Tracer transport timescales and the observed Atlantic‐Pacific lag in the timing of the Last Termination
Tracer transport timescales and the observed Atlantic‐Pacific lag in the timing of the Last Termination
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示踪剂运输时间尺度和观察到的大西洋-太平洋最后终止时间的滞后
DOI：
10.1029/2011pa002273
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
G. Gebbie
中科院分区：
文献类型：
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作者：
G. Gebbie
[1]根据一对底栖有孔虫的δ 18 O记录，最后一次终止的中点发生在大西洋深处比太平洋深处早4,000年，似乎意味着内部循环的转变，因为滞后时间比深部放射性碳年龄长得多。在这里，使用现代海洋环流的示踪剂传输模型对滞后由区域表面边界条件变化、海洋过境时间尺度造成的延迟以及温度和海水δ 18 O（δ 18 Ow）之间的相互作用引起的情况进行了量化。利用2,806个地表源的单个绿色函数反演方法，重建了近30,000年来地表温度和δ 18 Ow的时间历史，与有孔虫氧同位素数据、Mg/Ca导出的深部温度和冰川孔隙水记录相一致。因此，在海洋环流在冰期和现代之间相对没有变化的情况下，海盆间的滞后可以用南极洲周围相对较晚的局部冰川最大期来解释，即使在北大西洋δ 18 Owfalls之后，地表δ 18 Owf也继续上升。由于仍在上升的南极信号和正在下降的北大西洋信号的破坏性干扰，终端的信号到达太平洋核心站点延迟。这种情况之所以可能，是因为海洋不是一个单一的传送带，太平洋核心站点的所有沃茨以前都经过大西洋核心站点，而是太平洋核心站点更突出地沐浴在直接来自南极的沃茨中。
[1] The midpoint of the Last Termination occurred 4,000 years earlier in the deep Atlantic than the deep Pacific according to a pair of benthic foraminiferal δ18O records, seemingly implying an internal circulation shift because the lag is much longer than the deep radiocarbon age. Here a scenario where the lag is instead caused by regional surface boundary condition changes, delays due to oceanic transit timescales, and the interplay between temperature and seawater δ18O (δ18Ow) is quantified with a tracer transport model of the modern-day ocean circulation. Using an inverse method with individual Green functions for 2,806 surface sources, a time history of surface temperature andδ18Owis reconstructed for the last 30,000 years that is consistent with the foraminiferal oxygen-isotope data, Mg/Ca-derived deep temperature, and glacial pore water records. Thus, in the case that the ocean circulation was relatively unchanged between glacial and modern times, the interbasin lag could be explained by the relatively late local glacial maximum around Antarctica where surfaceδ18Ow continues to rise even after the North Atlantic δ18Owfalls. The arrival of the signal of the Termination is delayed at the Pacific core site due to the destructive interference of the still-rising Antarctic signal and the falling North Atlantic signal. This scenario is only possible because the ocean is not a single conveyor belt where all waters at the Pacific core site previously passed the Atlantic core site, but instead the Pacific core site is bathed more prominently by waters with a direct Antarctic source.