Quantifying the Export of Floodplain Soil Carbon to Arctic Rivers by Bank Erosion

Rowland, J. C.; Muss, J. D.; Shelef, Eitan; Stauffer, Sophie; Sutfin, Nicholas A.

doi:10.1130/abs/2016am-282561

Cited by 6 publications

(22 citation statements)

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“…(2019), with letters representing further sub‐divisions for our analysis to maintain image dimensions of 50–150 channel‐widths. Channel width ( B ) and number of threads ( N c ) are reported in previous work (Rowland et al., 2019; Sylvester et al., 2019). Optimum timesteps (Δ t ) were calculated using Equation 2 and rounded to the nearest year.…”

Section: Methodsmentioning

confidence: 90%

“…For bank‐based measurements, we leveraged data from single‐ and multi‐thread Arctic rivers collected by Rowland et al. (2019) (Table 1; Figure 1). Rowland et al.…”

Section: Methodsmentioning

confidence: 99%

“…Rowland et al. (2019) defined channel banks based on the presence of vegetation using GeniePro semi‐automated workflow (Perkins et al., 2005), and calculated the linear rates of bank erosion and accretion using SCREAM (Rowland et al., 2016). We focused on 11 reaches spanning 50–150 channel‐widths each, where the average channel‐thread width was wide enough for PIV analysis (>240 m); and where banks were mobile enough to migrate by at least one‐half the channel‐thread width over the 36‐year duration of Landsat imagery (i.e., the estimated migration timescale was ≤72 years; Table 1).…”

Section: Methodsmentioning

confidence: 99%

“… (a) World map showing the location of river reaches analyzed with particle image velocimetry, overlain with example NASA Landsat images of single‐thread channels (b, c; N c = 1, where N c is the average number of sub‐channels in a channel cross‐section; Egozi & Ashmore, 2008) and multi‐thread channels (d, e; N c > 1). Previous work has quantified channel migration in these reaches using centerline‐based dynamic time warping (blue circles; Sylvester et al., 2019) or bank‐based Spatially Continuous Erosion and Accretion Measurements (green circles; Rowland et al., 2019). Dashed boxes denote areas shown in Figures 3–5.…”

Section: Introductionmentioning

confidence: 99%

“…Linear rates of erosion/accretion are determined for each bank by the nearest‐neighbor distance to bank pixels in the subsequent image within the same erosion/accretion area (Figure 2b) (Rowland et al., 2016). SCREAM and similar bank‐based approaches have enabled researchers to quantify the mobility of both single‐ and multi‐thread rivers in the Arctic (Douglas et al., 2021; Rowland et al., 2016, 2019) and beyond (Langhorst & Pavelsky, 2023; Nagel et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

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Remote Sensing of Riverbank Migration Using Particle Image Velocimetry

2023

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Section: Methodsmentioning

confidence: 90%

“…For bank‐based measurements, we leveraged data from single‐ and multi‐thread Arctic rivers collected by Rowland et al. (2019) (Table 1; Figure 1). Rowland et al.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Remote Sensing of Riverbank Migration Using Particle Image Velocimetry

2023

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Arctic Permafrost Thawing Enhances Sulfide Oxidation

Kemeny,

Li,

Douglas

et al. 2023

Global Biogeochemical Cycles

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Permafrost degradation is altering biogeochemical processes throughout the Arctic. Thaw‐induced changes in organic matter transformations and mineral weathering reactions are impacting fluxes of inorganic carbon (IC) and alkalinity (ALK) in Arctic rivers. However, the net impact of these changing fluxes on the concentration of carbon dioxide in the atmosphere (pCO2) is relatively unconstrained. Resolving this uncertainty is important as thaw‐driven changes in the fluxes of IC and ALK could produce feedbacks in the global carbon cycle. Enhanced production of sulfuric acid through sulfide oxidation is particularly poorly quantified despite its potential to remove ALK from the ocean‐atmosphere system and increase pCO2, producing a positive feedback leading to more warming and permafrost degradation. In this work, we quantified weathering in the Koyukuk River, a major tributary of the Yukon River draining discontinuous permafrost in central Alaska, based on water and sediment samples collected near the village of Huslia in summer 2018. Using measurements of major ion abundances and sulfate (SO42‐) sulfur (34S/32S) and oxygen (18O/16O) isotope ratios, we employed the MEANDIR inversion model to quantify the relative importance of a suite of weathering processes and their net impact on pCO2. Calculations found that approximately 80% of SO42‐ in mainstem samples derived from sulfide oxidation with the remainder from evaporite dissolution. Moreover, 34S/32S ratios, 13C/12C ratios of dissolved inorganic carbon, and sulfur X‐ray absorption spectra of mainstem, secondary channel, and floodplain pore fluid and sediment samples revealed modest degrees of microbial sulfate reduction within the floodplain. Weathering fluxes of ALK and IC result in lower values of pCO2 over timescales shorter than carbonate compensation (∼104 yr) and, for mainstem samples, higher values of pCO2 over timescales longer than carbonate compensation but shorter than the residence time of marine SO42‐ (∼107 yr). Furthermore, the absolute concentrations of SO42‐ and Mg2+ in the Koyukuk River, as well as the ratios of SO42‐ and Mg2+ to other dissolved weathering products, have increased over the past 50 years. Through analogy to similar trends in the Yukon River, we interpret these changes as reflecting enhanced sulfide oxidation due to ongoing exposure of previously frozen sediment and changes in the contributions of shallow and deep flow paths to the active channel. Overall, these findings confirm that sulfide oxidation is a substantial outcome of permafrost degradation and that the sulfur cycle responds to permafrost thaw with a timescale‐dependent feedback on warming.This article is protected by copyright. All rights reserved.

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Sediment Entrainment and Slump Blocks Limit Permafrost Riverbank Erosion

Douglas

Dunne

Lamb

2023

Geophysical Research Letters

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Climatic warming and permafrost thaw are predicted to increase Arctic riverbank erosion, threatening communities and accelerating sediment, carbon and nutrient cycling between rivers and floodplains. Existing theory assumes that pore‐ice thaw sets riverbank erosion rates, but overpredicts observed erosion rates by orders of magnitude. Here, we developed a simple model that predicts more modest rates due to a sediment‐entrainment limitation and riverbank armoring by slump blocks. Results show that during times of thaw‐limited erosion, the river rapidly erodes permafrost and undercuts its banks, consistent with previous work. However, overhanging banks generate slump blocks that must thaw and erode by sediment entrainment. Sediment entrainment can limit bank and slump block erosion rates, producing seasonally averaged rates more consistent with observations. Importantly, entrainment‐limited riverbank erosion does not depend on water temperature, indicating that decadal erosion rates may be less sensitive to warming than predicted previously.

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Quantifying the Export of Floodplain Soil Carbon to Arctic Rivers by Bank Erosion

Cited by 6 publications

References 0 publications

Remote Sensing of Riverbank Migration Using Particle Image Velocimetry

Remote Sensing of Riverbank Migration Using Particle Image Velocimetry

Arctic Permafrost Thawing Enhances Sulfide Oxidation

Sediment Entrainment and Slump Blocks Limit Permafrost Riverbank Erosion

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