The global thermohaline circulation plays a major role in regulating global climate, driven by the formation of North Atlantic Deep Water (NADW). ODP Site 1063 on the Bermuda Rise, at the interface of NADW and Southern Ocean‐sourced water, appears an ideal location to study the relationships between ocean circulation and climate. This study reports Nd isotope ratios at Site 1063 that extend to ~1 Ma. The data show Nd isotope values during portions of interglacials that are much lower than modern NADW. However, interglacial Nd isotope values at Site 607, located within the core of NADW, off the abyssal seafloor in the North Atlantic, are consistently similar to modern NADW. In contrast to glacial values, we infer that interglacial Nd isotopes at Site 1063 are not representative of NADW and do not solely record water mass mixing. We conclude that the low Ndisotope ratios reflect regional particle‐seawater exchange as a consequence of input of freshly ground bedrock from the Canadian shield, which is eroded into the North Atlantic during major ice sheet retreats. The result is a deep, thin, and regionally constrained layer of seawater tagged with this anomalous low Nd isotope signature that is unrepresentative of the Atlantic Meridional Overturning Circulation (AMOC). We suggest that a benthic nepheloid layer, whose development is linked to the behavior of a deep‐recirculating gyre system, regulated by the interaction between the Gulf Stream and the deep western boundary current, facilitates the periodic masking of the Nd isotope signature of the North Atlantic AMOC end‐member in this region at these depths.

中文翻译：

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区分过去1 Myr期间深西部大西洋的冰川AMOC和冰川间非AMOC Nd同位素信号

在北大西洋深水（NADW）的形成的推动下，全球热盐循环在调节全球气候中起着重要作用。。在NADW和南部海洋水源交界处，百慕大上升线上的ODP站点1063是研究海洋环流与气候之间关系的理想场所。这项研究报告了在1063号站点的Nd同位素比率扩展至〜1 Ma。数据显示，在部分间冰期中的Nd同位素值远低于现代NADW。但是，位于北大西洋深海海底NADW核心内的607号站点的冰期Nd同位素值始终与现代NADW相似。与冰河值相反，我们推断出1063号点的冰河间Nd同位素不能代表NADW，也不能单独记录水质混合。我们得出的结论是，由于加拿大盾构的新近磨碎的基岩的输入，低Ndisotope比率反映了区域颗粒-海水交换，在主要冰原撤退时被侵蚀到北大西洋。结果是用这种异常的低Nd同位素特征标记的深层，薄层和受区域限制的海水层，不能代表大西洋子午线翻转循环（AMOC）。我们认为，由海湾流和西部深部边界流之间的相互作用调节的底栖胶体层的发育与深循环回旋系统的行为有关，有助于北部的Nd同位素特征的周期性掩盖。在这些深度处，大西洋AMOC在该地区的最终成员。