Sub-orbital climate instability and its relation to Late Pliocence intensification of Northern Hemisphere Glaciation, IODP Sites 1308 and 1313

1亿年前（Ma），当恐龙行走在地球上时，大多数科学家认为两极没有我们今天看到的大冰盖。这些冰帽是什么时候以及为什么形成的？他们成长得有多快？一旦建立，它们有多稳定？这些都是我们试图通过从海底收集的沉积物岩心生成过去气候变化记录来回答的一些问题。我们的技术之一是计算冰川从大陆上刮下来的小岩石碎片，这些碎片通过裂产和冰山漂流而到达海底。另一个是测量被困在微小的单细胞海洋动物有孔虫的碳酸钙外壳中的重氧和轻氧同位素（18 O/16 O）（从实验室实验中得知，对冰的体积和温度很敏感）的比率。我们已经有了过去100 Ma气候变化的半连续、半定量的图像。这种模式是一种逐渐的长期冷却加上几个大的“转变”到更多的冰川条件。叠加在这些变化上的是气候中具有明显节奏的规则周期（例如。轨道周期约为10万至4万年）。在我们有足够高分辨率的记录（特别是过去500 kyrs的记录）的地方，我们看到叠加在这些节奏上的是亚轨道尺度的振荡，涉及冰盖的前进/崩溃和海洋环流的变化，就像好莱坞大片《后天》中流行的那样。这些波动与我们对未来的担忧特别相关。它们表明，即使没有人类的干扰，整个气候系统，特别是北大西洋地区，也能够在几十年内极其迅速地进行大规模的重组（特别是对欧洲西北部的条件产生极端的后果）。有些人认为亚轨道尺度的振荡是由地球外部的力量驱动的（例如，地球的引力）。太阳辐射的变化）。其他人认为内力很重要，因为我们可以看到，在过去的500 kyrs，当冰盖很大时，亚轨道振荡被放大了。海洋沉积物中的冰筏碎片和氧同位素记录表明，北方半球从~2.72 Ma开始就存在大型永久性大陆冰盖。因此，一个大问题出现了：亚轨道尺度的气候变化是如何随着被认为放大它们的冰盖的形成而演变的？在寻求回答这个问题的过程中，我们过去一直受到缺乏连续的、高分辨率的、具有良好年龄控制的变化记录的阻碍。然而，在沉积物迅速堆积的地点仔细应用现代钻探方法有助于解决这些问题。我们建议解决上述问题，产生前所未有的连续性，分辨率和年龄控制从北大西洋的间隔2.84马至2.4马的新的古气候记录。通过确定亚轨道尺度气候不稳定性对冰期-间冰期状态的敏感性，我们可以看到气候边界条件自~ 2.8Ma以来的变化。

One hundred million years ago (Ma), when dinosaurs walked Earth, most scientists think that the poles were free of the large icecaps that we see today. When and why did these icecaps form? How rapidly did they grow? Once established, how stable were they? These are some of the questions that we seek to answer by generating records of past climate change from sediment cores collected from the seafloor. One of our techniques is to count small rock fragments that have been scrapped off the continents by glaciers and delivered to the seafloor by calving and drifting of icebergs. Another is to measure the ratio of heavy and light oxygen isotopes (18O/16O) (known from laboratory experiments to be sensitive to ice-volume and temperature) trapped in the fossilised calcium carbonate shells of tiny single cellular marine animals called foraminifers. We already have a semi-continuous, semi-quantitative picture of climate change over the past 100 Ma. The pattern is one of gradual long-term cooling plus several big 'shifts' to more glaciated conditions. Superimposed on these changes are regular cycles in climate with distinct rhythms (eg. orbital cycles of ~100, 40 thousand years). Where we have high-enough resolution records (of the last 500 kyrs in particular) we see that superimposed on these rhythms are sub-orbital scale oscillations involving ice-sheet advance/collapse and ocean circulation change as popularised in the Hollywood blockbuster 'The Day After Tomorrow'. These oscillations are especially relevant to our concerns about the future. They demonstrate that, even without man's interference, the climate system in general and the North Atlantic region in particular is capable of undergoing massive re-organization extremely rapidly, within even a few decades (with extreme consequences for conditions in NW Europe in particular). Some suggest that sub-orbital scale oscillations are driven by forces external to Earth (eg. changes in solar insolation). Others think that internal forces are important because, we can see that in the last 500 kyrs sub-orbital oscillations were amplified when ice-sheets are large. Records of ice-rafted debris and oxygen isotopes from marine sediments suggest that large permanent continental ice-sheets were present in the northern hemisphere from ~2.72 Ma. One big question that arises, therefore, is: - how does sub-orbital scale climate variability evolve as the ice-sheets that are thought to amplify them form? In seeking to answer this question we have been hampered in the past by the lack of continuous, high-resolution records of change with excellent age control. However, careful application of modern drilling methods to sites of rapidly accumulating sediment is helping to remedy these problems. We propose to address the above problem by generating new palaeoclimate records of unprecedented continuity, resolution and age-control from the North Atlantic for the interval 2.84 Ma to 2.4 Ma. By determining the sensitivity of sub-orbital scale climate instability to glacial-interglacial state we can see how climate boundary conditions have changed since ~ 2.8 Ma.