TY - JOUR
T1 - Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain
AU - Douglas, Madison M.
AU - Li, Gen K.
AU - Fischer, Woodward W.
AU - Rowland, Joel C.
AU - Kemeny, Preston C.
AU - West, A. Joshua
AU - Schwenk, Jon
AU - Piliouras, Anastasia P.
AU - Chadwick, Austin J.
AU - Lamb, Michael P.
N1 - Funding Information:
the Caltech Center for Environmental Microbial Interactions to Woodward W. Fischer; National Science Foundation Awards 2127442 and 2031532; the National Defence Science and Engineering Graduate Fellowship for Madison M.
Funding Information:
Financial support. We acknowledge financial support from the Department of Energy Office of Science, Biological and Environmental Research, Earth and Environmental Systems Sciences Division, Subsurface Biogeochemical Research Program Early Career Award to Joel C. Rowland; Caltech Terrestrial Hazards Observation and Reporting Center, Foster and Coco Stanback, the Linde Family, and the Resnick Sustainability Institute to Michael P. Lamb and Woodward W. Fischer; the Caltech Center for Environmental Microbial Interactions to Woodward W. Fischer; National Science Foundation Awards 2127442 and 2031532; the National Defence Science and Engineering Graduate Fellowship for Madison M. Douglas and Preston C. Kemeny; and the Fannie and John Hertz Foundation Cohen/Jacobs and Stein Family Fellowship for Preston C. Kemeny.
Publisher Copyright:
© 2022 Madison M. Douglas et al.
PY - 2022/5/10
Y1 - 2022/5/10
N2 - 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 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 the Yukon River watershed, Alaska, USA, with an average migration rate of 0.52g myr-1. We measured sediment total OC (TOC) content, radiocarbon activity, water content, bulk density, grain size, and floodplain stratigraphy. Radiocarbon activity and TOC content 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 the Koyukuk River erodes and re-deposits a substantial flux of OC each year due to its depth and high migration rate, generating a combined OC flux of a similar magnitude to the floodplain net ecological productivity. However, sediment being eroded from cutbanks and deposited as point bars had similar OC stocks (meang ±g 1g SD of 125.3±13.1g kgOCm-2 in cutbanks versus 114.0±15.7g kgOCm-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 substantial 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.
AB - 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 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 the Yukon River watershed, Alaska, USA, with an average migration rate of 0.52g myr-1. We measured sediment total OC (TOC) content, radiocarbon activity, water content, bulk density, grain size, and floodplain stratigraphy. Radiocarbon activity and TOC content 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 the Koyukuk River erodes and re-deposits a substantial flux of OC each year due to its depth and high migration rate, generating a combined OC flux of a similar magnitude to the floodplain net ecological productivity. However, sediment being eroded from cutbanks and deposited as point bars had similar OC stocks (meang ±g 1g SD of 125.3±13.1g kgOCm-2 in cutbanks versus 114.0±15.7g kgOCm-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 substantial 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.
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U2 - 10.5194/esurf-10-421-2022
DO - 10.5194/esurf-10-421-2022
M3 - Article
AN - SCOPUS:85130565039
SN - 2196-6311
VL - 10
SP - 421
EP - 435
JO - Earth Surface Dynamics
JF - Earth Surface Dynamics
IS - 3
ER -