Evolution of Carbon Cycle Dynamics (eCCD)

见牵头机构(布里斯托尔)：碳循环动力学的演变(ECCD)--全球碳循环概述：有多少碳储存在其相互关联的储存库(海洋、大气、生物圈、沉积物)以及它们之间的通量，随时间变化。例如，我们从地质记录中了解到，在过去的数亿年里，大气中二氧化碳的浓度变化很大。海洋的化学成分也会随着时间的推移而变慢，生活在海洋中的生物也会发生变化和进化。碳循环如何“运作”的细节，尤其重要的是，大气(以及气候)中的二氧化碳浓度受到多好(或不好)的调节，因此也在地质时间尺度上发生变化。这带来了挑战，例如，在理解过去全球变暖等事件的原因和后果以及它们如何与未来相关方面。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一切，无论是化学上的还是生物上的。特别是，矿物碳酸钙(CaCO3)，今天可以以白垩岩和石灰岩的形式找到，是海洋生物通常用来建造贝壳和骨骼的材料。因此，埋藏在沉积物中的CaCO3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，如果条件是酸性的，或者深度(因此压力)非常大，例如在开阔海洋的最底部，CaCO3将开始溶解在海水中。原来由生物产生的CaCO3中有多少残留在沉积物中，没有溶解在沉积物中，因此也告诉我们一些关于过去海洋化学、深度以及当可以从许多地点获得数据时的海洋环流的信息。从钻井船从海底打捞出的数百米沉积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，大自然一直对我们很友好，从富含碳酸盐海洋生物外壳的白色沉积物过渡到不含碳酸盐的粘土是很容易发现的。这一点代表了沉积到沉积物中的贝壳数量和溶解速度之间的平衡。因此，在表层海洋生物过程和深海化学和环流过程之间取得平衡。在这个项目中，我们将通过汇编过去几十年中从数百个不同的沉积物岩心中采集的记录，重建这个平衡点在不同的海洋盆地中的深度和时间变化。因为沉积物记录早在中生代就已经存在，早在恐龙灭绝之前就存在了，所以我们将从那里开始。然而，对我们将产生的曲线的解读并不直截了当，因为多重环境变化都会以不同的方向和强度推动和拉动这个平衡点。因此，我们还将在那里配置一个计算机模型，表示过去这些时间地球的气候和海洋、其碳循环、海洋化学和深海沉积物的组成。我们将利用这一点来探索碳循环中不同可能的变化如何影响平衡点，并通过与我们随时间变化的新曲线进行比较，解释过去1.5亿年来碳循环是如何变化的。这也将使我们能够理解碳循环以及气候变化的敏感性是如何及时受到扰动的，例如受到大规模温室气体排放的干扰。因此，我们不仅能够回答这样一个问题：就我们的全球环境对化石燃料的燃烧有多敏感而言，我们生活在一个特别“幸运”或“不幸”的时代，而且我们将知道为什么地球系统会以一定程度的敏感性做出反应。

see lead Institution (Bristol): Evolution of Carbon Cycle Dynamics (eCCD) - Summary The global carbon cycle: how much carbon is stored in its interconnected reservoirs (ocean, atmosphere, biosphere, sediments) as well as the fluxes between them, changes with time. For instance, we know from the geological record that the concentration of CO2 in the atmosphere has varied enormously over the last few hundred of millions of years. The chemistry of the oceans also slows varies with time, and the organisms living within the ocean change and evolve. The details of how the carbon cycle 'works', and of particular importance, how well (or not) the concentration of CO2 in the atmosphere (and hence climate) is regulated, thus also changes on geological time-scales. This creates challenges, for instance, in understanding the causes and consequences of past global warming like events and how they can be related to the future. The sediments slowly accumulating in the deep ocean reflect everything that goes on around them and above them, both chemically and biologically. In particularly, the mineral calcium carbonate (CaCO3), which can be found in the form of chalk and limestone rocks today, is a material commonly used in constructing shells and skeletons by marine organisms. Hence, the amount of CaCO3 being buried in sediments tells us something about ancient organisms and ecosystems. In addition, CaCO3 will start dissolving in seawater if the conditions are acidic or the depth (and thus pressure) is very intense, such as at the very bottom of the open ocean. How much of the CaCO3 originally created by organisms that remains and is not dissolved in sediments, thus also tells us something about past ocean chemistry, depth, and when data from many locations is available, ocean circulation. Looking for subtle changes in the composition of ancient mud in 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 us and the transition from white-colored sediments rich in the shells of carbonate marine organisms to clays devoid of carbonate is easy to spot. This point represents a balance between the amount of shells deposited to the sediments and the rate of dissolution. Hence a balance between surface ocean biological processes and deep ocean chemical and circulation processes. In this project by compiling the records from hundreds of different sediment cores recovered in the past decades, we will reconstruct how this balance point has change in depth and time in the different ocean basins. Because sediment records exist as far bask as the Mesozoic and well before the dinosaurs went extinct, we will start there. However, the interpretation of the curve we will produce is not straightforward, because multiple environmental changes can all push and pull this balance point in different directions and with different strengths. We will there fore also configure 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 for these times in the past. We will use this to explore how the different possible changes in the carbon cycle affect the balance point, and by comparing to our new curve through time, interpret how the carbon cycle has changed over the past 150 million years. This will also allow us to understand how the sensitivity of the carbon cycle and hence climate changes in time to being perturbed, such as by massive greenhouse gas releases. 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 to the burning of fossil fuels, but we will know why the Earth system responds with a certain degree of sensitivity.