Early Interglacial Legacy of Deglacial Climate Instability
Early Interglacial Legacy of Deglacial Climate Instability
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DOI：
10.1029/2019pa003661
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发表时间：
2019-08-01
影响因子：
3.5
通讯作者：
Thornalley, David
中科院分区：
文献类型：
--
作者：
Barker, Stephen;Knorr, Gregor;Thornalley, David
在上一个冰川周期中，大气二氧化碳的千年时间尺度变化与深海环流的扰动同时发生，这本身就反映在整个北大西洋区域地表条件的明显变化上。在这里，我们使用连续的代理记录来论证在过去的800 KYR中，即从第一次发生Heinrich事件(严格定义)之前开始，一直保持着等价的关系。我们的结果强调了内部气候动力在放大外部(日照)强迫气候系统在中更新世至晚更新世期间产生大规模冰川终止(消融)的重要性。我们发现，冰川终止的特征是在一段密集的冰筏漂流之后，随后突然转变为异常温暖的表面条件(相对于更逐渐演变的本底状态)，我们将其解释为反映了大西洋深海环流的突然恢复。根据我们的综合，这之后是一个持续数千年的强化(或至少是异常)翻转时期，直到达到平衡的间冰期条件，在此期间大气中的二氧化碳可能会减少。因此，我们的结果表明，海洋环流中的去冰期振荡可以对早期间冰期气候产生持久的影响，并突出了与一些以前的间冰期开始相关的大气二氧化碳超标的瞬变性质。因此，我们建议将这些时间间隔视为冰川消融过程的一部分。这对包括全新世在内的间冰期大气二氧化碳演化的研究具有重要意义。
Throughout the last glacial cycle millennial timescale variations in atmospheric CO2 occurred in parallel with perturbations in deep ocean circulation, which were themselves reflected by observable changes in surface conditions across the North Atlantic region. Here we use continuous proxy records to argue that an equivalent relationship has held throughout the last 800 kyr, that is, since before the first occurrence of Heinrich events (strictly defined). Our results highlight the importance of internal climate dynamics in amplifying external (insolation) forcing on the climate system to produce the large amplitude of glacial terminations (deglaciations) during the middle to late Pleistocene. We show that terminations are characterized by an interval of intense ice rafting followed by a subsequent and abrupt shift to anomalously warm surface conditions (with respect to the more gradually evolving background state), which we interpret to reflect an abrupt recovery of deep ocean circulation in the Atlantic. According to our synthesis, this is followed by a period of enhanced (or at least anomalous) overturning lasting thousands of years until equilibrium interglacial conditions are attained and during which atmospheric CO2 is likely to decrease. Our results therefore suggest that deglacial oscillations in ocean circulation can have a lasting influence on early interglacial climate and highlight the transient nature of atmospheric CO2 overshoots associated with the onset of some previous interglacials. Accordingly, we suggest that these intervals should be considered as a part of the deglacial process. This has implications for studies concerned with the evolution of atmospheric CO2 during interglacial periods including the Holocene.