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Volume 83, Issue 1
Displaying 1-6 of 6 articles from this issue
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Okitsugu WATANABE, Kazuhide SATOW, Tomomi YAMADA, Yasoichi ENDO, Hidek ...2021 Volume 83 Issue 1 Pages 3-12
Published: 2021
Released on J-STAGE: September 01, 2021
JOURNAL OPEN ACCESS -
Shin SUGIYAMA, Masahiro MINOWA, Masato ITO, Shiori YAMANE2021 Volume 83 Issue 1 Pages 13-25
Published: 2021
Released on J-STAGE: September 01, 2021
JOURNAL OPEN ACCESSAquatic environments under the Antarctic ice sheet have drawn attention since the discovery of subglacial hydrological systems consisted of lakes and water channels. The ice sheet base is an important boundary, where basal sliding, geothermal heating, erosion and deposition processes take place. Further, basal melting and subshelf ocean circulation are the keys to understand recent mass loss of the ice sheet. Despite its importance, however, in-situ observation of the subglacial environment is difficult because of the ice cover with a thickness ranging from several hundred meters to several kilometers. Hot-water drilling and borehole measurement techniques are the solutions for the direct observation. In this contribution, we review hot-water drilling and subglacial measurements previously performed in Antarctica. We also introduce our project at Langhovde Glacier as an example of hot-water drilling on an Antarctic outlet glacier, and discuss the future of subglacial exploration of the ice sheet.View full abstractDownload PDF (1838K) -
Masashi NIWANO, Teruo AOKI, Akihiro HASHIMOTO, Naga OSHIMA, Mizuo KAJI ...2021 Volume 83 Issue 1 Pages 27-50
Published: 2021
Released on J-STAGE: September 01, 2021
JOURNAL OPEN ACCESS -
Yukihiko ONUMA, Nozomu TAKEUCHI2021 Volume 83 Issue 1 Pages 51-66
Published: 2021
Released on J-STAGE: September 01, 2021
JOURNAL OPEN ACCESSReduction of snow and ice albedo causes a drastic mass loss of glaciers and the ice sheet in the Arctic region. The albedo of snow and ice is greatly reduced by inorganic impurities, such as aeolian mineral dust and black carbon, and also by organic impurities, such as microbes that live in the snow and ice. The effect of such biological impurities is called the bio-albedo effect, which can be found globally on glaciers and snowfields. The bio-albedo effect varies temporally and spatially due to its biological properties including growth, death, and migration. In addition, the bio-albedo effect shows distinctive spectral absorption due to various pigments contained in the cells. To quantify the bio-albedo effect, a physically based albedo model and a microbial growth model have been proposed by different studies recently. In this paper, we describe the mechanism of the bio-albedo effect and review its recent observations and model studies. The paper finally discuss future challenges in understanding and predicting the darkening of glaciers and ice sheet in the Arctic region.View full abstractDownload PDF (4490K) -
Naohiko HIRASAWA, Hideaki MOTOYAMA, Kyohei YAMADA, Konosuke SUGIURA, N ...2021 Volume 83 Issue 1 Pages 67-77
Published: 2021
Released on J-STAGE: September 01, 2021
JOURNAL FREE ACCESSAutomatic Weather Stations (AWSs) with ultrasonic snow depth sensors were newly installed at four sites. The installation was started in January 2016 and completed in October 2019. The sites are H128 in the coastal region, MD78 in the continental slope region with the katabatic wind, NRP in the inland high region on the upside of the continental slope, and NDF on the summit of the ice sheet. The purpose of this AWS system is to clarify the temporal variations of accumulations affected by synoptic-scale disturbances and diurnal variations while reflecting the regional characteristics over a wide area of the Antarctic ice sheet. This paper investigates the temporal variations of surface height observed at these four sites. The results are as follows: 1) The temporal changes of surface height include stepwise fluctuations and pulse-like fluctuations, and the rise in surface height is mainly caused by stepwise rises, rather than pulse-like fluctuations. 2) A comparison between H128 and NRP showed four cases in which surface height fluctuations appeared simultaneously over a wide area. The NOAA infrared image reveals that the cloud area associated with a synoptic-scale disturbance formed over the ice sheet. 3) The surface height is less likely to rise largely between different sites on the same day. 4) At the three sites other than NRP, a slow decline in surface height was observed during the warm season.View full abstractDownload PDF (3046K) -
─Examination of snow accretion development conditions by basic experiments─Yasushi KAMATA, Kohei MUROTANI, こうじ なかで, Daisuke TAKAHASHI, Kengo SATO ...2021 Volume 83 Issue 1 Pages 79-95
Published: 2021
Released on J-STAGE: September 01, 2021
JOURNAL OPEN ACCESSIn winter, when railway train run through snowy area, snow adheres to train bodies, and the accreted snow fall in warmer area and may cause damage to ground facilities. In order to study snow accretion control methods for the purpose of reducing such damage, it is required to reproduce the snow accretion situation by numerical simulation. However, snow accretion developmental conditions reflecting the snow accretion situation simulator is not clear. In this study, a cubic model was installed in a wind tunnel, and two types of experiments were carried out using artificial snow under the conditions of temperature −2℃ and wind speed from 2.5 to 10ms−1. One is a PIV (Particle Image Velocimetry) measurement experiment to investigate the air flow around the model and the motion of snow accretion particles, and the other is a snow accretion experiment to investigate the effects of wind speed and rotation angle of the model on the snow accretion shape. PIV measurements show that the airflow slows down near the model and changes its direction, but the flying snow particles collide with the accreted snow surface without decelerating along the wind direction and the particles that bounced off after the collision flowed along the snow accretion surface. From the snow accretion experiment, it was found that the angle between the wind direction and the snow accretion surface is almost constant for each wind speed even if the model is rotated. When flying snow particles collide with enough developed accreted snow surface, we assumed that the snow particles flow along the snow accretion surface after the collision and analyzed between wind speed and a velocity of the snow accretion surface direction component. As a result, the component velocity of the snow particles was almost constant even if the wind speed changed.View full abstractDownload PDF (5831K)
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