The 2015 Gorkha earthquake in Nepal triggered a large avalanche in Langtang, covering the village with avalanche debris and causing severe damage. The analysis of this disaster was conducted using an avalanche dynamics simulation, which estimated the potential hazards to the village. Avalanche dynamics simulations were performed using the TITAN2D model to obtain the appropriate input parameters for largescale avalanche flows. Using these input parameters, we calculated the avalanche flows for various initial volumes to obtain a lower bound for the potential hazard to Langtang Village. Based on the lower bound, it was estimated that both earthquake-induced and ice avalanches could threaten villages in the future. We also attempted to create a hazard map to estimate the areas around Langtang village where avalanches may have occurred. Using the Polynomial Chaos Quadrature, we were able to account for the uncertainties in the input parameters at a low computational cost.

In the Niseko area in Hokkaido, Japan, a unique set of rules -the “Niseko Rules”- control the opening and closing of gates to allow off-course skiing according to the avalanche danger level. In recent years, the need for scientific evidence that can correctly explain the Niseko Rules and the establishment of human resource training and organizational systems to ensure their continued operation has become apparent. Therefore, in collaboration with the local government and ski resorts, this study developed a system to generate snow redistribution information, which is important for determining avalanche risks in the Niseko area. The constructed system provides wind observation data at multiple points in ski resorts, wind spatial distribution simulations based on observational data, snow redistribution simulations based on wind spatial distribution simulations, and wind spatial distribution and snow redistribution forecast information based on meteorological forecasted data. Research has continued to improve the accuracy of these simulations. Agile research and development are also underway to improve the usability of the system in ski resorts and affected municipalities.

To understand the physics, chemistry, and ecosystems of sea ice and develop technologies for sea ice observation, multidisciplinary research for sea ice and under-ice water was conducted at the Saroma-ko Lagoon, Hokkaido, Japan from end of February to beginning of March 2023. Under-ice water properties were monitored to quantify heat budgets and interactions with sea ice biogeochemical properties. Sea ice cores were collected to understand the interaction with the under-ice water affected by river water discharge. Physical and biogeochemical parameters such as temperature, salinity, oxygen isotopic ratio, sea ice structure, environmental DNA, and concentrations of gases, nutrients, chlorophyll a, and trace metals were measured. Incubation experiments with ice algae were conducted. Equipment such as a melt probe for high vertical resolution sea ice sampling and a sea ice drilling robot to install under-ice communication devices were tested to develop the technologies for future Arctic and Antarctic expeditions. Multidisciplinary research of sea ice and under-ice water provided interactions between sea ice communities, including younger generations, that will be useful for future studies of sea ice in polar oceans.

The Hijiori avalanche test site, Ohkura Village, Yamagata Prefecture, Japan, was established during the winter of 2010/11 to observe small-scale avalanches in warmer regions. The site has been monitored by meteorological observation, and slope has been monitored using a web camera and UAV aerial photography since the winter of 2018/19. The regionʼs warm climate makes it prone to glide avalanches, and webcam monitoring has confirmed 56 avalanches in 13 winters, of which 97 % are glide avalanches. In winter, the wind direction is predominantly west-northwest or northwest. It is almost directly orthogonal to the ridge of the target slope, which makes it easy for cornices to develop. Simulations were also conducted using photographic and UAV data, which are being verified. To use the Hijiori avalanche test site more effectively in the future, we will continue to publish information that contributes to avalanche research by organizing the accumulated data.

Rising temperatures and melting of snow and ice since 2000 CE may result in coastal soil regions in Greenland providing more mineral particles to the Greenland ice sheet than before. To examine seasonal variations of the concentrations and source regions of mineral particles in recent snow in inland Northeast Greenland, we analyzed the total (i.e., soluble and insoluble) concentrations of major metallic elements (Al, Ca, and Fe) and the size distributions of mineral particles in snow pit samples covering 2013-2017 at the East Greenland Ice Core Project site. The total concentrations of metallic elements showed clear seasonality with spring maxima, indicating that the mineral particle concentrations peaked in this season. Volcanic products from the 2014-2015 eruptions of Bárðarbunga, Iceland, had little effect on the metallic element concentrations. The increased Ca/Al ratio, Ca solubility, and fine particle fraction (≤5 μm) in winter–spring indicated that the relative contributions of mineral particles originating from distant arid regions increased in those seasons. In summer–autumn, the Ca/Al ratio and Ca solubility decreased, and the coarse particle fraction (>5 μm) increased, suggesting that the relative contributions from coastal soil regions in Greenland increased in those seasons.

The northwestern Greenland ice sheet is a hot spot of the recent “Arctic Amplification” of climate change. Since 2012, we have continuously monitored surface weather conditions at the SIGMA-A site on the northwestern ice sheet and carried out several field campaigns to obtain in-situ data on snow physical conditions at the site. From 21 to 27 June 2023, we performed a research expedition at the SIGMA-A site for the first time since the coronavirus pandemic. In this report, we aim to describe our activities during the expedition, including 1) installation of a new automated weather station, 2) snow pit measurements to obtain near-surface profiles of snow grain shapes, snow density, and specific surface area of snow, and 3) weather forecast to support the expedition.

Permafrost and ground freezing/thawing processes are physically and eco-climatologically important factors in the terrestrial cryosphere. The model reproducibility of frozen ground affects the certainty and reliability of simulated eco-climate conditions in cold regions as well as on a global scale. This study evaluated the variations and their attributes in the model performance developed and employed in the recent decade regarding the subsurface thermal state using outputs from Japanese and international model intercomparison projects and reanalysis data. The simulated surface and subsurface physical states were compared at four Arctic sites under different frozen ground conditions (Fairbanks, Kevo, Tiksi, and Yakutsk). The results showed that despite large variations in the modeled permafrost temperature, all the models, including the reanalysis data, successfully reproduced the permafrost conditions for the continuous permafrost sites. In contrast, some models failed to reproduce the presence of permafrost for the sites in the discontinuous to isolated permafrost zones. Evaluations of near-surface ground temperature variability revealed that the overall wellness of the simulated ground thermal states relied on winter reproducibility. The importance of snowpack metamorphosis for adequate thermal insulation was confirmed and demonstrated. The results at the coastal tundra site imply the importance of snow cover redistribution and wind crust formation owing to strong winds, the lack of which resulted in overestimations of thermal insulation and overcooled near-surface ground by most models.

The propagation characteristics of sonic waves in snowpacks are important for internal structure exploration as well as the immediate rescue of people buried in snow avalanches. We buried a loudspeaker at the bottom of a snow pit and generated sonic waves of varying frequencies, primarily in the audible range; these waves were captured at the pit roof to examine sound propagation through the snowpack. The experiment was conducted in a pit with a disturbed snowpack to simulate an avalanche deposition with two average densities of 380 kg m⁻³ (loose fill) and 680 kg m⁻³ (dense fill). The results indicate that low-frequency (200-1000 Hz) waves are less attenuated than those at higher frequencies regardless of the snow density in the pit. Comparisons of sound propagation in loosely and densely filled snowpacks showed that sonic waves are less attenuated in densely filled snowpacks than in loosely filled snowpacks, especially at high frequencies (1.5-5.0-kHz band). The results of the acceleration spectral ratio and snow profile survey showed that sonic waves are amplified by multiple reflections in layers with a high physical property contrast. These facts suggest that sonic waves can be used to search for people buried in snow avalanches when the appropriate frequencies are selected depending on the diverse snowpack characteristics.

Shedding snow from highway structures, typically made of galvanized steel, can disrupt traffic, sometimes causing an accident. Here we examine the snow repellency of the galvanized steels —Zn–Al–Mg (ZAM) and Zn–Al (ZA)—whose surface was treated with a femtosecond laser. The treatment involves a laser fluence of 0.7 J/cm² at a scanning speed of 2.0 mm/s. It produces surface structures with both nano-ripples and a non-periodic distribution of sub-micron spacing covered by a fine, ripple-like, periodic nanostructure. The resulting contact angle (CA) of water droplets on the surface was found to be about 147.0° on the laser-treated ZAM surface and 131.6° on the laser-treated ZA surface. However, at two months of outdoor exposure in winter in Hokkaido, the contact angles had decreased, and in some cases, the surfaces had become hydrophilic (averaged CA＝21.8°). Then, during snowfall and with the surface near 0 °C, snow was shed from the hydrophilic laser-treated ZAM and ZA samples, but snow remained on the non-lased ZAM sample. We argue that the hydrophilicity of the laser-treated surfaces facilitates the evaporation of surface-warmed meltwater due to the greater melt–air interface area. Moreover, the treatment darkens the surface, thus promoting melting via warming due to greater solar radiation absorption. The hydrophilic surfaces of laser-treated ZAM and ZA were found to be effective at melting snow near 0 °C, but snow was found to suddenly accrete on both surfaces when the temperature fell to about −11 °C.

Basal ice motion is a key process in glacier flow, playing a crucial role in fast glacier motion and short-term ice speed variations. However, the mechanisms of basal motion remain poorly understood because direct observations are sparse. This paper reports the design and performance of a “ploughmeter” developed for deployment in a borehole to observe glacier basal motion and subglacial hydrology. The device measures three-dimensional acceleration and water pressure with sensors enclosed in a metal tube of 34 mm in diameter and 2.5 m in length and with a weight of 8.0 kg. Installed at the bottom of a borehole, the ploughmeter is dragged over the glacier bed as a result of glacier basal motion, which enables the study of signals related to basal motion and subglacial materials. Laboratory tests were conducted to investigate acceleration signals, which exhibited distinct characteristics depending on the material being ploughed. The ploughmeter showed stick-slip motion in gravel, with a tilting rate during the stick phase that correlated with the speed of the ploughing. The results suggest that the ploughing observations provide insight into subglacial materials and variations in basal ice motion. When the device is placed on a glacier surface, the seismic signals correlate with those obtained by a conventional seismometer in terms of the number of seismic events (r＝0.74) and the tremor amplitude (r＝0.54). Therefore, the ploughmeter offers an opportunity for measuring subglacial seismicity near the source location at the glacier base.