East Asian monsoon variability over the last seven glacial cycles recorded by a loess sequence from the northwestern Chinese Loess Plateau
East Asian monsoon variability over the last seven glacial cycles recorded by a loess sequence from the northwestern Chinese Loess Plateau
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DOI：
10.1029/2006gc001287
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发表时间：
2006-12
期刊：
影响因子：
3.7
通讯作者：
Youbin Sun;Jun Chen;S. Clemens;Qingsong Liu;J. Ji;Ruiji Tada
中科院分区：
文献类型：
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作者：
Youbin Sun;Jun Chen;S. Clemens;Qingsong Liu;J. Ji;Ruiji Tada
研究了中国西北黄土高原180 m厚的黄土-古土壤序列，建立了近7个冰期-间冰期旋回东亚季风变化的高分辨率记录。低场磁化率（χ，质量比）和平均晶粒尺寸分别作为东亚夏季和冬季风强度变化的代表。由于中国黄土高原西北部的成土作用弱于中国黄土高原中部，我们的χ和平均粒度记录显示亚洲夏季风的冰期-间冰期对比减弱，而亚洲冬季风的对比增强。我们的χ和粒度记录捕获的大多数轨道尺度东亚季风变化与中国黄土高原中部的报告相似，尽管分辨率更高。然而，在S1、S2和S3三个古土壤层中，χ的变化表现出明显的进动周期，与太阳辐照最大值相对应。此外，与黄土高原中部古土壤S5SS1（对应海洋同位素第13阶段）的χ显著增强不同，我们的新χ记录显示古土壤S4（对应海洋同位素第11阶段）的χ显著增强，这表明两个地区局地季风降水时间的地理差异。
A 180‐m‐thick loess‐paleosol sequence from the northwestern Chinese Loess Plateau was investigated to construct a high‐resolution record of the East Asian monsoon variability over the last seven glacial‐interglacial cycles. The low‐field magnetic susceptibility (χ, mass‐specific) and the mean grain size are used as proxies for changes in the intensity of the East Asian summer and winter monsoon, respectively. Because of the weaker pedogenesis at the northwestern Chinese Loess Plateau compared to the central Chinese Loess Plateau, our χ and mean grain size records show a muted glacial‐interglacial contrast for the Asian summer monsoon but an enhanced contrast for the Asian winter monsoon. Although better resolved, most orbital‐scale East Asian monsoon variations captured by our χ and grain size records are similar to those reported from the central Chinese Loess Plateau. Nevertheless, variations in χ exhibit clear precessional cycles in three paleosol layers (i.e., S1, S2, and S3), corresponding with solar insolation maxima. Furthermore, unlike χ records at the central Chinese Loess Plateau where χ is dramatically enhanced at paleosol S5SS1 (corresponding to marine isotope stage 13), our new χ record shows a major enhancement at paleosol S4 (corresponding to marine isotope stage 11), which indicates geographic differences in the timing of local monsoon precipitation in the two regions.