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Model predictions of long-lived storage of organic carbon in river deposits

Torres, Mark A. and Limaye, Ajay B. and Ganti, Vamsi and Lamb, Michael P. and West, A. Joshua and Fischer, Woodward W. (2017) Model predictions of long-lived storage of organic carbon in river deposits. Earth Surface Dynamics, 5 (4). pp. 711-730. ISSN 2196-632X.

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The mass of carbon stored as organic matter in terrestrial systems is sufficiently large to play an important role in the global biogeochemical cycling of CO_2 and O_2. Field measurements of radiocarbon-depleted particulate organic carbon (POC) in rivers suggest that terrestrial organic matter persists in surface environments over millennial (or greater) timescales, but the exact mechanisms behind these long storage times remain poorly understood. To address this knowledge gap, we developed a numerical model for the radiocarbon content of riverine POC that accounts for both the duration of sediment storage in river deposits and the effects of POC cycling. We specifically target rivers because sediment transport influences the maximum amount of time organic matter can persist in the terrestrial realm and river catchment areas are large relative to the spatial scale of variability in biogeochemical processes. Our results show that rivers preferentially erode young deposits, which, at steady state, requires that the oldest river deposits are stored for longer than expected for a well-mixed sedimentary reservoir. This geometric relationship can be described by an exponentially tempered power-law distribution of sediment storage durations, which allows for significant aging of biospheric POC. While OC cycling partially limits the effects of sediment storage, the consistency between our model predictions and a compilation of field data highlights the important role of storage in setting the radiocarbon content of riverine POC. The results of this study imply that the controls on the terrestrial OC cycle are not limited to the factors that affect rates of primary productivity and respiration but also include the dynamics of terrestrial sedimentary systems.

Item Type:Article
Related URLs:
URLURL TypeDescription
Torres, Mark A.0000-0002-9599-2748
Lamb, Michael P.0000-0002-5701-0504
West, A. Joshua0000-0001-6909-1471
Fischer, Woodward W.0000-0002-8836-3054
Additional Information:© 2017 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 03 May 2017 – Discussion started: 15 May 2017. Revised: 02 Aug 2017 – Accepted: 12 Sep 2017 – Published: 03 Nov 2017. Data availability: The raw data utilized in the study were compiled from previously published works and are available in the cited papers. In Table 2, we provide results derived from the data compilation. A working example of our sediment and carbon storage model is included as MATLAB script in the Supplement. All authors thank James Pizzuto and one anonymous reviewer for providing helpful comments that greatly improved the overall quality of the paper. Mark A. Torres acknowledges support from a Caltech Texaco postdoctoral research fellowship and the California Alliance for the Graduate and Professoriate. Ajay B. Limaye acknowledges support from National Center for Earth-surface Dynamics 2 (NCED2) Synthesis Postdoctoral Program. Vamsi Ganti acknowledges support from the Imperial College London’s Junior Research Fellowship. This work was supported by an award from the National Science Foundation to Michael P. Lamb (EAR 1427177) and the Caltech Discovery Fund. All authors acknowledge the participants of the GE126 course at Caltech (co-taught by Woodward W. Fischer, Michael P. Lamb, and A. Joshua West) for providing some of the early ideas that led to this work. Helpful criticism of a draft version of this paper was supplied by Joel Schiengross. The authors declare that they have no conflict of interest.
Funding AgencyGrant Number
Caltech Texaco Postdoctoral FellowshipUNSPECIFIED
California Alliance for the Graduate and ProfessoriateUNSPECIFIED
National Center for Earth-surface Dynamics 2 (NCED2) Synthesis Postdoctoral ProgramUNSPECIFIED
Imperial College LondonUNSPECIFIED
Caltech Discovery FundUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20180117-153815243
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Official Citation:Torres, M. A., Limaye, A. B., Ganti, V., Lamb, M. P., West, A. J., and Fischer, W. W.: Model predictions of long-lived storage of organic carbon in river deposits, Earth Surf. Dynam., 5, 711-730,, 2017
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84372
Deposited By: Tony Diaz
Deposited On:17 Jan 2018 23:49
Last Modified:03 Oct 2019 19:17

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