Climate response to orbital forcing during the Eocene deglaciated, high temperature, high CO2 state: New records from Sites 1210, 1258 & 1267

在过去的150年里，人类将大气中二氧化碳的含量从百万分之280(Ppmv)增加到了380ppmv。我们知道，这一人为价值比过去80万年来地球上看到的任何东西都要高得多，这是从南极洲冰层中捕获气泡的著名记录得出的。按照中国和印度的工业化速度，到本世纪末，大气中的二氧化碳浓度预计将达到750，或许1000ppmv。自始新世(大约5000万年前)以来，地球上就没有见过这样的浓度，当时我们的星球比今天温暖得多，冰川也少得多(见《新科学家》2008年6月21日的封面故事)。这些非凡的观察结果意味着，我们必须提高对这些古老地质气候稳定性的理解。在过去，这不可能以我们提出的方式进行，因为这项工作所需的各种地质材料(来自海洋深处的年代良好、保存完好和未受干扰的沉积物)是不可用的。然而，英国是一项重大的国际合作科学计划的一部分，该计划被称为(综合)大洋钻探计划或(I)ODP。在其作业的最后阶段(I)，ODP号发起了一场大规模的海底钻孔运动，以获取这类工作所需的始新世沉积物种类。我们每个人都深度参与了这场运动(见第一部分，我们的‘记录’)。我们的提案寻求资金，利用这些最近采集到的(I)ODP型沉积物，研究这个‘始新世温室’时期的自然气候变异性。具体地说，我们想要了解在这种冰川消融、高温、高二氧化碳水平的状态下，气候对地球太阳轨道的敏感性。我们计划通过将已有的化学技术应用于针头大小的有孔虫化石来生成表层和深海的古气候记录，这些化石的外壳是由碳酸钙制成的。我们工作的一个关键方面将是确定不同半球、纬度和海洋的温度和碳循环行为的节奏波动。我们的工作有可能找到新的方法来：1)解决关于在其他地质时期是否存在大量冰盖的持续争论。2)对海底CaCO3埋藏进行局部(表层海洋出口生产)与全球(深海‘酸度’)控制试验。

In the past 150 years mankind has increased the level of atmospheric carbon dioxide in the atmosphere from 280 parts per million by volume (ppmv) to 380 ppmv. We know that this anthropogenic value is much higher than anything seen on Earth in the last 800 thousand years from the famous records of air bubbles trapped in layers of ice cored in Antarctica. At the rate at which China and India are industrializing, by the end of this century, the concentration of CO2 in the atmosphere is predicted to reach 750, perhaps 1000 ppmv. These sorts of concentrations have not been seen on Earth since the Eocene (about 50 million years ago) when our planet was much warmer and less glaciated than today (see cover story, New Scientist, 21 June, 2008). These remarkable observations mean that we must improve our understanding of the stability of these ancient geological climates. In the past this would not have been possible in the way that we propose because the sorts of geological materials required for this work (well-dated, well-preserved and undisturbed sediments from the depths of the oceans) were not available. However, the UK is part of a major international collaborative science program called the (Integrated)Ocean Drilling Program or (I)ODP. In its last phase of operation (I)ODP instigated a major campaign of drilling holes in the sea floor to retrieve the sorts of Eocene sediments required for this sort of work. Each of us was heavily involved in this campaign (see Part I, our 'track records'). Our proposal seeks funding to study natural climate variability during this 'Eocene greenhouse' interval using these recently recovered (I)ODP sediments. Specifically, we want to understand the sensitivity of climate to Earth's orbit of the Sun under this deglaciated, high temperature, high CO2 level state. We plan to generate palaeoclimate records for the surface and deep ocean by applying established chemical techniques to pin-head sized fossils called foraminifera that make their shells from calcium carbonate. A key aspect of our work will be to determine the rhythmic fluctuations in temperature and carbon cycle behaviour across different hemispheres, latitudes and oceans. Our work has the potential to identify novel methods to: 1) Tackle ongoing debate over the existence of substantial ice sheets during other intervals of geologic time. 2) Test for local (surface ocean export production) versus global (deep ocean 'acidity') control on the burial of CaCO3 at the sea floor.