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1. Impacts of convective storms on runoff, erosion, and carbon export in a continuous permafrost landscape

   Repasch, M; Overeem, I; Arcuri, J; Anderson, S; Anderson, R; Cochran, C (June 2024, International Permafrost Association)

   na (Ed.)

   Permafrost holds more than twice the amount of carbon currently in the atmosphere, but this large carbon reservoir is vulnerable to thaw and erosion under a rapidly changing Arctic climate. Convective storms are becoming increasingly common during Arctic summers and can amplify runoff and erosion. These extreme events, in concert with active layer deepening, may accelerate carbon loss from the Arctic landscape. However, we lack measurements of carbon fluxes during these events. Rivers are sensitive to physical, chemical, and hydrological perturbations, and thus are excellent systems for studying landscape responses to thunderstorms. We present observations from the Canning River, Alaska, which drains the northern Brooks Range and flows across a continuous permafrost landscape to the Beaufort Sea. During summer 2022 and 2023 field campaigns, we opportunistically monitored river discharge, sediment, and organic carbon fluxes during several thunderstorms. During one notable storm, river discharge nearly doubled from ~130 m3/s to ~240 m3/s, suspended sediment flux increased 70-fold, and the particulate organic carbon (POC) flux increased 90-fold relative to non-storm conditions. Taken together, the river exported ~16 metric tons of POC over one hour of this sustained event, not including the additional flux of woody debris. Furthermore, the dissolved organic carbon (DOC) flux nearly doubled. Although these thunderstorm-driven fluxes are short-lived (hours to days), they play an outsized role in exporting organic carbon from Arctic rivers. Understanding how these extreme events impact river water, sediment, and carbon dynamics will help predict how Arctic climate change will modify the global carbon cycle. 

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2. Instantaneous discharge, suspended sediment, and organic carbon fluxes in the Canning River, Alaska, June-July 2022 and July-August 2023

   https://doi.org/10.18739/A2M61BR63  

   Repasch, Marisa; Overeem, Irina; Arcuri, Josie; Anderson, Suzanne; Anderson, Robert S (January 2024, NSF Arctic Data Center)

   This dataset contains measurements of river discharge, suspended sediment, and organic carbon fluxes in the Canning River, Alaska during one field campaign from 28 June to 10 July 2022 and a second field campaign from 21 July to 2 August 2023. The purpose of this dataset is to demonstrate the impact of summer convective storms on river suspended sediment and particulate organic carbon fluxes in Arctic Rivers. During the 2022 field campaign, we rafted down the Canning River starting on the upper Canning within the headwaters and ending near the mouth at the Beaufort Sea coast. During this campaign, we selected five locations along the active channel to conduct Acoustic Doppler Current Profiler (ADCP) surveys to measure river discharge and sample the river water for suspended sediment and particulate organic carbon, where T1 is the farthest upstream transect and T5 is the farthest downstream. During the 2023 field campaign, we collected instantaneous river discharge measurements of the Canning River in the headwaters at the Marsh Fork Bench Airstrip, at the Staines Airstrip, and on the Staines branch of the Canning River delta. We observed several thunderstorms during these field campaigns, during which the river water level and suspended load increased dramatically, prompting us to sample river suspended sediment during these events. This dataset includes ADCP measurements of river water discharge, suspended sediment concentrations, particulate and dissolved organic carbon concentrations, woody debris flux measurements, and estimates of instantaneous fluxes. 

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3. Increasing river sediment concentration and flux across the pan-Arctic

   https://doi.org/10.1038/s41561-026-01960-z  

   Tian, Shang; Li, Dongfeng; Zhang, Ting; McClelland, James W; Overeem, Irina; Lane, Stuart N; Spencer, Robert_G M; Wohl, Ellen; Sha, Anmeng; Zhao, Yi; et al (April 2026, Nature Geoscience)

   na (Ed.)

   Arctic rivers transport water, sediment and carbon, playing a central role in coastal stability and biogeochemical cycling. Although freshwater discharge to the Arctic Ocean has increased in recent decades, limited observations have hindered system-wide assessment of long-term, reach-level sediment dynamics. Here we develop a pan-Arctic-specific, satellite- and machine learning-based framework to reconstruct four decades of suspended sediment concentration dynamics for 4,331 river reaches. Our analysis reveals a significant increase in suspended sediment concentration in 40% of river reaches (858 out of 2,158) draining continuous permafrost zone, primarily driven by increasing discharge, intensified thermokarst disturbances and fires. The pan-Arctic land–ocean sediment flux averages 315 ± 33 Mt yr−1, with 198 ± 35 Mt yr−1 (63%) from the six major rivers (Yenisey, Lena, Ob’, Kolyma, Yukon and Mackenzie) and 117 ± 13 Mt yr−1 (37%) from 263 previously overlooked small- and medium-sized coastal rivers. The total land–ocean sediment flux has increased by ~15%, from ~299 ± 28 Mt yr−1 in the 1980s to 344 ± 29 Mt yr−1 in the 2010s. These results provide a baseline for pan-Arctic river sediment dynamics and underscore the essential yet underappreciated contribution of small- and medium-sized coastal rivers to Arctic landscape and carbon cycle changes. 

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4. River ice controls permafrost bank erosion across an Arctic delta

   https://doi.org/10.1002/esp.70189  

   Arcuri, Josie; Overeem, Irina; Repasch, Marisa; Anderson, Robert S; Anderson, Suzanne P; Koch, Joshua C; Urban, Frank (December 2025, Earth Surface Processes and Landforms)

   Lane, Stuart (Ed.)

   Abstract Bank erosion in Arctic rivers helps shape channel geometry, mobilizes carbon from permafrost and influences sediment delivery to the Arctic Ocean. On Alaska's Arctic coastal plain, rivers begin flowing during snowmelt in late spring while extensive river ice persists in channels, such that hydraulics are altered and water is kept cool. The effects of river ice on permafrost bank erosion are poorly understood, primarily due to a dearth of field observations and a lack of river ice in existing models. To address this knowledge gap, we developed a numerical model to simulate the melt of substrate interstitial ice and bank collapse along individual permafrost river banks. We parameterize the model with field observations from riverbanks in three different channels on the Canning River delta, which are disparately impacted by river ice during snowmelt. We explore the bank erosion produced without river ice in the model and with modern river ice model scenarios that we drive with different stages and water temperature boundary conditions. We also compare predicted erosion rates to observations from satellite imagery to validate this approach. In the model, banks are idealized as vertical profiles that rise 1–2 m above the river bed and are comprised of silt‐ to sand‐sized sediment with dense roots in the active layer. Underneath, we generalize bank ice content underneath the active layer to represent ice‐rich permafrost on the river corridor boundaries. The model predicts that these ice‐rich river banks can erode by 2–6 m/yr. Scenarios without ice underpredict erosion in the distributary channels. Scenarios with varying river ice for different deltaic channels produce erosion rates similar to observations. Our results suggest that the prolonged melt of thick river ice in a delta nonlinearly impacts permafrost bank erosion by blocking river discharge to certain branches, heightening stage across the distributary network and locally limiting river water warming. Given expected changes in air temperature and hydrology, future estimates of Arctic river bank erosion could be improved by considering river ice. 

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5. Depth‐Partitioning of Particulate Organic Carbon Composition in the Rising and Falling Stages of the Amazon River

   https://doi.org/10.1029/2023GC011273  

   Rosengard, Sarah Z; Moura, Jose_Mauro S; Spencer, Robert_G M; Johnson, Carl; McNichol, Ann; Steen, Andrew D; Galy, Valier (June 2024, Geochemistry, Geophysics, Geosystems)

   Abstract The Amazon River mobilizes organic carbon across one of the world's largest terrestrial carbon reservoirs. Quantifying the sources of particulate organic carbon (POC) to this flux is typically challenging in large systems such as the Amazon River due to hydrodynamic sorting of sediments. Here, we analyze the composition of POC collected from multiple total suspended sediment (TSS) profiles in the mainstem at Óbidos, and surface samples from the Madeira, Solimões and Tapajós Rivers. As hypothesized, TSS and POC concentrations in the mainstem increased with depth and fit well to Rouse models for sediment sorting by grain size. Coupling these profiles with Acoustic Doppler Current Profiler discharge data, we estimate a large decrease in POC flux (from 540 to 370 kg per second) between the rising and falling stages of the Amazon River mainstem. The C/N ratio and stable and radiocarbon signatures of bulk POC are less variable within the cross‐section at Óbidos and suggest that riverine POC in the Amazon River is predominantly soil‐derived. However, smaller shifts in these compositional metrics with depth, including leaf waxn‐alkanes and fatty acids, are consistent with the perspective that deeper and larger particles carry fresher, less degraded organic matter sources (i.e., vegetation debris) through the mainstem. Overall, our cross‐sectional surveys at Óbidos highlight the importance of depth‐specific sampling for estimating riverine export fluxes. At the same time, they imply that this approach to sampling is perhaps less essential with respect to characterizing the composition of POC sources exported by the river. 

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