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

   Repasch, Marisa; Arcurie, Josie; Overeem, Irina; Anderson, Suzanne P; Anderson, Robert S; Koch, Joshua C (June 2024, Proceedings of the 12th International Conference on Permafrost Whitehorse, Canada)

   Beddoe, Riley; Karunaratne, Kumari (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. Monitoring of Suspended Sediment Mineralogy in Puerto-Rican Rivers: Effects of Flowrate and Lithology

   https://doi.org/10.3390/min13020208  

   Mackowiak, Trevor J.; Perdrial, Nicolas (February 2023, Minerals)

   Climate change induced changes in river flow dynamics have the potential to change the composition of suspended sediments in crucial tropical river ecosystems, possibly affecting their resiliency. This study investigates how changes in river discharge and bedrock lithology affected the physiochemical nature of river suspended sediments over a typical year in three Puerto-Rican rivers. Suspended sediment samples were collected on filter membranes in 2006 from three watersheds of differing lithology (quartz-diorite, volcaniclastic, and mixed lithology) in the Luquillo Mountains, Puerto-Rico. By monitoring changes in suspended sediment mineralogical composition (determined by XRD and SEM) as a function of discharge, we determined how sediment loads responded to changes in hydrological input in a typical year. Results showed that bedrock lithology influenced river suspended sediment mineralogy, with the fraction of crystalline versus amorphous material strongly influenced by the dominant lithology of the watershed. Crystalline phases were associated with granodiorite bedrock compared to amorphous material dominating the volcaniclastic watersheds. Thus, the mineralogy of suspended sediments in the river systems was controlled by secondary minerals. Mineralogical results showed that, bearing quantitative changes upon hydrological events, suspended sediments in all three watersheds returned to baseline composition post storm events, suggesting that the three watersheds are resilient to the events recorded that year. While the long-term mineralogical analysis of the evolution of suspended material in the studied rivers provided insights into river response to hydrologic events, it also proved technically challenging as materials in suspension in such pristine rivers are sparse and poorly crystalline. 

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3. The Role of Glacier Erosion in Riverine Particulate Organic Carbon Export

   https://doi.org/10.1029/2023GB007721  

   Behnke, Megan I.; Fellman, Jason B.; Nagorski, Sonia; Spencer, Robert G. M.; Hood, Eran (November 2023, Global Biogeochemical Cycles)

   Abstract Biospheric particulate organic carbon (POC_bio) burial and rock petrogenic particulate organic carbon (POC_petro) oxidation are opposing long‐term controls on the global carbon cycle, sequestering and releasing carbon, respectively. Here, we examine how watershed glacierization impacts the POC source by assessing the concentration and isotopic composition (δ¹³C and Δ¹⁴C) of POC exported from four watersheds with 0%–49% glacier coverage across a melt season in Southeast Alaska. We used two mixing models (age‐weight percent and dual carbon isotope) to calculate concentrations of POC_bioand POC_petrowithin the bulk POC pool. The fraction POC_petrocontribution was highest in the heavily glacierized watershed (age‐weight percent: 0.39 ± 0.05; dual isotope: 0.42 (0.37–0.47)), demonstrating a glacial source of POC_petroto fjords. POC_petrowas mobilized via glacier melt and subglacial flow, while POC_biowas largely flushed from the non‐glacierized landscape by rain. Flow normalized POC_bioconcentrations exceeded POC_petroconcentrations for all streams, but surprisingly were highest in the heavily glacierized watershed (mean: 0.70 mgL⁻¹; range 0.16–1.41 mgL⁻¹), suggesting that glacier rivers can contribute substantial POC_bioto coastal waters. Further, the most heavily glacierized watershed had the highest sediment concentration (207 mgL⁻¹; 7–708 mgL⁻¹), and thus may facilitate long‐term POC_bioprotection via sediment burial in glacier‐dominated fjords. Our results suggest that continuing glacial retreat will decrease POC concentrations and increase POC_bio:POC_petroexported from currently glacierized watersheds. Glacier retreat may thus decrease carbon storage in marine sediments and provide a positive feedback mechanism to climate change that is sensitive to future changes in POC_petrooxidation. 

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4. Hydroclimate Drives Seasonal Riverine Export Across a Gradient of Glacierized High‐Latitude Coastal Catchments

   https://doi.org/10.1029/2022WR033305  

   Jenckes, J.; Munk, L. A.; Ibarra, D. E.; Boutt, D. F.; Fellman, J.; Hood, E. (April 2023, Water Resources Research)

   Abstract Glacierized coastal catchments of the Gulf of Alaska (GoA) are undergoing rapid hydrologic fluctuations in response to climate change. These catchments deliver dissolved and suspended inorganic and organic matter to nearshore marine environments, however, these glacierized coastal catchments are relatively understudied and little is known about total solute and particulate fluxes to the ocean. We present hydrologic, physical, and geochemical data collected during April–October 2019–2021 from 10 streams along gradients of glacial fed to non‐glacial (i.e., precipitation) fed, in one Southcentral and one Southeast Alaska region. Hydrologic data reveal that glaciers drive the seasonal runoff patterns. The ẟ¹⁸O signature and specific conductance show distinctive seasonal variations in stream water sources between the study regions apparently due to the large amounts of rain in Southeast Alaska. Total dissolved solids concentrations and yields were elevated in the Southcentral region, due to lithologic influence on dissolved loads, however, the hydroclimate is the primary driver of the timing of dissolved and suspended yields. We show the yields of dissolved organic carbon is higher and that the δ¹³C_POCis enriched in the Southeast streams illustrating contrasts in organic carbon export across the GoA. Finally, we illustrate how future yields of solutes and sediments to the GoA may change as watersheds evolve from glacial influenced to precipitation dominated. This integrated analysis provides insights into how watershed characteristics beyond glacier coverage control properties of freshwater inputs to the GoA and the importance of expanding study regions to multiple hydroclimate regimes. 

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5. High frequency turbidity data and storm event characteristics of three urban streams in Cleveland, Ohio

   https://doi.org/10.4211/hs.a249f3100f924ad09600c9d3de2183b6  

   Safdar, Suffiyan; Jefferson, Anne; Costello, David; Blinn, Andrew (August 2024, Hydroshare)

   This dataset contains turbidity data and storm event characters of three urban watersheds in Cuyahoga County, Ohio. Turbidity data were collected at a frequency of 10 minutes using in-situ Cyclop-7 turbidimeters designed by Turner Designs and integrated with a Cyclops-7 logger by Precision Measurement Engineering, Inc. Data were collected for three years from September 2018 to 2021. Turbidity data is harmonized with instantaneous discharge data from USGS stream gages. Event characteristics contains runoff, precipitation and antecedent characteristics. The data support the findings of the study titled "Urbanization and Suspended Sediment Transport Dynamics: A Comparative Study of Watersheds with Varying Degree of Urbanization using Concentration-Discharge Hysteresis". 

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