Timing and impact of variable Arctic outflow on the Atlantic Meridional Overturning Circulation

北大西洋深水（NADW）构成了大西洋翻转经向环流（AMOC）的主要深海洋流，在全球范围内分布热量，影响维持海洋生态系统和人类渔场的营养物质分布，而其强度的变化与整个新生代的生产力、洋流强度、区域和全球气候的变化有关。NADW是源自拉布拉多海和北冰洋的深层洋流的混合物。后一个组成部分对NADW的贡献在很大程度上受到连接北欧海和冰岛两侧北大西洋盆地的两个门户的深度的影响。这些通道浅于1500米，北极溢水量将直接随通道相对深度的变化而变化。冰川时期海平面的降低和冰岛地下地幔活动的周期性增加，有效地抬高了陆地和海底，将直接限制寒冷和密集的北极水的涌入，在地质时间尺度上削弱了NADW和总体AMOC。该项目将利用锰铁地壳在地层中记录洋流特征的能力，追踪NADW组分强度、来源和物源的过去变化。利用北大西洋两个关键地区的样品，将产生高分辨率同位素记录，以研究在过去20-30 Ma期间NADW如何响应冰川和地幔脉冲而变化。这些记录将使用一种新的时间校准方法，该方法基于天文参数及其对这些样品化学特征的影响。获得的信息将用于未来的气候模型，预测这一主要洋流对扰动的反应。

The North Atlantic Deep Water (NADW) constitutes the major deep oceanic current of the Atlantic Overturning Meridional Circulation (AMOC), distributing heat throughout the globe and affecting nutrients distribution sustaining marine ecosystems and human fishing grounds, whilst variations in its intensity have been linked to changes in productivity, current strength, regional and global climate throughout the Cenozoic. The NADW is a mixture of deep currents originating from the Labrador Sea and the Arctic Ocean. Contribution from the latter component to NADW is largely influenced by the depth of the two gateways connecting the Nordic Sea to the North Atlantic basins on either side of Iceland. These gateways are shallower than 1500 m and the volume of Arctic overflow will vary directly in response to changes in the relative depth of the passages. Lower sea level during glaciations and periodic increased mantle activity under Iceland, effectively raising land and seafloor, will directly constrain the influx of cold and dense Arctic Water, weakening the NADW and overall AMOC on geological time scales.This project will exploit the capacity of ferromanganese crusts to record the signature of oceanic currents in their stratigraphy to track past changes in the strength, source, and provenance of the NADW components. Using samples from two key localities in the North Atlantic, high-resolution isotope records will be produced to investigate how the NADW varied over the last 20-30 Ma in response to glaciations and mantle pulses. These records will be dated using a new method for time calibration based on astronomical parameters and their influence on the chemical signature of these samples. The information gained will be used to inform future climate models predicting the response of this major oceanic current to disturbances.