Dr Robert Hilton
I research how erosion and weathering processes at Earth’s surface act to transfer carbon dioxide between the atmosphere and long-term, geological storage in sedimentary deposits. I seek to better understand the feedbacks between these carbon transfers and the climate system, and thus how Earth surface processes may damp (or amplify) climate change through the carbon cycle.
To do this, I quantify carbon transfers in field locations around the world. These include tectonically active settings (Taiwan; New Zealand; Sichuan, China; Peruvian Andes), high mountains (European Alps) and high latitudes (Mackenzie River Basin, Canada). I combine direct sampling of rivers, soils, biomass, marine sediments and geochemical analysis, along with field and remote–sensing based observation and hydrometric monitoring. In particular, I measure stable (12C, 13C, 14N and 15N) and radioactive isotopes (14C) of organic matter to understand the source and processing of organic matter in river systems. In addition, I seek to develop and apply redox-sensitive trace elements and their isotopes (e.g. rhenium) in river catchments to quantify oxidative weathering processes. These techniques are applied with an aim to better understand how Earth surface processes impact the global carbon cycle.
I'm currently leading the European Research Council (ERC) funded project (Starting Grant 2015) "ROC-CO2: Carbon dioxide emissions by rock-derived organic carbon oxidation" (http://roc-co2.weebly.com/).
I completed my PhD at the Department of Earth Sciences, University of Cambridge on 'Erosion of organic carbon from active mountain belts' (May 2009). Prior to this I had completed my BA/MSci in Natural Sciences (Geological Sciences) at the University of Cambridge (June 2004).
In 2008 I moved to Paris, where I worked as a Post-doctoral Research Associate at L'Institut de Physique du Globe (IPG) in the Laboratoire de Géochimie et Cosmochimie.
Since October 2009, I've been at Durham University, where I was promoted to Reader in October 2015, with a return to IPG in Paris (2012) as Professeur Invité.
I serve as Associate Editor at Earth Surface Dynamics (from 2013) and Chemical Geology (from 2015) and am a regular reviewer for a wide range of international journals. In 2014, I was presented with the Outstanding Young Scientist Award of the European Geosciences Union (EGU) in recognition of my ‘innovative contributions to the identification of the role of mountain belts in the global organic carbon cycle’.
1. Carbon dioxide emissions from weathering of rock-derived organic carbon
Oxidation of organic carbon in sedimentary rocks is one of the major, natural carbon dioxide emissions to the atmosphere. Despite this recognition, this flux is very poorly constrained by measurements and the controls on this major CO2 emission are not well known.
This topic forms my major research direction over the next 5 years under the ERC Starting Grant ROC-CO2 (http://roc-co2.weebly.com/). Previous NERC-funded (New Investigator Grant) research helped further develop and apply novel tracers of oxidative weathering (rhenium). Using this tracer in Taiwan revealed the importance of physical erosion on setting the rate of CO2 emission by this process. This work has provided the first quantification of the organic carbon budget of a mountain belt, showing erosion and weathering in Taiwan result in a net accumulation of organic carbon at present.
ERC-funded research (including NERC-funded research by Kate Horan 2014-) is seeking to quantify this process in other mountain belts and other river catchments, while assessing how glacial erosion processes may enhance this oxidative weathering flux.
2. Carbon export from the terrestrial biosphere by erosion
Erosion of the terrestrial biosphere can result in the export of carbon by rivers. The transfer of this particulate organic carbon represents a potential loss of net primary productivity if oxidised following erosion. However, if exported by rivers it may instead contribute to long-term storage of carbon away from the atmosphere, and ultimately contribute to geological carbon dioxide drawdown. Mountain belts are thought to be very important in this transfer because they experience high erosion rates and carbon is exported along with mineral sediment which may help to bury organic matter.
My research has sought to quantify the erosional fluxes of carbon from mountain forests around the world, and assess what controls these transfers. Research in Taiwan, New Zealand and the Andes has shown how important it is to correct for the input rock-derived organic carbon from sedimentary rocks (‘fossil’ or ‘petrogenic’). I have used stable isotopes, element ratios and radiocarbon (via NERC-funded research) to track and quantify organic carbon source and provide constraint on carbon export from the biosphere at the highest rates of erosion on Earth. I have also sought to understand how erosion impacts forest turnover (via landsliding) and nutrient status (e.g. nitrogen export).
Recent work has tracked the fate of organic carbon eroded from mountains in large river systems (e.g. the Amazon) and in offshore depositional environments (offshore Taiwan) to better understand how erosion impacts the carbon cycle.
3. Extreme geomorphic events and biogeochemical transfers
High magnitude geomorphic events may play an important role in governing the impact of erosion on global biogeochemical transfers. This is because they are capable of eroding large amounts of organic matter at the same time as large volumes of clastic sediment, potentially exporting materials quickly through river systems. In addition, they represent potential links between climatic variability (e.g. extreme flood events) and tectonics (e.g. earthquakes) and carbon export fluxes from mountain belts. However, it has proved to be extremely difficult to measure riverine fluxes associated with extreme geomorphic events.
My NERC-funded research in Taiwan has assessed the role of large floods triggered by tropical cyclones (typhoons) on organic carbon export by mountain rivers. It proposed a link between tropical cyclone frequency and carbon export and burial. Recent work with PhD student (Kathryn Clark 2010-2014) has identified the important role of flood events in carbon export from the Andes.
We are currently investigating the impact of the 2008 Wenchuan earthquake on sediment and biogeochemical cycles. The earthquake triggered >50,000 landslides in the Longmen Shan. Royal-Society and National Science Foundation-China –funded research is currently assessing how the event impacted both dissolved chemical weathering-derived fluxes and erosion and export of organic carbon from the biosphere.
4. High latitude carbon transfers
Soils at the northern high latitudes contain approximately double the carbon content of the pre-industrial atmosphere. This vast carbon reservoir is located in a region very sensitive to climatic change on geological timescales, and to change over the coming century. Ongoing NERC and CNS funded research in the Mackenzie River Basin, the largest source of particulate organic carbon to the Arctic Ocean, seeks to better understand how erosion of these soils may modify this carbon stock and lead to a longer-term stabilisation (through sedimentary burial) and/or release carbon by exposing aged-organic matter to degradation processes.
- Fluvial geochemistry
- Earth surface processes
- Isotope geochemistry of terrestrial organic matter
- Quantitative geomorphology
- Geological carbon cycle
Indicators of Esteem
- 2014: Award: 2014 Outstanding Young Scientist of the European Geosciences Union (EGU), GM Division
- 2009: NERC Radiocarbon Facility Research Highlight: Highlighting the research output of the publication Hilton et al., 2008, Nature Geoscience 1(11), 759-762
- 2009: NERC Science Highlight : "Taiwanese typhoons bury carbon at sea", for the publication Hilton et al., 2008, Nature Geoscience 1(11), 759-762
- Hilton, R.G. Climate regulates the erosional carbon export from the terrestrial biosphere. Geomorphology. 2017;277:118-132.
- Li, G., West, A.J., Densmore, A.L., Jin, Z., Zhang, F., Wang, J., Clark, M. & Hilton, R.G. Earthquakes drive focused denudation along a tectonically active mountain front. Earth and Planetary Science Letters. 2017;472:253-265.
- Clark, K.E., Hilton, R.G., West, A.J., Robles Caceres, A., Grocke, D.R., Marthews, T.R., Ferguson, R.I., Asner, G.P., New, M. & Malhi, Y. Erosion of organic carbon from the Andes and its affects on ecosystem carbon dioxide balance. Journal of Geophysical Research - Biogeosciences. 2017;122:449-469.
- Turowski, J.M., Hilton, R.G. & Sparkes, R. Decadal carbon discharge by a mountain stream is dominated by coarse organic matter. Geology. 2016;44:27-30.
- Wang, J., Jin, Z., Hilton, R.G., Zhang, F., Li, G., Densmore, A. L., Gröcke, D. R., Xu, X. & West, A. J. Earthquake-triggered increase in biospheric carbon export from a mountain belt. Geology. 2016;44:471-474.
- Jin, Z., West, A.J., Zhang, F., An, Z., Hilton, R.G., Yu, J., Wang, J., Li, G., Deng, L. & Wang, X. Seismically enhanced solute fluxes in the Yangtze River headwaters following the A.D. 2008 Wenchuan earthquake. Geology. 2016;44:47-50.
- Clark, K.E., West, A.J., Hilton, R.G., Asner, G.P., Quesada, C.A., Silman, M.L., Saatchi, S.S. Farfan-Rios, W., Martin, R.E., Horwath, A.B., Halladay, K., New, M. & Malhi, Y. Storm-triggered landslides in the Peruvian Andes and implications for topography, carbon cycles, and biodiversity. Earth Surface Dynamics. 2016;4:47-70.
- Wang, J., Jin, Z., Hilton, R.G., Zhang, F., Densmore, A.L., Li, G. & West, A.J. Controls on fluvial evacuation of sediment from earthquake-triggered landslides. Geology. 2015;43:115-118.
- Hilton, R.G., Galy, V., Gaillardet, J., Dellinger, M., Bryant, C., O’Regan, M., Gröcke, D.R., Coxall, H., Bouchez, J. & Calmels, D. Erosion of organic carbon in the Arctic as a geological carbon dioxide sink. Nature. 2015;524:84-87.
- West, A. J., Hetzel, R., Li, G., Jin, Z., Zhang, F., Hilton, R. G. & Densmore, A. L. Dilution of 10Be in detrital quartz by earthquake-induced landslides: Implications for determining denudation rates and potential to provide insights into landslide sediment dynamics. Earth and Planetary Science Letters. 2014;396:143-153.
- Hilton, R. G., Gaillardet, J., Calmels, D. & Birck, J.-L. Geological respiration of a mountain belt revealed by the trace element rhenium. Earth and Planetary Science Letters. 2014;403:27-36.
- Dellinger, M., Gaillardet, J., Bouchez, J., Calmels, D., Galy, V., Hilton, R. G., Louvat, P. & France-Lanord, C. Lithium isotopes in large rivers reveal the cannibalistic nature of modern continental weathering and erosion. Earth and Planetary Science Letters. 2014;401:359-372.
- Kao, S. J., Hilton, R. G., Selvaraj, K., Dai, M., Zehetner, F., Huang, J. C., Hsu, S. C., Sparkes, R., Liu, J. T., Lee, T. Y., Yang, J. Y. T., Galy, A., Xu, X. & Hovius, N. Preservation of terrestrial organic carbon in marine sediments offshore Taiwan: mountain building and atmospheric carbon dioxide sequestration. Earth Surface Dynamics. 2014;2:127-139.
- Bouchez, J., Galy, V., Hilton, R. G., Gaillardet, J., Moreira-Turcq, P., Pérez, M. A., France-Lanord, C. & Maurice, L. Source, transport and fluxes of Amazon River particulate organic carbon: insights from river sediment depth-profiles. Geochimica et Cosmochimica Acta. 2014;133:280-298.
- Hilton, R. G., Galy, A., West, A. J., Hovius, N. & Roberts, G.G. Geomorphic control on the δ15N of mountain forests. Biogeosciences. 2013;10:1693-1705.
- Clark, K.E., Hilton, R.G., West, A.J., Malhi, Y., Gröcke, D.R., Bryant, C.L., Ascough, P.L., Robles Caceres, A. & New, M. New views on old carbon in the Amazon river: Insight from the source of organic carbon eroded from the Peruvian Andes. Geochemistry, Geophysics, Geosystems. 2013;14:1644-1659.
- Hilton, R.G., Galy, A., Hovius, N., Kao, S.J., Horng, M.J. & Chen, H. Climatic and geomorphic controls on the erosion of terrestrial biomass from subtropical mountain forest. Global Biogeochemical Cycles. 2012;26:GB3014.
- Hilton, R.G., Galy, A., Hovius, N. & Horng, M.J. Efficient transport of fossil organic carbon to the ocean by steep mountain rivers: An orogenic carbon sequestration mechanism. Geology. 2011;39:71-74.
- Hilton, R.G., Meunier, P., Hovius, N., Bellingham, P.J. & Galy, A. Landslide impact on organic carbon cycling in a temperate montane forest. Earth Surface Processes and Landforms. 2011;36:1670-1679.
- Hilton, R.G., Galy, A., Hovius, N., Horng, M.J. & Chen, H. The isotopic composition of particulate organic carbon in mountain rivers of Taiwan. Geochimica et Cosmochimica Acta. 2010;74:3164-3181.
- Hilton, R.G., Galy, A. & Hovius, N. Riverine particulate organic carbon from an active mountain belt: importance of landslides. Global Biogeochemical Cycles. 2008;22:GB1017.
- Hilton, R.G., Galy, A., Hovius, N., Chen, M.C., Horng, M.J. & Chen, H. Tropical-cyclone-driven erosion of the terrestrial biosphere from mountains. Nature Geoscience. 2008;1:759-762.
- 2016: European Research Council Starting Grant (ERC-StG-2015), ROC-CO2, European Commission, £1,071,211.42, 2016-03-01 - 2021-02-28
- 2013: British Society for Geomorphology Early Career Grant - "Erosion of carbon from high-latitude peatlands: Isotopic insight into fluvial transfer in the Mackenzie River Basin" - £7,999
- 2012: Royal Society Research Grant (PI-Hilton) - "Earthquake-triggered carbon dioxide sequestration: Role of co-seismic landslides in organic carbon transfer" - £15,000
- 2011: The role of physical erosion in the weathering of fossil organic carbon: An investigation using the trace element rhenium (£76935.99 from NERC - Natural Environment Research Council)