Late Pliocene deep Atlantic δ¹³C data have been interpreted as evidence for enhanced Atlantic Meridional Overturning Circulation (AMOC) compared to the present, but this hypothesis is not supported by the Pliocene Model Intercomparison Project (PlioMIP). Here, we adopt a new approach to assess variability in deep ocean circulation based on paired stable carbon (δ¹³C) and oxygen isotopes (δ¹⁸O) of benthic foraminifera, both (semi)conservative water mass tracers. Assuming that deep Atlantic benthic δ¹³C‐δ¹⁸O variability is predominantly driven by mixing, we extrapolate the δ¹³C‐δ¹⁸O data outside the sampled range to identify the end‐members. At least three end‐members are needed to explain the spatial δ¹³C‐δ¹⁸O variability in the deep North Atlantic Ocean: two Northern Component Water (NCW) and one Southern Component Water (SCW) water masses. We use a ternary mixing model to quantify the mixing proportions between SCW and NCW in the deep Atlantic Ocean. Our analysis includes new data from Ocean Drilling Program Sites 959 and 662 in the eastern equatorial Atlantic and suggests that the AMOC cell was deeper during the M2 glacial than during late Pliocene interglacials. Moreover, we identify a new cold and well‐ventilated water mass that was geographically restricted to the southeast Atlantic Ocean between 3.6 and 2.7 Ma and did not contribute significantly to the δ¹³C‐δ¹⁸O variability of the rest of the basin. This high‐δ¹³C high‐δ¹⁸O water mass has led to the misconception of a reduced latitudinal δ¹³C gradient. Our analyses show that the late Pliocene δ¹³C gradient between NCW and SCW was similar to the present‐day value of 1.1‰.

中文翻译：

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利用底栖有孔虫δ13C-δ18O数据的三元混合模型方法重建上新世晚期大西洋深水混合

晚上新世深大西洋δ ^13个C数据已经被解释为相对于当前加强大西洋经向翻转环流（AMOC）的证据，但不支持这个假说，新世模式比较计划（PlioMIP）。在这里，我们采用一种新的方法基于成对稳定碳（δ深海循环评估可变性¹³ C）和氧同位素（δ ¹⁸ O）底栖有孔虫的，两者（半）保守的水质量示踪剂。假设深大西洋底栖δ ¹³ C-δ ¹⁸ ö变异主要由混合驱动，我们推断δ ¹³ C-δ ¹⁸O超出采样范围的数据以识别端成员。都至少需要三个端元解释空间δ ¹³ C-δ ¹⁸ Ø深北大西洋变化：北部两个组件水（NCW）和一个南方组件水（SCW）水团。我们使用三元混合模型来量化大西洋深海中SCW和NCW之间的混合比例。我们的分析包括来自赤道东大西洋的959和662号海洋钻探计划站点的新数据，并表明MOC冰期的AMOC单元比上新世间冰期的更深。此外，我们发现了一个新的冷水和通风良好的水团，该水团在地理上局限于3.6-2.7 Ma之间的东南大西洋，并且对δ的贡献不大。¹³ C-δ ¹⁸澳盆的其余部分的可变性。这种高δ ¹³ 1C高δ ¹⁸ ö水的质量，导致减小的纬度δ的误解¹³ Ç梯度。我们的分析表明，该新世末δ ¹³ NCW和SCW℃之间梯度相似的1.1现今值‰。