We recently discovered the world's largest tropical peatland complex, spanning an area larger than England, in the heart of Africa. This proposal brings together an interdisciplinary team of scientists to study this newly discovered ecosystem. Our goal is to understand how the peatland became established, how it functions today, and how it will respond to human-induced climate change and differing future development pathways. We will use the results to inform critical policy decisions about the region. Peat is partially decomposed plant matter. Peatlands are some of the most carbon-dense ecosystems on Earth. Covering 3% of Earth's land surface, they store one-third of soil carbon. A recent NERC-funded PhD, led by CongoPeat PI Professor Lewis, showed for the first time that the largest wetland in Africa, in the central Congo Basin, contains extensive peat deposits. This research, published in 2017 in Nature, estimates that the peatland stores 30 billion tonnes of carbon (C). By comparison, in 2016, UK emissions were 0.1 billion tonnes of C. Our discovery increases global tropical peatland C stocks by 36%. We know very little about this new globally important ecosystem. Our data show peat accumulation began about 10,600 years ago, when central Africa's climate became wetter. Accumulation has been slow - on average just 2 m has accumulated over this period - but it is unknown whether this is due to a constant slow build-up of peat and C, or fast rates interspersed with losses in drier periods. Our evidence suggests that the peatlands are fed by rainfall, but such peatlands usually form domes ('raised bogs'), yet satellite data do not show this feature. Thus, we do not know how this peatland system developed, how it functions today, or how vulnerable it is to future climate and land use changes. Tropical peatlands in SE Asia have been extensively damaged by drainage for industrial agriculture, particularly oil palm, with serious biodiversity, climate and human health implications. Oil palm is now rapidly expanding across Africa. Congolese peatlands could become a globally significant source of atmospheric CO2 if they are drained, leading to their decay. A prerequisite of following a different development pathway is a scientific understanding of the region. The CongoPeat proposal therefore brings together leading experts from six UK universities, a science-policy communication specialist, and five Congolese partner organisations, to gain: 1. An integrated understanding of the origin and development of the central Congo peatland complex over the last 10,000 years. We will analyse peat deposit sequences from across the region, extracting preserved pollen grains, charcoal, and chemical markers, to reconstruct the changing environment through time. We will use an unmanned aerial vehicle to map peatland surface topography, and develop a mathematical model of peatland development. 2. A better estimate of the amount of C stored in the peat, its distribution, and the amounts of important greenhouse gases, CO2, methane, and nitrous oxide, being exchanged with the atmosphere. This will be achieved via extensive fieldwork to map peat distribution, and by installing intensive measurement stations to determine the flows of C into and out of the ecosystem. 3. An understanding of the possible future scenarios for the Congo peatlands. A range of models will be used to simulate the possible impacts of future climate and land-use change on the peatland, at local to global scales. Finally, we will effectively communicate these results to policy-makers in Africa and internationally via briefings and active media engagement. The CongoPeat team will produce the first comprehensive assessment of the genesis, development, and future of the world's largest tropical peatland, enabling the UK to retain world-leading expertise in understanding how the Earth functions as an integrated system and how humans are changing it.

During recent decades and centuries, pools and fluxes of C, N and P in UK ecosystems have been transformed by the spread and fertiliser-based intensification of agriculture, by atmospheric pollution, and now by fossil-fuel induced climate change. We need to understand the processes that determine these effects, in order to improve the sustainability of agriculture, preserve carbon stocks, control the eutrophication of terrestrial and freshwater ecosystems, and reduce nutrient delivery to the sea and greenhouse gas emissions. Contemporary pools of C, N and P in soils and sediments reflect processes occurring on a range of timescales (up to 1000 years or more for organic matter turnover in soils) and also over a range of spatial scales. We propose research to address long-term, large scale processing of C, N and P in the environment. The principal objective is to account for observable terrestrial and aquatic pools, concentrations and fluxes of C, N and P on the basis of past inputs, biotic and abiotic interactions, and transport processes, in order to address the following scientific questions; 1. Over the last 200 years, what have been the temporal responses of soil C, N and P pools in different UK catchments to nutrient enrichment? 2. What have been the consequent effects on C, N and P transfers from land to the atmosphere, freshwaters and estuaries? 3. How have terrestrial and freshwater biodiversity responded to increases in ecosystem productivity engendered by nutrient enrichment at different locations? We aim at an integrated quantitative description of the interlinked land and water pools and annual fluxes of C, N and P for the UK over time. Central to the project is the application, development and parameterisation of mechanistically-based models applicable over long timescales and at a broad spatial scale. The models will be designed to exploit the large number of existing biogeochemical data for the UK, with new targeted measurements to fill important gaps. A key ingredient is radiocarbon data for natural organic matter in soils and waters, which provide a unique means of estimating longer-term turnover rates of organic matter. The project is organised into seven workpackages, as follows. WP1 Data. This involves the collation and management of monitoring and survey data and literature searches. Data will be required for driving and parameterising models. WP2 New measurements. Gap-filling information will be obtained about C & N releases from fuels, soil concentrations of C, N, P, and radiocarbon, vegetation contents of C, N and P, a major effort on soil denitrification, riverine organic matter including radiocarbon contents. WP3 Atmospheric model. This will use a variety of data, and atmospheric physics, to describe N deposition at 5 km2 resolution for the UK from 1800 to the present, and take into account emissions from industry and agriculture. WP4 Terrestrial models. Models will be developed and parameterised to describe (a) biogeochemical cycling of C, N and P in natural and agricultural soils, simulating losses by gaseous evasion and solute leaching, and (b) physical erosion. WP5 Aquatic models. These will describe sediment transport of organic matter (including C, N and P), lake processing, denitrification, and groundwater transport. Point source inputs will be quantified. WP6 Integrated Model. The IM will bring together the models from WP3-5 within a grid-based hydrological system, applicable to the whole of the UK. Through the IM we will answer Questions 1 and 2, producing temporal and spatial terrestrial and aquatic outputs for representative catchments. The IM will include estimates of uncertainty and be applicable for future scenario analysis. WP7 Biodiversity. Model output from WP3-6 will be used to analyse terrestrial plant diversity and diatom diversity in lake sediments, thereby addressing Question 3.

Over 100 million people drink groundwaters containing naturally occurring arsenic (As) higher than the WHO guide value (10 ppb). In Bangladesh alone, 20% of all deaths in impacted areas are attributable to such exposure (ARGOS, 2010) - this corresponds to about 30,000 premature deaths every year. Studies provide evidence for both in-aquifer and near-surface sediment As sources. ISLAM (2004) demonstrated that As release occurs from within the aquifer sediments & highlighted the importance of organic matter (OM) in this process. BENNER (2008) & POLIZZOTTO (2008) have suggested, instead, that As release mostly occur in near-surface sediments BEFORE entering the aquifer. Determining the relative importance and controls of As release from the near surface sediments (typically 5 m - 15 m depth) from that which occurs within the aquifer, as well as assessing the various controls on As once in solution, are critical if we are to develop the required process oriented understanding of As mobility in drinking water supplies. Identifying study areas that reveal these processes is hard. For example, massive groundwater abstraction in the densely populated areas of West Bengal and Bangladesh has resulted in a complex subsurface hydrological environment which makes tracking As release mechanisms almost impossible. However, the absence of such extensive abstraction in As-rich aquifers of Cambodia means that this subsurface hydrological environment remains largely unaltered. Recent work by project partners (Stanford) means that a representative high As area has been identified and the hydrogeology established - but not on a scale or with the geochemical techniques required to establish a full understanding. We will drill 77 new and relatively inexpensive boreholes at the Cambodian site after using geophysics (supplied by our BGS partner) to determine the best locations. These new wells will allow us to collect samples across established As hotspots at a scale over which the As release process must be operating. Three well nests will sample an oxbow lake overlying an As contaminated aquifer, a sand 'window' through the overlying clay sediments and a control through the clay sediment overlying the As contaminated main aquifer. Two further well sequences will allow sampling of the main aquifer along its flow path. A 5-20m tube-well separation represents ~5-250 years of aquifer chemical evolution. Our Cambodian partners at RUPP & RDI will give local logistic support. We have been working closely our NERC Radiocarbon Lab partner. We show within our proposal that 14-C dating of organic matter in sediments and of dissolved inorganic and organic carbon in groundwaters provides a profound technique for identifying organic matter sources, central to resolving As release mechanisms. Similarly, pilot work withour NERC stable isotope facility partner has shown the utility of applying delta-18O and delta-D data to quantify surface water input into the main aquifer. Both of these approaches, combined with Manchester anion, cation and inorganic assay of sediments as well as tritium and 4-He techniques to date any young water input or ancient fluid contribution, will provide a fully comprehensive geochemical approach. With the high spatial resolution of sampling we expect this approach to make a major contribution in: i) quantifying the flux of As on a spatial scale alongside secular changes in As hazard from these two potential As sources; ii) identifying the dominant source of OM responsible for driving As release from these locations; and iii) identifying the controlling processes and mechanisms responsible for As release in these profiles. Together this understanding will enable the development of a quantitative model with predictive capacity that will inform governmental agencies responsible for drinking water and irrigation supplies to assess how continuation of, or changing, water use practice will impact future water supply As risks.

The Atlantic Ocean's conveyor belt circulation is a fundamental component of the global climate system, transporting heat from low to high latitudes, and thus warming Northern Europe. The strength of this circulation is thought to have varied abruptly in the past, giving rise to rapid climate changes of more than 10 degrees C in a decade during the last glacial period. Changes of this nature today would have a severe impact on society, so we want to know more about the sensitivity of this circulation. In order to do this, we will study intervals of rapid climate and circulation change in the past. To better understand these past circulation changes we will reconstruct the concentration of radiocarbon in surface and deep waters in the North Atlantic Ocean. This is known as a radiocarbon reservoir age, and it is highly sensitive to the rate of ocean circulation. Therefore, by reconstructing reservoir ages, we can tell how quickly the ocean was circulating during intervals of rapid climate change. We also need to know what the reservoir age was in the past if we want to use radiocarbon as a dating tool, to tell the age of geological and archeological objects and events. Radiocarbon can be thought of as a stopwatch for a geological sample. For a marine sample, however, there is already some time on the clock when we press go. This extra time before starting the clock is the reservoir age, and we must know what it is in order to accurately tell geological time. By reconstructing reservoir ages, we will therefore improve understanding of rapid circulation and climate change, and also improve the most important dating tool used in earth and archeological sciences. To reconstruct radiocarbon reservoir ages we need to measure the radiocarbon content of a sample, and also to know its age independently, so we can work out what was already on the clock when the sample formed. To do this we will make radiocarbon measurements on shells taken from sediment cores from the North Atlantic, and pair them with a range of exciting new techniques that can tell their age. Firstly we will look for layers of volcanic ash in the sediment cores, which we can date using their argon content, and match to precisely dated ash layers in ice cores and on Iceland. Secondly we can look at changes in sea surface temperature records, and match these to the same events that are precisely dated in ice cores. Thirdly we will use the concentration of thorium in sediments to tell how much sediment accumulated between these ash and temperature tie points. Fourthly, we will combine all this information using statistical modelling, which will also provide a good measure of the uncertainty in our results. This work will create maps of reservoir ages and how they changed in the North Atlantic over the last 10 to 50 thousand years, with a special focus on times of rapid climate change. To help us link the reservoir ages to different circulation regimes, we will use a climate model that can simulate radiocarbon. We will make this model's ocean circulation operate in different ways, and see which circulations best match our data. This will allow us to better understand how ocean circulation changed in the past to cause rapid climate change, and improve confidence in how ocean circulation may operate in the future. Finally, we will package our reservoir age maps into a tool that can be used by earth scientists and archeologists to improve their radiocarbon dating.

Public summary Climate changes have been attributed to the increasing concentrations of greenhouse gases (e.g. CO2) in our atmosphere. These measured increases in atmospheric CO2 are partly controlled by changes in the ability of the world's oceans to absorb CO2 at the surface (e.g. via diffusion and the biological pump) versus release of old carbon to the atmosphere from deep ocean reservoirs (e.g. via upwelling and out gassing). Of the world's oceans, the Southern Ocean has been identified (by models) as playing a major role in modulating global atmospheric CO2, particularly on glacial-interglacial timescales. This is because surface nutrients are high indicating their incomplete utilisation by the biological pump, and because wind driven changes in ocean circulation can bring old carbon stored in deep ocean reservoirs to the surface. Changes in the strength of the Southern Hemisphere Westerly Winds (SHW) influence Southern Ocean circulation and control how much of this carbon rich deep water reaches the ocean surface. Thus any change in the strength or position of the SHW such as the recently observed intensification of the winds, could influence whether the Southern Ocean acts as a net source or sink of atmospheric CO2. At present our understanding of past changes in the SHW is based mainly on geological proxy records from South America, one record from South Africa, and two from New Zealand. With the exception of Campbell Island there are no studies of changes in the SHW in the Southern Ocean where the core of the SHW wind belt is located. This lack of spatial resolution has been identified by Stager et al. (2012) as a major limitation in our understanding of past climate. As a result, although present General Circulation Models use a variety of processes (biology, ocean chemistry, and ocean physics), they either fail to produce the magnitude of past atmospheric CO2 variations or do not agree with geologic field data. Here we propose to substantially improve the spatial resolution of the geological data by generating proxy records in each of the three major sectors of the Southern Ocean, focusing on sub-Antarctic islands situated in the core belt of the SHW. We apply a novel diatom proxy for past wind strength independently controlled by a range of standard sedimentological and biogeochemical proxies. The new proxy is based on the direct transfer of sea spray across the islands by wind, and its effect on the salinity of west coast lakes and ponds. This works on sub-Antarctic islands where there is a marked west-east conductivity gradient in water bodies across the island. This conductivity gradient determines which diatom communities are present in the lakes. Once this diatom- conductivity relationship is established quantitatively, the subfossil diatom communities deposited in radiocarbon dated sediment cores can be used to reconstruct changes in conductivity through time, and hence past relative wind strength. We have demonstrated that this approach works at Macquarie Island and we have also tested its feasibility at Marion and Campbell Islands. This proposal is for funding to support further work on Campbell and Marion Islands, and in the Cape Horn archipelago. To interpret our data we will carry out a series of General Circulation Model runs to explore the long term changes in SHW strength and the processes driving them, by taking advantage of the new Paleoclimate Modelling Intercomparison Project 3 (PMIP3) AOGCM (climate model) simulations. These experiments will allow comprehensive model-observation evaluation of the new proxy wind strength reconstructions. Ultimately this work will help provide improved boundary conditions for models which simulate the impact of past changes in wind strength on the upwelling of deep ocean carbon reservoirs, and improve our understanding of the relationship between past changes in global atmospheric CO2 and temperature.