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1.
冰芯记录中末次间冰期-冰期旋回气候突变事件的研究进展 总被引：9，自引：2，他引：9
冰芯记录中的气候变化是古气候研究中的重要组成部分. 极地、中低纬度和热带地区的冰芯记录表明, 在冰期间冰期旋回大尺度气候变化背景下, 全球经历了一系列数百年至千年时间尺度的快速气候突变事件, 诸如末次间冰期的干冷事件、末次冰期的DansgaardOeschger事件、 Heinrich事件和Younger Dryas事件等, 虽然这些穿插在冰阶中的暖湿气候事件、间冰阶中的干冷气候事件的成因、机制和影响范围还存在明显的不确定性. 主要介绍不同区域冰芯记录中末次间冰期冰期旋回这些气候突变事件发生的时间、过程和机制等的研究进展. 相似文献
2.
Role of late glacial to mid-Holocene climate in catchment weathering in the central Tibetan Plateau 总被引：1，自引：0，他引：1
The lightness (L*) and concentrations of Rb, Sr and organic carbon (Corg) have been measured in the age-constrained lake sediment cores recovered from Co Ngoin in the central Tibetan Plateau. Dissolved Sr flux is a dominant control on the variation of Rb/Sr ratios in the sediments. Variations in color and geochemical proxies of Co Ngoin sediments display a continuous history of late glacial to mid-Holocene chemical versus physical weathering intensity in response to past climatic changes between approximately 13,500 and 4500 cal yr B.P. A lower chemical weathering under a late glacial climate was followed by a higher weathering during the Holocene Optimum. Weathering intensity in the central Tibetan Plateau catchment also responds to well-known climatic events, such as the Younger Dryas (YD), and possibly the Holocene Event 5 (HE-5). Although there are differences in time or duration of the climatic events, many of the well-known late glacial to mid-Holocene events occurred in high-elevation Co Ngoin where atmospheric circulation might play a hemispherical role in climatic forcing. The sediment hiatus since c. 4200 14C yr B.P. in the Co Ngoin indicates a period of desiccation that was probably associated with a sharp decrease in summer monsoon strength. Our lascustrine results not only imply catchment weathering variations in response to late glacial to mid-Holocene climatic conditions in the central plateau, but also provide further evidence for global connections between regional climates. 相似文献
3.
The Late Precambrian Luoquan Formation occurring on the southern margin of the North China platform is of important significance for the study of the tectonics, palaeogeography, palaeoclimatology and regional stratigraphy of the North China and Yangtze platforms. The origin of diamictites of the formation has long been a subject of controversy. Recently a certain type of cross bedding structure has been recognized in the massive diamictite. Analysis of the process of deposition indicates that the structure was formed by the basal melt-out process of the glacier and, to some extent, its form is the manifestation of the primary structure of basal debris-rich glacial ice. The discovery of this sedimentary structure is inducive to the understanding and reconstruction of the features and environmental conditions for the development of the glaciers in the Luoquan Glacial Epoch. 相似文献
4.
Abstract The Late Precambrian Luoquan Formation occurring on the southern margin of the North China platform is of important significance for the study of the tectonics, palaeogeography, palaeoclimatology and regional stratigraphy of the North China and Yangtze platforms. The origin of diamictites of the formation has long been a subject of controversy. Recently a certain type of cross bedding structure has been recognized in the massive diamictite. Analysis of the process of deposition indicates that the structure was formed by the basal melt-out process of the glacier and, to some extent, its form is the manifestation of the primary structure of basal debris-rich glacial ice. The discovery of this sedimentary structure is inducive to the understanding and reconstruction of the features and environmental conditions for the development of the glaciers in the Luoquan Glacial Epoch. 相似文献
5.
John C. Frye 《Quaternary Research》1973,3(2):275-283
The Quaternary of the continental interior of the United States is characterized by deposits from glacial ice, with associated outwash and eolian deposits, and by alluvial deposits produced by the same climatic pulses. Erosional incision of valleys occurred early in the glacial pulse, outwash deposition during the waning phase of the pulse, and soil formation during times of relative stability between the glacial pulses. These features of deposition, erosion, and soil formation are presented in a series of curves. One way the marine record could be correlated with that of the continental interior is to compare and match the physical records of both environments. 相似文献
6.
冰湖是研究气候变化的重要指标之一,了解冰湖分布和变化的特征,对认识冰川与气候之间关系和冰湖溃决灾害评估有着重要意义。运用遥感资料监测念青唐古拉山西段近40a来的冰湖分布及其变化,并结合DEM研究冰湖垂直分布的变化,探讨影响冰湖分布和变化的可能因素。研究结果表明:(1)研究区冰湖数量和面积近年来都呈迅速增加趋势,冰湖增加150个,冰湖面积增加4.384km2。气温升高、冰川融水增加是冰湖增多和面积增大的主要原因;(2)冰湖垂直分布变化明显,新增冰湖个数峰值位于海拔5 500～5 700m,占新增冰湖总数的61%;新增冰湖面积峰值在海拔5 400～5 700m,占新增湖总面积的44%;冰湖面积在大部分海拔高度上均呈扩张态势;(3)海拔高于5 400m的区域,1991-2009年新增的冰湖数量远多于1972-1991年。冰湖在高海拔区分布的变化对念青唐古拉山区冰川消融以及气候垂直变化具有一定的指示作用。 相似文献
7.
Discovery and Significance of Quaternary Glacial Vestiges in the Hexigten Area of the Southern Da Hinggan Mountains, Inner Mongolia 总被引：4，自引：0，他引：4
SUN Hongyan TIAN Mingzhong WU Fadong ZHANG Jianping China University of Geosciences Beijing E-mail: shywch@.com 《《地质学报》英文版》2005,79(4):564-569
1 Introduction Hexigten is situated at the eastern part of the Inner Mongolian Plateau, south of the Da Hinggan Mountains and northwest of Chifeng City, Inner Mongolia, China. It is also at the junction of the Da Hinggan Mountians, Inner Mongolian Plateau and Yanshan Mountains. It is about 650 km north of Beijing. The geographic coordinates are 116?30'?118?20'E and 42?20'?44?10'N (Fig. 1). The elevation range is from 1100 m to 1700 m, and the highest peak (2029 m) of the Da Hinggan… 相似文献
8.
FRANK LEHMKUHL LEWIS A. OWEN 《Boreas: An International Journal of Quaternary Research》2005,34(2):87-100
Abundant glacial geologic evidence present throughout Tibet and the bordering mountains shows that glaciers have oscillated many times throughout the late Quaternary. Yet the timing and extent of glacial advances is still highly debated. Recent studies, however, suggest that glaciation was most extensive prior to the last glacial cycle. Furthermore, these studies show that in many regions of Tibet and the Himalaya glaciation was generally more extensive during the earlier part of the last glacial cycle and was limited in extent during the global Last Glacial Maximum (marine oxygen isotope stage 2). Holocene glacial advances were also limited in extent, with glaciers advancing just a few kilometers from their present ice margins. In the monsoon-influenced regions, glaciation appears to be strongly controlled by changes in insolation that govern the geographical extent of the monsoon and consequently precipitation distribution. Monsoonal precipitation distribution strongly influences glacier mass balances, allowing glaciers in high altitude regions to advance during times of increased precipitation, which are associated with insolation maxima during glacial times. Furthermore, there are strong topographic controls on glaciation, particular in regions where there are rainshadow effects. It is likely that glaciers, influenced by the different climatic systems, behaved differently at different times. However, more detailed geomorphic and geochronological studies are needed to fully explore regional variations. Changes in glacial ice volume in Tibet and the bordering mountains were relatively small after the global LGM as compared to the Northern Hemisphere ice sheets. It is therefore unlikely that meltwater draining from Tibet and the bordering mountains during the Lateglacial and early Holocene would have been sufficient to affect oceanic circulation. However, changes in surface albedo may have influenced the dynamics of monsoonal systems and this may have important implications for global climate change. Drainage development, including lake level changes on the Tibetan plateau and adjacent regions has been strongly controlled by climatic oscillations on centennial, decadal and especially millennial timescales. Since the Little Ice Age, and particularly during this century, glaciers have been progressively retreating. This pattern is likely to continue throughout the 21st century, exacerbated by human-induced global warming. 相似文献
9.
10.
Climatic variations in China during the Quaternary have long been a question of debate. Considerable data now available support Professor Li Siguang's (J. S. Lee) suggestion that there were four glacial periods. In this later years the views of Professor Li have received support from more recent information demonstrating that a further glacial period and periglacial phenomena preceded the Boyang Period.During the Quaternary 3,500,000 years ago there were a number of climatic fluctuations in China, having an amplitude of over 10°C and a cycle of 104 to 105 years. Each fluctuation lasted from the onset of one glacial period to that of the next, encompassing a glacial period and an interglacial. Tab 1 provides a comparison between the glacial periods in China during the Quaternary and those in other regions of the world. 相似文献
11.
The vegetation and the climatic context in which the first hominins entered and dispersed in Europe during the Early Pleistocene are reconstructed, using literature review and a new climatic simulation. Both in situ fauna and in situ pollen at the twelve early hominin sites under consideration indicate the occurrence of open landscapes: grasslands or forested steppes. The presence of ancient hominins (Homo of the erectus group) in Europe is only possible at the transition from glacial to interglacial periods, the full glacial being too cold for them and the transition interglacial to glacial too forested. Glacial–interglacial cycles forced by obliquity showed paralleled vegetation successions, which repeated c. 42 times during the course of the Early Pleistocene (2.58–0.78 Ma), providing 42 narrow windows of opportunity for hominins to disperse into Europe.The climatic conditions of this Early Pleistocene vegetation at glacial-interglacial transitions are compared with a climatic simulation for 9 ka ago without ice sheet, as this time period is so far the best analogue available. The climate at the beginning of the present interglacial displayed a stronger seasonality than now. Forest cover would not have been hampered though, clearly indicating that other factors linked to refugial location and soils leave this period relatively free of forests. Similar situations with an offset between climate and vegetation at the beginning of interglacials repeated themselves throughout the Quaternary and benefitted the early hominins when colonising Europe.The duration of this open phase of vegetation at the glacial–interglacial transition was long enough to allow colonisation from the Levant to the Atlantic.The twelve sites fall within rather narrow ranges of summer precipitation and temperature of the coldest month, suggesting the hominins had only a very low tolerance to climate variability. 相似文献
12.
南海东部69柱粒度分维指标与气候代用指标的分形比较及其意义 总被引：3，自引：0，他引：3
南海69柱粒度数据分析表明,晚更新世以来,粒度在0.2~11μm的标度范围内具有分形特征,粒度分维值DS为1.72~2.02,平均1.84;不同时期粒度分维值明显不同,氧同位素1期(冰后期)为1.88,氧同位素2期(冰期)为1.81,温暖的冰后期粒度分维值高且变化幅度大,寒冷的冰期粒度分维值低且变化幅度小,表明粒度分维值DS对沉积物的形成环境演化具有良好的指示意义。运用R/S分析法,对69柱沉积物的粒度分维值DS、UK37法估算的表层海水古温度、浮游有孔虫的δ18O、δ13C及其转换函数计算的冬季表层海水古温度、夏季表层海水古温度、季节性温差、沉积物SiO2、CaCO3含量9项指标进行尺度重整分析计算,得到其时间序列分维值DH分别为1.2855、1.1712、1.2659、1.4244、1.2719、1.2214、1.2979、1.1366、1.1609。虽然这些气候指标是用不同物理单位测量的,但运用分形分析可以对它们进行数学比较,粒度分维值DS与季节性温差二者的时间序列分维值DH最接近,从分形理论方面进一步证实粒度分维值DS的变化主要反映气候的冷暖变化。综合粒度分维值DS及其他气候代用指标分析,识别出南海东部全新世以来的4次突发事件。 相似文献
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14.
中国黄土研究新进展 (二)古气候与全球变化 总被引：11，自引：3，他引：11
本文扼要介绍最近几年来在中国黄土高分辨率气候地层、第四纪古气候演化型式以及冷期和暖期中黄土高原古气候空间格局研究方面的一些新进展。根据土壤地层学与地球化学、地球物理学手段的结合,2.5 Ma来的中国黄土系列可划分出37个大的气候旋回,其中含74个气候阶段,这74个气候阶段又可细分为110个次级阶段。第四纪气候振荡的幅度受气候周期长短所控制。从冷期到暖期的气候转换具有突变性,从暖期到冷期的气候转换具有渐变性。冷期堆积的黄土与暖期形成的土壤在性状上都有地带性分布的特征。 相似文献
15.
Accurate chronological records are critical for studying the alluvial fan sequences emplaced during local/global climatic changes but, in general, there are no satisfactory, quantitative dating methods available. In situ -produced 10 Be concentrations have been measured in quartz boulders exposed on Sulawesian late Quaternary fan surfaces. These concentrations suggest that the two fan units evidenced by geomorphic study were emplaced during two distinct major climatic events. The calculated minimum exposure ages imply abandonment ages of 11 kyr and 120 kyr, for the younger and older units, respectively. This study demonstrates that using both the neutron and muon components implicated in the in situ 10 Be production, surficial erosion rates can be estimated and alluvial fans dated. In particular, it shows that in situ 10 Be may be used to date fan emplacement during the last 120 kyr under humid tropical conditions, significantly helping to constrain continental palaeoclimatology. 相似文献
16.
G. Delisle 《第四纪科学杂志》1998,13(4):325-333
A series of numerical models on permafrost growth and decay are presented with special emphasis on the climatic conditions in western Europe during the last glacial stage. Numerical modelling of growth and decay of the active layer suggests penetration depths in the range between 0.6 to 1.4 m. Permafrost is estimated to have grown, depending on the sediment type, to a thickness of 90 m to 140 m in northern Germany and The Netherlands within 10 000 y during the peak period of the last glacial stage. Permafrost continued to exist at depth for about 2000 y after the climatic improvement following the Younger Dryas. Permafrost growth under rivers and lakes is shown to be unlikely under the climatic conditions of the last glacial stage in northern Germany. A time period of 10 000 to 42 000 years and a massive climatic excursion (of the order of > 11°C) is required to remove the thick permafrost layers in Siberia and Alaska of today. © 1998 John Wiley & Sons, Ltd. 相似文献
17.
MIS 3时期青藏高原东南部稻城古冰帽冰进事件研究 总被引：1，自引：1，他引：0
深海氧同位素3阶段（Marine Isotope Stage 3,MIS 3）是全球气候演化过程中特殊的时期,对深入认识区域古气候、古环境演变具有重要意义。青藏高原东南部稻城古冰帽是第四纪冰川作用历史和古气候研究的理想区域,许多学者在该区进行了冰川地貌学和年代学研究。目前,该区域在MIS 3阶段是否存在冰川前进事件仍存在争论。现着重从洞穴石笋、高原冰芯、海洋沉积、古湖孢粉等记录来总结我国MIS 3阶段的气候环境状况,并搜集高原及周边地区MIS 3阶段冰进事件的记录,结合稻城古冰帽区已发表的MIS 3阶段的年代数据来探讨稻城古冰帽区MIS 3阶段的冰川前进的可能性。结果表明：稻城古冰帽区MIS 3阶段（43~53 ka）发生了大规模冰进事件,这可能是由于该冰帽区处于相对冷湿环境且受到了西南季风的影响。本研究可为区域气候重建与环境演变提供新的依据。 相似文献
18.
施雅风和李吉均（1994）在总结80年代以来中国冰川学研究的新进展中,提出了3个有待深化和争论的问题：1）不同地区最大冰期出现先后差别的原因尚不清楚;对是否存在一种与季风区相反的模式,即冰期与雨期同步;3）在冰期变化中"气候因素与构造因素何者为主".这3个问题也可以说是本世纪冰川学研究留给下世纪的3个问题．它的解决只有冰川学、气候学和地球动力学等的结合才有可能文章拟对此3个问题提点看法,以期"抛砖引玉"． 相似文献
19.
沙鲁里山是研究第四纪冰川的最佳场所之一。可划分四个冰期,第一冰期为大陆冰盖,第二、三期及现代冰川为山岳冰川;整体反映第四纪地壳不断抬升,气候不断变暖,冰川不断向高山退缩的过程。 相似文献
20.
R. Henrich T. Wagner P. Goldschmidt K. Michels 《International Journal of Earth Sciences》1995,84(1):28-48
Various models of surface and deep-water circulation in the Norwegian-Greenland Sea (NGS) have been proposed for the last two glacial to interglacial transitions. Although much progress has been made in understanding the sedimentary response to climatic and oceanographic changes, conflicting interpretations have been developed. To clarify some of these discrepancies and to test or modify the existing circulation concepts, a multiparameter approach is applied, combining sedimentological, micropaleontological, organic-geochemical and isotopic methods. On the basis of indicative properties a combined litho- and organofacies concept is developed and calibrated with modern depositional settings beneath different surface water masses. Sedimentary regimes are then derived for glacial and deglacial settings.Atlantic water intrusions in the NGS reveal complex and highly dynamic patterns for the last two glacial and interglacial periods, with repetitive inflows during Isotope Stage 6 and a high variability in Isotope Stage 5. Specific facies patterns show maximum extensions of Atlantic Water intrusions during the climatic highstands 5.5.1, 5.3 and 5.1 and narrowest intrusions in the cool phases 5.4 and most pronounced in 5.2. In contrast, different glacio-marine depositional regimes depict variable sea ice coverage and supply of ice-rafted debris. Most conspicuous are short-term depositional events marked by diamictons, which are related to the high instabilities of continental ice sheets. Some of the diamictons seem to occur contemporaneously with Heinrich layers H1 and H2. The probable temporal and obvious phenomenological concidence of Heinrich layers and NGS diamictons suggests a common trigger mechanism which caused an almost simultaneous disintegration of huge continental ice masses along the shelves of North America and the eastern margin of the NGS.A previous estuarine circulation model claims regional upwelling along the eastern margin of the NGS for specific periods of the last deglaciation. The organic character of sediments covering the same time intervals show a clear predominance of reworked fossil organic matter and thus does not support the estuarine model. 相似文献