The common thread that runs through my research interests is a desire to understand how the long-term carbon cycle influences and interacts with Earth surface geochemical cycling and maintains planetary habitability. I approach this central goal by developing and applying (isotope) geochemical tools, underpinned by developing a robust understanding of the modern systems, and of the fidelity of proxy archives. I am also increasingly interested in how we can enhance natural processes for the geomitigation of greenhouse gases. Specific research foci include:

In the HELGES laboratories, we specialise in making precise and accurate measurements of metal isotope ratios. Underpinning any interpretation of these isotope ratios is the need for quantitative knowledge of how these isotope ratios are distributed and fractionate in the environment. I'm interested in how we can quantify these fractionations (on scales from cellular to global) and use them within mass-balance frameworks to gain otherwise unattainable insights. I'm also interested in how we can improve measurement quality, whether analytically (e.g. by optimising double-spike calibration and inversion schemes) or in the clean lab (e.g. by minimising sample requirements or improving element purification routines). Please feel free to contact me and/or Dr. Bei Chen if you are interesting in working with the HELGES facilities!

As an essential nutrient for many groups of organisms, and also as a tracer of silicate weathering, silicon (isotope) geochemistry finds many applications. I work to understand how we can interpret silicon geochemistry in modern systems, and how we can apply these insights as a uniquely powerful proxy for past weathering and biogeochemical cycling, on timescales from human to millennial to geological. I'm particularly interested in how we can disentangle the imprint of continental (palaeo)weathering processes from biological cycling on ocean silicon isotope ratios over the late Quaternary glacial cycles, as well as how diagenetic processes might act to modify the silicon and oxygen isotope composition of biogenic silica as it is progressively buried in ocean sediments.

The fact that the habitability of our planet has been maintained over essentially the entirety of its existence is largely thanks to silicate weathering, a natural process by which CO₂ is slowly removed from the atmosphere. The rate of CO₂ removal is related to climate - and thus atmospheric CO₂ - providing the necessary negative feedback, or planetary 'thermostat' on geological timescales. Weathering is also the source of most nutrients to ecosystems and influences how landscape form and evolve, giving it huge relevance across the geosciences.

I'm particularly interested in learning more about the relationship between weathering and climate, and how this relationship can be modified by other processes - especially erosion and biological activity - to act as both a response to and a driver of, global climate. One way we can approach this is by using the sedimentary record to tell us about how weathering has responded to past climate perturbations, for example across the Paleocene-Eocene Thermal Maximum (PETM) or the Middle Eocene Climatic Optimum (MECO). Recent years have also seen rapid developments in our understanding of other processes within the so-called 'long-term' carbon cycle, including the role of clay mineral formation in ocean sediments (i.e. 'reverse weathering'). We also appreciate more the importance of weathering not driven by carbonic acid, and the influence of organic carbon cycling. Together with colleagues, including Dr. Emily Stevenson and Dr. Hella Wittmann, I am working to understand how the balance between these various fluxes varies across a gradient of climate and erosion rates in the Himalayas.

To have any hope of meeting global climate goals, the priority must be to reduce greenhouse gas emissions as much and as rapidly as possible. Beyond this, we will still need techniques to actively remove CO₂ from the atmosphere to counteract hard-to-abate residual emissions and to mitigate any climate overshoot. 'Enhanced Weathering' is a technique that may lead to large volume carbon dioxide removal (CDR) with millennium-scale storage and at competitive cost. The basic principle is that we can enhance the natural silicate weathering CO₂ sink by distributing finely ground reactive (ultra)mafic rock, e.g. basalts, on agricultural soils. Models predict that Enhanced Weathering alone could exceed the CDR targets of the German Climate Protection Act, but they lack empirical ground-truthing and the necessary protocols to quantify Enhanced Weathering at field scales. We also don't have a good understanding of the long-term impacts - both positive and negative - on soil and ecosystem health, or on societal acceptance. I'm working, together with colleagues from RIFS and the University of Antwerp, to address some of these issues. Specifically, I'm interested in how we can exploit the tools and insights garnered from decades of natural weathering studies to develop methods to quantify CO₂ removal and to optimise Enhanced Weathering deployment strategies in Germany and beyond.