Comprehensive analysis of Atlantic Circulation during Heinrich-Event 1 & 2

大西洋经向翻转环流（AMOC）的动力是全球气候系统的关键因素之一。它对热量和碳从地表进入深海的再分配产生了至关重要的影响，反之亦然。因此，评估AMOC的敏感性是古气候学的一个重大挑战。这里的重点是大陆冰融化带来的过量淡水输入如何影响其倾覆力，从而影响北部高纬度地区的热量供应。这种强迫作用可以通过在末次冰川期（即所谓的“海因里希事件”）调查冰山向北大西洋开放的极端喷发事件期间的行为来检验。近年来，大量研究提供了丰富的海洋沉积物231Pa/230Th测量数据，成功证明了该示踪剂对AMOC自然变率重建的重要价值。在这个项目中，我们测量了海因里希事件1和海因里希事件2中许多沉积物岩心的Pa/Th，从而有力地增加了大西洋深层环流研究中可用的Pa/Th数据库。这些测量伴随着沉积物样品中生物成因蛋白石含量的测定。在Heinrich-Events 1和Heinrich-Events 2之前、期间和之后，AMOC的强度和几何形状可以用逆模型方法从这个新数据库中得到。通过这种方式，我们的目标是回答Heinrich-Events是否导致AMOC停止，或者相反，Heinrich-Events是否是AMOC变化的结果。因此，在北大西洋北部潜在的冰盖融化和降水增加的背景下，海因里希事件可能会显示一个模式情景，提高我们对AMOC即将对气候变化的响应的理解。

The dynamic of the Atlantic Meridional Overturning Circulation (AMOC) is one of the key players in the global climate system. It crucially influences the redistribution of heat and carbon from surface into the deep sea and vice versa. Therefore, assessing the sensitivity of the AMOC is a major challenge for paleoclimatology. Here the focus is set on how excessive freshwater input through melting of continental ice can affect its overturning vigour and, hence, heat supply to high northern latitudes. Such forcing can be tested by investigating its behaviour during extreme iceberg discharge events into the open North Atlantic during the last glacial period, so called ¿Heinrich-Events¿. In recent years numerous studies have provided a wealth of 231Pa/230Th measurements in marine sediments, successfully demonstrating the important value of this tracer for the reconstruction of the natural variability of the AMOC. In this project we measure Pa/Th in numerous sediment cores across Heinrich events 1 and 2 thus strongly augmenting the available database of Pa/Th for the investigation of the Atlantic Ocean deep circulation studies. These measurements are accompanied by the determination of the biogenic opal content of the sediment samples. Strength and geometry of the AMOC before, during and after the Heinrich-Events 1 and 2 can be derived from this new database in an inverse model approach. By this we are aiming for answering the question if Heinrich-Events either caused cessations of AMOC or if maybe in contrast Heinrich-Events are the result of AMOC changes. Thus, in the context of potential ice shield melting and increasing precipitation in the northern North Atlantic, Heinrich-Events may display a model scenario improving our understanding of the upcoming response of AMOC on climate changes.