Abstract There is compelling evidence that millennial climate variability of the last glacial period was associated with significant changes in the Atlantic Meridional Overturning Circulation (AMOC). Several North Atlantic sedimentary Pa/Th records indicate a consistent and large Pa/Th increase across millennial-scale events, which has been interpreted as considerable reduction in North Atlantic Deep Water (NADW) formation. However, the use of sedimentary Pa/Th as a pure kinematic circulation proxy is challenging because Pa and Th are also highly sensitive to changes in particulate flux intensity and composition that might have occurred across these millennial scale events. In this study, we use the Pa/Th enabled iLOVECLIM Earth System Model of intermediate complexity to evaluate the impact of changes in biogenic particle flux intensity and composition on the Atlantic Pa/Th. We find that in our model, changes in Particulate Organic Carbon (POC), and to a lesser extent biogenic opal production, can significantly affect the sedimentary Pa/Th, possibly explaining up to 30% of the observed North Atlantic Pa/Th increase across Heinrich stadial 1. The sedimentary Pa/Th response is also likely sensitive to shifts in the geographical distribution of the particles, especially in high scavenging regions. Our study suggests that a decrease in opal production in the northwest Atlantic can induce a far field Pa/Th increase in a large part of the North Atlantic basin. Therefore, local monitoring of particle fluxes may not be sufficient to rule out any influence of changing particle fluxes on sedimentary Pa/Th records.

中文翻译：

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模拟生物颗粒通量强度和成分对沉积 Pa/Th 的影响

摘要 有令人信服的证据表明，末次冰期的千年气候变率与大西洋经向翻转环流 (AMOC) 的显着变化有关。几项北大西洋沉积 Pa/Th 记录表明，在千年尺度事件中，Pa/Th 持续且大幅增加，这被解释为北大西洋深水 (NADW) 形成的显着减少。然而，使用沉积 Pa/Th 作为纯粹的运动环流代理具有挑战性，因为 Pa 和 Th 也对这些千年尺度事件中可能发生的颗粒通量强度和组成的变化高度敏感。在这项研究中，我们使用 Pa/Th 启用的中等复杂性的 iLOVECLIM 地球系统模型来评估生物粒子通量强度和成分变化对大西洋 Pa/Th 的影响。我们发现，在我们的模型中，颗粒有机碳 (POC) 的变化以及较小程度的生物蛋白石生产，可以显着影响沉积 Pa/Th，这可能解释了观察到的北大西洋 Pa/Th 增加的 30% Heinrich stadial 1. 沉积的 Pa/Th 响应也可能对颗粒地理分布的变化敏感，尤其是在高清除区。我们的研究表明，西北大西洋蛋白石产量的减少会导致北大西洋盆地大部分地区的远场 Pa/Th 增加。所以，