MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
Institute of Geosciences, University of São Paulo, São Paulo, Brazil.
Sci Rep. 2017 May 8;7(1):1561. doi: 10.1038/s41598-017-01629-z.
The modern state of the Atlantic meridional overturning circulation promotes a northerly maximum of tropical rainfall associated with the Intertropical Convergence Zone (ITCZ). For continental regions, abrupt millennial-scale meridional shifts of this rainbelt are well documented, but the behavior of its oceanic counterpart is unclear due the lack of a robust proxy and high temporal resolution records. Here we show that the Atlantic ITCZ leaves a distinct signature in planktonic foraminifera assemblages. We applied this proxy to investigate the history of the Atlantic ITCZ for the last 30,000 years based on two high temporal resolution records from the western Atlantic Ocean. Our reconstruction indicates that the shallowest mixed layer associated with the Atlantic ITCZ unambiguously shifted meridionally in response to changes in the strength of the Atlantic meridional overturning with a southward displacement during Heinrich Stadials 2-1 and the Younger Dryas. We conclude that the Atlantic ITCZ was located at ca. 1°S (ca. 5° to the south of its modern annual mean position) during Heinrich Stadial 1. This supports a previous hypothesis, which postulates a southern hemisphere position of the oceanic ITCZ during climatic states with substantially reduced or absent cross-equatorial oceanic meridional heat transport.
现代大西洋经向翻转环流状态促进了与热带辐合带（ITCZ）相关的热带降雨北移最大值。对于大陆地区，这种雨带的千年尺度突然的经向移动已有充分记录，但由于缺乏稳健的代理和高时间分辨率记录，其海洋对应物的行为尚不清楚。在这里，我们表明浮游有孔虫组合在大西洋 ITCZ 中留下了明显的特征。我们应用此代理，根据来自北大西洋的两个高时间分辨率记录，研究了过去 30000 年来大西洋 ITCZ 的历史。我们的重建表明，与大西洋 ITCZ 相关的最浅混合层明显地随着大西洋经向翻转的强度变化而发生经向移动，在 Heinrich 冷期 2-1 和新仙女木期期间向南位移。我们得出结论，在 Heinrich 冷期 1 期间，大西洋 ITCZ 位于约 1°S（比现代年平均位置偏南约 5°）。这支持了先前的假设，即在跨赤道海洋经向热输送大大减少或不存在的气候状态下，海洋 ITCZ 位于南半球。
