Identifying Dansgaard/Oeschger Cycles during the Penultimate Glacial

在这个项目中，将确定倒数第二个冰期的Dansgaard/Oeschger事件，在距今17万至13万年之间，并精确确定每个事件的开始和持续时间。Dansgaard/Oeschger事件是末次冰期持续时间短、反复出现的温暖事件，似乎遵循一定的周期性。最初，它们是通过在格陵兰岛钻探的冰芯中稳定氧同位素组成的快速变化观察到的。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10万年里，在欧洲阿尔卑斯北部边缘的洞穴化石的稳定氧同位素组成中也观察到了他们的指纹。然而，关于第二次冰期的Dansgaard/Oeschger事件的信息有限。格陵兰岛的冰芯没有覆盖这段时间，因为没有这样年龄的冰。海洋沉积物在这一时期的代用物中清楚地显示出类似Dansgaard/Oeschger的模式，但很难从这些档案中获得精确的年表。在这个项目中，我们有四个来自阿尔卑斯山北部的石笋，它们生长在第二次冰川时期。在很长的时间间隔内，它们成对同时生长，因此具有高度的可重复性。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，铀钍法将用于建立精确的年表。因此，这种方法能够大大提高我们对第二次冰期这些气候变化年代学的认识，并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.