We introduce a new hypothesis concerning the role of internal climate dynamics in the non-linear transitions from interglacial to glacial (IG-G) state since the Mid Pleistocene Transition (MPT). These transitions encompass large and abrupt changes in atmospheric CO₂, ice volume, and temperature that we suggest involve critical interactions between insolation and high amplitude oscillations in ocean/atmosphere circulation patterns. Specifically, we highlight the large amplitude of millennial-scale climate oscillations across the transition from Marine Isotope Stage (MIS) 5 to 4, which we argue led to amplified cooling of the deep ocean and we demonstrate that analogous episodes of extreme cooling systematically preceded glacial periods of the last 800 kyr. We suggest that such cooling necessitates a reconfiguration of the deep ocean to avoid a density paradox between northern and southern-sourced deep waters (SSW), which could be accomplished by increasing the relative volume and or salinity of SSW, thus providing the necessary storage capacity for the subsequent (delayed) and relatively abrupt drawdown of CO₂. We therefore explain the transient decoupling of Antarctic temperature from CO₂ across MIS 5/4 as a direct consequence of millennial activity at that time. We further show that similar climatic decoupling typically occurred during times of low obliquity and was a ubiquitous feature of IG-G transitions over the past 800 kyr, producing the appearance of bimodality in records of CO₂, benthic δ¹⁸O and others. Finally we argue that the apparent lack of bimodality in the pre-MPT record of benthic δ¹⁸O implies that the dynamics associated with IG-G transitions changed across the MPT.

中文翻译：

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自中更新世过渡以来极端海洋-大气振荡在冰川条件发展中的系统作用

我们引入了一个新的假设，涉及自中更新世过渡（MPT）以来内部气候动力学在从间冰期到冰期（IG-G）状态的非线性过渡中的作用。这些转变包括大气CO ₂、冰体积和温度的巨大且突然的变化，我们认为这些变化涉及海洋/大气环流模式中日照和高振幅振荡之间的关键相互作用。具体来说，我们强调了从海洋同位素阶段（MIS）5到4过渡期间千禧年规模的气候振荡的大幅变化，我们认为这导致了深海的冷却加剧，并且我们证明了类似的极端冷却事件系统地发生在冰川期之前最后 800 kyr 的周期。我们认为，这种冷却需要对深海进行重新配置，以避免北部和南部深水（SSW）之间的密度悖论，这可以通过增加SSW的相对体积和/或盐度来实现，从而提供必要的存储容量用于随后（延迟）且相对突然的 CO ₂下降。_{因此，我们将 MIS 5/4 期间南极温度与 CO 2}的短暂脱钩解释为当时千禧年活动的直接结果。我们进一步表明，类似的气候脱钩通常发生在低倾角时期，并且是过去 800 kyr IG-G 转变的普遍特征，在 CO ₂、底栖 δ ¹⁸ O 等记录中产生双峰性的出现。最后，我们认为，MPT 前海底 δ ¹⁸ O 记录中明显缺乏双峰性，这意味着与 IG-G 转变相关的动力学在整个 MPT 中发生了变化。