Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain
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 permafr...
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Online Access: | https://doi.org/10.5194/esurf-10-421-2022 https://esurf.copernicus.org/articles/10/421/2022/ |
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ftcopernicus:oai:publications.copernicus.org:esurf98425 2023-05-15T15:16:37+02:00 Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain Douglas, Madison M. Li, Gen K. Fischer, Woodward W. Rowland, Joel C. Kemeny, Preston C. West, A. Joshua Schwenk, Jon Piliouras, Anastasia P. Chadwick, Austin J. Lamb, Michael P. 2022-05-10 application/pdf https://doi.org/10.5194/esurf-10-421-2022 https://esurf.copernicus.org/articles/10/421/2022/ eng eng doi:10.5194/esurf-10-421-2022 https://esurf.copernicus.org/articles/10/421/2022/ eISSN: 2196-632X Text 2022 ftcopernicus https://doi.org/10.5194/esurf-10-421-2022 2022-05-16T16:22:34Z 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 0.52 m yr −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 (mean ± 1 SD of 125.3±13.1 kg OC m −2 in cutbanks versus 114.0±15.7 kg OC 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 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. Text Arctic permafrost Yukon river Alaska Yukon Copernicus Publications: E-Journals Arctic Yukon Earth Surface Dynamics 10 3 421 435 |
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Open Polar |
collection |
Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
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 0.52 m yr −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 (mean ± 1 SD of 125.3±13.1 kg OC m −2 in cutbanks versus 114.0±15.7 kg OC 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 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. |
format |
Text |
author |
Douglas, Madison M. Li, Gen K. Fischer, Woodward W. Rowland, Joel C. Kemeny, Preston C. West, A. Joshua Schwenk, Jon Piliouras, Anastasia P. Chadwick, Austin J. Lamb, Michael P. |
spellingShingle |
Douglas, Madison M. Li, Gen K. Fischer, Woodward W. Rowland, Joel C. Kemeny, Preston C. West, A. Joshua Schwenk, Jon Piliouras, Anastasia P. Chadwick, Austin J. Lamb, Michael P. Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain |
author_facet |
Douglas, Madison M. Li, Gen K. Fischer, Woodward W. Rowland, Joel C. Kemeny, Preston C. West, A. Joshua Schwenk, Jon Piliouras, Anastasia P. Chadwick, Austin J. Lamb, Michael P. |
author_sort |
Douglas, Madison M. |
title |
Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain |
title_short |
Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain |
title_full |
Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain |
title_fullStr |
Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain |
title_full_unstemmed |
Organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain |
title_sort |
organic carbon burial by river meandering partially offsets bank erosion carbon fluxes in a discontinuous permafrost floodplain |
publishDate |
2022 |
url |
https://doi.org/10.5194/esurf-10-421-2022 https://esurf.copernicus.org/articles/10/421/2022/ |
geographic |
Arctic Yukon |
geographic_facet |
Arctic Yukon |
genre |
Arctic permafrost Yukon river Alaska Yukon |
genre_facet |
Arctic permafrost Yukon river Alaska Yukon |
op_source |
eISSN: 2196-632X |
op_relation |
doi:10.5194/esurf-10-421-2022 https://esurf.copernicus.org/articles/10/421/2022/ |
op_doi |
https://doi.org/10.5194/esurf-10-421-2022 |
container_title |
Earth Surface Dynamics |
container_volume |
10 |
container_issue |
3 |
container_start_page |
421 |
op_container_end_page |
435 |
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1766346904529010688 |