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Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model

Croissant, Thomas and Hilton, Robert G. and Li, Gen K. and Howarth, Jamie and Wang, Jin and Harvey, Erin L. and Steer, Philippe and Densmore, Alexander L. (2021) Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model. Earth Surface Dynamics, 9 (4). pp. 823-844. ISSN 2196-632X. doi:10.5194/esurf-9-823-2021.

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In mountain ranges, earthquakes can trigger widespread landsliding and mobilize large amounts of organic carbon by eroding soil and vegetation from hillslopes. Following a major earthquake, the landslide-mobilized organic carbon can be exported from river catchments by physical sediment transport processes or stored within the landscape where it may be degraded by heterotrophic respiration. The competition between these physical and biogeochemical processes governs a net transfer of carbon between the atmosphere and sedimentary organic matter, yet their relative importance following a large landslide-triggering earthquake remains poorly constrained. Here, we propose a model framework to quantify the post-seismic redistribution of soil-derived organic carbon. The approach combines predictions based on empirical observations of co-seismic sediment mobilization with a description of the physical and biogeochemical processes involved after an earthquake. Earthquake-triggered landslide populations are generated by randomly sampling a landslide area distribution, a proportion of which is initially connected to the fluvial network. Initially disconnected landslide deposits are transported downslope and connected to rivers at a constant velocity in the post-seismic period. Disconnected landslide deposits lose organic carbon by heterotrophic oxidation, while connected deposits lose organic carbon synchronously by both oxidation and river export. The modeling approach is numerically efficient and allows us to explore a large range of parameter values that exert a control on the fate of organic carbon in the upland erosional system. We explore the role of the climatic context (in terms of mean annual runoff and runoff variability) and rates of organic matter degradation using single pool and multi-pool models. Our results highlight the fact that the redistribution of organic carbon is strongly controlled by the annual runoff and the extent of landslide connection, but less so by the choice of organic matter degradation model. In the context of mountain ranges typical of the southwestern Pacific region, we find that model configurations allow more than 90 % of the landslide-mobilized carbon to be exported from mountain catchments. A simulation of earthquake cycles suggests efficient transfer of organic carbon out of a mountain range during the first decade of the post-seismic period. Pulsed erosion of organic matter by earthquake-triggered landslides is therefore an effective process to promote carbon sequestration in sedimentary deposits over thousands of years.

Item Type:Article
Related URLs:
URLURL TypeDescription
Li, Gen K.0000-0002-6300-3570
Howarth, Jamie0000-0003-4365-0292
Harvey, Erin L.0000-0002-6167-9438
Steer, Philippe0000-0003-2710-6553
Densmore, Alexander L.0000-0003-0629-6554
Additional Information:© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 8 November 2020 – Discussion started: 23 November 2020; Revised: 4 May 2021 – Accepted: 8 June 2021 – Published: 2 August 2021. We thank referees Sébastien Carretier and Aaron Bufe for their comments, which improved the paper. This research was supported by a UK Natural Environment Research Council Standard Grant (NE/P013538/1) to Robert G. Hilton, Alexander L. Densmore and Jamie D. Howarth as well as a Rutherford Foundation Postdoctoral Fellowship (RFTGNS1201-PD) to Jamie D. Howarth and a COFUND Junior Research Fellowship at Durham University to Jin Wang. Review statement: This paper was edited by Jean Braun and reviewed by Sebastien Carretier and Aaron Bufe. Code availability: The code used in this research study may be made available by request to the corresponding author. Data availability: All underlying data used in this research study may be made available by request to Robert G. Hilton. Author contributions: TC, GL and RGH designed the study. TC, GL, RGH and PS developed the theoretical description of the processes. JW, ELH and RGH ran the quantification of the soil organic carbon content. TC analyzed the data and interpreted them with inputs from RGH, JH and ALD. TC and RGH wrote the paper with inputs from all co-authors. The authors declare that they have no conflict of interest.
Funding AgencyGrant Number
Natural Environment Research Council (NERC)NE/P013538/1
Rutherford FoundationRFTGNS1201-PD
Durham UniversityUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20210929-194929524
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Official Citation:Croissant, T., Hilton, R. G., Li, G. K., Howarth, J., Wang, J., Harvey, E. L., Steer, P., and Densmore, A. L.: Pulsed carbon export from mountains by earthquake-triggered landslides explored in a reduced-complexity model, Earth Surf. Dynam., 9, 823–844,, 2021
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111099
Deposited By: Tony Diaz
Deposited On:04 Oct 2021 19:21
Last Modified:04 Oct 2021 20:28

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