External forcing mechanisms controlling the Qiongdong upwelling in the northern South China Sea during the Holocene
External forcing mechanisms controlling the Qiongdong upwelling in the northern South China Sea during the Holocene
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DOI：
10.1016/j.gloplacha.2022.104021
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发表时间：
2022-12
影响因子：
3.9
通讯作者：
Chao Huang;Yinmin Yang;Fajin Chen;D. Kong;Jin Xu;Chunqing Chen;Q. Zhu;Xin Huang
中科院分区：
文献类型：
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作者：
Chao Huang;Yinmin Yang;Fajin Chen;D. Kong;Jin Xu;Chunqing Chen;Q. Zhu;Xin Huang
南海北部沿岸上升流控制着区域海洋生产力，从而影响蓝色经济。然而，人们对百年尺度的上升流变化及其相关的强迫机制知之甚少，这主要是由于缺乏仪器和历史时期之外的高分辨率上升流记录。在这里，我们根据海南岛东海岸上升流区的高分辨率（~30 年）δ15N 记录重建了过去 7000 年季风引起的上升流变化。测定δ13C、δ15N、C/N、TOC和生物蛋白石来验证GH6核心中海洋有机质的主要来源，并使用δ15N值来指示浮游植物利用硝酸盐的变化。结果显示出明显的百年尺度的变化，通常与太阳活动、热带辐合带（ITCZ）的纬度变化和厄尔尼诺南方涛动（ENSO）频率同步。我们得出的结论是，百年尺度的上升流强度主要是由外部太阳强迫引起的，内部反馈如 ITCZ 的纬度变化和 ENSO 变化作为放大太阳变化信号的中介。我们的新发现表明，外部强迫机制对人类世之前的上升流变化产生了重大影响，在预测低纬度地区上升流变化的未来时应考虑到这一点。
Coastal upwelling along the northern South China Sea controls regional marine productivity and thereby influences blue economies. However, centennial-scale upwelling variability and its associated forcing mechanisms are poorly understood, primarily due to the lack of high-resolution upwelling records beyond the instrumental and historical periods. Here we reconstruct monsoon-induced upwelling variations over the past 7000 years, based on a high-resolution (∼30 yr) δ15N record from the upwelling zone off the east coast of Hainan Island. δ13C, δ15N, C/N, TOC and biogenic opal are determined to verify the dominant source of marine organic matter in the GH6 core, and δ15N values are used to indicate the variations in nitrate utilization by phytoplankton. The results show distinct centennial-scale variability, which is generally synchronous with solar activity, latitudinal shifts of the Intertropical Convergence Zone (ITCZ), and El Niño-Southern Oscillation (ENSO) frequency. We conclude that the centennial-scale upwelling intensity was predominately induced by external solar forcing, with internal feedback such as latitudinal shifts of the ITCZ and ENSO variability as a mediator amplifying the solar variation signal. Our new findings indicate that external forcing mechanisms exerted a significant influence on upwelling variations before the Anthropocene and should be considered when producing future projections of upwelling changes at low latitudes.