10 Sep 2025

Snow Depth Measurements from Arctic Tundra and Boreal Forest Collected During NASA SnowEx Alaska Campaign

Abstract: Boreal forest and Arctic tundra environments collectively hold the largest percentage of global terrestrial seasonal snow cover. Тhe in-situ snow measurement network is sparse and costly in these remote northern regions. Here, we complement existing snow depth monitoring in Arctic tundra and boreal forest by presenting an extensive (64°N–70°N) snow depth dataset and description of ground-based snow depth measurements collected during the NASA SnowEx Alaska intensive field campaign, March 7–16, 2023. We also report the accuracy of snow depth measurements in shallow boreal forest and Arctic tundra snowpack and share considerations in developing the consistent and repeatable snow depth data collection procedures. Snow depth measurements and technical validation described in this paper can serve as a robust product for testing snow remote sensing techniques, and for providing a reference dataset for climatological and hydrological studies.

10 Sep 2025

Mapping the Vulnerability of Boreal Permafrost in Central Alaska in Relation to Thaw Rate, Ground Ice, and Thermokarst Development

Abstract: Permafrost roughly affects half the boreal region in Alaska and varies greatly in its thermophysical properties and genesis. In boreal ecosystems, permafrost formation and degradation respond to complex interactions among climate, topography, hydrology, soils, vegetation, and disturbance. We synthesized data on soil thermal conditions and permafrost characteristics to assess current permafrost conditions in central Alaska, and classified and mapped soil landscapes vulnerable to future thaw and thermokarst development. Permafrost soil properties at 160 sites ranged from rocky soils in hillslope colluvium and glacial till, to silty loess, to thick peats on abandoned floodplains and bogs, across 64 geomorphic units. To assess the vulnerability of permafrost to climate variability and disturbance, we differentiated permafrost responses in terms of rate of thaw, potential thaw settlement, and thermokarst development. Using a rule-based model that uses geomorphic units for spatial extrapolation at the landscape scale, we mapped 10 vulnerability classes across three areas ranging from high potential settlement/low thaw rate in extremely ice-rich loess to low potential settlement/high thaw rate in rocky hillslope colluvium. Vulnerability classes corresponded to thermokarst features developed in response to past climates. Differing patterns in permafrost vulnerability have large implications for ecosystem trajectories, land use, and infrastructure damage from thaw.

10 Sep 2025

Detachment and Transport of Composition B Detonation Particles in Rills

Abstract: The partial detonation of munitions used in military exercises leaves behind energetic particles on the surface of soil. Energetic particles deposited by incomplete detonations can then dissolve and be transported by overland flow and potentially contaminate ground and surface waters. The objective of this study was to evaluate the mechanisms of transport of Composition B, a formulation that includes TNT and RDX during overland flow. The transport of Composition B was examined using a rill flume with three flow rates and four energetic particle sizes. After each erosion simulation, energetic particles remaining on the soil surface were measured along with energetics dissolved in runoff, in suspended sediment, and in infiltration. Smaller particle sizes led to greater transport in both solution and sediment. The properties of the energetic compounds also influenced transport. More TNT was transported in runoff than RDX, likely due to TNT’s higher solubility and dissolution rates, however, overall, dissolved energetics in runoff and infiltration accounted for very little of the total transport. Most transport of Composition B was the result of the physical movement of energetic particles and flakes by erosion forces. This study’s results allow for improved prediction of Composition B transport during overland flow.

10 Sep 2025

Geology, Geomorphology, and River Engineering in the Memphis-to-Rosedale Reach, Lower Mississippi River

Abstract: This study examines the geology and geomorphology of the Mississippi River between Memphis, Tennessee, and Rosedale, Mississippi, with a focus on the Tertiary (65 to 2 million years) surface and how the present-day river has impacted this surface. Previous mapping efforts involving the Tertiary surface by the US Army Corps of Engineers are reviewed. Relevant maps are included as plates herein to facilitate wider dissemination. Today’s channel has deepened through time due to river engineering, which includes oxbow cutoffs and hardening of river banks with revetment and training dikes to prevent uncontrolled bank caving and channel migration. The course of the river was fixed in place by 1962. The thalweg of the river intersects the Tertiary surface at Helena, Arkansas, at the Hardin oxbow cutoff, and near the vicinity of Memphis, Tennessee. At these three locations, the Tertiary surface occurs at shallow elevations and in close proximity to where Tertiary sediments outcrop. A deeply buried alluvial valley is present in the Tertiary surface. Erosion of Jackson Group sediments in this valley exposes the underlying Claiborne Group sediments. Jackson and Sunflower oxbow cutoffs occur in the deepest parts of the alluvial fill.

10 Sep 2025

Light Availability Calculator for Identifying Suitable Habitat for Light-Limited Aquatic Vegetation

Purpose: The purpose of this Ecosystem Management and Restoration Research Program Technical Note (EMRRP TN) is to introduce a geospatial Light Availability Calculator, designed to inform suitable habitat selection for light-limited, submerged aquatic vegetation (SAV) species. The need and intended use for the Light Availability Calculator is first described. Then, the scientific and mathematical formulations underpinning the calculator are explained. Finally, recommendations for calculator inputs reflective of various user needs (simple and rapid versus complex and time intensive) are described.

10 Sep 2025

Evaluation of the Plate Load Test for Design of Rigid Airfield Pavements Using Various Plate Sizes

Abstract: This report addresses the state of knowledge of the plate load test and modulus of subgrade reaction (k), industry’s desire to simplify the plate load test, and the effect of the k-value on rigid pavement design. The report traces back the theory behind the k-value over 150 years to evaluate the current state of knowledge. A total of 144 plate load tests were executed on three subgrade materials under varying base course thick-nesses. Plate load testing was designed to evaluate various plate sizes and testing standards (e.g., the military standard CRD-C 655-96 and the ASTM International [commonly called ASTM] standard ASTM D1196-21). By measuring plate load tests on varying base course thicknesses, field-measured effective k-curves were developed. Overall, results show that kASTM was higher than kCRD. Although a smaller plate setup produced similar results, additional variability was introduced when using smaller plates. The results of the field data imply that the current effective k-curves underestimate the global stiffness contribution provided by the base layer. Findings suggest the analytically generated effective k-curves validate the measured k-values in the field.

10 Sep 2025

Cellulose Nanofibers Impart Melt Resistance to Ice Through Optical and Thermal Mechanisms

Abstract: Ice is ubiquitous in cold regions with historical significance as a key structural material. Contemporary efforts to leverage ice for the construction of large structures have incorporated cellulose-based reinforcing materials to increase strength. While an increased resistance to melting has been observed, it has not been investigated. Herein, we provide evidence that cellulose nanofibers (CNFs), as a heterogeneous component to synthetic ices, increase melt resistance through optical and thermal mechanisms. Specifically, we investigated the effect of 0.1−1.0 wt % CNFs on the reflectance, thermal conductivity, and melt rate of ice. The presence of CNFs increased reflectance of ice from 20 to 70% at 640 nm. Thermophysical measurements revealed that CNFs both slow melting and facilitate freezing and do not statistically affect the specific heat capacity of ice. Measurements with light flash analysis revealed that CNFs reduce thermal conductivity up to 10%. Overall CNFs reduced the melt rate of ice by 10× with only 1.0 wt % CNF. These results demonstrate that insoluble CNFs impart melt resistance to ice by both optical and thermal mechanisms, results that provide an interesting combination of controls for ice stability and formation to optimize ice material properties for high performance applications in cold regions.

9 Sep 2025

Projecting the Longevity of Coastal Foredunes Under Stochastic Meteorological and Oceanographic Forcing

Abstract: Coastal foredunes serve as critical buffers between the ocean and beach-adjacent infrastructure, yet these features are at increasing risk of destruction from future storms and changes in sea level. Quantifying potential future hazards to dunes is complicated by an inability to forecast the exact sequencing and magnitude of future oceanographic and meteorological forcings. We used a stochastic weather emulator capable of generating time series of wind and wave properties to force a reduced complexity morphologic model to assess potential accretional and erosional dune volume changes over the next century. Inclusion of background beach erosion rates and sea level changes instead drives more frequent net volumetric dune erosion. At decadal scales, volume changes of the dune are shown to be dominated by the magnitude of shoreline change rate in locations rapidly retreating. For stable and mildly eroding shorelines, shoreline changes and changes in the still water level influence timescales of dune destruction. Sets of probabilistic simulations are used to show gradual wind-driven sediment gains can compensate for episodic wave-driven losses over the long term. However, in the case of higher sea levels, more frequent dune collision results in less time for dune recovery between major storms.

9 Sep 2025

Distinct Sandbar Behavior on a Gently Sloping Shoreface Sea-Breeze Dominated Beach

Abstract: Sandbars are common features in sandy nearshore environments that readily migrate in response to changing hydrodynamic conditions and can provide coastal protection by inducing wave breaking and through sediment feeding to the beach. A comprehensive 9-year data set of weekly to bi-weekly surveys of the beach and shallow nearshore, undertaken on an accretive micro-tidal sea-breeze dominated beach along the southeastern coast of Mexico, are presented here that shed new insights into hydrodynamic drivers of inner surf zone sandbar and shoreline dynamics. During spring-summer, short period waves drive offshore sandbar migration. Winter storms generate more energetic swell waves that induce onshore sandbar migration. Seasonal changes of shoreline and inner sandbar position are coupled, with on-shore sandbar migration being synchronous to seasonal shoreline advance, suggesting a gradual feeding of sediment from the bar system onto the beach. Analysis of the data are used to explore the physical drivers of sub-seasonal sandbar evolution at the site. The sandbar dynamics in the study area, showing an opposite behavior to conventional expectation of storm-induced offshore transport, are well correlated to seasonal changes of waves properties. This distinct sandbar behavior might be present at other gently sloping shoreface sea-breeze dominated sandy beaches.

9 Sep 2025

Active Layer and Permafrost Microbial Community Coalescence Increases Soil Activity and Diversity in Mixed Communities Compared to Permafrost Alone

Abstract: Permafrost is experiencing rapid degradation due to climate warming. Dispersal of microbial communities from the seasonally-thawed active layer soil into newly thawed permafrost may influence community assembly and increase carbon release from soils. We conducted a laboratory soil mixing study to understand how carbon utilization, heterotrophic respiration, and microbial community structure were affected when active layer and permafrost soils were mixed in varying proportions. Active layer soil and permafrost collected from two sites in Alaska were mixed in five different ratios and incubated for 100 days at 10°C. Respiration rates were highest in the 100% active layer soils, averaging 19.8 µg C-CO2 g−1 dry soil d−1 across both sites, and decreased linearly as the ratio of permafrost increased. Mixing of the two soil layers resulted in utilization of a more diverse group of carbon substrates compared to permafrost alone. Additionally, combining active layer and permafrost soils increased microbial diversity and resulted in communities resembling those from the active layer when soils were mixed in equal ratios. Understanding the effects of active layer-permafrost mixing on functional potential and soil organic matter decomposition will improve predictions of carbon-climate feedbacks as permafrost thaws in these regions.