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

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.

2 Sep 2025

Airborne Bacteria over Thawing Permafrost Landscapes in the Arctic

Abstract: Rapid warming in the Arctic, outpacing global rates, is driving significant changes in cryospheric landscapes, including the release of long-preserved microorganisms. This study focuses on thawing permafrost in Northern Alaska, where microbes previously preserved in frozen soils are introduced into thermokarst lakes, rivers, and coastal waters and may also become airborne as bioaerosols. We present the first microbial composition measurements of bioaerosols in Alaska, identifying their local sources, such as soils, water bodies, and vegetation. Although sea/brackish water is the dominant bioaerosol contributor, we provide the first evidence of permafrost microbial signatures in bioaerosols from permafrost-laden regions. Permafrost is highly enriched with ice nucleating particles (INPs), which play a crucial role in cloud formation, precipitation processes, and radiation budget despite their relatively low atmospheric concentrations. With rising Arctic temperatures, increased permafrost thaw could result in higher levels of airborne permafrost-derived microbes and biological INPs active at warmer subzero temperatures. This, in turn, could enhance precipitation, further accelerating the permafrost thaw. Our findings emphasize the complex interactions between terrestrial changes and atmospheric processes, revealing a potential feedback loop that could intensify permafrost thaw and its broader environmental impacts.