Palaeo-oceanographical archives in the Mediterranean Sea indicate the occurrence of Sapropel depositions, which are characteristic of anoxic bottom conditions and of a stratified sea. The impact of such drastic changes in the thermohaline circulation of the Mediterranean Sea on the large-scale circulations in the North Atlantic basin is not fully understood. Here we evaluate the impact of a direct perturbation of the Mediterranean Sea circulation through different idealized simulations with freshwater release rates of 20, 50, 100, and 200 mSv (1 mSv = 10³ m³/s), using a the IPSL-CM5A-LR global coupled atmosphere-ocean model, with simulations up to 1000 years long. The simulations are compared to available data for the Mediterranean Sea and the North Atlantic. The Neodymium isotopic composition (ε_Nd) anomalies in the North Atlantic are clearly dependent on the rate of fresh water release in the Mediterranean Sea, and subsequent modification of Atlantic meridional overturning circulation (AMOC) intensity and subpolar gyre (SPG) extension. Based on comparison with seawater ε_Nd records from Rockall Trough, we suggest that a limited release of freshwater around 50 mSv may be more representative of hydrological conditions of the Mediterranean Sea during the Sapropel S1 deposition. Our results indicate that a decrease in Mediterranean overflow was clearly a factor in the intensification of upper AMOC following the Early Holocene period, when a large eastward expansion of the subpolar gyre is simulated. Also, eastward expansion of the subpolar gyre due to freshwater release in the Mediterranean (e.g. Sapropel-like events) and its impact on the ε_Nd signature highlight the fact that the modification of ocean circulation in the North Atlantic basin might be more complex than a straightforward change in the AMOC, since there may also be a large impact on barotropic circulation. The simulations also produce a significant decrease in the ε_Nd values of the Iceland-Scotland Overflow Water (between −3.5 and − 1.3 ε_Nd unit), which is consistent with changes observed during the S1 event in the reconstructions. Thus the 3-dimensional changes in baroclinic and barotropic circulations of the ocean, as reconstructed in some ε_Nd records, are broadly consistent with the sensitivity simulations performed, and might thus be partly related to changes in Mediterranean overflow, which would have contributed to modification of the Atlantic Ocean circulation following a complex 3-dimensional pattern that is detailed in the paper.

地中海海中的古海洋学档案表明发生了腐殖质沉积，这是缺氧海底条件和分层海的特征。尚未完全了解地中海热盐循环中这种剧烈变化对北大西洋盆地大规模环流的影响。在这里，我们通过不同的理想化模拟（淡水释放率分别为20、50、100和200 mSv（1 mSv = 10 ³  m ^3）来评估地中海环流直接扰动的影响/ s），使用IPSL-CM5A-LR全球耦合大气-海洋模型，其模拟长达1000年之久。将模拟与地中海和北大西洋的可用数据进行比较。钕同位素组成（ε_钕）在北大西洋异常是明显依赖于淡水释放在地中海和大西洋经向翻转环流（AMOC）强度和副极地环流（SPG）延伸后续修改的速率。根据与海水比较ε_钕根据Rockall Trough的记录，我们建议在Sapropel S1沉积期间，大约50 mSv的淡水有限释放可能更能代表地中海的水文条件。我们的结果表明，当模拟新的次极回旋向东大扩张时，地中海中上溢的减少显然是全新世早期之后上部AMOC加剧的一个因素。此外，副极地环流的东扩由于地中海淡水释放（如腐泥般的事件）和其对冲击ε_钕签名突出了这样一个事实，即北大西洋盆地的海洋环流变化可能比AMOC的直接变化更为复杂，因为这也可能对正压环流产生很大影响。模拟还产生在一个显著降低ε_钕冰岛-苏格兰溢流水的值（-3.5之间，并且- 1.3 ε_钕单元），这是与在重建中的S1事件期间观察到的变化是一致的。因此，该3维变化在海洋中的斜压和正压循环，如重建在一些ε_钕 记录，与所进行的敏感性模拟基本一致，因此可能部分与地中海溢流的变化有关，地中海溢流的变化将按照本文详述的复杂3维模式对大西洋环流的变化做出贡献。