Ice core data have shown that atmospheric CO₂ concentrations during interglacials were lower before the Mid‐Brunhes Event (MBE, ~430 ka), than after the MBE by around 30 ppm. To explain such a difference, it has been hypothesized that increased bottom water formation around Antarctica or reduced Atlantic Meridional Overturning Circulation (AMOC) could have led to greater oceanic carbon storage before the MBE, resulting in less carbon in the atmosphere. However, only few data on possible changes in interglacial ocean circulation across the MBE have been compiled, hampering model‐data comparison. Here we present a new global compilation of benthic foraminifera carbon isotopic (δ¹³C) records from 31 marine sediment cores covering the last 800 ka, with the aim of evaluating possible changes of interglacial ocean circulation across the MBE. We show that a small systematic difference between pre‐ and post‐MBE interglacial δ¹³C is observed. In pre‐MBE interglacials, northern source waters tend to have slightly higher δ¹³C values and penetrate deeper, which could be linked to an increased northern sourced water formation or a decreased southern sourced water formation. Numerical model simulations tend to support the role of abyssal water formation around Antarctica: Decreased convection there associated with increased sinking of dense water along the continental slopes results in increased δ¹³C values in the Atlantic in agreement with pre‐MBE interglacial data. It also yields reduced atmospheric CO₂ as in pre‐MBE records, despite a smaller simulated amplitude change compared to data, highlighting the need for other processes to explain the MBE transition.

中文翻译：

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碳13同位素揭示了最近800 ka的冰间期之间有限的海洋环流变化

冰芯数据表明，在中间断裂事件（MBE，约430 ka）之前，冰间期大气中的CO ₂浓度要比MBE之后低约30 ppm。为了解释这种差异，已经假设南极周围的底部水形成增加或大西洋子午向翻转循环（AMOC）减少可能导致MBE之前更多的海洋碳储存，从而导致大气中的碳减少。但是，关于跨MBE的冰川间海洋环流可能变化的数据很少被汇编，这妨碍了模型数据的比较。这里我们介绍底栖有孔虫的碳同位素的一个新的全球汇编（δ ¹³C）来自31个海洋沉积物芯的记录，覆盖最后800 ka，目的是评估整个MBE的冰川间海洋环流的可能变化。我们发现，与前之间的小系统性差异后MBE间冰期δ ¹³观察下进行。在预MBE间冰期，北方源水域倾向于具有略高δ ¹³ C值和穿透更深，这可能与增加的北方源水的形成或降低的南部源水的形成。数值模式模拟结果倾向于支持深海的水形成的环绕南极洲的作用：减少对流出现在δ增加沿陆坡结果增加下沉的浓水有关的¹³与MBE之前的冰间数据一致，大西洋中的C值。尽管与数据相比模拟幅度变化较小，但与MBE之前的记录相比，它还减少了大气中的CO ₂，这突出表明需要其他过程来解释MBE过渡。