Evolution of Carbon Cycle Dynamics (eCCD)

全球碳循环--有多少碳储存在其相互关联的储存库（海洋、大气、陆地上的植物和土壤、深海沉积物）中，以及它们之间的通量，并不是一成不变的。我们从地质记录中知道，在过去的几亿年里，大气中二氧化碳的浓度变化很大。海洋的化学性质也随着时间的推移而逐渐变化，生活在其中的生物也在调整和进化。因此，碳循环如何“工作”，特别是在面临破坏时大气CO2（以及气候）的调节程度（或不调节），也会在地质时间尺度上发生变化。这对理解过去全球变暖等事件的原因和后果以及这些事件如何与未来潜在的变化相关提出了挑战。在深海中缓慢积累的沉积物反映了它们周围和上面发生的化学和生物变化。我们特别感兴趣的是矿物碳酸钙（CaCO 3），今天可以以白垩和石灰岩的形式发现。CaCO 3被某些海洋生物用于构建外壳和骨骼。因此，埋藏在沉积物中的CaCO 3的数量告诉我们一些关于古代生物和生态系统的信息。此外，如果条件太酸性或深度（以及压力）太大，CaCO 3将开始溶解在海水中。因此，有多少碳酸钙最初是由表面的生物体产生的，它们逃脱了下面沉积物的溶解，被埋藏并保存在地质记录中，可以告诉我们一些关于化学，深度的信息，当来自许多地方的数据可用时，过去的海洋环流。在钻井船从海底采集的数百米的沉积物岩心中寻找古代泥浆成分的细微变化，有点像大海捞针。然而，大自然对我们很好，从富含死亡海洋生物碳酸盐外壳的白色沉积物到缺乏碳酸盐的粘土的过渡很容易发现。这一点代表了沉积到沉积物中的贝壳物质的数量与这些贝壳的溶解速度之间的微妙平衡。因此，这反映了表层海洋生物过程与深海化学和环流之间的某种关系。这些因素的任何变化都将驱动富含CaCO 3或没有任何碳酸盐分泌生物痕迹的沉积物。在这个项目中，我们将汇编自20世纪60年代以来已恢复的数百个不同沉积物岩心的记录。将确定这些岩心中的“平衡点”（如果存在的话），并将所有确认信息联合收割机结合起来，重建这个平衡点在不同海洋盆地中的深度和时间变化。由于某些岩心中沉积物的年龄可以追溯到多佛的白色悬崖沉积之前，我们将从那里开始记录。对我们曲线的解释并不完全简单，因为多种环境影响都以不同的方向和强度推拉平衡点。因此，我们还将使用一个计算机模型来表示地球的气候和海洋，其碳循环，海洋化学和深海沉积物的组成。我们将使用这个模型来探索全球碳循环的不同方面如何影响平衡点，并通过将模型预测与我们的新曲线进行比较，解释碳循环和大气pCO 2（以及气候）的敏感性如何在过去的1.5亿年中受到大规模温室气体释放的干扰。因此，我们将不仅能够回答这个问题：我们生活在一个特别“幸运”或“不幸”的时代，就我们的全球环境对燃烧化石燃料的敏感程度而言，而且我们将知道为什么。

The global carbon cycle - how much carbon is stored in its interconnected reservoirs (ocean, atmosphere, plants and soils on land, sediments in the deep sea) as well as the fluxes between them, is not set in stone. We know from the geological record that the concentration of CO2 in the atmosphere has varied enormously over the last few hundred million years. The chemistry of the oceans also gradually changes with time and the organisms living within it adjust and evolve. As a result, how the carbon cycle 'works', and particularly, how well (or not) atmospheric CO2 (and hence climate) is regulated in the face of disruption, also changes on geological time-scales. This creates challenges to understanding the causes and consequences of past global warming like events and how such events can be related to potential future changes. Sediments slowly accumulating in the deep ocean reflect what goes on around and above them, both chemically and biologically. Of particular interest to us is the mineral calcium carbonate (CaCO3), which can be found in the form of chalk and limestone rocks today. CaCO3 is used by certain marine organisms for constructing shells and skeletons. Hence, the amount of CaCO3 that in buried in sediments tells us something about ancient organisms and ecosystems. In addition, CaCO3 will start dissolving in seawater if the conditions too are acidic or the depth (and thus pressure) too great. How much CaCO3 originally created by organisms at the surface that escapes dissolution in sediments below to be buried and preserved in the geological record can thus tell us something about the chemistry, depth, and when data from many locations is available, the circulation of the ocean in the past. Looking for subtle changes in the composition of ancient mud in the hundreds and hundreds of meters of sediment core recovered from the ocean floor by drill ship would be a little like looking for a needle in a haystack. However, Nature has been kind to us and the transition from white-colored sediments rich in the carbonate shells of dead marine organisms to clays devoid of carbonate is easy to spot. This point represents a fine balance between the amount of shell material being deposited to the sediments and the rate of dissolution of these shells. Hence, this reflects a certain relationship between surface ocean biological processes and deep ocean chemistry and circulation. Any change in these factors will drive sediments rich in CaCO3 or devoid of any trace of carbonate secreting organisms. In this project we will compile the records from many hundreds of different sediment cores that have been recovered since the 1960s. Will identify the 'balance point' in these cores (if one exists) and combine all the confirmation to reconstruct how this balance point has changed in depth and time in the different ocean basins. Because the age of the sediments in some cores extends back to well before the white cliffs of Dover were deposited, we will start our record there. The interpretation of our curve will not be entirely straightforward, because multiple environmental influences all push and pull the balance point in different directions and with different strengths. We will therefore also use a computer model representation of the Earth's climate and oceans, its carbon cycle, ocean chemistry, and the composition of sediments in the deep sea. We will use this model to explore how the different aspects of the global carbon cycle affect the balance point, and by comparing model predictions to our new curve, interpret how the carbon cycling and the sensitivity of atmospheric pCO2 (and hence climate) to being perturbed by massive greenhouse gas release, has changed over the past 150 million years. Hence we will not only be able to answer the question: do we live in a particularly 'lucky' or 'unlucky' time in terms of how sensitive our global environment is burning fossil fuels, but we will know why.