Supervisors: Dr Craig Smeaton, Dr William McCarthy 

Globally, there is recognition by landowners that understanding the quantity of organic carbon (OC) in their soils is crucial to the management of their lands both today and in the future. Currently, the accurate estimation of the quantity of soil organic carbon (SOC) requires highly specialised equipment and expertise, hindering the wide scale measurement of SOC across land-use sectors (agriculture, leisure, sport, etc.).

Recent developments of hand held Near Infrared Spectrometry (NIR) and Uncrewed Aerial Vehicles (UAV) with multispectral cameras has opened new opportunities to quantify SOC at a range of scales.  This field deployable technology project data in real time to tablets or mobile phones to generate high quality visual data sets at relatively low cost (~£5000-15,000). Modern NIR platforms can be harnessed to facilitate cost efficient measurement of SOC both in-situ and in the laboratory by non-specialists to a high degree of accuracy. UAVs have the ability to survey large areas using photogrammetry and with the addition multi-spectral cameras have been shown to be able to measure plant health and soil properties including OC. 

For the accurate estimation of OC, the spectra produced by NIR and multispectral cameras must be calibrated using bespoke calibrations. Currently, these calibrations are lacking for many environments.

The MSc (Res) will seek to develop new SOC calibrations for both NIR and multispectral data for golf course soils to allow quantification of SOC by non-specialists. The project will develop the NIR calibrations using 3 - 5 golf course with differing characteristics. This will be achieved through the comparison of OC content from different soil samples measured using advanced analytical methods (elemental analysis) and NIR spectra from in-situ and laboratory measurements produced by a handheld spectrometer (NIRvascan or Neospectra). The calibration developed from this analysis will be integrated into an easy-to-use open software package for non-specialist to quantify SOC at their course. At each site a UAV survey will be carried out to produce a multi-spectral map of each course to test the possibility of linking UAV produced spectra to in-situ measurements using the handheld NIR with a view to providing SOC estimates from across large parcels of land on a scale of 0.2 - 10km²

Objectives

1. Develop a new NIR to OC calibration for golf course soils.
2. Test the quality of low-cost handheld NIR spectrometers.
3. Investigate the possibility of linking multispectral data produced by a UAV to insitu NIR measurements.
4. Develop of standardised methodology to calculate SOC stock by non-specialists. Communicate and demonstrate the newly developed approach to the measurement of SOC to end-users.

This is a funded project

For the period spent at the University of St Andrews, the scholarship will comprise a full fees award (£6,711). The project is funded by the Royal and Ancient Foundation.

Informal enquiries to Dr Craig Smeaton – cs244@st-andrews.ac.uk and Dr William McCarthy – wm37@standrews.ac.uk.

Supervisors: Graeme MacGilchrist, Andrew Styles

The Southern Ocean is responsible for approximately half of the ocean’s uptake of carbon dioxide and 40-100% of the excess heat absorbed by the ocean. Despite the Southern Ocean’s importance in the climate system, significant uncertainties remain regarding the variability and drivers of its ventilation processes - the exchange of water between the surface and deeper layers. These processes regulate the uptake of heat and carbon dioxide by the ocean, thus influencing the limits and timescales of climate change1.

This project aims to investigate the interannual variability of ventilation in the Southern Ocean by deploying and analysing simulated ‘fluid parcel’ trajectories. These trajectories will reveal when and where volumes of water last interacted with the atmosphere, offering insights into the timescales and intensity of ventilation processes2,3. A recent study has shown that almost all ventilation in the Southern Ocean occurs between August and November2, but this project will explore whether certain years exhibit particularly intense ventilation events. Statistical analyses will also assess whether these years correspond to atmospheric or oceanic events, such as shifts in the Southern Annular Mode.

In collaboration with the British Antarctic Survey (BAS), the student will have the opportunity to gain expertise in model data analysis while regularly engaging with the diverse team of polar scientists at BAS. Throughout the project, the student will develop a familiarity with the Southern Ocean and contribute to a deeper understanding of its role in the climate system.

1. Localized subduction of anthropogenic carbon dioxide in the Southern Hemisphere oceans. https://doi.org/10.1038/ngeo1523

2. Spatial and temporal patterns of Southern Ocean Ventilation. https://doi.org/10.1029/2023GL106716

3. Demons in the North Atlantic: Variability of Deep Ocean Ventilation https://doi.org/10.1029/2020GL092340

Supervisors: Dr Nicola Allison and Prof Adrian Finch 

Calcareous organisms e.g. molluscs and foraminifera, produce calcium carbonate (CaCO3) shells which provide the organism with tissue support and/or protection from predators and the physical environment. These organisms are of significant ecological and/or economic importance. Rising atmospheric CO2 is altering the dissolved inorganic carbon (DIC) chemistry of seawater and decreasing seawater pH (ocean acidification). At the present day, surface and shallow seawaters are typically supersaturated with respect to the main CaCO3 minerals and dissolution of CaCO3 structures under these conditions is unlikely. However microbial respiration in the porewaters of coastal sediments produces additional CO2 which further reduces porewater pH and enhances CaCO3 dissolution (Lunstrum and Berelson, 2022). In this project, the student will investigate how ocean acidification is altering the porewater chemistry of UK coastal sediments and affecting the preservation of infaunal biological CaCO3 structures. The student will undertake field measurements of sediment porewater chemistry and measure shell dissolution. The student will join a NERC-funded team and will develop specific skills in tracking the dissolved inorganic carbon system in seawater as well as in scientific writing, data analysis, statistics, problem solving and presenting. 

References:  

Lunstrum A, Berelson W. CaCO3 dissolution in carbonate-poor shelf sands increases with ocean acidification and porewater residence time. Geochim. Cosmochim. Acta, 329:168-84, 2022. 

Supervisors: Dr Nicola Allison and Prof Adrian Finch, University of St Andrews 

Prof Jody Webster, University of Sydney 

 The aim of this project is to reconstruct climate variability in the Central Pacific by analysing Porites spp. fossil corals from the Hawaiian Islands. The aragonite skeletons of tropical coralsare invaluable archives of past climate information, recording information on the seawater composition, temperature and pH at the time of their deposition (Thompson, 2022). The student will analyse selected modern and fossil Hawaiian coral specimens for palaeoproxies to reconstruct past seawater temperatures and conditions. Selected specimens will be drilled at ~monthly resolution and analysed by ICP-MS or will be analysed by secondary ion mass spectrometry to allow selective analysis of the primary coral skeleton (Allison et al., 2005). The data will be used to infer climate utilising recent advances in the interpretation of palaeoproxies (e.g. Cole et al., 2021). The student will estimate seasonal sea surface temperature (SST) variations, glacial-interglacial temperature change and the amplitude and frequency of interdecadal climate events. Such high resolution palaeoproxy data are critical for understanding global palaeoclimate and in testing and validating global climate models for predicting 21st century climate change. 

References:  

Cole C, Finch AA, Hintz C, Hintz K, Yu Y, EIMF and Allison N, Massive Porites spp. corals exhibit reduced skeletal Sr/Ca temperature sensitivity at low seawater pCO2. Geochimica et Cosmochimica Acta, 314, 55-67, 2021. 

Thompson DM. Environmental records from coral skeletons: A decade of novel insights and innovation. Wiley Interdisciplinary Reviews: Climate Change.13(1):e745, 2022. 

Supervisors: Dr Andrea Burke, Dr Will Hutchison 

Sulfate aerosols from volcanic eruptions are the largest natural forcing of climate over the last several thousand years, and thus volcanic eruptions provide an opportunity to investigate the behaviour and sensitivity of the climate system to external forcing.  Sulfate layers in polar ice cores provide a high-resolution and continuous record of global volcanism through time (e.g. Sigl et al. 2015) and these sulfate layers can provide important insights into the frequency and climatic forcing of volcanic eruptions. However, a key requirement to accurately interpret these records is the ability to distinguish whether the sulfate came from the stratosphere (with associated greater climate forcing potential) or if the sulfate was from a local eruption proximal to the ice sheet. Multiple sulfur isotope analyses can be used to identify if the ice core sulfate was formed in the stratosphere, thus providing a means to improve volcanic forcing records (e.g. Burke et al., 2019;2023).  The aim of this project will be to measure sulfur isotopes on ice core samples by MC-ICP-MS to improve the volcanic forcing record of the 18^th century, and investigate the climatic response from these eruptions using compiled paleoclimate databases over this time period. 

Burke, Andrea, et al. "Stratospheric eruptions from tropical and extra-tropical volcanoes constrained using high-resolution sulfur isotopes in ice cores." Earth and planetary science letters 521 (2019): 113-119. 

Burke, Andrea, et al. "High sensitivity of summer temperatures to stratospheric sulfur loading from volcanoes in the Northern Hemisphere." Proceedings of the National Academy of Sciences 120.47 (2023): e2221810120. 

Sigl, Michael, et al. "Timing and climate forcing of volcanic eruptions for the past 2,500 years." Nature 523.7562 (2015): 543-549. 

Supervisors: Dr Hana Jurikova, Dr James W.B. Rae 

Throughout Earth’s history, CO₂ is thought to have exerted a fundamental control on climatic and environmental changes. On geological time-scales long-term CO₂ change is considered to have been mainly regulated by volcanic outgassing and the chemical weathering feedback, while short-term changes in atmospheric CO₂ have prominently occurred during mass extinction events linked to episodes of massive volcanism and/or extra-terrestrial phenomena. This view of the long and short-term key drivers of CO₂ change on Earth, however, fundamentally suffers from the lack of quality and high-resolution atmospheric CO₂ estimates, in particular in time intervals beyond the reach of the marine sediment record. 

Focusing on an interval of choice, the student will reconstruct atmospheric CO₂ levels from the rock record, alongside changes in seawater chemistry. Possible intervals include the early Palaeozoic biodiversification and end-Ordovician extinction, land colonisation of plants and end-Devonian mass extinction, the Late Palaeozoic Ice Age and Permian-Triassic mass extinction, Triassic greenhouse and end-Triassic mass extinction, Jurassic ocean anoxic events and biodiversity crises, or Cretaceous events and mass extinction. Long and short-term drivers of atmospheric CO₂ and global changes will be investigated, and the role of background CO₂ and climate state on inducing a mass extinction examined.  

To do this, the student will employ novel isotopic and elemental approaches to fossil remains of marine organisms preserved in the rock record. Boron isotopes will be used to reconstruct ocean pH and atmospheric CO₂ (Jurikova et al., 2020; Rae et al., 2021). This method has been successfully applied to constrain changes in CO₂ over the Cenozoic, but deep-time reconstructions remain sparse (Jurikova et al., 2020). The acquired data will be placed in context of previously published literature and ultimately synthesised with the aid of geochemical and climate models and numerical techniques.  

References:  

Jurikova et al. 2020, Nat. Geosci. 13, 745–750, https://doi.org/10.1038/s41561-020-00646-4 

Rae et al. 2021, Ann. Rev. Earth Planet Sci. 49, 599–631, https://doi.org/10.1146/annurev-earth-082420-063026 

Foster et al. 2017, Nat. Comm. 8, 14845, https://doi.org/10.1038/ncomms14845 

Supervisor: Prof Rob Wilson 

Over the last 20 years, substantial dendroclimatological work has focused on utilizing tree core samples taken from upper tree-line sites from Alberta, British Columbia, Yukon and across into Alaska to develop tree-ring based reconstructions of past summer temperatures across NW North America. We now have a comprehensive understanding of the dynamics of past summer temperatures for at least the last 1000 years for much of NW North America. It is well proven that recent climate change is now outside the range of natural climate variability based on the last 1000 years. What are the implications of this recent warming? 

In June 2021, southern British Columbia experienced extremely hot summer temperatures with the all-time high of 49.6 ^oC being recorded at Lytton. The following day, 90% of Lytton was destroyed by a wildfire. Although this tragedy is well documented, the impact of the extreme summer temperatures of 2021, embedded within a longer-term warming trend, on high elevation forest productivity and health has not been examined. In the summer of 2023, we will re-visit key upper tree line mature Engelmann spruce (Picea engelmannii) forest sites in southern British Columbia that were sampled in 1998 for dendroclimatic research - some close to Lytton - to update the site chronologies. These samples will be available for processing for this Masters project. The aim of this study will be to model whether the high elevation spruce forests are still temperature limited or are now experiencing thermal stress in a warming world. Thermal stress could well lead to decreases in tree productivity, woodland decline, and substantial ecosystem disequilibrium. 

References:   

White, R.H., Anderson, S., Booth, J.F., Braich, G., Draeger, C., Fei, C., Harley, C.D., Henderson, S.B., Jakob, M., Lau, C.A. and Mareshet Admasu, L., 2023. The unprecedented Pacific Northwest heatwave of June 2021. Nature Communications, 14(1), p.727. 

Wilson, R., Rao, R., Rydval, M., Wood, C., Larsson, L.Å. and Luckman, B.H., 2014. Blue Intensity for dendroclimatology: The BC blues: A case study from British Columbia, Canada. The Holocene, 24(11), pp.1428-1438. 

Supervisors: Prof Rob Wilson and Dr Coralie Mills 

Blue Intensity (BI) is an image analysis method that allows the cheap measurement of relative wood density from tree ring samples. To date, no exploration of the utility of BI on deciduous trees has been performed. Both ring porous and diffuse porous deciduous wood types pose a significant challenge for BI data. However, preliminary explorative work using BI data generated from the latewood of Oak samples from 5 sites in Scotland has shown that the between site common signal in BI is stronger than for traditional ring-width (RW). This project will expand the network of Oak tree-ring sites across Scotland, measure both RW and BI from the samples and examine the spatial coherence of the data, the climate response extant in these data and test the utility of using BI to enhance dendro-historical dating of Oak as well as Oak’s BI potential for dendroclimatology. 

References:  

Wilson, R., Wilson, D., Rydval, M., Crone, A., Büntgen, U., Clark, S., Ehmer, J., Forbes, E., Fuentes, M., Gunnarson, B.E. and Linderholm, H.W., 2017. Facilitating tree-ring dating of historic conifer timbers using Blue Intensity. Journal of Archaeological Science, 78, pp.99-111. 

Supervisor: Dr Michael Byrne 

Climate change is the critical challenge facing humanity. The impacts of global warming are already being experienced around the world, with the rapidly increasing risk of severe heatwaves a particularly dangerous threat to societies and ecosystems (Fischer & Knutti 2015; Byrne 2021). The exceptional summer of 2022 – the hottest on record in Europe, with the UK breaking the 40°C threshold for the first time – is an ominous portent of the future. 

The aim of this project will be to improve predictions of how extreme temperatures will change over future decades and centuries. Using a combination of state-of-the-art climate models and data analysis, the physical processes influencing extreme temperatures will be investigated with the aim of reducing uncertainty in extreme temperatures predictions. 

Through this MSc project, you will be trained in several aspects of physical climate science including atmospheric dynamics, heatwaves, climate modelling and climate change. You will also be trained in highly sought-after technical skills in computational modelling, high-performance computing, and ‘big data’ analyses. 

References: 

Byrne (2021): Nature Geoscience, vol. 14, pp. 837-841. 

Fischer & Knutti (2015): Nature Climate Change, vol. 5, pp. 560–564. 

Supervisors: Tim Kinnaird, Imogen Simpson-Mowday, Geography Department, University of Girona, Catalonia, Spain 

This project will investigate and date agricultural terraces distributed in the High Muga Valley and Upper Vallespir, Pyrenees, along the frontier imposed in 1659 dividing Catalonia into France and Spain. Archaeological research intends to elucidate 1. when these terraces were constructed; and 2. subsequent uses and organisational transitions diachronically. Scientific dating is essential as regional documentary evidence for terraces is often proxy and partial. The questions concerning these terraces and their transformations relate to improving knowledge of the overall landscape archaeology of this upland, agro-silvo-pastoral landscape through the longue durée.  In this study area, questions pertain as to when and in what circumstances terraces emerged, and their organisational relationships and changes within the wider agro-silvo-pastoral land-management systems. OSL dating and historic landscape characterisation (HLC) should elucidate landscape transformations and terrace constructions connected to adaptations within local lifeways in later Prehistory; pinpoint terrace constructions and or modifications during the Roman and/or mysterious Early Middle Ages; demonstrate associations with later Medieval upland landscape organisation.  Furthermore, dating could shed light upon the temporal relationships between terraces and ‘common’ lands and changes within land-use and organisation relative to shifts from the Old to Early Modern regimes. Without such dating comprehension of these terrace histories remains obscure. 

Through this project, you will receive training in field survey and excavation (Easternmost Pyrenees, France and Spain), apply your geoscience skillset to archaeological investigations, in laboratory analysis with optically stimulated luminescence profiling and dating (OSL PD) and GIS-based HLC methods. The results will provide fascinating insights into the history of the landscape; but they will also be useful for current and future challenges in managing landscape change. The terraces might be very ancient, but they were built to provide benefits that are still very important, such as controlling the flow of water, reducing the erosion of soil, and improving the stability of mountainsides. 

Supervisors: Dr Will Hutchison and Dr Aaron Naden  

A detailed record of past volcanic events is critical for preparing society for future eruptions. The finest time-resolved archive of volcanism on Earth is the record of ash and aerosol fallout found in polar ice cores.  Yet, for most of these eruptions we have no idea which volcano was responsible. 

Ice cores contain a rich cryptotephra record, and by undertaking chemical analysis of these glass shards we can pinpoint the geotectonic setting and source of these mystery eruptions. At present, the identification of ice-core cryptotephra is done manually by optical and electron microscopy. This process is laborious and an inefficient use of both person and instrument time. 

This project aims to overcome these issues by developing automated methods for particle classification in the polar ice cores. As ash particles are only 10-50 um in diameter, we will develop specialist imaging techniques available at the St Andrews Electron Microscopy Facility. These include secondary electron and backscatter electron imaging, as well as Energy Dispersive Spectroscopy and Raman spectroscopy to characterize their chemistry. 

Initially, we will develop these automated techniques for well-characterized tephra test samples. This will allow us to quantify the efficiency and accuracy of the method and then we apply the approach to samples from the ice-core tephra archive. This project has the potential to rapidly increase our ability to automatically identify tephra, and therefore radically improve our understanding of past volcanism on Earth.  

References:  

Iverson et al. 2017. Advancements and best practices for analysis and correlation of tephra and cryptotephra in ice (Quaternary Geochronology) 

Maffezzoli et al. 2023. Detection of ice core particles via deep neural networks (The Cryosphere) 

Supervisors: Graeme MacGilchrist (UStA), Emma Nicholson (UCL) and Will Hutchison (UStA) 

The growth of phytoplankton in the surface of the ocean forms the base of the ocean food web, supporting marine life across the planet. This primary production depends on a number of essential factors, including the availability of sunlight, the supply of essential nutrients, and the chemical properties of the seawater. Volcanic activity ejects a vast array of chemical species from the lithosphere into the atmosphere. The majority of this effuse settles on nearby land or ocean, with potential impacts on primary production and the local biosphere. Explosive volcanism is thought to enhance ocean production through its supply of iron. 

Satellites have been observing its surface for the last several decades. Through assessment of the wavelength of visible light, these observations provide a long time-series of surface ocean primary production across the globe, including near sites of volcanic activity. 

In this project, we will assess the impact of volcanism on ocean primary production using satellite observations across a wide selection of regions exhibiting both passive and explosive volcanism. The primary question is whether satellites reveal an effect of volcanism on primary production? Several exciting questions follow: What is the reason for this effect, or the absence of it? What elements in the volcanic plume are responsible? Are there spatial differences, or any changes in this effect over time, such as when volcanic activity shifts? Can the effect be detected in other observational platforms, such as autonomous floats or ship-board surveys? 

This project is well-suited to someone with a mathematical, physical, or earth science background, who is interested in expanding their understanding of oceanic biological and physical processes, as well as volcanism and Earth's geochemistry. The research question is sufficiently broad that it could expand in many directions, depending on the student's interests. It will provide a wealth of technical experience in remote sensing, computational data analysis, and statistics, as well as introducing the student to a multitude of data sources. Undertaking this project will equip the student exceptionally well for further postgraduate study or a career in a diverse array of industries, such as Earth System observation, data science, or environmental geochemistry. 

References 

Duggen, Svend, Peter Croot, Ulrike Schacht, and Linn Hoffmann. 2007. ‘Subduction Zone Volcanic Ash Can Fertilize the Surface Ocean and Stimulate Phytoplankton Growth: Evidence from Biogeochemical Experiments and Satellite Data’. _Geophysical Research Letters_ 34 (1). [https://doi.org/10.1029/2006GL027522](https://doi.org/10.1029/2006GL027522). 

Longman, Jack, Martin R. Palmer, Thomas M. Gernon, Hayley R. Manners, and Morgan T. Jones. 2022. ‘Subaerial Volcanism Is a Potentially Major Contributor to Oceanic Iron and Manganese Cycles’. _Communications Earth & Environment_ 3 (1): 1–8. [https://doi.org/10.1038/s43247-022-00389-7](https://doi.org/10.1038/s43247-022-00389-7). 

Supervisors: Graeme MacGilchrist (UStA) and Daphné Lemasquerier (UStA) 

Zonal jets are east-west currents observed in a variety of planetary flows, from the atmospheres of gas giants like Jupiter to Earth’s oceans. Despite being ubiquitous features of planetary flows, the fundamental dynamics of zonal jets in turbulent (chaotic) flows remains poorly understood. The presence of these jets has important implications for the overall dynamics of planetary circulation and climate. In Earth's ocean, for example, they are thought to affect transport of heat, momentum, and passive elements, with crucial consequences for energy and heat budgets, carbon dioxide uptake, and pollutant dispersal. 

In this project, we are interested in the feedback of zonal jets on the turbulent transport and mixing of fluid properties. We will aim to quantify the efficiency of meridional (north-south) transport in the presence of jets. To do so, we will numerically simulate the trajectories of synthetic particles in planetary fluid flows, and undertake a statistical analysis to quantify their dispersion. The student will have the freedom to analyse a variety of flows depending on their own interests, from idealized turbulent simulations to experiments to realistic ocean currents. The project will address questions such as: What sets the magnitude of turbulent transport in strongly anisotropic flows? How do zonal jets modulate transport? How does this modulation vary depending on the degree of zonation of the turbulence? Is it possible to theoretically model the feedback effect of zonal jets? 

This project is well suited to someone with a mathematical or physical science background, with an interest in expanding their understanding of fluid dynamics and planetary circulation. The research question is sufficiently broad that it could expand in many directions, depending on the student's specific interests. The student will develop highly transferable technical skills in computational data analysis, statistics, numerical modelling, and use of high-performance computing systems. 

References 

Groeskamp, Sjoerd, Joseph H. LaCasce, Trevor J. McDougall, and Marine Rogé. 2020. ‘Full-Depth Global Estimates of Ocean Mesoscale Eddy Mixing From Observations and Theory’. _Geophysical Research Letters_ 47 (18): e2020GL089425. [https://doi.org/10.1029/2020GL089425](https://doi.org/10.1029/2020GL089425). 

Klocker, Andreas, Raffaele Ferrari, and Joseph H. LaCasce. 2012. ‘Estimating Suppression of Eddy Mixing by Mean Flows’. _Journal of Physical Oceanography_ 42 (9): 1566–76. [https://doi.org/10.1175/JPO-D-11-0205.1](https://doi.org/10.1175/JPO-D-11-0205.1). 

Supervisors: James Rae, Andrea Burke, Graeme MacGilchrist 

The Arctic Ocean and its surrounding subpolar basins lie at the epicentre of modern climate change.  Current trends and future predictions show rapid loss of sea ice, with major implications for biological productivity, resource availability, and global climate.  However although these conditions are alarming, the Arctic has experience rapid climate change at earlier points in its history: over the last 3 million to 20 thousand years the Arctic region saw abrupt changes in marine productivity, fundamentally different modes of ocean circulation, and storage and release of CO2.  The geological past may thus hold the key to understanding the modes of operation of the Arctic environment in the future.  This project seeks to understand the modes of environmental change in the subpolar North Pacific and North Atlantic, by creating high resolution records of past changes in ocean pH, CO2, temperature, circulation, and biological productivity. The project will take advantage of cutting edge geochemical techniques available in the St Andrews Isotope Geochemistry labs (STAiG), including boron isotope analysis.  Timescales of specific interest include the millennial-scale climate changes of the last glacial cycle, intervals of past deglaciation, and the warmer than present climate of the Pliocene, with the flexibility to tailor the interval in line with the student’s interests. 

Supervisors: James Rae, Hana Jurikova, James Barnet  

CO2 exerts a major control on Earth’s environment, including ocean acidity and global climate.  Human carbon emissions have elevated CO2 levels to 420 ppm, substantially higher than at any time in the 800,000 year ice core record.  If we want to understand how Earth’s environment and climate will respond to a high CO2 world, we need to look deeper into the geological past (e.g. Tierney et al., 2020).   

This project will use boron isotopes in marine carbonates to reconstruct atmospheric CO2 in key warmer-than-present intervals of the last 100 Million years.  By examining the relationship between CO2 and global climate, we will constrain climate sensitivity, providing critical bounds on this crucial parameter for future climate predictions.  These data will also allow us to better examine key CO2 thresholds for major ice growth and retreat, and to better understand the processes governing CO2 change on a range of timescales. 

CO2 reconstructions will be based on the boron isotope composition of foraminifera (Foster & Rae 2016), which reflects water pH – and thus CO2 chemistry.  This method has provided several high profile reconstructions during this time period (e.g. Gutjahr et al., 2017), yet few high-resolution records currently exist (see Rae et al., 2021).  The aim of this project is to transform this with detailed new boron isotope reconstructions of atmospheric CO2. 

Foster & Rae (2016), AnnRev, 44, (207-237); Gutjahr et al. (2017), Nature 548.7669 (2017): 573; Rae, et al., (2021). AnnRev, 49.; Tierney, et al. (2020). Past climates inform our future. Science, 370(6517), p.eaay3701. 

Supervisors: James Rae, Andrea Burke, Graeme MacGilchrist 

The cause of glacial-interglacial CO2 cycles is a first order, unsolved question in climate science.  Although a number of viable mechanisms for glacial CO2 change have been proposed, suitable data to provide robust tests of these have been lacking.  A major missing piece of this puzzle is the nature of CO2 storage in the deep ocean during glacial periods (Rae et al., 2018).  

This project will quantify the extent and nature of deep ocean CO2 storage during the last glacial cycle, constraining the roles of changes in respired carbon, carbonate compensation, sea ice, and ocean circulation (MacGilchrist et al., 2019).  

Deep ocean CO2 reconstructions will be based on the boron concentration (B/Ca) and isotope composition (d11B) of benthic foraminifera (Rae et al., 2011), which record ΔCO32- and pH respectively.  To quantify CO2 storage by the biological pump, we will reconstruct deep ocean oxygen using a suite of novel trace elements in foraminifera and bulk sediments, complemented by carbon isotope gradients between different species of benthic foraminifera (e.g. Hoogakker et al., 2015), and preserved alkenone fluxes (Anderson et al., 2019).  Interpretation will be guided by a suite of experiments with simple models of the ocean carbon cycle.  The balance between data generation, large dataset analysis, and modelling can be matched to suit student interest.  

Anderson et al. (2019), Global Biogeochemical Cycles 33: 301-317; Gottschalk et al. (2016), Nature Comms. 7, 1-11; Hoogakker et al. (2015), Nature Geoscience 8.1 40; MacGilchrist, et al. (2019), Science Advances 5.8 eaav6410; Rae et al. (2011), EPSL, 302, 403-413; Rae, et al. (2018), Nature 562(7728), 569-573 

Applying novel isotope proxies to planetary accretion, differentiation and evolution

Supervisor: Dr Paul Savage

Our labs are interested in developing and applying novel isotope proxies to understanding the materials involved in, and the processes which controlled how our planet, and other rocky planets accreted, differentiated, and evolved. Recent projects have included the utilisation of Si, Cu and Zn isotopes by high resolution MC-ICP-MS. If you are interested in working on investigating what these novel isotope systems can tell use about the Early Earth and Solar System, please get in touch.

Supervisor: Dr Eva Stüeken 

Reconstructions of biogeochemical nitrogen cycling in deep time have traditionally focused on organic-rich sedimentary rocks. However, there are other potential archives of nitrogen that may yield important new insights, including nitrate stored in carbonates, salts and adsorbed to oxide minerals. The aim of this project is to use a combination of experiments and natural samples to explore these archives and quantitatively assess their potential to advance understanding of nutrient cycles over Earth’s history. Techniques will include ion chromatography, gas-source mass spectrometry, and photometry.  

Supervisor: Dr Eva Stüeken 

Most phosphorus on Earth occurs as sparingly soluble phosphate; however, research over the past decade has revealed that a number of high-energy processes are able to reduce phosphate to the more soluble form phosphite. Furthermore, phosphite may form from the dissolution of iron-phosphide minerals in meteorites. The goal of this project is the investigate samples of sedimentary rocks associated with meteorite impacts to determine if phosphite generation was widespread and significantly affected the biogeochemical phosphorus cycle during or after these events. Techniques will include microscopy, ion chromatography, photometry and ICP-MS.   

Supervisor: Sami Mikhail, Eva Stüeken, and Nick Gardiner 

If we are wrong about the geochemical behaviour of nitrogen in igneous systems, then all geobiological and environmental models are based on inaccurate starting points. This is because magmatism dictates the initial distribution of elements, thus all geobiological and environmental cycles commence with igneous geology. Only after volcanic eruptions and the emplacement of plutons do other systems pick up what is available and begin their cycles. Conventional thinking held that magmatic nitrogen is speciated as N₂, which is incompatible, inert, and volatile (e.g., Marty, 1995). However, it is now understood that nitrogen mostly exists in high temperature systems as ammonium (NH₄⁺; Mikhail & Sverjensky, 2014). Thus, the behaviour of N in igneous systems should not match what was previously assumed. Our exploration of the frontiers of nitrogen geochemistry involved the construction of a bespoke laboratory facility at St Andrews and optimised for the accurate determination of N abundances and N isotope ratios from silicate materials with trace quantities of nitrogen (Boocock et al., 2020). We have used this facility to examine the behaviour of N during magmatic differentiation by studying one co-genetic suite (basalt-andesite-dacite-rhyolite) of aphyric lavas from Hekla volcano, Iceland (Boocock et al., 2023a), and the intra-mineral partitioning and stable isotope fractionation of N between feldspars and micas in the Loch Doon zoned (calc-alkaline) pluton, Scotland (Boocock et al., 2023b). These studies have revealed that N is not always lost from differentiating magmatic systems and is instead progressively enriched in a manner strikingly similar to incompatible large ion lithophile elements, such as rubidium (Boocock et al., 2023a). We also find that the exchange of N between different mineral phases imparts a significant isotope fractionation effect (Boocock et al., 2023b).  These two findings have huge potential to fundamentally transform our understanding of the N cycle. This project will further examine the intra-mineral partitioning and stable isotope fractionation of nitrogen between co-existing mineral phases hosted in igneous rocks from zoned plutons to constrain and assess the controls on the behaviour of nitrogen during igneous differentiation.  

References Cited 

Boocock. T.J., Mikhail, S., Prytulak, J., Di Rocco, T., Stüeken., E.E. 2020. Nitrogen mass fraction and stable isotope ratios for fourteen geological reference materials: Evaluating the applicability of Elemental Analyser versus Sealed Tube Combustion methods. Geostandards and Geoanalytical Research, doi: 10.1111/ggr.12345  

Boocock, TJ., Mikhail, S., Boyce, AJ., Prytulak, J., Savage, PS., Stüeken, ES. 2023a. A primary magmatic source of nitrogen to the Earth’s crust. Nature Geoscience, 16, 521–526  

Boocock, TJ., Stüeken, ES., Bybee, GM., König, R., Boyce, AJ., Buisman, I., Prytulak, J., Mikhail, S. 2023b. Equilibrium partitioning and isotopic fractionation of nitrogen between biotite, plagioclase, and K-feldspar during magmatic differentiation. Geochimica et Cosmochimica Acta, 356, 116-128  

Marty, B. 1995. Nitrogen content of the mantle inferred from N₂–Ar correlation in oceanic basalts. Nature. 377, 326–329 

Mikhail, S., Sverjensky, D.A. 2014. Nitrogen speciation in upper mantle fluids and the origin of Earth’s nitrogen-rich atmosphere. Nature Geoscience, 7, 816–819 

Supervisor: Sami Mikhail, Eva Stüeken, and Nick Gardiner  

Quantifying changes in biomass burial through time has occupied scientists for over half a century (e.g., Wickman, 1956). Organic carbon is a strong reductant and so the burial of biomass constitutes an indirect source of O₂ that may have driven atmospheric oxygenation (Canfield, 2021). However, there is no agreement in the literature concerning the scale of change in biomass burial from the Archean to the present. For example, recent models find no agreement, with predictions from no statistically significant change to a more than ten-fold increase over the past 3.5 billion years (Mikhail et al., 2023 and references therein), which highlights the need for independent empirical constraints (this study). We have explored this frontier of science and found that granites produced via the melting of sediments show statistically significant increases in their N abundances in the phanerozoic compared with the Proterozoic and Archean samples (Mikhail et al., 2023). Collectively, these data are most straightforwardly explained by an absolute increase in biomass burial in the late Proterozoic or early Phanerozoic by a relative factor of between 5 and 8 (Mikhail et al., 2023) because N is concentrated in biomass (e.g., Redfield, 1934). However, with the current data we do not know the timing or rate of the nitrogen increase because we have no data between 550-1500 Ma. Excitingly, new samples have been acquired with an age range of 700-1100 Ma. This time-period overlaps with the rise of complex life and the Neoproterozoic Oxygenation Event – the largest rise in atmospheric O₂ in Earth’s history and a strong candidate for when the rise of biomass burial may have occurred. This project will analyse sedimentary-derived granites using our bespoke gas-line linked to a Thermo Mat253 isotope ratio mass spectrometer optimised the analysis of trace quantities of nitrogen (Boocock et al., 2020) to hopefully reveal the timing for the rise of nitrogen and therefore the date when biomass burial began to increase.  

References Cited 

Canfield, D.E. 2021. Carbon cycle evolution before and after the great oxidation of the atmosphere: American Journal of Science. 321, 297–331 

Mikhail, S., Stüeken, E.E., Boocock, T.J., Athey, M., Mappin, N., Boyce, A.J., Liebmann, J., Spencer, C.J., Bucholz, C.E. Strongly peraluminous granites provide independent evidence for an increase in biomass burial across the Precambrian-Phanerozoic boundary. Geology (in press) 

Boocock. T.J., Mikhail, S., Prytulak, J., Di Rocco, T., Stüeken., E.E. 2020. Nitrogen mass fraction and stable isotope ratios for fourteen geological reference materials: Evaluating the applicability of Elemental Analyser versus Sealed Tube Combustion methods. Geostandards and Geoanalytical Research, doi: 10.1111/ggr.12345  

Redfield, A. C. in James Johnstone Memorial Volume (ed. R. J. Daniel) 177–192 (Univ. Press of Liverpool, 1934) 

Wickman, F.E. 1956. The cycle of carbon and the stable carbon isotopes: Geochimica et Cosmochimica Acta. 9, 136–153 

Supervisor: Dr Onyedika A. Igbokwe and Dr Alessandro Verdecchia (RUB) 

Natural fracture networks often form a system of connected discontinuities, which can greatly enhance the effective permeability in carbonate (rocks) reservoirs. These networks play an increasingly important role in subsurface fluid movement and can determine the success or failure of the development of large E&P, geothermal energy, and heat production projects. Therefore, characterizing their physical and hydraulic properties becomes very crucial for any NetZero solutions that aim to use carbonates as an energy reservoir, storage site or a combination of the latter.  

We have acquired drone imagery and partly analysed the Devonian carbonate rocks of North Rhein Westfalen (NRW) Germany. Devonian carbonate rocks, underlining a vast portion of NRW in Western Germany, have a stratigraphic thickness (up to 1,300 m). Their outcrop analogues are exposed in several quarries in the region and have been affected by at least three main fracture sets: WSW-ENE-trending and S-dipping fractures parallel to the Ennepe Thrust, WSW-ENE-trending and N-dipping bedding-parallel fractures, and NNW-SSE-trending sub-vertical fractures parallel to the regional post-Variscan normal faults. 

This project will be divided into two parts. The first part will involve a structural and statistical interpretation of acquired drone data using GIS software. This interpretation will be used to create a tectonic model which can describe observed network geometries. The second part will use Multiple Point Statistics (MPS) to translate the interpreted network into statistical features and the Discrete Fracture Network (DFN), which can accurately describe the observed geometry from high-quality imagery (from 10 cm to 1000 m scale). Training in GIS and fracture modelling will be offered, and the student will develop in-depth knowledge of geomechanical modelling of fracture network systems.      

References 

Igbokwe, O.A., Timothy, J.J., Kumar, A., Ciao, X., Mueller, M., Bertotti, G., Meschke, G., Immenhauser, A., (2023). Impact of stress regime change on the permeability of a naturally fractured carbonate buildup (Latemar, The Dolomites, Northern Italy). First review, Geomechanics for Energy and the Environment Journal, Preprint. https://eartharxiv.org/repository/dashboard/3621/ 

Pederson, C., Mueller, M., Lippert, K., Igbokwe, O. A., Riechelmann, S., Lersch, S., Benger, P., Verdecchia, A. & Immenhauser, A. (2021): Impact of a regional fault zone on the properties of a deep geothermal carbonate reservoir unit (Devonian of NRW). – Z. Dt. Ges. Geowiss., 172: 339–364, Stuttgart. 

Verdecchia, A., Pederson, C., Smeraglia, L., Lippert, K., Immenhauser, A., and Harrington, R.: Discrete fracture network analysis of Devonian carbonate rocks in Western Germany: Implications for deep geothermal energy, heat exploitation and anthropogenic fault reactivation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4620, https://doi.org/10.5194/egusphere-egu22-4620, 2022. 

Bruna, P.-O., Straubhaar, J., Prabhakaran, R., Bertotti, G., Bisdom, K., Mariethoz, G., and Meda, M.: A new methodology to train fracture network simulation using multiple-point statistics, Solid Earth, 10, 537–559, https://doi.org/10.5194/se-10-537-2019, 2019. 

Supervisor: Dr Onyedika A. Igbokwe, Dr Will McCarthy and Dr Alessandro Verdecchia (RUB) 

This project will quantify the fracture pattern from acquired drone data with NetworkGT in GIS software or any open-source code, develop the DFN model, and estimate permeability tensors.  Training in GIS and fracture modelling will be offered, and the student will develop in-depth knowledge of geomechanical modelling of fracture network systems. Basic knowledge of Python, Matlab or R is essential.  

References 

Igbokwe, O.A., Timothy, J.J., Kumar, A., Ciao, X., Mueller, M., Bertotti, G., Meschke, G., Immenhauser, A., (2023). Impact of stress regime change on the permeability of a naturally fractured carbonate buildup (Latemar, The Dolomites, Northern Italy). First review, Geomechanics for Energy and the Environment Journal, Preprint. https://eartharxiv.org/repository/dashboard/3621/ 

Pederson, C., Mueller, M., Lippert, K., Igbokwe, O. A., Riechelmann, S., Lersch, S., Benger, P., Verdecchia, A. & Immenhauser, A. (2021): Impact of a regional fault zone on the properties of a deep geothermal carbonate reservoir unit (Devonian of NRW). – Z. Dt. Ges. Geowiss., 172: 339–364, Stuttgart. 

Verdecchia, A., Pederson, C., Smeraglia, L., Lippert, K., Immenhauser, A., and Harrington, R.: Discrete fracture network analysis of Devonian carbonate rocks in Western Germany: Implications for deep geothermal energy, heat exploitation and anthropogenic fault reactivation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4620, https://doi.org/10.5194/egusphere-egu22-4620, 2022. 

Bruna, P.-O., Straubhaar, J., Prabhakaran, R., Bertotti, G., Bisdom, K., Mariethoz, G., and Meda, M.: A new methodology to train fracture network simulation using multiple-point statistics, Solid Earth, 10, 537–559, https://doi.org/10.5194/se-10-537-2019, 2019.