Nd isotopes of sediments, foraminifera and fish debris of the western North Atlantic

Understanding changes in ocean circulation during the last deglaciation is crucial to unraveling the dynamics of glacial-interglacial and millennial climate shifts. We used neodymium isotope measurements on postdepositional iron-manganese oxide coatings precipitated on planktonic foraminifera to reconstruct changes in the bottom water source of the deep western North Atlantic at the Bermuda Rise. Comparison of our deep water source record with overturning strength proxies shows that both the deep water mass source and the overturning rate shifted rapidly and synchronously during the last deglacial transition. In contrast, any freshwater perturbation caused by Heinrich event 1 could have only affected shallow overturning. These findings show how changes in upper-ocean overturning associated with millennial-scale events differ from those associated with whole-ocean deglacial climate events.阐明末次冰消期大洋环流的演变规律，对于解析冰期-间冰期以及千年尺度气候波动的动力学机制至关重要。本研究通过对附着于浮游有孔虫（planktonic foraminifera）之上的沉积后铁锰氧化物包膜开展钕同位素（neodymium isotope）测试，重建了百慕大海隆区域西北大西洋深海区的底水来源变化。将本研究获得的底水来源记录与大洋翻转强度代用指标进行对比后发现，在末次冰消转型期，深水团来源与翻转速率均发生了快速且同步的改变。与之相反，由海因里希事件1（Heinrich event 1）引发的任何淡水扰动，仅能对浅层翻转环流产生影响。本研究结果揭示了与千年尺度事件相关的上层大洋翻转环流变化，与全大洋尺度冰消期气候事件相关的环流变化之间的差异。