The Sea Ice Physico-Chemistry and Ecosystems 2024 (SLOPE2024) workshop was conducted in the Saroma-ko Lagoon, Hokkaido, Japan from the middle of February to the beginning of March 2024. The aim of SLOPE2024 was to study the physical, chemical, and biological characteristics and processes of the sea ice environment, develop/intercompare methods, test equipment, and train/educate personnel for studies of polar regions. We compared the biogeochemical and physical ice characteristic between ice originating from seawater and river water. The ferrous iron (Fe(II)) content of under-ice water was measured by luminolchemiluminescence detection using the standard addition method. For an intercomparison experiment, the difference in sea ice chlorophyll a concentration between freeze-drying and thawing methods was tested. In addition, sinking rate, flux, and size distribution of particles beneath sea ice were examined. Furthermore, we carried out experiments on sea-salt aerosol emission from sea ice and for the effect of sea ice cracks on the biogeochemical components in an artificial crack pool. Finally, the workshop explored how each of us gathered here imagine the Arctic in this place where we feel like being a part of the Arctic-ness, just as we are part of our society and the Earth.
After conducting 5.5 m borehole temperature measurements near the summit of Mt. Sashirui, Hokkaido, Japan, the first occurrence of permafrost in the Shiretoko mountain range has been newly confirmed. The observation point, a wind-swept site, is covered by an alpine wind-exposed dwarf shrub community. The observation of mean annual ground surface temperature and the estimation of mean annual air temperature at this point were both close to the thresholds of onset of permafrost formation. However, thermal insulation by bryophyte and lichen cover in summer and effective heat transfer through frozen shrub branches and a thin snow layer during cold spells are likely to sustain this permafrost. Continuous long-term measurements of ground temperatures at this site are expected to be important for monitoring climate change in mountain areas of the Shiretoko region.
Convective precipitation in the Kanto Plain of Japan during winter is not well understood due to limited detailed observations of atmospheric conditions, cloud and precipitation characteristics. This study analyzed a convective precipitation event on 26 January 2019, using surface meteorological observations, radar data, and measurements from a ground-based microwave radiometer and disdrometer at Tsukuba. The results revealed that convective clouds developed along a convergence line in the lower atmosphere, within a synoptic field characterized by an intensified winter monsoon. Stability indices derived from the microwave radiometer indicated increasing atmospheric instability prior to the precipitation event, which was attributed to increasing surface temperatures combined with the inflow of cold air into the upper atmosphere. During the event, two separate precipitation events were recorded at Tsukuba. A rapid increase in liquid water path was observed approximately 10 minutes before the first event. Disdrometer analysis revealed that graupel particles in the first event and graupel and small particles in the second were dominant, respectively. The average particle mass was also larger in the first event. Photographs of precipitation particles from citizen science showed that particles in the first event were more densely rimed compared to those in the second. These differences in precipitation characteristics are suggested to result from variations in the convective clouds, either isolated or organized. These findings could contribute to improved nowcasting of convective snowfall in the Kanto Plain during winter.
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.
Basal ice motion is a key process in glacier flow, playing a crucial role in fast glacier motion and shortterm 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 34mm 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.
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/cm(2) at a scanning speed of 2.0 mm/s. It produces surface structures with both nanoripples 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 degrees on the laser-treated ZAM surface and 131.6 degrees 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 degrees). Then, during snowfall and with the surface near 0 degrees C, snow was shed from the hydrophilic laser-treated ZAM and ZA samples, but snow remained on the nonlased 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 degrees C, but snow was found to suddenly accrete on both surfaces when the temperature fell to about - 11 degrees C.
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.
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 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 region's 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 B & aacute;r & eth;arbunga, Iceland, had little effect on the metallic element concentrations. The increased Ca/Al ratio, Ca solubility, and fine particle fraction (<= 5 mu m) 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 mu m) increased, suggesting that the relative contributions from coastal soil regions in Greenland increased in those seasons.
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 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.
Snow algae are photosynthetic microbes growing on snowpacks and are commonly observed in mountain areas in Japan. In this study, we report the snow algal blooms observed in Mt. Echigo-Komagatake located in Niigata prefecture, Japan. Field investigation was conducted in late June of 2021 on a snow patch located in an alpine zone at an altitude of 2000 m above sea level. Patches of snow with red, green, or brown color were observed on the snowpack. Microscopic observation showed that the colored snow contained various morpho-types of snow algal cells, which appeared to be similar to those previously reported in Japan. The algal communities of the colored snow were mostly dominated by red spherical cells, which is likely to be Sanguina nivaloides, and consistent with those of the red snow reported in other alpine snowpacks in Japan. However, some samples showed a community consisting of various cell types, including multiple species of genus Chloromonas. The difference in community structure may be due to distance from vegetation around the snow patch, nutrient conditions of the snow, and/or growth period of the algae. The snow algal blooms of Mt. Echigo-Komagatake can be characterized by the appearance of various colors and algal communities on a snowpack.
Long-term hourly data records of the Automated Meteorological Data Acquisition System (AMeDAS) with snow depth measurements at three high elevation sites were analyzed in central Japan to assess the decadal scale winter climate variabilities with the effects of observation biases. Year-to-year variations of persistent snow cover periods (PSCPs) did not show a significant shortening trend with the delays of starting the PSCP associated with El Nino in December and forward to the ending of the PSCP with nationwide warming in March. Significant warming trends in the surface air temperature averaged in PSCPs were not identified, and length of the PSCP strongly contributed to the year-to-year variations of monthly averaged winter air temperatures. Long-term variabilities of precipitation records were primarily affected by changing the gauge type and data resolutions. After a simple correction of gauge undercatch by air temperature and wind speed, the amount of precipitation increased by around 20 % at the northern station but only by 3 % in the south due to frequent rain-on-snow events. In the two northern stations, snowfall amounts on the order of around 10 % were estimated to be missing in the precipitation records, where a long-term decreasing trend in occurrences of freezing precipitation was also found. The statistics calculated by AMeDAS data were verified using the data of the Vaisala Present Weather Detector in the Sugadaira Highland.
An atmosphere-sea ice-ocean interaction study was conducted at the Saroma-ko Lagoon, Hokkaido, Japan from 27 February to 9 March 2021. Air-sea ice CO2 flux measurements were conducted by eddy covariance and chamber methods together with meteorological observations. Sea ice cores were collected to understand the interaction between the atmosphere and under-ice water with respect to fluxes of heat and biogeochemical components. Physical and biogeochemical parameters such as temperature, salinity, ice structure, environmental DNA, and concentrations of gases, nutrients, and trace metals were measured. Under-ice water properties were monitored to quantify heat budgets and interactions with sea ice biogeochemical properties. Incubation experiments with ice algae were conducted. Equipment such as air-sea ice CO2/CH4 flux chambers, an eddy covariance system, a trace metal analyzer, and a pump and sampler for environmental DNA were tested and compared to prepare for future Arctic and Antarctic expeditions. In addition, movies and pictures were taken under the auspices of the educational program of Hokkaido University (LASBOS) to enhance educational programs in ocean science. The field campaign activities provided useful information for inter-comparison research and future studies of sea ice in polar oceans.
In order to construct reliable deposited-aerosol database on the Anthropocene (from 1850 to 2020), we obtained a 250-meter-long ice core from the Southeastern Greenland Dome on May and June 2021, where is one of the highest accumulation domes in Greenland. The age of the ice core at a depth of 250 m was roughly estimated to be AD 1827 based on the timescale from a previously analyzed shallower ice core. The age of the sampled ice core satisfied the prerequisite conditions for constructing aerosol deposition database for Anthropocene. In addition, surface elevation, borehole temperatures, and internal stratigraphy of the ice sheet were performed, and meteorological and snow-pit observations were also conducted. Furthermore, we sampled aerosol and snow from the ice sheet for chemical and physical analyses.
