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

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.