11 May 2026

Hydrologic Mechanisms for 2022 Yellowstone River Flood and Comparisons to Recent Historic Floods

Abstract: In June 2022, a historic flood event occurred in the headwaters of the Yellowstone River Basin. The flood resulted in millions of dollars in damages and substantial interruptions to Yellowstone National Park. The 2022 flood event was substantially higher in magnitude than other high- peak flow events over the last 30 years. The high discharge was primarily due to the combination of hydrologic mechanisms initiated by rain-on-snow, including a high- elevation snowpack that peaked later than average. However, the contributions of each hydrologic driver, rain and snow, have not been quantified and could be important for understanding future flood events in the region. The contribution of snowmelt to the total terrestrial water input (TWI) varied throughout the area, yet was concentrated in the headwaters of the Yellowstone, Stillwater, and Boulder rivers, along with the headwaters of Rock Creek in Wyoming and Montana. The primary atmospheric contributions to the TWI during the 2022 event were precipitation from moisture transported from the Pacific Ocean that converged over the Greater Yellowstone Area (GYA) and snowmelt from residual snowpack in the northeast part of Yellowstone National Park.

6 May 2026

Two-Dimensional Thermal and Dynamical Strain in Landfast Sea Ice from InSAR: Results From a New Analytical Inverse Method and Field Observations

Abstract: Observing continuous strain in sea ice at geophysical scales of tens of meters to kilometers requires displacement measurements made with millimeter-scale precision. Satellite-based interferometric synthetic aperture radar (InSAR) provides such precise measurements of relative surface displacement over broad spatial areas at regular intervals and, unlike point displacement measurements, it allows confident delineation of continuously deforming regions. However, InSAR only captures the 1-D component of surface displacement parallel to a radar’s lines-of-sight. Additional analysis is required to translate between these 1-D observations and the horizontal or vertical displacements they arose from. Previous studies utilize an iterative inverse model to constrain estimates of horizontal surface displacement from InSAR. Here we build upon that work outlining a new analytical inverse modeling method for quantifying displacement and strain over continuous regions of sea ice and provide comparison between model results and independent displacement observations. We demonstrate the inverse method over both landfast and drifting ice along the Alaskan coastline. These intercomparisons highlight environments in which displacements inverted from interferograms may be used as an independent estimator of surface strain, as well as the potential for the outlined inverse methods to be used in conjunction with other observing methods.

5 May 2026

Permafrost and Rain Influence Summer Hydrologic Flowpaths in Boreal Catchments

Abstract: Flowpaths of water through catchments influence water quality and flow regimes of streams. Depths of dominant flowpaths respond to variation in climate and catchment characteristics, such as topography, vegetation, and soil type. In high‐latitude regions, the depth and spatial extent of permafrost influences catchment hydrology, and thawing permafrost might change sources and pathways of water supplying solutes and flow to streams. We estimated contributions of precipitation, soil water, and groundwater flowpaths to streams during the open‐water period after snowmelt by applying a Bayesian mixing model to 4–6 years of observed solute concentrations in five catchments of boreal Alaska. The relative contribution of groundwater to streams varied from 12% to 82% across catchments and years and declined as spatial extent of permafrost increased from 25% to 58% across catchments, indicating potential for increased infiltration and drainage as permafrost thaws. Temporal patterns in precipitation also influenced flowpaths. The mean annual contribution of precipitation to streamflow increased in years with more rain. Groundwater contribution increased, on average, in years with few large storms, suggesting deepening flows due to seasonal ground thaw or loss of shallow water to evapotranspiration. In contrast, groundwater contributed less in years when large storms delivered most of the year's rain in late summer or autumn. Overall, spatial and temporal variation in relative flowpath contributions to streams suggest that permafrost thaw will deepen flowpaths, but increasing precipitation expected in high‐latitude regions under warming climate might obscure this effect by routing water via shallow flowpaths following large storms.

4 May 2026

Freshwater Wetland Carbon Flux Analysis Pertinent to the Net Emissions Analysis Tool Improvement: Method Development and Testing

Palustrine wetlands are ecosystems of interest due to their capacity to sequester large amounts of greenhouse gases. This field study in Washington and Idaho was conducted as proof of concept of methods for measuring carbon emissions in palustrine wetlands. The regions of Washington and Idaho were chosen as they span three different Environmental Protection Agency (EPA) Level 1 ecoregions in a relatively close geological area. Data were collected across all three ecoregions in an effort to detail the potential differences between palustrine wetlands within them. Carbon dioxide flux measurements were compared across two instruments: LICOR 8,100A and CIRAS-4. Supporting data related to vegetation and site characteristics were incorporated into the overall analyses. Results suggest that carbon dioxide flux varies in relation to several factors. Additional research will be required to inform the application of site-specific data which can improve the application of tools designed to quantify project scale estimates for net greenhouse gas emissions.

28 Apr 2026

Is the Ordinary High Water Mark Ordinarily at Bankfull? Applying A Weight-of-Evidence Approach to Stream Delineation

Abstract: The ordinary high water mark (OHWM) is a regulatory boundary essential to identifying the lateral jurisdictional limits of rivers and streams in the United States (U.S.). Bankfull is a scientific concept that has been defined and identified in a multitude of ways by scientists. Geomorphologist and hydrologist have long recognized that there can be variability in the identification of bankfull depending on how bankfull is defined. Furthermore, this variability is only increased by the inherent variability in stream characteristics that occurs along a reach of channel. Because of the overlap in the regulatory definition of OHWM and the scientific definitions of bankfull, one of the primary purposes of the study is to apply the definition of OHWM and compare it to bankfull in a variety of channel types in different climatic, hydrologic, and geologic settings. Our results show that there is a clear overlap between the identification of the OHWM and bankfull elevations. Regulatory practitioners are generally not specialized in fluvial geomorphology and yet are tasked with consistently and accurately identifying the OHWM in a variety of stream types throughout the U.S. Therefore, we also present how to apply a weight-of-evidence approach through a clear step-by-step process to potentially improve consistency and accuracy in identification of OHWM and bankfull by both scientists and non-scientists.

23 Apr 2026

Applications of Snow-Covered Areas from Unoccupied Aerial Systems (UAS) Visible Imagery: A Demonstration in Southeastern New Hampshire

Abstract: Remote sensing observations of snow-covered areas (SCA) are important for monitoring and modeling energy balances, hydrologic processes, and climate change. For an agricultural field, we produced 12 snow cover maps from UAS imagery during an approximately 3-week-long spring snowmelt period. SCA maps were used to characterize snow cover patterns, validate satellite snow cover products, translate satellite Normalized Difference Snow Index (NDSI) to fractional SCA (fSCA), and downscale satellite SCA observations. Compared to manually delineated SCA, the UAS SCA accuracy was 85%, with misclassifications due to shadows, ice, and patchy snow conditions. During snowmelt, UAS-derived maps of bare earth patches exhibited self-similarity, behaving as fractal objects over scales from 0.01 to 100 m2. As a validation tool, the UAS-derived SCA showed that satellite snow cover observations accurately captured the fSCA evolution during snowmelt (R2 = 0.93−0.98). A random forest satellite downscaling model, trained using 20 m Sentinel-2 NDSI observations and 20 cm vegetation and terrain features, produced realistic (>90%accuracy), high-resolution SCA maps. While similar to traditional Sentinel-2 SCA in most conditions, downscaling snow cover significantly improved performance during periods of patchy snow cover and produced more realistic bare patches. UAS optical sensing demonstrates the potential uses for high-resolution snow cover mapping and recommends future research avenues for using UAS SCA maps.

20 Apr 2026

Permafrost Pore Structure and its Influence on Microbial Diversity: Insights from X-Ray Computed Tomography

Abstract: Soil pore structure plays a critical role in shaping soil microbial communities, which directly influence biogeochemical cycling. A notable impact of soil pore structure on microbial communities is the inverse relationship between microbial diversity and hydrological pore connectivity, where increased hydrological pore connectivity reduces microbial diversity. Although well-studied in temperate systems, the importance of hydrological pore connectivity on soil microbial community diversity in permafrost soils is largely unknown. Although once thought to be devoid of microbial activity, more recent advances demonstrate permafrost is an active ecosystem albeit less than most unfrozen soil. Thus, these principles that govern unfrozen soils could remain impactful in permafrost. In this study, our objective was to quantify permafrost pore structure and determine if the inverse relationship between soil hydrological pore connectivity and microbial diversity persists in permafrost. To address these objectives, we analyzed eight permafrost cores from three distinct sites in Alaska. To quantify soil pore characteristics, we scanned intact permafrost using X-ray computed tomography. The Euler characteristic number was used to measure pore connectivity and serve as a proxy for potential hydrological connectivity, as direct measurement of hydrological connectivity was not possible. DNA and RNA were extracted from the scanned permafrost and analyzed via amplicon sequencing of the 16S region to quantify the total and active microbial community diversity. We found that permafrost soil shares characteristics with temperate soils despite limits in our analytical resolution (i.e., at an instrument scanning resolution of 20 µm, only macro-scale features (>75 µm) could be quantified). For example, we found that pores in the range of 75–1000 µm are the dominant pore size class and a positive relationship between total porosity and pore connectivity. Additionally, we identified pore connectivity as a potential driver of microbial diversity and provided evidence that conditions before the formation of permafrost exert a strong legacy effect on currently observed permafrost microbial diversity. These insights help to explain how soil physical structure acts to influence microbial communities in this extreme environment.

14 Apr 2026

Performance Assessment of Microencapsulated Phase Change Materials with Low to High Thermoregulation Range in Asphalt Binder

Abstract: This study aims to assess the impact of microencapsulated phase change materials (MPCMs) on thermoregulation effect and binders’ performance. Accordingly, three MPCMs with melting points 6°C, 28°C, and 37°C were blended with PG 58-28 and PG 64-22 binders at dosages of 5%–20% by binder weight. Subsequently, laboratory experiments were conducted to examine impact on thermoregulation and rheological parameters including enthalpy change, complex modulus, Glover- Rowe parameter, creep stiffness, creep slope, fatigue, and rut factors. The findings showed that increasing MPCMs’ dosage in both control binders led to increased enthalpy change, indicating successful thermoregulation and capsules’ survival during blending. Rheological investigation depicted increasing complex modulus, creep stiffness and Glover-Rowe parameter in modified binders compared to control binders regardless of MPCMs’ thermoregulation range. However, Dynamic shear rheometer and Bending beam rheometer may not adequately capture their thermoregulation impact under steady-state conditions, necessitating use of temperature sweep test to validate influence on complex modulus and phase angle due to their thermoregulation capability. Temperature sweep test showed that within thermoregulation range, MPCMs with melting points 6°C and 28°C showed comparable fatigue resistance to respective control binders up to 10% dosage. Meanwhile, around melting point, MPCM with 37°C melting point enhanced rutting resistance.

14 Apr 2026

Changes in Permafrost Bacterial Community Composition After Thaw Across Multiple Alaskan Locations

Abstract: Increasing temperatures due to climate change are causing extensive permafrost thaw, impacting microbial communities and their processes. We conducted a laboratory thaw study comprising six Alaskan permafrost samples collected across a variety of locations to investigate how microbiome communities from different locations shift when experiencing the same thaw regime (stepwise increases in temperature over an 8-week incubation). The samples varied in bulk soil pH (4.45–6.59), water content (28%–265%), and carbon content (1%–29%). We surveyed the microbial community structure at each location pre- and post-thaw and determined whether communities were driven by stochastic or deterministic ecological assembly processes. We found that community composition and community assembly all varied by location. Dominant phyla were Firmicutes, followed by Actinobacteria and Proteobacteria. The deterministic process, homogeneous selection, was observed for five sites and was the most prevalent community assembly process at three of those sites, both pre- and post-thaw. At the two other sites, a combination of deterministic and stochastic processes influenced pre- and post-thaw community structure, with a large increase in drift post-thaw. Collectively, our findings suggest that permafrost attributes, such as edaphic conditions and pre-thaw community structure, exert an influence on the composition of microbial communities after thaw. However, the extent of this influence varies with location. The heterogeneous response of permafrost communities to thaw disturbance poses a significant challenge in accurately predicting the trajectory of microbial communities in response to climate change.

8 Apr 2026

Incubation Temperature and Urea Addition Impact Bacterial Composition and Voltage Output by Electroactive Bacteria

Abstract: Soil based terrestrial microbial fuel cells, traditionally used as batteries, could also serve as biosensors whereby the addition of an anthropogenic compound changes their voltage output. The ability and rate of electron transmission at the anode surface shifts based on external stimuli. This study investigates microbial response to diurnal temperature cycles and whether the shifts obscure voltage changes induced by the addition of urea. Replicate tMFCs were constructed with either 70 mg/ml urea or water and incubated at either a 25 ◦C static or 10 ◦C to 25 ◦C cycling temperature regime. Voltage was measured for 30 days and the tMFC electrodes were destructively sampled to determine bacterial taxonomy. Though voltage of all tMFCs increased throughout the incubation period, those exposed to urea had an output of 692 mV compared to 1011 mV observed in the controls. In both control and urea tMFCs, maximum voltage output during peak performance was significantly greater in the static temperature incubation than in cyclic. Bacterial diversity was significantly higher in the control tMFCs and was significantly higher at the cathode surface under cyclic temperature conditions. A previously trained machine learning model was able to accurately discern control vs. urea tMFCs despite the diurnal temperature conditions with 99% accuracy. These data show that diurnal temperature fluctuations had minimal impact on the bacterial community, and the presence of a contaminant was a strong predictor of tMFC community composition.