Holocene intensification of the East Asian summer monsoon: timing and mechanism

来源 :地球环境学报 | 被引量 : 0次 | 上传用户:huangjl41
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
The Holocene history of the East Asian summer monsoon is of special importance to constraining the predictions of the precipitation pattern and hydrologic cycle in eastern Asia under the background of global warming in the near future.The timing of intensification of the summer monsoon during the Holocene,however,is still debated due partly to uncertainties of radiocarbon dating of different materials and partly to discontinuities of the sedimentary sequences resulting from changes in the facies.Daihai and Hulun Lakes are located in the modern northern limit of the summer monsoon and particularly sensitive to changes in the monsoon precipitation.Highresolution,multi-proxy records of the sediment cores recovered in the central part of the lakes document changes in the hydrology and ecology of the lake regions and reveal a detailed process of East Asian summer monsoon variations during the Holocene.During the early Holocene before 8000 cal a BP,and herbs and shrubs dominated the Daihai Lake basin in company with patches of mixed pine and broadleaved forests,indicating a dry climate.The input of terrestrial organic matter to the lake was decreased,denoting weak surface runoff in the lake catchment.In Hulun Lake,dry steppe prevailed over the lake region,and the pollen-derived mean annual precipitation was low.Low-salinity D.stevensoni was abundant,warm-adapted Ilyocypris spp.was scarce,and cold-adapted C.neglecta and C.of.houae appeared frequently,denoting fresh but cold waters of the lake.Coming to the middle Holocene after 8000 cal a BP,largescale covers of mixed coniferous and broadleaved forests were developed in the Daihai Lake basin,marking a humid climate.A greater amount of terrestrial organic matter was transported to the lake,implying intensified surface runoff in the lake catchment.In Hulun Lake,grasses and birch forests expanded,and the mean annual precipitation increased markedly.Ilyocypris spp.flourished,and Mg/Ca,Sr/Ca and δ~(18)O of ostracode-shell carbonates were as low as those during the early Holocene,implying that the lake water was still fresh but became warmer.These data indicate that the East Asian summer monsoon was not intensified until 8000 cal a BP,showing a lag of 3000 cal a behind the maximum summer insolation in the Northern Hemisphere.We suggest that the time lag between the summer monsoon intensification and the maximum summer insolation might result from a stagnant northward retreat of the polar front in the North Pacific Ocean due to the existence of remnant ice sheets in the Northern Hemisphere,which would hamper the northward penetration of the summer monsoon front,thereby suppressing the monsoon precipitation over northern China. The Holocene history of the East Asian summer monsoon is of special importance to constraining the predictions of the precipitation pattern and hydrologic cycle in eastern Asia under the background of global warming in the near future. The timing of intensification of the summer monsoon during the Holocene, however, is still debated due partly to uncertainties of radiocarbon dating of different materials and partly to discontinuities of the sedimentary sequences resulting from changes in the facies. Daihai and Hulun Lakes are located in the modern northern limit of the summer monsoon and particularly sensitive to changes in the monsoon precipitation. High resolution, multi-proxy records of the sediment cores recovered in the central part of the lakes document changes in the hydrology and ecology of the lake regions and reveal a detailed process of East Asian summer monsoon variations during the Holocene. the early Holocene before 8000 cal a BP, and herbs and shrubs dominated the Daihai L ake basin in company with patches of mixed pine and broadleaved forests, indicating a dry climate. the input of terrestrial organic matter to the lake was decreased, denoting weak surface runoff in the lake catchment. Hulun Lake, dry steppe prevailing over the lake region , and the pollen-derived mean annual precipitation was low. Low-salinity D. stevensoni was abundant, warm-adapted Ilyocypris spp.was scarce, and cold-adapted C. negative and C.of.houae had frequently, denoting fresh but cold waters of the lake. Coming to the middle Holocene after 8000 cal a BP, largescale covers of mixed coniferous and broadleaved forests were developed in the Daihai Lake basin, marking a humid climate. A large amount of terrestrial organic matter was transported to the lake, implying intensified surface runoff in the lake catchment. Hulun Lake, grasses and birch forests expanded, and the mean annual precipitation increased markedly. Ilyocypris spp. flouredished, and Mg / Ca, Sr / Ca and δ ~ (18) O of ostracode- shell carb onates were as low as those during the early Holocene, implying that the lake water was still fresh but became warmer. the data indicate that the East Asian summer monsoon was not intensified until 8000 cal a BP, showing a lag of 3000 cal a behind the maximum summer insolation in the Northern Hemisphere. We suggest that time lag between the summer monsoon intensification and the maximum summer insolation might result from a stagnant northward retreat of the polar front in the North Pacific Ocean due to the existence of remnant ice sheets in the Northern Hemisphere, which would hamper the northward penetration of the summer monsoon front, so suppressing the monsoon precipitation over northern China.
其他文献
本文介绍了有线数字电视信号的形成过程及网络维护要求,详细阐述了信道功率、调制误差率、误码率的概念和用QAM测试仪来分析星座图与信号质量和系统问题的关系。 This paper
  The occurrence and abundance of different ostracod species are sensitive to changes in environmental factors, especially to the temperature and the salinity
会议
Constant levels of perceptual quality of streaming video is what ideall users expect. In most cases, however, they receive time-varying levels of quality of vid
  This study aims to reveal Holocene environmental changes on the bases of the physical and chemical analyses of the sediment core obtained from Lake Khuvsgul
会议
看准大方向,及时布局,伏设奇兵,敢于投入,敢于拼搏,敢于坚持,敢于胜利,这才是战略家的气魄和智慧嫦娥落月,玉兔巡航,神话在这一刻变成现实。"登月同我们有什么关系?"在几乎所有现场互动中,问得最多的还是这个老问题。无论是出于个人好奇,还是体现对公共财政支出的监督,人们都难免有此一问。毕竟,探月工程的投入绝不是一个小数目。
期刊
去年11月24日凌晨,我国运载能力最大的长征五号火箭从南海之滨的中国文昌航天发射场起飞,将嫦娥五号探测器成功送入地月转移轨道,顺利迈出了嫦娥五号任务月球采样返回的第一步。这是在嫦娥四号完成人类首次月背着陆后,时隔近两年后中国航天器重返月球,也是持续不断的人类探月活动中,40多年来首次去月球挖取"岩石土壤"。
期刊
分享三菱欧蓝德高端汽车音响改装作业过程。试听对比之后,车主对摩雷高端汽车音响组合:摩雷意蕾限量版+顶级功放MOSCONI的靓丽音质表现所深深吸引。甜润悦耳的高音,醇厚富有
  The idea of bi-polar seesaw has persisted for nearly two decades, motivating intensive research of models and records to investigate phase relationship of a
会议
  The Asian monsoon evolution has been significantly influenced by the orbital forcings, especially by the insolation variations induced by precession.From 19
会议
在北京,随着房价上扬,许多购房人顶着风险选择了没有国家认可的合法产权证、开发成本低的乡产权房。然而,这一高房价下的现实选择,却很难走出无产权的现实困境  今年刚大学毕业的杨萌,在学姐学长“租房不如买房”“既自住又投资”的劝导下,开始四处奔波“相房”。她惊喜的告诉记者,最近发现京郊有许多每平方米2500元至4000元的房子,这一价格只有市区内的一半,甚至比同一区域的一些房子都要便宜得多。  一打听,