Variation of summer monsoon intensity in the North China Plain and its response to abrupt climatic events during the early-middle Holocene
Variation of summer monsoon intensity in the North China Plain and its response to abrupt climatic events during the early-middle Holocene
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全新世早中期华北平原夏季风强度变化及其对突发气候事件的响应
DOI：
10.1016/j.quaint.2020.03.033
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发表时间：
2020
影响因子：
2.2
通讯作者：
Guoqiang Ding
中科院分区：
文献类型：
--
作者：
Chenzhi Li;Bing Li;Yuecong Li;Bishan Chen;Qinghai Xu;Wensheng Zhang;Wei Liu;Guoqiang Ding
宁晋坡古湖是全新世中国平原北部最大的湖泊，其连续的沉积记录具有重建夏季风强度和高分辨率确定湖泊对突发性气候事件的响应的潜力。结果表明：(1)KYR BP以来，该区地球化学气候变化指数(C)(1.16)、泥沙堆积速率(SAR)(0.007 cm/年)和中值粒径(Md)(20.6μm)最低，而干旱指数(0.0323)、铁锰比(0.0088)和粘粒含量(17.3%)最高；表明中国平原北部降水偏少，宁津坡古湖流域化学风化和侵蚀强度较弱。(2)KYR BP期间，C指数(1.36)、砂粒含量(19.1%)、粉砂含量(68.0%)、Md(27.2μm)和SAR(0.019 cm/a)显著增加。这些特征表明，气候逐渐变湿，化学风化和侵蚀强度增加，入湖径流增加，湖平面上升。(3)在7.7~5.5世纪，C指数(1.5 6)、粉粒含量(71.8%)、SAR(0.030 cm/a)达到最大值，而Fe/Mn比值(0.0068)、含沙量(14.4%)、Md(21.4gμm)降至最低水平。气候温暖湿润，入湖径流量大，流域化学风化作用强，水位达到全新世最高。(4)KYR BP以来，C指数(1.26)和SAR(0.011 cm/年)显著下降，含沙量(28.2%)和Md(18.3μm)达到最高水平。这些特征表明，尽管这一时期洪涝灾害频繁，但气候逐渐干旱，对宁晋坡古湖的径流减少，流域内的化学风化和侵蚀强度减弱，湖平面下降。(5)除了在中国北部季风区记录到的全球记录的8.2亿卡、5.3亿卡和4.2亿卡的气候突变事件外，还记录到了一次全新世中期的气候突变事件，约7.2亿卡。在中国北部季风区，这些事件可能被全新世中期以来异常活跃的ENSO放大了。
Ningjinpo paleolake was the largest lake in the North China Plain during the Holocene, and its continuous sedimentary record has the potential to reconstruct the summer monsoon intensity and determine the limnological response to abrupt climatic events at a high resolution. Here we use AMS14C dating and analyses of grain-size and major element contents, and the results show that: (1) During 11.5–10.0 cal kyr BP, the geochemical climate change index (C) (1.16), sediment accumulation rate (SAR) (0.007 cm/yr) and median particle diameter (Md) (20.6 μm) are the lowest within the section, while the geochemical drought index (0.0323), Fe/Mn ratio (0.0088) and clay content (17.3%) are the highest, which indicate that the North China Plain received less precipitation, and chemical weathering and erosional intensity in the Ningjinpo paleolake catchment were weak. (2) During 10.0–7.7 cal kyr BP, the C index (1.36), content of sand (19.1%) and silt (68.0%), Md(27.2 μm) and SAR (0.019 cm/yr) increase significantly. These characteristics indicate that the climate gradually became wetter, chemical weathering and erosion intensity increased, and there was increased runoff to the lake, which raised the lake level. (3) During 7.7–5.5 cal kyr BP, the C index (1.56), silt content (71.8%) and SAR (0.030 cm/yr) increase to the highest, while the Fe/Mn ratio (0.0068), sand content (14.4%) and Md(21.4 μm) decrease to their lowest levels. These suggest the climate was warm and humid, the runoff to the lake was large, chemical weathering in the catchment was strong, and the water level of the lake reached the maximum for the Holocene. (4) During 5.5–3.3 cal kyr BP, the C index (1.26) and SAR (0.011 cm/yr) decrease substantially, whereas the sand content (28.2%) and Md(18.3 μm) increase to the highest levels. These characteristics demonstrate that the climate gradually became arid, the runoff to Ningjinpo paleolake was reduced, the intensity of chemical weathering and erosion in the catchment weakened, and the lake level decreased, although the high frequency of floods in this period. (5) In addition to the globally-recorded abrupt climatic events at ~8.2 cal kyr BP, ~5.3 cal kyr BP and ~4.2 cal kyr BP, which were recorded in the northern monsoon region of China, an abrupt climatic event in the middle Holocene, at ~7.2 cal kyr BP, was also recorded. In the northern monsoon region of China, these events may have been amplified by unusually active ENSO since the middle Holocene.