Human activity has led to an increase in pCO2 and methane levels from pre-industrial times to today. While the former increase is primarily due to fossil fuel burning, the increase in methane concentrations is more complex, reflecting not only direct human activity but also feedback mechanisms in the climate system related to temperature and hydrology-induced changes in methane emissions. To unravel these complex relationships, scientists are increasingly interrogating ancient climate systems. Similarly, one of the major challenges in palaeoclimate research is understanding the role of methane biogeochemistry in governing the climate of ice-free, high-pCO2 greenhouse worlds, such as during the early Paleogene (around 50Ma). The lack of proxies for methane concentrations is problematic, as methane emissions from wetlands are governed by precipitation and temperature, such that they could act as important positive or negative feedbacks on climate. In fact, the only estimates for past methane levels (pCH4) arise from our climate-biogeochemistry simulations wherein GCMs have driven the Sheffield dynamic vegetation model, from which methane fluxes have been derived. These suggest that Paleogene pCH4 could have been almost 6x modern pre-industrial levels, and such values would have had a radiative forcing effect nearly equivalent to a doubling of pCO2, an impact that could have been particularly dramatic during time intervals when CO2 levels were already much higher than today's. Thus, an improved understanding of Paleogene pCH4 is crucial to understanding both how biogeochemical processes operate on a warmer Earth and understanding the climate of this important interval in Earth history. We propose to improve, expand and interrogate those model results using improved soil biogeochemistry algorithms, conducting model sensitivity experiments and comparing our results to proxy records for methane cycling in ancient wetlands. The former will provide a better, process-orientated understanding of biogenic trace gas emissions, particularly the emissions of CH4, NOx and N2O. The sensitivity experiments will focus on varying pCO2 levels and manipulation of atmospheric parameters that dictate cloud formation; together, these experiments will constrain the uncertainty in our trace greenhouse gas estimates. To qualitatively test these models, we will quantify lipid biomarkers and determine their carbon isotopic compositions to estimate the size of past methanogenic and methanotrophic populations, and compare them to modern mires and Holocene peat. The final component of our project will be the determination of how these elevated methane (and other trace gas) concentrations served as a positive feedback on global warming. In combination our work will test the hypothesis that elevated pCO2, continental temperatures and precipitation during the Eocene greenhouse caused increased wetland GHG emissions and atmospheric concentrations with a significant feedback on climate, missing from most modelling studies to date. This work is crucial to our understanding of greenhouse climates but such an integrated approach is not being conducted anywhere else in the world; here, it is being led by international experts in organic geochemistry, climate, vegetation and atmospheric modelling, and palaeobotany and coal petrology. It will represent a major step forward in our understanding of ancient biogeochemical cycles as well as their potential response to future global warming.

Over a 6 million square km region of the central Pacific ocean, at abyssal depths of almost five thousand metres, lies a vast mineral resource in the form of small potato-sized deposits called polymetallic nodules. They are highly-enriched in metals of importance for industry, including the development of new sustainable technologies. Although the region lies in international waters, countries have now signed 16 exploration contracts with a UN-organised international regulator and the United Kingdom is sponsor to two of these, covering an area more than the size of England. It is a requirement of both the regulator and the sponsoring state to ensure that serious harm is avoided to the marine ecosystem in this region - a hitherto untouched deep-sea wilderness. Developing a sustainable approach to polymetallic nodule mining is a challenge as the nature and importance of the Pacific abyssal ecosystem is largely unknown, as are the capacity of the ecosystem to cope with and recover from mining impacts. Our project aims to provide the critical scientific understanding and evidence-base to reduce the risks of this industrial development, taking advantage of two new and unique opportunities to solve these problems in a single programme. Firstly, the UK contractor that holds the UK-sponsored exploration contract (UK Seabed Resources) is planning a mining test in 2023, which will allow us to test the immediate impacts of a seabed mining vehicle for the first time. Secondly, as a partner in the first full-scale mining test done in 1979, they have been able to release new data on the location and results of a 40-year old large-scale mining operation. Our project team have secured access to data and test plans, to allow detailed experimental evaluation of impact and recovery from realistic mining disturbance on a decadal scale of vital relevance to understanding the long-term sustainability of deep-sea mining. The project aims to better understand the ecosystem in the Pacific abyss and how the different components interact and interconnect. We will start by assessing the water and its dynamic flows over time and space. This complex physical environment will be monitored for a year to capture its variabilities, particularly "storm events" near the seabed. We will use this to make predictions about where the sediment plume generated by mining will be transported and settle back to the seafloor. We then assess the linkages between the water, sediment surface and sub sediments, evaluating the natural cycling of nutrients and metals that is important to maintain ecosystem health. The impacts of mining and recovery of these processes will be assessed. Mining will lead to changes in the structure of the seabed, its shape and the physical nature of the sediments, which will be mapped and linked to biological patterns. The biological processes that lead to these patterns will be assessed by detailing the life histories and reproduction of the organisms present and their connectivity between areas near and far, and then determining their role in maintaining structured communities of life, a high biodiversity and a functioning food web. We will then evaluate the functions in the ecosystem that these organisms provide, which help maintain a healthy ecosystem. The impact of mining and recovery of all these patterns and processes will be determined using our experimental areas to assess the biological and functional consequences of disturbance in the deep sea. These changes are likely complex, so a range of mathematical models will be used to better understand and predict the consequences of mining activities at larger time and space scales. Such predictive power, along with the evidence from the scientific assessment, will provide information that is critical for understanding and reducing the environmental risk of future mining activities.