this area over four stages. The initial stage was from 10,200 to 8,900 cal a BP, during which the climate changed from cold-dry to warm-humid. The second stage （8,900-7,400 cal a BP） was characterized by a warm and dry climate. However, at approximately 7,400 cal a BP, the climate began to become cold andhumid, which continued until 3,300 cal a BP. The last stage, from 3,300 cal a BP to present, was characterized as cold and increasingly arid. Climatic events of the early and mid-late Holocene showed that the area was significantly affected by the westerlies. However, the mid-Holocene climate in Taro Co was controlled by the Indian monsoon. The mid-late Holocene depositional environment record of Taro Co was very important to further elaborate the degree of influence by the westerlies or Indian monsoon.     

Peat record reflecting Holocene climatic change in the Zoige Plateau and AMS radiocarbon dating

Through the use of reliable AMS dating of high resolution (15-30 years) peat and the establishment of monsoon climate proxies sequence, we have been able to recognize several cold, dry events in the Tibetan Plateau during the Holocene. The more obvious ones occurred around 12800, 11300, 10200, 9580, 8900, 6400, 4400, 3700, 2800 and 1500 cal. aBP. These events correlate well with both ice rafting events recorded in high latitude North Atlantic Ocean sediment cores and cooling events in the low latitude SST. Spectral analysis indicates high frequency climate variation on centennial-millennial time scale during the Holocene. This further reflects Holocene climate instability and the existence of centennial-millenium scale rhythm in mid latitude areas as well.