Dynamics of the Earth System In REcovery ('DESIRE')

就像我们现在所做的那样，在遥远的地质过去的某些时候，有大量的温室气体排放到大气中，比如二氧化碳。在岩石记录中，我们发现了气候变暖和降雨模式变化的证据。地球是如何从这种“温室”状态中恢复过来的？给气候降温的明显方法是移除添加的二氧化碳，并以一种不会迅速泄漏回大气的形式将其掩埋。通过一些复杂的地球化学和生物诡计，地球可以将花岗岩等岩石变成白垩岩和石灰岩，其中含有与钙紧密结合的碳原子，将碳锁定数百万年(多佛尔白色悬崖中的碳已经安全地储存在那里超过6500万年！)另一种埋藏碳的方法是以有机物的形式存在，地球系统有一种非常有趣的机制来保存这种碳，这种机制涉及到臭鸡蛋释放出的气体--硫化氢。它可以与有机物反应，形成更能抵抗细菌分解的新分子。这个过程有点像制造汽车轮胎(从散布在我们城市和农村的轮胎数量来看，这种轮胎似乎具有很强的抗腐蚀性)。那么，海洋中的哪些条件导致有机质得到最大程度的保存和埋葬，以及用腐蛋保存有机物对大气二氧化碳和气候到底有什么影响？计算机模型是很好的工具，可以帮助回答这个问题。我们如何在计算机模型中理解和表示地球的气候系统，虽然还远远不是完美的，但正在逐步改善。气候系统主要涉及物理，尽管大多数学生可能会从学校得出这样的结论：物理很容易。更难理解的是化学和生物，特别是当它出现在海洋底部臭气熏天的(硫酸盐)泥浆中时。然而，理解这一点很重要，因为如果细菌耗尽海底的所有氧气，它们将突然发现更难分解在海洋表面的阳光下生活和生长的微型植物(浮游植物)的所有死亡“身体”，并在它们死亡时沉入海底。因此，我将开发一个化学反应的计算机模型，以表示硫化氢如何将浮游植物中的有机物转化为沉积物中更具抵抗力的形式。使用这个模型，我首先可以更好地理解可能产生生产石油(和天然气)的完美岩石的条件。除了全球碳循环和气候模型，我还将利用地质记录来帮助理解不同恢复模式的可能性和重要性，并将调查和比较过去两次全球变暖事件：古新世-始新世最高温度(PETM)约5500万年前(Ma)和早侏罗世的海洋缺氧事件(OAEs)(约183 Ma-Toarcian OAE)期间这些身体被埋葬在硫酸盐泥浆中的情况。通过这一切，我希望能够更好地理解碳埋藏量的增加如何帮助地球系统从温室气候中恢复过来，并测试地球系统是否可能有一种特殊的应急机制-如果气候变得太热，海洋中的氧气开始耗尽-随着氧气开始在海洋中耗尽，硫化氢的产生，以及更多的掩埋或有机物。

As we are doing now, at times in the distant geological past, there were massive releases of greenhouse gases such as CO2 to the atmosphere. In the rock record we find evidence for a warming of climate and change in rainfall patterns. How does the Earth recover from being put into this 'greenhouse' state? The obvious way of cooling climate is to remove the CO2 that has been added and to bury it in a form that will not quickly leak back to the atmosphere. By some complicated geochemical and biological trickery, the Earth can turn rocks such as granite into chalks and limestones, which contains carbon atoms bound tightly to calcium, locking up carbon for millions and millions of years (the carbon in the white cliffs of Dover has been safely stored there for over 65 millions years!). Another way to bury carbon is as organic matter and the Earth system has a really fascinating mechanism for preserving this carbon involving the gas given off by rotten eggs - hydrogen sulphide. This can react with organic matter to form new molecules that are more resistant to being broken down by bacteria. The process is a bit like making car tires (which appear highly resistant to decay judging by how many seem to lie strewn across our cities and countryside). So what conditions in the ocean lead to the most preservation and hence burial of organic matter, and what impact on atmospheric CO2 and climate does preserving organic matter with rotten eggs really have? Computer models are great tools and can help answer this. How we understand and represent the Earth's climate system in computer models, while still far from perfect, is progressively improving. Mostly the climate system involves physics, and despite what most students may conclude from school: physics is easy. More difficult to understand is chemistry and biology, particularly when it occurs in smelly (sulphidic) mud sitting at the bottom of the ocean. Yet this is important to understand, because if bacteria were to use up all the oxygen at the ocean floor, they would suddenly find it much harder to break down all the dead 'bodies' of the microscopic plants (phytoplankton) that live and grow in the sunlight at the ocean surface and sink down to depth when they die. I will therefore develop a computer model of chemical reactions to represent how hydrogen sulphide can turn the organic matter from phytoplankton into a much more resistant form in the sediments. Using this model I can firstly better understand the conditions that might produce the perfect rocks for producing oil (and gas). Together with a global carbon cycle and climate model, I will also utilize the geological record to help understand what is possible and how important the different modes of recovery are, and will investigate and compare the burial of these dead bodies in sulphidic mud during two past global warming events: Paleocene-Eocene Thermal Maximum ('PETM') ~55 million years ago (Ma) and the Ocean Anoxic Events ('OAEs') of the early Jurassic (ca. 183 Ma - the Toarcian OAE). From all this, I expect to be able to understand better how increases in the amount of carbon being buried helps the Earth system recover from greenhouse climates and test whether the Earth system might have a special emergency mechanism - if climate gets too warm and oxygen starts to run out in the ocean - the production of hydrogen sulphide as oxygen starts to run out in the ocean and increased burial or organic matter.