Almost all active caldera volcanoes host hydrothermal systems that circulate a mixture of seawater, meteoric water and magmatic fluids through the subsurface geology to seeps or vents on the seafloor. These fluids can explosively interact with magma in volcanic eruptions and can change the physical properties of their host rocks, influencing both the likelihood of eruptions occurring and their explosivity. The nature of these interactions is poorly understood, including how fluid flow changes during periods of magmatic intrusion, how the hydrothermal system connects magmatic fluids to the surface and the spatial distribution and extent of alteration/mineralisation. While we know hydrothermal fluid flow plays an important role in modulating eruption dynamics, as long as these fundamental knowledge gaps exist it is impossible to forecast, with any degree of accuracy, what this effect will be which makes understanding hazards and impacts in eruption scenarios difficult. In this proposal we will combine novel controlled source electromagnetic mapping of porosity and permeability, with passive seismic mapping of hydrothermal fluid flow in the shallow subsurface, constrained by heat flow measurements and surface and subsurface sampling to characterise the porosity and permeability of the Santorini hydrothermal system. Santorini has been selected as the ideal natural laboratory to test these relationships because it is exceptionally well characterised geophysically and geologically, has a diversity of hydrothermal vents and has experienced recent activity which can be used to test modelling. We will quantify how magmatic fluids are partitioned between vents to identify the primary pathways for magmatic volatile escape, and quantify the impact hydrothermal mineralisation has had on the physical strength of the seafloor. Once we have a full picture of the system in its current state we will use mapping, fluid inclusions, mineralogy and the sedimentary record to establish how vent locations, subsurface fluid pathways, and fluid fluxes, temperatures and chemistries responded to the 2011/12 period of unrest. These data will be used to constrain the boundary conditions for a hydrothermal system model, which can be used to predict how the system will respond to future periods of intrusion both at Santorini and at other caldera systems around the world. This project will provide a step change in our understanding of hydrothermal interactions with volcanoes and our ability to predict their response to changes in the magmatic system. This has implications not just for understanding volcanic eruptions, but also for understanding metal and volatile fluxes from the mantle to the ocean and atmosphere, the development of economic metal deposits in these systems, the impact on ecological communities of intrusive and extrusive volcanic events, geothermal energy production, and for hazard forecasting and mitigation. The project will push the frontiers of knowledge by combining cutting edge geophysical and geochemical techniques to produce a model of a caldera hydrothermal system at a resolution previously not possible, and by developing modelling tools that would allow the application of these findings to other systems. The project is ambitious but achievable and benefits from a large team of international expert proponents, partnerships with other large international projects and high-quality pre-existing data upon which to build.

Volatile organic compounds (VOCs) in the marine environment and the atmospheric oxidative capacity over the ocean are critical but poorly understood components of the Earth System. There are tens of thousands of different VOC species in air, and they react with the hydroxyl radical (OH) and determine the reactivity of the atmosphere - often referred to as the oxidative capacity (the ability for air to cleanse itself). The oxidative capacity is key for climate through OH oxidation of methane and for air quality (e.g. via formation of ozone). Yet ~1/4 of the observed total OH reactivity over the ocean remains unexplained. VOCs are also precursors to secondary organic aerosol (SOA), which have the potential to enable particle growth to cloud condensation nuclei (CCN). Over the ocean and far away from anthropogenic sources where aerosol concentrations are typically low, clouds are far more sensitive to changes in aerosol than over land, highlighting the essential need to understand marine VOCs. Yet to date, the number of intensive VOC studies over land outnumbers studies over the ocean by orders of magnitude. The ocean contains a vast number of VOCs. Beyond a few well-studied gases, the inventory of these sea-air emissions is in its infancy due to the paucity of measurements. Compared to recent observations, models consistently underpredict the marine atmospheric concentrations of many VOCs, the total oxidative capacity, and marine SOA, strongly suggesting poorly constrained or unidentified oceanic emissions of VOCs. The highly uncertain VOC fluxes take the forms of "known unknowns" and "unknown unknowns". For the known unknowns, some VOCs are thought to be produced by marine biota or by photochemistry in seawater, but their oceanic emissions are poorly quantified. For the unknown unknowns, there are VOC fluxes or production pathways that we currently have little clue about, including light- or ozone-driven production from the sea surface. The sources and cycling of SOA over the background ocean are also poorly understood. While sea spray tends to dominate marine aerosol mass, SOA can be an important source of submicron particles and affect the abundance of CCN and so cloud droplets. In this project, we will combine a) intensive and comprehensive field measurements using novel instrumentation, b) innovative laboratory studies of physicochemical/biological processes, and c) state-of-the- art modeling on multiple scales to paint an unprecedented, holistic picture of reactive carbon and OH cycling in the background marine atmosphere. Constrained by atmospheric observations of total OH reactivity and total organic carbon mass, we will substantially improve flux estimates of established VOCs, identify new VOC emission sources, and evaluate their atmospheric impact. The fundamental questions we will address are: 1) Which VOCs exchange between the ocean and the atmosphere and what are their fluxes? 2) What are the physicochemical/biological processes that determine these fluxes? 3) What are the impacts of these marine VOCs on oxidative capacity, aerosol, clouds, and climate? COCO-VOC will achieve a step-change in understanding of VOC and OH cycling in the background environment, thereby constraining the sensitivities of VOCs, aerosol, and the global atmospheric oxidative capacity to changes in anthropogenic and natural emissions. This work will enable more accurate predictions of chemistry and climate in the past, present, and future. The new understanding will also offer insight into potential natural climate feedback processes caused by climate- driven changes in ocean-atmosphere VOC fluxes.

This research proposal links to the International Ocean Discovery Program (IODP) Expedition 396 which will drill several scientific research boreholes along the offshore Norwegian continental margin. The Norwegian margin is one of the best studied examples of a passive rifted margin associated with voluminous magmatic activity. However, key scientific questions associated with the origins of magmatism and its impacts on global climate at this time remain. The objectives of the cruise cover a wide range of high impact scientific research areas including assessing the role of the Iceland plume on excess magmatism, understanding along axis variations in magmatism, determining the nature and depositional environment of volcanism, and assessing the role that magmatism played in driving global warming (Paleocene Eocene Thermal Maximum or PETM) at this time. A secondary goal of the expedition is to appraise the potential of permanent carbon capture and storage (CCS) in the volcanic sequences. This research project will address several of the EXP 396 objectives focusing on three specific areas of research. Objective 1: Understanding the interplay between magmatism and eruption environments during rifting. Volcanic cores will be used to appraise how volcanism and the environment of eruption changed in space and time during continental rifting. Detailed facies analyses of the volcanic sequences will be undertaken to reveal whether the eruptions occurred within subaerial, marginal, or subaqueous environments. Geophysical logging data will be used alongside core observations to build a comprehensive and integrated volcanological model for the borehole penetrated sequences. The geophysical volcanic model will then be used to calibrate extensive 3D seismic surveys in the area which in turn will enable mapping of volcanic facies over large parts of the margin. This aspect of the project will enable new understanding about how extrusive magmatism is linked to margin scale base-level changes which in turn will give new data for testing competing models for volcanic rifted margin evolution such as plume-pulsing versus plate tectonics. Objective 2: Appraising the carbon capture and storage (CCS) potential of break-up related volcanic sequences. Pilot studies on Iceland (Carbfix) and in Washington State, USA (Wallula), have demonstrated that CO2 reacts with basaltic rocks to form carbonate minerals, effectively permanently storing the CO2. Permanent storage clearly reduces the risk of leakage and has been demonstrated to occur over incredibly rapid timescales on the order of a few years. The huge volume of offshore break-up related volcanic sequences that will be tested during EXP. 396 could offer an alternative storage site for permanent storage of anthropogenic CO2. Volcanic sequences can have good reservoir properties, however, extensive weathering and alteration can also significantly diminish and clog up the pore structure. Within this study petrophysical analyses of volcanic cores will be performed to give important new constraints on the reservoir potential and sealing capacity of the Atlantic margin volcanic sequences. Objective 3: Understanding the temporal and spatial evolution of magma petrogenesis within the province and its potential role in driving the PETM. Geochemical analyses from the various volcanic sequences will be used to appraise whether elevated and/or fluctuating mantle temperatures led to excess magmatism in mid-Norway. Regional datasets will be compared to appraise how melting changed along the margin and whether these results resolve competing plume or plate tectonic models. Some sites will target hydrothermal vents associated with break-up related intrusions which caused massive emissions of Greenhouse gases. High resolution core-log-seismic appraisal coupled with isotopic dating of the ejecta layers will hopefully improve the age constraints on these processes in order to better appraise links to the PETM.

Plankton are organisms that in essence drift in the oceans. They range from microbial organisms to jelly fish and krill. Plankton have played a key role in planetary ecosphere functioning (having produced half of the atmospheric oxygen that we breath, and also most of the limestone and much of the non-coal fossil fuels). They continue to play an important role in climate change events, food sustainability (fisheries), down to local societal levels in harmful algal blooms and sea-snot (beach foam) events. This project will provide the foundation for pivotal developments in marine science, namely configuring plankton for the digital twins of the oceans. Digital twins (DTs) are computer-based analogues for real systems; well-known examples are flight simulators and many reality-based video game platforms. DTs are heavily used in engineering and in business, providing design and testing platforms. They are especially useful for 'what-if?' testing. However, it is critical that the end user has trust that the platform they are using does indeed describe a digital twin that would be deemed satisfactory to experts in the real system. This work comprises essential underpinning for the UK and international initiatives to produce within this decade digital twins of oceanic processes of societal importance, including the United Nations Digital Twins of the Oceans (DITTO) initiative. The idea behind DITTO, for example, is to see the generation of DT platforms, freely available to the public with a suitable graphic-user-interface, to support education, management and decision making. Some of these may be within game-like platforms to engage and inform the public about plankton (why their local beach is out-of-bounds due to harmful algal bloom or jelly-fish, for example), while other platforms will support science policy and management. Despite the critical importance of plankton in marine ecology, the current generation of computer descriptions ('models') provides only a poor caricature of the real organisms that is quite unsuitable for digital twin applications. The reasons for this include a lack of suitable data to directly support modelling, and a hitherto poor interaction between modelers and those empiricists who study real plankton. The project will work by exploiting 'expert witness validation', an approach similar to that of the famous Turing test for artificial intelligence, which aims to produce models that are sufficiently realistic in their behaviour that experts in the subject (plankton) cannot tell the difference. The project will work with experts in each plankton group to reach a consensus on what computer models of different plankton types should behave like such that they could be considered as a 'digital twin'. The one-year project will see the production of reference-type materials (such as check-lists, and example response patterns) to guide future development of plankton models, specifically for digital twin applications to ensure that the description of these organisms accords with the expectations of experts in the field.

The balance between the production of organic carbon during phytoplankton photosynthesis and its consumption by bacterial, zooplankton and phytoplankton respiration determines how much carbon can be stored in the ocean and how much remains in the atmosphere as carbon dioxide. The amount of organic carbon stored in the ocean is as large as the amount of carbon dioxide in the atmosphere, and so is a key component in two global carbon cycle calculations needed to avoid a global temperature rise of more than 1.5 degrees C: the calculation of the technological and societal efforts required to achieve net zero carbon emissions and the calculation of the efficiency of ocean-based engineering approaches to directly remove carbon dioxide from the atmosphere. Yet, despite its vital role, our ability to predict how ocean carbon storage will change in the future is severely limited by our lack of understanding of how plankton respiration varies in time and space, how it is apportioned between bacteria and zooplankton and how sensitive it is to climate change-induced shifts in environmental conditions such as increasing temperature and decreasing oxygen. This woeful situation is due to the significant challenge of measuring respiration in the deep-sea and the uncoordinated way in which these respiration data are archived. This project will directly address these two problems. We will take advantage of our leadership and participation in an international programme which deploys thousands of oceanic floats measuring temperature, oxygen and organic carbon in the global ocean, in an international team of experts focused on quantifying deep-sea microbial respiration, and our experience of collating international datasets, to produce an unprecedented dataset of bacterial and zooplankton respiration. We will derive estimates of respiration based on data from floats, so that together with estimates derived from recently developed methods including underwater gliders, the new database will include respiration measurements calculated over a range of time and space scales. Crucially, respiration rates will be coupled with concurrent environmental data such as temperature, oxygen and organic carbon. This dataset will enable us to quantify the seasonal and spatial variability of respiration and derive equations describing how respiration changes with the proportion of bacteria and zooplankton present and with the chemical and physical properties of the water. These equations can then be used in climate models to better predict how respiration and therefore ocean carbon storage will change in the future with climate-change induced shifts in temperature, oxygen, organic carbon and plankton community. We will take part in a hybrid hands-on and online international training course on observations and models of deep-water respiration targeted to early career researchers from developing and developed countries to showcase the useability of the respiration database and the global array of oceanic floats. We will also prepare Science Festival exhibits on observing life in the deep ocean for schoolchildren. The deliverables of the project - a unique global open-access database of respiration measurements, new equations describing the sensitivity of respiration to changing temperature and oxygen suitable for climate models and online training materials for early career researchers - are of benefit to scientists who aim to predict how a changing climate will affect the storage of carbon in the ocean, educators who train the next generation of ocean scientists and practitioners, policy makers who need to quantify nationally determined contributions to actions limiting global warming, and scientists, engineers, lawyers, governing bodies and commercial companies designing, evaluating and implementing ocean-based carbon dioxide removal technologies.