Preprints
https://doi.org/10.5194/esurf-2021-80
https://doi.org/10.5194/esurf-2021-80

  03 Nov 2021

03 Nov 2021

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

Organic carbon burial by river meandering partially offsets bank-erosion carbon fluxes in a discontinuous permafrost floodplain

Madison M. Douglas1, Gen K. Li1, Woodward W. Fischer1, Joel C. Rowland2, Preston C. Kemeny1, A. Joshua West3, Jon Schwenk2, Anastasia P. Piliouras2, Austin J. Chadwick1, and Michael P. Lamb1 Madison M. Douglas et al.
  • 1Division of Geological and Planetary Science, California Institute of Technology, Pasadena, CA, 91125, USA
  • 2Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
  • 3Department of Earth Sciences, University of Southern California, Los Angeles, CA, 90089, USA

Abstract. Arctic river systems erode permafrost in their banks and mobilize particulate organic carbon (OC). Meandering rivers can entrain particulate OC from permafrost many meters below the depth of annual thaw, potentially enabling OC oxidation and the production of greenhouse gases. However, the amount and fate of permafrost OC that is mobilized by river erosion is uncertain. To constrain OC fluxes due to riverbank erosion and deposition, we collected riverbank and floodplain sediment samples along the Koyukuk River, which meanders through discontinuous permafrost in central Alaska. We measured sediment total OC (TOC), radiocarbon content, water content, bulk density, grain size, and floodplain stratigraphy. Radiocarbon abundance and TOC were higher in samples dominated by silt as compared to sand, which we used to map OC content onto floodplain stratigraphy and estimate carbon fluxes due to river meandering. Results showed that sediment being eroded from cutbanks and deposited as point bars had similar OC stocks (mean ± 1SD of 125.3 ± 13.1 kgOC m−2 in cutbanks versus 114.0 ± 15.7 kgOC m−2 in point bars) whether or not the banks contained permafrost. We also observed radiocarbon-depleted biospheric OC in both cutbanks and permafrost-free point bars. These results indicate that a significant fraction of aged biospheric OC that is liberated from floodplains by bank erosion is subsequently re-deposited in point bars, rather than being oxidized. The process of aging, erosion, and re-deposition of floodplain organic material may be intrinsic to river-floodplain dynamics, regardless of permafrost content.

Madison M. Douglas et al.

Status: open (until 01 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Madison M. Douglas et al.

Madison M. Douglas et al.

Viewed

Total article views: 431 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
342 87 2 431 15 1 3
  • HTML: 342
  • PDF: 87
  • XML: 2
  • Total: 431
  • Supplement: 15
  • BibTeX: 1
  • EndNote: 3
Views and downloads (calculated since 03 Nov 2021)
Cumulative views and downloads (calculated since 03 Nov 2021)

Viewed (geographical distribution)

Total article views: 410 (including HTML, PDF, and XML) Thereof 410 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 06 Dec 2021
Download
Short summary
Arctic rivers erode into permafrost and mobilize organic carbon, which can react to form greenhouse gasses or get re-buried in floodplain deposits. We collected samples on a permafrost floodplain in Alaska to determine if more carbon is eroded or deposited by river meandering. The floodplain contained a mixture of young carbon fixed by the biosphere and old, re-deposited carbon. Thus, sediment storage may allow Arctic river floodplains to retain aged organic carbon even when permafrost thaws.