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1.
控制东亚气候的东亚季风夏季风北界的内蒙古盐湖沉积物记录了晚第四纪末次冰川冰期以来的气候冷暖干湿变化特征及各类重要的气候事件。通过对内蒙古伊克昭盟杭锦旗盐海子Ｙａ０１孔岩心沉积物的有机碳、碳氮比、碎屑矿物成熟度、磁化率、氧碳稳定同位素和沉积物成分的研究表明,全新世大暖期起止时间为８￣４ｋａＢ．Ｐ．,其气候特征为暖干型。这一气候特点可与中国北方黄土、冰川、冲绳海槽沉积物及南海有孔虫Ｐｕｌｌｅｎｉａｔｉ  相似文献   

2.
通过对内蒙古东部现代东亚季风界线两侧的浑善达克沙地和呼伦贝尔沙地风成砂-古土壤剖面的光释光、~(14)C年代和沉积物主、微量元素地球化学的分析,重建内蒙古东部末次冰消期以来气候变迁过程。浑善达克沙地的浩来呼热剖面(hsh1-09)显示了末次冰消期以来3次暖湿气候期,分别对应末次冰消期、全新世大暖期、中世纪暖期。呼伦贝尔沙地的嵯岗剖面(CG-09)表现了全新世大暖期和中世纪暖期两次的暖湿气候期。这一过程是对东亚夏季风的响应,大致反映了内蒙古东部末次冰消期以来的东亚夏季风两次不同程度增强及大暖期结束的南退过程。通过对比前人研究结果,全新世中期东亚夏季风较强,在内蒙古东部大约距今4 ka开始减弱、南退;中世纪暖期夏季风强度较弱,持续时间短。  相似文献   

3.
粘土矿物在黄河源区古气候研究中的应用   总被引：17，自引：2，他引：15  
沉积物中粘土矿物的组成具有一定的古气候指示意义。利用沉积物中粘土矿物的组成探讨了黄河源区全新世的古气候变迁。通过X衍射方法分析了一个全新世地层剖面的粘土矿物类型和含量的变化,这些粘土矿物主要由伊利石、伊蒙混层矿物和少量的高岭石、绿泥石组成。对粘土矿物含量变化的分析和对比研究表明,黄河源区在全新世的气候寒冷干燥,即使在大暖期也显得温凉。全新世的气候演变可划分为3个阶段,即早全新世的干冷期、中全新世的温凉期(大暖期)和晚全新世的干冷期。在大暖期,在7 0kaB P 和5 0kaB P 前后发生了两次较强的降温事件。  相似文献   

4.
从内蒙古伊盟盐海YaO2孔氧碳同位素资料中可以看到:东亚季风气候在22 000aBP时由第四纪末次冰期气候开始转入末次间冰期气候。东亚季风带第四纪末次冰期时的气候环境是湿冷的淡化期。而末次间冰期的气候环境是热干的成盐期。其次,末次冰期以来,气候由湿冷转变为热干,5400aBP时气候达到热干的大暖期的最热点。之后又逐级降至现代暖趋冷的气候特征。东亚季风气候带的末次间冰期开始界线在22 000aBP左右。δ18O资料告诉我们内蒙古高原第四纪末次冰期曾有过冰川或冰盖地貌景现,在22000aBP以后才消融进入第四纪末次间冰期。  相似文献   

5.
云南宣威4.6万年以来洞穴石笋古气候变化记录   总被引：7，自引：0，他引：7  
石笋是高分辨地记录古气候环境变化的主要信息载体之一。本文通过对宣威下水龙洞 1号石笋进行α能谱铀系测年及碳、氧同位素分析,获得了距今 46.1ka至 2.75ka高分辨率的古气候演变信息。其年龄与δ18O值的记录在纵向上的变化具有明显的韵律性特征,可与深海岩芯V2 8～ 2 3 8同位素记录所揭示的第 3阶段、2阶段和 1阶段进行对比。反映 46.1ka以来宣威地区的气候波动与全球的气候变化具有明显的一致性。但是,区内是气候变化的敏感区,是东亚季风与印度洋季风交互作用的特殊区域,存在有明显的地区性气候变化特征,在整个末次冰期时段 (4 6.1～8.1ka)气候总体偏温暖,10.2 5ka为新仙女木冷事件的最冷终止点。在全新世大暖期时段的 7.1～ 3.7ka间显示气候温暖湿润,而在 3.7～ 2.75ka间伴随太阳辐射和印度洋西南季风强度的减弱,气候有明显的降温趋势。此外,石笋的碳、氧同位素显示的气候冷暖变化是,主沉积旋回以万年级、千年级和百年级为周期性变化;亚旋回以千年级和百年级为周期性变化。  相似文献   

6.
内蒙古辉腾锡勒全新世中晚期环境变迁的孢粉记录   总被引：1，自引：0，他引：1  
通过对内蒙古中部辉腾锡勒湖泊沉积特征及孢粉组合特征的综合分析,重建了该地区全新世中晚期以来气候环境变化过程。研究结果表明,该地区5390 a以来气候总体上由温湿转变为冷干,具体可以分为5个阶段: 5390 ~ 3970 a,以温暖偏湿气候为主; 3970 ~ 3300 a,气候仍为温和偏湿; 3300 ~ 2380 a,A/C比值明显降低,标志着全新世大暖期结束,凉偏干气候显著; 2380 ~ 1160 a,气候转为凉湿,为大暖期结束后一个特殊湿润时期; 1160 a以来气候向温凉偏干转变。   相似文献   

7.
选择位于西风区的乌伦古湖为研究对象,利用AMS 14 C测年手段,建立了乌伦古湖沉积岩芯全新世以来的时间序列.对湖泊沉积物中的介形类组合特征及其壳体氧碳同位素的综合分析表明,全新世以来乌伦古湖地区气候环境演变经历了3个阶段:9985～5250cal.aB.P.为剖面最湿润阶段,气候经历了温干-冷湿-暖湿的转变,湖水水位和湖面相应地经历了由浅变深、由小变大的变化,出现了高湖面特征;5250～1255cal.aB.P.为剖面最干燥阶段,气候由早期暖干向中后期暖湿转变,湖泊水位先下降后回升;1255cal.aB.P.以来先低温后升温,气候干燥,降水较少,湖水位降低.乌伦古湖介形虫记录的气候环境演化不但与孢粉资料记录相吻合,而且与周边区域环境变化记录一致,很好地响应了区域环境和全球气候突变事件,在百年尺度上主要遵循西风带模式,表现为冷湿暖干组合特征.  相似文献   

8.
对甘肃敦煌伊塘湖沉积物进行了野外钻探采样,采用光释光测年技术确定了沉积物的年代,测定了总有机碳含量(TOC)、碳氮比(TOC/TN)和有机质稳定碳同位素组成(δ13℃org)等环境代用指标.结果表明,23ka至今,湖区沉积物δ13℃org在-27.84‰～-22.86‰之间变化,可与TOC对比.干旱气候条件下湖泊沉积物的δ13℃org变化主要受到沉水植物和挺水植物含量变化的控制,生长于较深水的沉水植物δ13Corg值偏正,而生长于较浅水的挺水植物δ13℃org值偏负;另外,部分时期有外源陆生植物产生的有机质输入,影响沉积物的碳同位素值.总体上,干旱区湖相沉积物δ13Crg值可指示湖水面的变化、间接指示气候干湿变化.δ13Corg变化的时间序列显示出明显的冰期-间冰期变化,从末次盛冰期到全新世暖期可将伊塘湖的环境演化分为4个阶段:23～ 13ka是一个气候不稳定时期,整体呈冷干并且湖面水位偏低,但后期有转暖的趋势;13～9ka为冰期向全新世暖期的过渡阶段;9～5ka整体湖面水位偏高、气候暖湿,含有短时间的干事件;5ka至今有变干的趋势.23ka以来,伊塘湖区的湖泊环境演化受全球大气环流与水汽输送路径控制.  相似文献   

9.
钱作华  许靖华  袁遵 《化工矿产地质》2002,24(2):96-100,120
从内蒙古伊盟盐海子Ya02孔氧碳同位素资料中可以看到,东亚季风气候在22000aBP时由第四纪末次冰期气候开始转入末次间冰期气候,东亚季风带第四纪末次冰期时的气候环境是湿冷的淡化期,而末次冰期的气候环境是热干的成盐期.其次,末次冰期以来,气候由湿冷变为热干,5400aBP时气候达到热干的大暖期的最热点,之后又逐级降至现代暖趋冷的气候特征,东亚季风气候带的末次间冰期开始界线在22000aBP左右,δ^18O资料告诉我们内蒙古高原第四纪末次冰期曾有过冰川或冰盖地貌景观,在22000aBP以后才消融进入第四纪末次间冰期.  相似文献   

10.
全新世温暖期中低温事件的初步研究   总被引：23，自引：1，他引：23  
王开发 《第四纪研究》1990,10(2):168-174
在第四纪气候中,全新世是气候转暖期,尤其是全新世中期为其最暖期,然而在温暖期中,却普遍发现有短暂的降温时期,世界各地均有存在。根据中国全新世各地的孢粉植物群、动物化石、西部冰川消长、海面升降变化以及天文背景等研究证实,在中国全新世温暖期中,确实存在一次短暂的降温事件,并有其重要的地学意义。  相似文献   

11.
利用1961-2011年我国东北地区(包括黑龙江、吉林、辽宁、内蒙古东部)的冬季降水资料,分析了东北地区冬季降水量的时空分布和冬季降水日数的时空分布,对比分析了东亚冬季风对我国东北地区冬季降水的影响. 结果表明：东北地区冬季降水量和降水日数分布有明显的区域差异,以内蒙古东南部、辽宁西北部、吉林西部、黑龙江西南部为低值中心,外围辽宁东部,吉林南部,黑龙江东部、中北部、北部,内蒙古东北部等地区为高值区;冬季降水量年际变化呈增加的线性趋势,1980年代中期以后冬季降水量的高值和低值都有明显的增大;年降雪日数年际变化呈线性增加趋势. 1948-2011年东亚冬季风强度指数的结果表明,东亚冬季风呈明显的线性减弱趋势,弱东亚季风主要集中在20世纪80年代中期以后,除内蒙古东南部等少数区域外,我国东北大部分地区的冬季降水量都和东亚冬季风呈负相关. 对应地,东北地区冬季降水量增大,年际变化的幅度变化增大,降水日数增量较小,这可能与东北地区冬季极端降水天气和干旱天气增加有关. 在东亚范围内,我国东北地区冬季降水多年200 hPa U风增强、500 hPa高压减弱、850 hPa东海南风增强,冬季降水少年则相反.  相似文献   

12.
Fluctuations in climatic proxies of the Milanggouwan section in the Salawusu River valley of the Ordos Plateau (Inner Mongolia, China) during Marine Isotope stage 3 (MIS 3) coincide well with sedimentary cycles for palaeo‐mobile dune sands alternating with fluvial–lacustrine facies and palaeosols. We compared the palaeo‐mobile dune sands with modern mobile dune sands (products of a cold and dry climate dominated by the East Asian winter monsoon), whereas the fluvial–lacustrine facies and palaeosols were controlled by a wet–warm climate similar to that of the East Asian summer monsoon. The MIS 3 climate of the Salawusu River valley appears to have experienced at least nine wet–warm and ten cold–dry fluctuations, divided into five stages: MIS 3e (58 900–49500 yr BP), MIS 3d (49 500–40 700 yr BP), MIS 3c (40 700–36 900 yr BP), MIS 3b (36 900–27 000 yr BP) and MIS 3a (27 000–22 300 yr BP). The 19 cold–warm climatic fluctuations corresponded roughly to the GRIP and Guliyan records, and with fluctuations in the North Atlantic climate. Notable peaks in the spectral analysis occurred at 19 500 yr, 1020 yr, 640 yr and 500 yr. Our results show that the millennial–centennial climate was closely related to the relative strengths of East Asian monsoons, which are controlled by the North Atlantic thermohaline circulation, and which is also closely linked to the Sun's precession period. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

13.
Wen, R. L., Xiao, J. L., Chang, Z. G., Zhai, D. Y., Xu, Q. H., Li, Y. C. & Itoh, S. 2009: Holocene precipitation and temperature variations in the East Asian monsoonal margin from pollen data from Hulun Lake in northeastern Inner Mongolia, China. Boreas, 10.1111/j.1502‐3885.2009.00125.x. ISSN 0300‐9483. Quantitative palaeoclimatic reconstruction with the weighted averaging partial least squares method was applied to the pollen profile from Hulun Lake in northeastern Inner Mongolia. The data provide a detailed history of variations in precipitation and temperature over the northeastern margin of the East Asian summer monsoon during the Holocene. A warm and dry climate prevailed over the lake region until c. 8000 cal. BP. During the period c. 8000–4400 cal. BP, precipitation increased markedly and temperature gradually declined. The interval between c. 4400 and 3350 cal. BP was marked by extremely dry and relatively cold conditions. Precipitation recovered from c. 3350 to 1000 cal. BP, with temperatures rising c. 3350–2050 cal. BP and dropping c. 2050–1000 cal. BP. During the last 500 years, the climate of the lake region displayed a general trend of warming and wetting. While Holocene temperature variations in the mid‐high latitude monsoonal margin were controlled by changes in summer solar radiation in the Northern Hemisphere, they could also be related to the strength of the East Asian summer monsoon. The lack of precipitation during the early Holocene could be attributed to the weakened summer monsoon resulting from the existence of remnant ice sheets in the Northern Hemisphere. Changes in the monsoonal precipitation during the middle to late Holocene would have been associated with the ocean–atmosphere interacting processes occurring in the western tropical Pacific.  相似文献   

14.
A consensus on Holocene climate variability at the modern northern fringe of the East Asian summer monsoon (EASM) region remains elusive. Here, we present a pollen-based reconstruction of vegetation history and associated climate variations of a sediment core from Huangqihai Lake, central Inner Mongolia. During 10.7 to 8.8 cal kaBP, typical steppe with small patches of forest dominated the lake area, suggesting a moderately wet climate, followed by ameliorating climatic conditions until 8.0 cal kaBP as deduced by the expansion of forest. Typical steppe recovered the lake area between 8.0 and 7.2 cal kaBP, reflecting a deterioration of climatic conditions; in combination with other proxy records in the study region, we noticed that severe aridity was prevailed in the lake area between 8.0 and 7.6 cal kaBP. During 7.2 to 3.2 cal kaBP, abundant tree pollen indicated dominance of forest-steppe around the lake, marking regionally wet conditions. A notable absence of broadleaved trees after 5.2 cal kaBP reveals a slight drying trend, and climate deterioration from 4.5 to 4.1 cal kaBP might be linked to the 4.2 ka event. After 3.2 cal kaBP, a transition to steppe was associated with dry conditions in the region. Based on our pollen record and prior paleoclimatic reconstructions in the Huangqihai Lake region, there was a generally-accepted, stepwise shift to a wet climate during the early Holocene, an overall humid climate from 7.2 to 3.2 cal kaBP, and then severe drought for the rest of the Holocene. Moreover, regional comparisons among pollen records derived from lakes situated in the temperate steppe region suggested a roughly synchronous pattern of vegetation and climate changes during the Holocene and demonstrated an intensified EASM during the middle Holocene.  相似文献   

15.
Zhuyeze palaeolake is a terminal lake situated in the arid northern China in the East Asian monsoon margin. In order to examine the Holocene palaeoclimatic change in the East Asian monsoon margin, Qingtu Lake section (QTL) from Zhuyeze palaeolake is sampled in high resolution. Palaeoclimatic proxies such as grain size, carbonate, TOC, C/N and δ13C of organic matter, were analyzed; eleven 14C samples and six optically stimulated luminescence (OSL) samples were dated to provide chronological control. We also investigated the geomorphic features of lake shorelines in this area. The results show that the climate was warm and dry in early-Holocene (9.5-7.0 cal ka BP), cool and humid in mid-Holocene (7.0-4.8 cal ka BP), and increasingly drier in late-Holocene (since 4.8 cal ka BP). Comparisons of our records with other records in adjacent areas, as well as with the records in the Asian monsoon areas, suggested that changes in effective moisture was synchronous in East Asian monsoon marginal zone (i.e. the pattern of dry early-Holocene, humid mid-Holocene, and aridity-increasing late-Holocene), and that the moisture optimum during the Holocene was out-of-phase between Asian monsoon margin and Asian monsoonal dominated region, possibly due to the high temperature at that time.  相似文献   

16.
The Barkol Lake, as a closed inland lake, is located at the northeast Xinjiang in northwest China. A combination of geochemical indicators including δ18O and δ13C of carbonate, TOC, carbonate contents, as well as grain size proxies and magnetic susceptibility of sediments obtained from a newly recovered section at this lake, provides a high-resolution history of climatic change in the past 9400 years. Multi-indicators reflect that Holocene climatic change in the study region generally follows the Westerly Wind pattern of Holocene, and three climatic periods can be identified. Between 9400 and 7500 cal a B.P., climate was characterized by relatively drier and colder condition. From 7500 to 5800 cal a B.P., a relatively warmer and moister climate prevailed, but between 5800 and 3500 cal a B.P., climate shifted towards warmer and drier conditions. A relatively colder and wetter climate prevailed during 3500∼1000 cal a B.P., then it changed towards cold and dry between 1000 and 500 cal a B.P.; after 500 cal a B.P., climate changed towards warm and dry conditions again. This study reflects that during the Middle Holocene (from ca 7000 to 3500 cal a B.P.), variations of carbonate δ18O of sediments from several lakes in the northern Xinjiang were synchronous with that of Qinghai Lake, where was strongly influenced by the South Asian monsoon; however, after 3500 cal a B.P. this consistency was interrupted, possibly resulting from a re-domination of the Westerly Wind and the retreat of South Asian monsoon in the northern Xinjiang.  相似文献   

17.
来自东亚夏季风北界内蒙古一个盐湖的岩心沉积物内发现粗粒沉积物 ,既可沉积在湖泊收缩期 ,也可以沉积在沙丘再次活动时期。这些沉积物有机磷含量低而碎屑组分高 ,说明它沉积在一种干旱的环境中 ;反之 ,有机质含量高而碎屑组分低的细粒沉积物则最终沉积在高湖面期 ,这是因为砂坪呈围迁状态及风成尘埃较好地保存于水体中。所揭示的三个湿期分别是 13.4～ 8kaBP、6 .4～ 5 .8kaBP和4.2～ 3.1kaBP ,第一期最湿 ,其次是第三期、第二期。上述干和湿期自始至终和早先发现的同一个干旱和半干旱转换带一致 ,但是 ,这和中国大陆东部、台湾岛、冲绳海槽和中国南海所揭示的湿润的全新世大暖期不一样 ,而且 ,全新世最冷期 (4～ 2kaBP)则对应内蒙古的一个湿期 (即 4.2～ 3.1kaBP) ,这些差别可能是由于高蒸发量远远地超过了较高的季风降水量 ,这是确定夏季风北界在该地区有效湿度的一个关键标志。  相似文献   

18.
A high-resolution pollen and Pediastrum record, spanning 12,500 yr, is presented for Lake Bayanchagan (115.21°E, 41.65°N, and 1355 m a.s.l.), southern Inner Mongolia. Individual pollen taxa (PT-MAT) and the PFT affinity scores (PFT-MAT) were used for quantitative climatic reconstruction from pollen and algal data. Both techniques indicate that a cold and dry climate, similar to that of today, prevailed before 10,500 cal yr B.P. The wettest climate occurred between 10,500 and 6500 cal yr B.P., at which time annual precipitation was up to 30–60% higher than today. The early Holocene increases in temperature and precipitation occurred simultaneously, but mid-Holocene cooling started at approximately 8000 cal yr B.P., 1500 yr earlier than the drying. Vegetation reconstruction was based on the objective assignment of pollen taxa to the plant functional type. The results suggest that this region was dominated by steppe vegetation throughout the Holocene, except for the period 9200 to 6700 cal yr B.P., when forest patches were relatively common. Inner Mongolia is situated at the limit of the present East Asian monsoon and patterns of vegetation and climate changes in that region during the Holocene probably reflect fluctuations in the monsoon's response to solar insolation variations. The early to middle Holocene monsoon undoubtedly extended to more northern latitudes than at present.  相似文献   

19.
Pollen-assemblage data from a sediment core from Hulun Lake in northeastern Inner Mongolia describe the changes in the vegetation and climate of the East Asian monsoon margin during the Holocene. Dry steppe dominated the lake basin from ca. 11,000 to 8000 cal yr BP, suggesting a warm and dry climate. Grasses and birch forests expanded 8000 to 6400 cal yr BP, implying a remarkable increase in the monsoon precipitation. From 6400 to 4400 cal yr BP, the climate became cooler and drier. Chenopodiaceae dominated the interval from 4400 to 3350 cal yr BP, marking extremely dry condition. Artemisia recovered 3350-2050 cal yr BP, denoting an amelioration of climatic conditions. Both temperature and precipitation decreased 2050 to 1000 cal yr BP as indicated by decreased Artemisia and the development of pine forests. During the last 1000 yr, human activities might have had a significant influence on the environment of the lake region. We suggest that the East Asian summer monsoon did not become intensified until 8000 cal yr BP due to the existence of remnant ice sheets in the Northern Hemisphere. Changes in the monsoon precipitation on millennial to centennial scales would be related to ocean-atmosphere interactions in the tropical Pacific.  相似文献   

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