Timing of the descent into the last Ice Age determined by the bipolar seesaw
Timing of the descent into the last Ice Age determined by the bipolar seesaw
复制标题
DOI：
10.1002/2014pa002623
复制
发表时间：
2014-06-01
期刊：
影响因子：
--
通讯作者：
Diz, Paula
中科院分区：
文献类型：
--
作者：
Barker, Stephen;Diz, Paula
我们提出了来自大西洋东南部的浮游有孔虫动物群和同位素记录，这些记录突出了过去100 kyr中千年尺度变化的本质。我们根据格陵兰岛温度变化、海洋环流和大西洋东南深处碳酸盐保存之间的经验联系，为我们的记录导出了一个假设驱动的年龄模型。我们的研究结果扩展了早期的发现，即在海洋同位素阶段（MIS） 3-2和最后一次消冰期的最大突变事件中，南北之间存在反相位（跷跷板）关系。特别地，我们发现海因里希横盘与推断的副热带热锋南移相平行。随后是锋面的明显反弹，北方恢复了间期条件。我们的研究结果也揭示了冰川作用的机制。最后一次消冰是一个半球间不同步叠加的全球对称变化，与之相反，我们发现在MIS 4（类似于70 ka）开始时进入完全冰川条件的下降表现出半球间同步。我们认为，这种全球同步下降到冰川MIS 4的先决条件是轨道变化，但时间最终由海洋/大气环流模式的突变决定，即两极跷跷板。
We present planktonic foraminiferal fauna and isotope records from the SE Atlantic that highlight the nature of millennial-scale variability over the last 100 kyr. We derive a hypothesis-driven age model for our records based on the empirical link between variations in Greenland temperature, ocean circulation, and carbonate preservation in the deep SE Atlantic. Our results extend earlier findings of an antiphase (seesaw) relationship between north and south for the largest abrupt events of Marine Isotope Stage (MIS) 3-2 and the last deglaciation. In particular, we find that Heinrich Stadials were paralleled by inferred southward shifts of the thermal Subtropical Front. These were followed by pronounced rebounds of the front with the return to interstadial conditions in the north. Our results also shed light on the mechanism of glaciation. In contrast to the last deglaciation, which was a globally symmetric change superposed by interhemispheric asynchronicity, we find that the descent into full glacial conditions at the onset of MIS 4 (similar to 70 ka) displayed interhemispheric synchrony. We suggest that this globally synchronous descent into glacial MIS 4 was preconditioned by orbital changes, but the timing was ultimately determined by abrupt changes in ocean/atmosphere circulation patterns i.e., the bipolar seesaw.