I have sought to challenge existing paradigms in my field, while providing leadership that defines future research directions and delivers on ambitious international projects. Over the 2022-2025 period, these research activities can be summarised across four themes
1) Global rates of CO2 release by rock organic carbon oxidation:
We have forward a step changes in our understanding of the CO2 release during weathering of rock organic carbon, by quantifying rates across landscapes for the first time. In the final package of the ERC Starting Grant (2016-2022: ROC-CO2) delivered in Oxford, this research cumulated in the first global assessment of CO2 release by rock organic carbon weathering (Zondervan et al., 2023, Nature, University press release). We found it offset the well-studied CO2 sink by silicate weathering, calling into question how the long-term carbon cycle works.
2. Uncovering an unrecognised positive feedback in the carbon cycle:
We designed the first field experiments to directly measure CO2 release during weathering to demonstrate that CO2 release from rock weathering increased with temperature as positive feedback not recognised in models of the Earth system. As part of my ERC Consolidator Grant (2022-2027: RIV-ESCAPE), we have found that this positive feedback is widespread and underway in the Arctic in thawing mineral permafrost (Walsh et al., 2024, Science Advances, University press release). This research strand is being taken forward in a NERC Pushing the Frontiers award ‘Accelerated carbon dioxide release from sedimentary rocks in a warming world’, assessing how this process responds to ongoing deglaciation and linking climate change to CO2 release
3. Greenhouse gas release from river surfaces and terrestrial landscapes:
Ongoing research within the ERC-funded RIV-ESCAPE project concerns the major fluxes of greenhouse gases CO2 and CH4 from river surfaces. Early outputs from this work have established how permafrost-derived carbon contributes to river CO2 fluxes in a major Arctic River. Active fieldwork campaigns are establishing the underlying processes and vectors of change.
4. Carbon cycle solutions:
As part of a growing solution focused theme, we are interested in the impacts of proposed enhanced rock weathering methods (for atmospheric carbon dioxide removal) on river geochemistry. We are also exploring how mineral-organic matter interactions contribute to carbon storage in soils and sediments.
These four strands are support by NERC Pushing the Frontier grants, ERC and the Leverhulme Trust. These sustained research outcomes have seen me invited to give the Keynote at the Steepest Descent meeting of the European Geosciences Union (EGU) 2022, Vienna. I have also given invited talks on carbon cycle themes at the 2023 EGU Conference and the 2023 Goldschmidt Conference. Since 2022, I have given invited research seminars at leading international (ETH Zurich, Switzerland; North Carolina State University, USA) and UK universities (University of Leeds, University of Cambridge, University of Southampton and National Oceanography Centre).
