The bi-polar seesaw and CO2: Is there anything special about 'Terminal seesaw events'?

近年来出现了一种解释晚更新世冰期-间冰期气候转变的新范式。根据这一范式，在“轨道”和“千年”时间尺度上运行的机制之间不再有明确的区别。因此，冰河时代缓慢的轨道（日晒）速度将产生强烈的正反馈，这种反馈本身可能在更短的时间尺度上出现。大气中二氧化碳的冰期-间冰期波动是这一概念的象征；它们显然对冰期-间冰期辐射强迫做出了重要贡献，但它们似乎是通过与不对称半球间气候异常（“两极跷跷板”）有关的快速变化而积累起来的。然而，并非所有大气CO2的快速变化都与冰期-间冰期转变有关。这就提出了一个重要的问题：在过去，是什么控制了千年二氧化碳的变化，以及冰期消融与冰期中期二氧化碳脉冲有什么特别之处（如果有的话）。目前的数据不允许我们充分地解决这些问题。现在需要的是一套新的南大洋上涌和深水通风的高分辨率重建数据，这些数据可以与冰芯年代学联系起来，从而与北大西洋气候突变的类似详细记录进行比较。该项目旨在提供这些重建，从而使我们对过去千年二氧化碳变化的理解建立在比迄今为止可能的更可靠的观测基础上。

A new paradigm has emerged in recent years for explaining late Pleistocene glacial-interglacial climate transitions. According to this paradigm, a clear distinction between mechanisms that operate on 'orbital' and on 'millennial' timescales is no longer made. The slow orbital (insolation) pacing of the ice-ages would thus engender strong positive feedbacks, which could themselves emerge on much shorter timescales. Glacial-interglacial fluctuations in atmospheric CO2 are emblematic of this notion; they clearly make an important contribution to glacial-interglacial radiative forcing, but they appear to accrue through rapid changes that are somehow linked with asymmetric inter-hemispheric climate anomalies (the 'bipolar seessaw'). However, not all rapid changes in atmospheric CO2 are associated with glacial-interglacial transitions. This raises the important question of what has controlled millennial CO2 changes in the past, and what (if anything) is special about deglacial versus mid-glacial CO2 pulses. Current data does not allow us to address these questions adequately. What is needed is a new set of high-resolution reconstructions of Southern Ocean up-welling and deep-water ventilation, which can be linked to the ice-core chronology and thus compared with similarly detailed records of abrupt North Atlantic climate variability. This project sets out to provide these reconstructions, and on thus place our understanding of past millennial CO2 variability on a more robust observational footing than has hitherto been possible.