The Mid-Pleistocene transition (MPT; 1200 to 800 thousand years, kyr) is marked by the shift from 41-kyr to 100-kyr interglacial-glacial cyclicity without substantial change in the astronomical forcing. This change in climate response relied on internal feedback processes including interaction between ice sheet/sea ice, ocean circulation and the carbon cycle. It was suggested that a major perturbation of global oceanic carbon chemistry occurred at around 900 ka (Marine Isotope Stage, MIS, 24–22) although the mechanism responsible for the change is still to be elucidated. To investigate the link between the Atlantic Meridional Overturning Circulation (AMOC) and oceanic carbon storage for the past 1100 kyr, we combined neodymium isotopic composition (¹⁴³Nd/¹⁴⁴Nd or ε_Nd) recorded in foraminiferal authigenic fractions with epibenthic foraminiferal δ¹³C and δ¹⁸O from two cores in the North- and South-east Atlantic Ocean. Glacial/interglacial ε_Nd amplitude is smaller before the 900-ka event than after the event. The 900-ka event is marked by increase in seawater ε_Nd at both sites. These observations are consistent with previous studies, suggesting basin-wide ε_Nd changes. Combined with existing data, these new results reveal a persistent meridional gradient of seawater ε_Nd in the Atlantic Ocean over the past 1100 kyr. By comparing the reconstructions with numerical modelling results, we propose that weaker AMOC and changes in Nd sources to the North Atlantic were the main reasons for the observed ε_Nd shift at the 900-ka event in relation to the evolution of the Northern hemisphere cryosphere. The influence of enhanced Southern Ocean overturning circulation on ε_Nd values was estimated to be minor_. Seawater ε_Nd and benthic δ¹³C relationship for the whole study period indicates the presence of carbon-rich glacial deep water (>3000 m) in the North and the South Atlantic, in particular at MIS 22 and 24. This suggests that, in addition to weaker AMOC, reduction of deep-water ventilation and/or air-sea exchange in the Southern Ocean could have been responsible for the observed low benthic δ¹³C values. Together with increased biological productivity due to iron fertilization in the Southern Ocean, the physical process significantly contributed to the deep Atlantic carbon storage during the 900-ka event and the subsequent glacial periods.

中更新世过渡期（MPT； 1200至80万年，基尔）的特征是从41 kyr到100 kyl的冰期-冰期循环转变，而天文学强迫没有实质性变化。气候变化的这种变化依赖于内部反馈过程，包括冰盖/海冰，海洋环流和碳循环之间的相互作用。有人指出，尽管造成这种变化的机制尚待阐明，但全球海洋碳化学的主要扰动发生在900 ka左右（海洋同位素阶段，MIS，24-22）。为了研究过去1100年的大西洋子午俯覆环流（AMOC）与海洋碳储量之间的联系，我们结合了钕同位素组成（¹⁴³ Nd / ¹⁴⁴ Nd或_εNd）记录在与底栖有孔虫δ有孔虫自生分数¹³ C和δ ¹⁸从两个核心的北部和南部，东濒大西洋O操作。冰/间ε_钕振幅小于事件之后的900-KA事件之前要小。900-KA事件被上升海水ε标记_钕在两个站点。这些观察结果与先前的研究相一致，表明全流域ε_钕变化。结合现有数据，这些新结果显示出海水的持续子午梯度_εNd在过去1100年的时间里，在大西洋上空 通过重建与数值模拟结果相比较，我们建议较弱AMOC和钕源北大西洋变化是所观察到的ε的主要原因_钕相在900-KA事件转移到北半球冰冻圈的变化。增强的南部海洋翻转环流对ε的影响_的Nd值，估计是轻微的_。海水ε_钕和底栖δ ¹³整个研究期间的C关系表明，在北大西洋和南大西洋，特别是在MIS 22和24处，存在着富含碳的冰川深水（> 3000 m）。这表明，除了较弱的AMOC以外，还降低了深水通风和/或在南大洋海-气交换可能是负责观测的底栖δ ¹³ C值。加上由于南大洋的铁肥化而提高的生物生产力，物理过程极大地促进了900-ka事件和随后的冰川时期深层大西洋的碳储存。