Identifying Dansgaard/Oeschger Cycles during the Penultimate Glacial

在这个项目中，将确定倒数第二次冰川中的Dansgaard/Oeschger事件，即距今17万到13000年之间的事件，并将准确地确定每一事件的开始和持续时间。Dansgaard/Oeschger事件是最后一次冰川期间短暂且重复的温暖事件，似乎遵循一定的周期性。最初，它们是通过格陵兰岛上钻探的冰芯稳定氧同位素组成的快速变化而被观察到的。它们似乎在北半球大部分地区的各种气候档案中留下了它们发生的迹象。例如，在过去10万年来，他们的指纹也在欧洲阿尔卑斯山北缘洞穴的稳定氧同位素组成中被观察到。然而，关于倒数第二次冰川期间丹斯加德/奥施格事件的信息有限。格陵兰岛的冰芯不包括这个时间间隔，因为没有这种年龄的冰可用。这一时期的海洋沉积物在其替代物中清楚地显示出Dansgaard/Oeschger式的模式-然而，从这个档案中很难获得准确的年代学。对于这个项目，我们有四个生长在倒数第二次冰川期间的北阿尔卑斯山的石笋。在很长的时间间隔内，它们成对地同时生长，因此获得了高度的重复性。稳定的氧同位素分析将为这些快速气候变化的存在提供强有力的证据，铀-钍方法将被用来建立精确的年代学。因此，这一方法能够大大提高我们对倒数第二次冰期期间这些气候变化的年代学的了解，并将有助于了解它们对北半球气候的影响及其周期性。

In this project, Dansgaard/Oeschger events in the penultimate glacial, between 170 000 to 130 000 years before present, will be identified and the beginning and the duration of each event will be precisely determined. Dansgaard/Oeschger events are short-lasting and repeating warm episodes during the last glacial and seem to follow a certain cyclicity. Originally, they were first observed by fast variations in the stable oxygen isotope composition of ice cores drilled on Greenland. They seem to left hints of their occurrence in various climate archives over large parts of the northern hemisphere. Their finger prints, for example, were also observed in the stable oxygen isotope composition of speleothems from the northern rim of the European Alps over the last 100 000 years. However, information about the Dansgaard/Oeschger events during the penultimate glacial is limited. Greenlands ice cores do not cover this time interval since no ice of such age is available. Marine sediments clearly show Dansgaard/Oeschger like pattern in their proxies in this period - however a precise chronology is difficult to obtain from this archive. For this project we have four stalagmites from the northern Alps which grew during the penultimate glacial. Over large time intervals pairs of them grew contemporaneously, so that a high degree of reproducibility is granted. Stable oxygen isotope analyses will provide strong evidence for the existence of these fast climate variations and the uranium-thorium method will be used to establish a precise chronology. Thus, this approach is able to contribute significantly to improve our knowledge of the chronology of these climate variations during the penultimate glacial and will help to understand their impacts on climate in the northern hemisphere and their cyclicity.