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Abstract The thawing of permafrost in the Arctic has led to an increase in coastal land loss, flooding, and ground subsidence, seriously threatening civil infrastructure and coastal communities. However, a lack of tools for synthetic hazard assessment of the Arctic coast has hindered effective response measures. We developed a holistic framework, the Arctic Coastal Hazard Index (ACHI), to assess the vulnerability of Arctic coasts to permafrost thawing, coastal erosion, and coastal flooding. We quantified the coastal permafrost thaw potential (PTP) through regional assessment of thaw subsidence using ground settlement index. The calculations of the ground settlement index involve utilizing projections of permafrost conditions, including future regional mean annual ground temperature, active layer thickness, and talik thickness. The predicted thaw subsidence was validated through a comparison with observed long-term subsidence data. The ACHI incorporates the PTP into seven physical and ecological variables for coastal hazard assessment: shoreline type, habitat, relief, wind exposure, wave exposure, surge potential, and sea-level rise. The coastal hazard assessment was conducted for each 1 km²coastline of North Slope Borough, Alaska in the 2060s under the Representative Concentration Pathway 4.5 and 8.5 forcing scenarios. The areas that are prone to coastal hazards were identified by mapping the distribution pattern of the ACHI. The calculated coastal hazards potential was subjected to validation by comparing it with the observed and historical long-term coastal erosion mean rates. This framework for Arctic coastal assessment may assist policy and decision-making for adaptation, mitigation strategies, and civil infrastructure planning. 

This paper presents a second-order, implicit numerical model for one-dimensional, large strain thaw consolidation of ice-rich, fine-grained permafrost. The phase composition of permafrost at sub-freezing temperatures is determined using an unfrozen water content model that accounts for both capillary and adsorptive unfrozen water. The model incorporates secondary compression to improve the accuracy of long-term thaw consolidation simulations. The algorithm incorporates conduction, advection, and phase change in heat transfer and simultaneous occurrence of primary consolidation and secondary compression. Benchmarking and verification of the model show good agreement with existing numerical models. The proposed model is validated against experimental observations. The model indicates that adsorbed unfrozen water dominates over a wide range of sub-freezing temperatures, while capillary unfrozen water freezes at temperatures just below the freezing point. Numerical simulations suggest that ignoring secondary compression can lead to underestimation of excess pore pressure and settlement during both thaw and post-thaw consolidation. Void ratio and average degree of consolidation are overestimated when secondary compression is not considered. The effect of secondary compression on excess pore pressure and void ratio during thawing becomes more pronounced in thicker, field-scale permafrost layers. Results from this study highlight the importance of considering adsorptive and capillary unfrozen water to determine permafrost composition and incorporating secondary compression in thaw consolidation modeling and thaw settlement estimation for long-term civil infrastructure planning in cold regions. The proposed model provides a comprehensive framework for simulating thaw consolidation processes in permafrost regions. 

The degradation of permafrost alters deformation and long-term strength, posing challenges to existing and future civil infrastructure in Northern Alaska. Long-term strength is a critical parameter in the design of civil projects; yet, to our best knowledge, data on the creep deformation and long-term strength of undisturbed permafrost in Northern Alaska remain limited. Soil particle fraction, unfrozen water content, temperature, and salinity may interactively affect creep deformation and long-term strength of permafrost; however, their interactive effects are not well understood. In this study, field samples of relatively undisturbed permafrost from the upper 1.5 m of the Arctic Coastal Plain near Utqiaġvik, Alaska, were first retrieved and analyzed. The permafrost was characterized as saline ice-rich silty sand and nonuniformly distributed ice. We conducted constant stress creep tests, unconfined compression strength tests, and unfrozen water content tests to assess the mechanical and physical properties of the permafrost cores. The results indicated that the long-term strength of the permafrost decreased by nearly 90% from −10°C to −2°C. At −10°C, the long-term strength increased by approximately 120% as the soil particle fraction rose from 0.14 to 0.26. The strengthening effect of soil particles diminished at higher temperatures and higher salinity due to the influence of unfrozen water. A quantitative tool has been developed to predict the long-term strength of ice-rich permafrost, incorporating the effects of soil particle fraction and temperature. The findings of this study can potentially support infrastructure design and planning in Northern Alaska in the context of a warming climate. 

The Arctic is experiencing accelerated warming at up to four times the rate of temperate regions, driving permafrost thawing and ground ice melting, which, in turn lead to coastal bluff failure and accelerated erosion. The primary mechanisms behind Arctic coastal bluff failures include the formation of thermoerosional niches at the bluff’s toe and warming-induced reductions in ground strength, making Arctic coastal bluff failure a complex thermal-mechanical coupling process. Most existing studies have focused on coastal bluff failures in temperate regions, but the unique failure mechanism in the Arctic remain underexplored. This study addresses this gap by developing a thermalmechanical coupling model to study the failure mechanism of a permafrost bluff failure that occurred in 2023–2024 in Utqia˙gvik, Alaska. The model incorporates pore ice phase change, thaw-induced reductions in permafrost stiffness and strength, and the effects of thermoerosional niches, cracks, and ice wedges. Stability analysis is conducted via the local factor of safety (LFS) method to account for spatial variations in permafrost strength and stiffness. Ground-penetrating radar (GPR) data from the August 2024 site survey were employed to characterize site conditions, and ground temperature data were used to validate the model. The results revealed two primary failure zones: one near the ground surface and another at the bluff’s toe. The total area of these two failure zones expanded with ongoing thaw. Besides, the results indicated that the increase in thaw thickness, the growth in niche length, and the presence of cracks exacerbate bluff instability, and bluff failure is likely to initiate along the ice wedge–permafrost interface. 

This paper presents an implicit numerical model for one-dimensional thaw consolidation of saturated permafrost using finite volume approach. The model couples heat transfer with consolidation deformation and accounts for conduction, advection, phase change in heat transfer, and large strain in consolidation. The Crank–Nicolson method is used to obtain transient solutions. The overall approximation of the numerical scheme is of second-order accuracy. Numerical simulations are conducted to analyze the thaw consolidation behaviors in a finite soil layer. Numerical results indicate that, in a finite soil layer, thaw penetration and settlement have nonlinear relationships with the square root of time with decreasing rate. The excess pore water pressure and void ratio at the thaw front decrease with time. Thaw consolidation behaviors can be strongly influenced by the thermal conductivity of soil grains. The advection heat-transfer mechanism has a negligible effect on thaw consolidation in low-permeability soil. 

In June 2023, one faculty member and two undergraduate students in civil engineering at Pennsylvania State University collaborated with Iḷisaġvik College to host the 2023 STEM Summer Camp in Utqiaġvik, Alaska. The 5-day camp accommodated 16 Indigenous Alaskan middle school students with the goal to foster the next generation in STEM careers in Arctic Alaska. The camp included hands-on, competitive activities and region-specific experimental activities. Trips to local research and cultural centers provided insight into STEM career opportunities. The camp piqued students’ interest in STEM subjects and STEM-related careers and equipped them with some foundational knowledge to advance their studies. In preparation for the 2024 STEM summer camp again in Utqiaġvik, the organizers partnered with a local middle school in State College, PA, to host a series of STEM activities. This paper presents these STEM activities, lessons learned, and areas for future improvement.