Ocean biogeochemical cycles and ecosystems are an important part of the 'Earth system' - the set of interlinked physical, chemical and biological processes, which shape the environment at the Earth's surface. These biogeochemical cycles are not only important for the oceans themselves (their composition and the kinds of creatures that live in them) but also for the climate of the planet, through their fundamental influence on the composition of the atmosphere (in particular, 'greenhouse' gases such as carbon dioxide, and other climatically important gases such as di-methyl sulphide). Historically, global ocean biogeochemical models have used simple representations of biological processes that are constrained tightly by the physical and chemical environment, using assumptions such as single-nutrient limitation and constant Redfield ratios - utilization and release of elements in constant proportions. As our knowledge has grown, the shortcomings of this approach have become increasingly apparent, giving rise to progressively more elaborate models of the ecosystem - from models that include a single explicitly modelled plant (phyto-) and animal (zoo-) plankton to increasingly, a variety of different functional types of plankton that mediate different geochemical transformations. While these more complex models have the potential to reproduce more faithfully ocean biogeochemistry and how it will respond to changes in climate and ocean circulation, the increased complexity brings with it the penalty that many more parameters must be known in order to specify the system. It is not necessarily clear how to validate such models - that is, to tell how well they are working - or what is the optimum complexity of model required to address a given problem. We are proposing a consortium of several groups involved in biogeochemical modelling in the UK. Currently, the groups work separately, each on models occupying a different place on the spectrum of complexity sketched above. In MARQUEST they will co-operate, comparing the predictions of their models and analyzing the causes of their differences and similarities. We will also examine more fundamental modelling approaches to the planktonic ecosystem, with the aim of clarifying what we can expect from the current types of model. New research outputs from MARQUEST will include: the development of new methods of validating models, making use of remote sensing ocean colour data, in-situ data sets and the observations ongoing in major European programmes such as Carbo-Ocean and Euroceans: comparison of different ecosystem models run in the same circulation codes: development of a module to simulate the coastal ecosystems, but useable in global ocean biogeochemical simulations, and an accurate physical simulation of the North Atlantic guided by data assimilation into which ecosystem simulations can be embedded. This will enable detailed comparison of ecosystem models with observations over recent decades, including a hindcast of the variation in air-sea fluxes of gases - of great use for helping to constrain both land and ocean components of the sink for anthropogenic carbon dioxide. We will also make best estimates of the evolution of the CO2, oxygen and di-methylsuiphide fluxes from ocean to atmosphere over the next 50 and 100 years.

Submarine turbidity currents are arguably the volumetrically most important process for moving sediment across our planet. They form the largest sediment accumulations (submarine fans) on earth, and single flows can transport ten times the annual flux from all of the world's rivers. However, the most remarkable feature of turbidity currents is how few direct measurements are available from these flows, as they are notoriously difficult to monitor in action. This is a stark contrast to other major sediment transport processes, such as rivers for which we have many thousands of direct measurements. Powerful long run-out turbidity currents are especially difficult to monitor, yet it is these flows that build submarine fans. Such flows are important because they break sea-floor cables that carry > 95% of global data traffic, including internet and financial markets that underpin daily lives. The velocity of turbidity currents that reach beyond the continental slope had previously been measured in just five locations, primarily from cable breaks that only record averaged front velocities. Their sediment concentration had never been measured directly. This globally important sediment transport process is therefore poorly understood, and laboratory or numerical models for such flows are poorly validated. This PhD student will analyse a remarkable dataset comprising the first synchronous velocity and concentration profiles for turbidity currents beyond the continental slope, collected at a cost of > $1M by CASE partner Chevron and co-workers in the Congo Canyon (from 2009-2013). This is the first time that high temporal resolution (>1/min) synchronous profiles of both velocity and concentration have been measured for turbidity currents beyond the continental slope. They are also the fastest (2.5 m/s) turbidity currents yet measured by instruments. The data were collected for a major oil and gas pipeline that will need to cross the Congo Canyon. This is a challenging project as previous cable breaks show the canyon is regularly swept by powerful flows. The data comes from moorings with downward pointing Acoustic Doppler Velocity Profilers (ADCPs) that measure velocity and acoustic backscatter. Backscatter is partly dependent on grain size, but also records changes in sediment concentration. Initial results were surprising for two reasons. First, flows had surprising durations of several days, with average speeds of ~1 m/s. Interestingly, it was observed that the larger flows always had a similar duration of ~6 days. This seems to indicate the establishment of an equilibrium flow configuration over the first 150 km of the canyon. Several hypothesis have been put forward to explain this behaviour, however, none of them have yet been validated. Second, the measured turbulence intensity decreased as flow speeds increased, this counter-intuitive relation suggests damping of turbulence by elevated suspended sediment concentrations. Although it has been speculated previously that turbulence damping by sediment may be of fundamental importance, such damping has never previously been documented in direct observations from full scale flows in the field. Thus, the relation between turbulence damping and sediment concentration remains to be validated in real submarine flows. A numerical model is needed to test hypotheses that equilibrium flow configurations produce multi-day flows, and to explore how turbulence dampening may affect submarine flows. Such numerical model will benefit from the well-mapped bathymetry of the Congo canyon (from Chevron and past publications by IFREMER). In this proposal we will use a state-ofthe-art fully three-dimensional numerical model that has been developed over the last eight years by project partner Complex Flow Design AS (CFD), Norway. This model is unique due to its 3D approach and its capability to introduce sediment concentration effects into its turbulence model.

Plankton in the ocean, microscopic plants (phytoplankton) and tiny animals (zooplankton) that eat the plants, are vital to marine life and to Earth's climate. They form the base of food chains that support ocean ecosystems, and remove carbon from the atmosphere and bury it in (or export it to) the ocean depths. It is currently thought that plankton are responsible for removing 6 billion tonnes of carbon from the atmosphere each year; fossil fuel burning releases about 10 billion tonnes of carbon into the atmosphere annually. Without this export of carbon in the ocean, atmospheric CO2 would be twice the current concentration. The importance of plankton to food chains and carbon export depends on the species of plankton. Larger phytoplankton are better at supporting food chains and at exporting carbon because (1) larger phytoplankton sink quicker, removing carbon away from the sea surface and contact with the atmosphere, and (2) larger phytoplankton support larger zooplankton, which are eaten by fish and which also excrete large, fast-sinking faecal pellets which quickly transfer carbon away from the atmosphere. We have discovered a new link between which types of plankton can grow and the tides flowing over a mid-ocean ridge. The ocean is layered, with warmer, less dense layers at the surface and colder, denser layers deeper in the ocean. When tidal currents flow up and down the flanks of a mid-ocean ridge, these layers are pushed up and down, causing waves on the layers called "internal tidal waves". These internal tidal waves reach up to the sun-lit upper ocean, where photosynthesis by the phytoplankton takes place. We think these waves have two important effects. (1) The waves cause mixing between the layers of ocean, bringing nutrients from deep in the ocean up to the phytoplankton; this will help extra phytoplankton growth, but crucially it is also known that extra nutrient supplies allow larger species of phytoplankton to grow. (2) The waves move the phytoplankton up and down; this provides more light to the phytoplankton, because as they are moved upward they get closer to the light at the sea surface and are able to grow more. Thus, we think that the internal tidal waves create more growth of larger plankton over a mid-ocean ridge, which means better food for marine food chains and more carbon exported away from the atmosphere. This new link may explain why ridges support such diverse ecosystems, and it also means that the ocean over ridges is far better at exporting carbon than we previously thought. We have calculated that, for the whole Atlantic Ocean, including the tidal effect of the mid-Atlantic ridge adds about 50% to current estimates of how much carbon the plankton export. This means that current understanding of the ocean's role in Earth's climate, which ignores the ridge-tide effect, significantly underestimates how much CO2 plankton remove from the atmosphere. We need to fix this because our predictions of our future climate depend on having correct descriptions of the processes that govern atmospheric CO2. We will conduct an expedition to the mid-ocean ridge in the S. Atlantic. We will measure the internal tidal waves and the upward mixing of nutrients, and the effect the waves have on light received by phytoplankton. We will measure how fast the phytoplankton and zooplankton grow in response to these waves, how the species of plankton change over the ridge, and how much carbon is exported downward over the ridge compared to the adjacent ocean basin. This will be the first time that internal tidal waves are linked to patterns of carbon export in the ocean: internal tidal waves occur wherever there are ridges or seamounts in the ocean and our results will have important global implications for our understanding of ocean food webs and Earth's climate.

Doctoral Training Partnerships: a range of postgraduate training is funded by the Research Councils. For information on current funding routes, see the common terminology at https://www.ukri.org/apply-for-funding/how-we-fund-studentships/. Training grants may be to one organisation or to a consortia of research organisations. This portal will show the lead organisation only.

Prediction of changing coastal morphology over timescales of decades raises scientific challenges to which there are not yet widely applicable solutions. Yet improved predictions are essential in order to quantify the risk of coastal erosion, which is significant in its own right and also one of the main mediators of coastal flood risk. Whilst 'bottom-up' process-based models provide valuable evidence about hydrodynamic, sediment transport and morphodynamic processes in the short term, their predictive accuracy over scales of decades is for the time being fundamentally limited. Meanwhile, behavioural systems models, that focus on the main processes and feedback mechanisms that regulate coastal form have been shown to have predictive capability at the mesoscale (10-100 years and 10-100 km). However, their application has been limited to a rather narrow sub-set of coastal forms. The iCoast project is based upon a hierarchical systems concept which combines (i) the beneficial features of process-based models, (ii) a new generation of coastal behavioural systems models, and (iii) an extended approach to coastal systems mapping, which can be used to systematise and formalise different sources of knowledge about coastal behaviour. All the software developed within iCoast will be open source and OpenMI compliant. The research is focussed upon four deliverables that have been identified as major challenges in the NERC Natural Hazards Theme: Deliverable 1 will be an overall systems framework. The successful approach to coastal systems mapping developed by French et al. will be extended and applied to all of the England and Wales, making use of a new systems mapping tool. These new coastal systems maps can both supersede the coastal cells and sub-cells currently used in shoreline management planning and provide an evidence-based framework for more quantitative modelling. Therein, hydrodynamic and sediment transport coastal area models will be implemented at a broad spatial scale in order to provide evidence of wave and tidal forcings and sediment pathways. The systems framework will be implemented in open source software tools and coupled with methods for uncertainty analysis. Deliverable 2 will provide a new generation of behavioural geomorphic modules, which can be linked to enable simulation of coupled coastal-estuary-offshore landform behaviour at a meso-scale. Existing reduced complexity behavioural modules, several of which are held in-house within the iCoast consortium (SCAPE, ASMITA, various versions of 1-line beach models) will be reviewed and development and incremental improvement opportunities will be identified. They will be researched intensively by a team with unique experience of this type of model development. The scope of data-based modules that can exploit the growing datasets from coastal observatories will also be extended. The models will be integrated within a systems framework in order to study emergent properties and explore key sensitivities. Deliverable 3 will entail application and validation of two distinct coastal regions: the Suffolk Coast (Sub-Cell 3c) and Liverpool Bay (Sub-Cells 11a/11b), exploring the sensitivities of these coastal regions to changes in sediment supply resulting from sea-level rise, climate change and coastal management scenarios. This will yield the results needed for high impact publication and the demonstrations that are essential to build confidence in new approaches being transferred into practice. Deliverable 4 will facilitate knowledge transfer of the new methods through a range of dissemination mechanisms, including tutorials, manuals and knowledge transfer workshops. Our open source modelling strategy will initiate a community modelling approach in the coastal research community, at the same time as maximising access by practitioners to the knowledge generated at a time when requirements for coastal adaptation urgently require new predictive capability.