黄恩清,
赵蔓,
王跃,
田军
同济大学海洋地质国家重点实验室, 上海 200092

基金项目: 国家自然科学基金项目(批准号:41776054)和国家重点基础研究发展计划项目(批准号:2018YFE0202401)共同资助


详细信息

作者简介: 黄恩清, 男, 36岁, 副教授, 海洋地质专业, E-mail:ehuang@tongji.edu.cn

中图分类号: P532;P736.4

收稿日期:2020-07-08
修回日期:2020-09-23
刊出日期:2020-11-30

Quaternary precession cycles of sea-surface oxygen isotope records from the tropical western Pacific

Huang Enqing,
Zhao Man,
Wang Yue,
Tian Jun
State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092



MSC: P532;P736.4

--> Received Date: 08 July 2020
Revised Date: 23 September 2020
Publish Date: 30 November 2020


摘要
摘要:表层海水氧同位素记录是重建低纬水循环演化历史的一个重要手段，但受到区域降水-蒸发平衡、洋盆间水汽再分配、陆地淡水输入、洋流混合等众多因素的影响，其气候意义的解读十分复杂。文章收集和计算了过去45万年以来热带西太平洋-南海数个站位剩余海水氧同位素的波动历史。发现这些记录存在显著的岁差周期，并且在岁差周期上呈现出同相变化，即在北半球夏季辐射量的高值期，表层海水同位素出现正偏移现象。结合同位素数值模拟结果，推测岁差低值促发了两个机制：一是热带辐合带平均位置北移，导致从热带大西洋往太平洋的水汽输送量下降，二是太平洋向亚洲大陆输出的水汽增多，陆地液态水储库增大。这两个机制共同导致热带西太平洋淡水减少，使得表层同位素出现偏重现象。并且这两个机制的效应超过了大洋内部降水变化的影响，导致表层海水同位素出现大空间尺度上的一致性变化。
关键词: 低纬水循环/
季风/
水汽输送/
更新世/
降水同位素

Abstract:Sea-surface δ¹⁸O is an important approach to understand the history of the low-latitude hydrological cycle. However, the climate interpretation of sea-surface δ¹⁸O can be complicated by a set of factors, including regional precipitation-evaporation balance, water-vapor redistribution among ocean basins, continental runoff and ocean-current homogenization. In this study, through using parallel records of planktonic foraminiferal δ¹⁸O and Mg/Ca-sea surface temperature reconstructions, we calculated residual δ¹⁸O changes at several sites in the tropical western Pacific-South China Sea over the past 450 thousand years. These sites(MD05-2904, ODP1145, MD05-2901, KX973-22-4, MD01-2386, MD06-3067 and GeoB17426) together cover a latitude range from 2.19°S to 19.46°N, and a longitude range from 110.74°E to 159.23°E. We find these residual δ¹⁸O records show strong and in-phase variance at the precession bands, which are relatively enriched when Northern Hemisphere summer insolation is strong. This is contrast to stalagmite δ¹⁸O records from southern China and residual δ¹⁸O reconstructions from the tropical Atlantic, where δ¹⁸O were relatively depleted during precession minima. The reconstructed sea-surface δ¹⁸O variations are well matched with previously published simulation results.
We infer that the precession minima can have triggered two mechanisms in the tropical Pacific. First, a northward migration of the Intertropical Convergence Zone has resulted in a reduced moisture transport from the tropical Atlantic to the Pacific via the Central America. Second, strengthened summer monsoons have increased a moisture flux from the Pacific to Asian landmasses, giving rise to an expansion of liquid-water reservoir in the land. Both mechanisms can reduce the freshwater amount in the tropical western Pacific and thus increase sea surface δ¹⁸O. Moreover, the effect of these two mechanisms can overwhelm that of regional precipitation changes within ocean basins, generating uniform changes in residual δ¹⁸O at a large spatial extent.
Key words:low-latitude hydrological cycle/
monsoon/
moisture flux/
Pleistocene/
precipitation isotope composition



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