Hydrological and ecosystem response to abrupt changes in the Indian monsoon during the last glacial, as recorded by sediments from Xingyun Lake, Yunnan, China
Hydrological and ecosystem response to abrupt changes in the Indian monsoon during the last glacial, as recorded by sediments from Xingyun Lake, Yunnan, China
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DOI：
10.1016/j.palaeo.2015.01.005
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发表时间：
2015-03
期刊：
影响因子：
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通讯作者：
Duo Wu;Aifeng Zhou;Xuemei Chen;Junqing Yu;Jiawu Zhang;Huiling Sun
中科院分区：
文献类型：
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作者：
Duo Wu;Aifeng Zhou;Xuemei Chen;Junqing Yu;Jiawu Zhang;Huiling Sun
印度夏季风是中国西南地区降水的主要水汽来源，在区域环境变化和经济社会发展中发挥着重要作用，因为夏季风的突然变化会导致农作物歉收和洪水泛滥，影响到大量人口的生计。然而，除了洞穴记录外，最后一次冰川期间ISM的突然变化在陆地记录中没有很好的记录。本文介绍了中国西南部云南省星云湖的沉积记录，时间跨度为36.4亿年龄段至13.4年龄段(1万亿年龄段)，它记录了一系列千年尺度事件的发生，可能反映了ISM的突然减弱。来自陆地木材碎片的七个AMS14C年代提供了一个可靠的年代学。结果表明，粗沉积物含量(~30μm)的增加对应于盘状藻浓度、磁性矿物粒度、碳酸盐含量和C/N比的增加，这些指标共同指示了低湖平面时期。此外，花粉分析表明，在ISM突然减弱期间，栎属植物增加，蕨类植物减少，表明环境较干燥。在研究的时间间隔内，记录了9次湖平面突变，其中3次与海因里希事件1至3有关。我们的研究支持这样的假设，即随着大量冰山涌入北大西洋的冷事件以及相应的大西洋经向翻转环流减缓，ITCZ的平均纬度范围向南移动。由于大气遥相关，与ISM降水相关的降水相应减少，导致云南河流径流减少。
The Indian Summer Monsoon (ISM) is the major moisture source of precipitation in southwest China and plays an important role in regional environmental change and in economic and social development, since abrupt changes of the ISM can cause crop failures and flooding that impact the livelihood of a large population. However, with the exception of speleothem records, abrupt changes of the ISM during the last glacial are not well documented in terrestrial records. Here we present a sediment record from Xingyun Lake in Yunnan Province, southwest China, spanning the interval 36.4 ka BP to 13.4 ka BP (1 ka = 1000 cal a) which documents the occurrence of a series of millennial-scale episodes which may reflect the abrupt weakening of the ISM. Seven AMS14C dates from terrestrial wood fragments provide a robust chronology. The results demonstrate that increases in the coarse sediment fraction (> 30 μm) correspond to increases in the concentration ofPediastrum, the grain size of magnetic minerals, carbonate content and C/N ratios, which together indicate episodes of low lake level. In addition, pollen analysis indicates thatQuercus(oak) increased and that ferns decreased during intervals of abrupt weakening of the ISM, indicating a drier environment. Nine abrupt shifts to a low lake level are documented for the studied interval and three of them are correlative with Heinrich events 1 to 3. Our study supports the hypothesis that, in response to the cold events in the North Atlantic associated with massive iceberg influxes and the corresponding slowing down of Atlantic meridional overturning circulation, the mean latitudinal extent of the ITCZ shifted southwards. As a result of an atmospheric teleconnection there was a corresponding decrease in precipitation associated with ISM precipitation, which caused reduced fluvial runoff in Yunnan.