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

北大西洋深水(NADW)构成了大西洋的主要深海洋流，颠覆了子午线环流(AMOC)，在全球范围内分配热量，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生产力、海流强度、区域和全球气候的变化有关。NADW是起源于拉布拉多海和北冰洋的深水洋流的混合体。后一部分对北大西洋和北大西洋的贡献在很大程度上受连接北欧海和冰岛两侧北大西洋盆地的两个门户的深度影响。这些航道浅于1500米，北极溢流量将直接随航道相对深度的变化而变化。冰川期间较低的海平面和冰岛下方地幔活动的周期性增加，有效地提高了陆地和海底，将直接限制冷密北极水的流入，在地质时间尺度上削弱NADW和整个AMOC。该项目将利用铁锰结壳在其地层中记录洋流特征的能力，追踪NADW组分的强度、来源和来源的过去变化。利用来自北大西洋两个关键地点的样品，将产生高分辨率同位素记录，以研究NADW在过去20-30 Ma内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进行年代测定，该方法基于天文参数及其对这些样品的化学特征的影响。获得的信息将被用于未来的气候模型，预测这一主要洋流对干扰的反应。

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.