Spatio-temporal expressions of precessional-scale stalagmite δ18O variations from the Asian monsoon area
Spatio-temporal expressions of precessional-scale stalagmite δ18O variations from the Asian monsoon area
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DOI：
10.1016/j.palaeo.2021.110720
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发表时间：
2022-01
期刊：
影响因子：
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通讯作者：
Shushuang Liu;Dianbing Liu;Yongjin Wang;Lingzhe Zou;Hui Gao
中科院分区：
文献类型：
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作者：
Shushuang Liu;Dianbing Liu;Yongjin Wang;Lingzhe Zou;Hui Gao
中国南方两个洞穴石笋δ 18 O（δ 18 Os）的变化揭示了海洋同位素阶段（MIS）5和MIS 9.3-MIS 8.3的明显的岁差旋回。在这些地点，MIS 5.5和MIS 9的δ 18 Os值相对低于MIS 5.3、5.1和MIS 8，并分别向MIS 5.1和MIS 8.3逐渐增加。在30° N以南的其它洞穴记录中也可观察到类似的δ 18 O变化模式。δ 18的这种南方变率模式与北方夏季太阳辐射、大陆冰盖面积和大气CO2浓度的变化密切相关，表明夏季太阳辐射对季风水汽向陆输送的直接强迫作用可以进一步受到地球边界条件的调制。而30° N附近及以北地区的δ 18 Os记录显示了一个相对稳定的岁差周期，其中岁差极小值（Pmin）期间的δ 18 Os值相似。这种区域差异意味着在Pmin期间，季风水汽向北传播的强度可能在北方站点保持不变。此外，阻尼效应可能会限制18 O耗尽的水分转移到中纬度和高纬度洞穴遗址，特别是在间冰期高峰期（即，MIS5.5，MIS 9），这可能与西风急流南部边缘的移动和热带辐合带的平均位置有关。另一种可能性可能是，更多的本地再循环或近源（同位素富集）的水分促成了北方站点的降水变化。
Changes in orbital-scale stalagmite δ18O (δ18Os) recorded from two caves in southern China reveal a clear precessional cycle during Marine Isotope Stage (MIS) 5 and from MIS 9.3 to MIS 8.3. At these sites, δ18Osvalues in MIS 5.5 and MIS 9 were relatively lower than MIS 5.3, 5.1 and MIS 8, and gradually increased towards MIS 5.1 and MIS 8.3, respectively. A similar pattern of variability of δ18Oscan be observed in other cave records south of 30° N. This southern mode of variability of δ18Osclosely mimics changes in northern summer insolation, the areal extent of continental ice sheets and atmospheric CO2concentrations, suggesting that the direct forcing of summer insolation on landward transport of monsoonal moisture can be further modulated by the Earth's boundary conditions. In contrast, δ18Osrecords around 30° N or northward register a relatively stable precessional cycle, among which δ18Osvalues during the precession minimum (Pmin) are similar. This regional disparity implies that during the Pmin, the strength of northward propagation of monsoonal moisture probably remained constant at northern sites. Moreover, a dampening effect may have limited18O-depleted moisture transfer to mid- and high-latitude cave sites, especially during peak interglacials (i.e., MIS 5.5, MIS 9), which may be associated with shifts in the southern edge of the Westerly jet and the average position of the Intertropical Convergence Zone. Another possibility could be that more locally-recycled or near-sourced (isotopically-enriched) moisture contributed to precipitation changes at the northern sites.