Preprints
https://doi.org/10.5194/esurf-2020-95
https://doi.org/10.5194/esurf-2020-95

  23 Nov 2020

23 Nov 2020

Review status: this preprint is currently under review for the journal ESurf.

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

Thomas Croissant1, Robert G. Hilton1, Gen Li2, Jamie Howarth3, Jin Wang1,a, Erin L. Harvey1,b, Philippe Steer4, and Alexander L. Densmore1 Thomas Croissant et al.
  • 1Department of Geography, Durham University, Durham, DH1 3LE, United Kingdom
  • 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
  • 3School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
  • 4Universite de Rennes 1, CNRS, Géosciences Rennes – UMR 6118, 35000 Rennes, France
  • anow at: SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
  • bnow at: School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK

Abstract. In mountain ranges, earthquakes can trigger widespread landsliding and mobilise large amounts of organic carbon by eroding soil and vegetation from hillslopes. Following a major earthquake, the landslide-mobilised 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 mobilisation, with a description of the physical and biogeochemical processes involved after the 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 modelling 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 and multi-pool models. Our results highlight 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 southwest Pacific region, we find that model configurations allow for 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 therefore offers an effective process to promote carbon sequestration in sedimentary deposits over thousands of years.

Thomas Croissant et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Thomas Croissant et al.

Thomas Croissant et al.

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