研究者データベース

箕輪 昌紘(ミノワ マサヒロ)
低温科学研究所 雪氷新領域部門
助教

基本情報

所属

  • 低温科学研究所 雪氷新領域部門

職名

  • 助教

学位

  • 環境科学(2017年03月 北海道大学)

ホームページURL

J-Global ID

研究キーワード

  • 氷床   パタゴニア氷原   カービング   氷河   Earth Science   Glaciers   

研究分野

  • 環境・農学 / 環境動態解析
  • 自然科学一般 / 大気水圏科学

職歴

  • 2021年08月 - 現在 北海道大学 低温科学研究所
  • 2021年10月 - 2022年04月 第63次南極観測隊 夏隊
  • 2020年04月 - 2021年04月 名古屋大学 環境科学研究科
  • 2018年05月 - 2020年03月 Universidad Austral de Chile
  • 2017年04月 - 2018年04月 北海道大学 低温科学研究所
  • 2017年11月 - 2018年03月 第59次南極観測隊 夏隊
  • 2017年05月 - 2017年09月 アラスカ大学フェアバンクス校 visiting scholar
  • 2014年12月 - 2015年03月 アラスカ大学フェアバンクス校 visiting scholar

学歴

  • 2012年04月 - 2017年03月   北海道大学   大学院地球環境科学研究院

所属学協会

  • 国際雪氷学会   日本地球惑星連合   日本雪氷学会   

研究活動情報

論文

  • 利尻島ヤムナイ沢雪渓における 2021 年現地調査報告
    波多 俊太郎, 杉山 慎, 箕輪 昌紘, 日下 稜, 近藤 研, Wang Yefa, 渡邊 果歩
    北海道の雪氷 41 39 - 42 2022年 [査読無し]
  • 東南極ラングホブデ氷河における底面滑りの直接観測
    近藤 研, 杉山 慎, 箕輪 昌紘
    北海道の雪氷 41 35 - 38 2022年 [査読無し][通常論文]
  • 南極ラングホブデ氷河における 2021/22 年の熱水掘削
    杉山 慎, 近藤 研, 箕輪 昌紘
    北海道の雪氷 41 31 - 34 2022年 [査読無し]
  • Shin Sugiyama, Masahiro Minowa, Yasushi Fukamachi, Shuntaro Hata, Yoshihiro Yamamoto, Tobias Sauter, Christoph Schneider, Marius Schaefer
    Nature Communications 12 1 2021年12月 
    AbstractWater temperature in glacial lakes affects underwater melting and calving of glaciers terminating in lakes. Despite its importance, seasonal lake temperature variations are poorly understood because taking long-term measurements near the front of calving glaciers is challenging. To investigate the thermal structure and its seasonal variations, we performed year-around temperature and current measurement at depths of 58–392 m in Lago Grey, a 410-m-deep glacial lake in Patagonia. The measurement revealed critical impacts of subglacial discharge on the lake thermal condition. Water below a depth of ~100 m showed the coldest temperature in mid-summer, under the influence of glacial discharge, whereas temperature in the upper layer followed a seasonal variation of air temperature. The boundary of the lower and upper layers was controlled by the depth of a sill which blocks outflow of dense and cold glacial meltwater. Our data implies that subglacial discharge and bathymetry dictate mass loss and the retreat of lake-terminating glaciers. The cold lakewater hinders underwater melting and facilitates formation of a floating terminus.
  • Y. Iizuka, S. Matoba, M. Minowa, T. Yamasaki, K. Kawakami, A. Kakugo, M. Miyahara, K. Fujita, A. Hashimoto, M. Niwano, T. Tanikawa, T. Aoki
    Bulletin of Glaciological Research 39 1 - 12 2021年10月 [査読有り]
  • Masahiro Minowa, Shin Sugiyama, Masato Ito, Shiori Yamane, Shigeru Aoki
    NATURE COMMUNICATIONS 12 1 2021年07月 [査読有り]
     
    Basal melting of ice shelves is considered to be the principal driver of recent ice mass loss in Antarctica. Nevertheless, in-situ oceanic data covering the extensive areas of a subshelf cavity are sparse. Here we show comprehensive structures of temperature, salinity and current measured in January 2018 through four boreholes drilled at a similar to 3-km-long ice shelf of Langhovde Glacier in East Antarctica. The measurements were performed in 302-12m-thick ocean cavity beneath 234-412m-thick ice shelf. The data indicate that Modified Warm Deep Water is transported into the grounding zone beneath a stratified buoyant plume. Water at the ice-ocean interface was warmer than the in-situ freezing point by 0.65-0.95 degrees C, leading to a mean basal melt rate estimate of 1.42ma(-1). Our measurements indicate the existence of a density-driven water circulation in the cavity beneath the ice shelf of Langhovde Glacier, similar to that proposed for warm-ocean cavities of larger Antarctic ice shelves. Basal melting of ice shelves is the principal driver of recent ice mass loss in Antarctica. The study reports comprehensive structures of temperature, salinity and current under an ice shelf in East Antarctica obtained by borehole measurements.
  • Naoko Nagatsuka, Kumiko Goto-Azuma, Akane Tsushima, Koji Fujita, Sumito Matoba, Yukihiko Onuma, Remi Dallmayr, Moe Kadota, Motohiro Hirabayashi, Jun Ogata, Yoshimi Ogawa-Tsukagawa, Kyotaro Kitamura, Masahiro Minowa, Yuki Komuro, Hideaki Motoyama, Teruo Aoki
    CLIMATE OF THE PAST 17 3 1341 - 1362 2021年06月 [査読有り]
     
    Our study is the first to demonstrate a high-temporal-resolution record of mineral composition in a Greenland ice core over the past 100 years. To reconstruct past variations in the sources and transportation processes of mineral dust in northwestern Greenland, we analysed the morphology and mineralogical composition of dust in the SIGMA-D ice core from 1915 to 2013 using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results revealed that the ice core dust consisted mainly of silicate minerals and that the composition varied substantially on multi-decadal and inter-decadal scales, suggesting that the ice core minerals originated from different geological sources in different periods during the past 100 years. The multi-decadal variation trend differed among mineral types. Kaolinite, which generally formed in warm and humid climatic zones, was abundant in colder periods (1950-2004), whereas mica, chlorite, feldspars, mafic minerals, and quartz, which formed in arid, high-latitude, and local areas, were abundant in warmer periods (1915-1949 and 2005-2013). Comparison to Greenland surface temperature records indicates that multi-decadal variation in the relative abundance of these minerals was likely affected by local temperature changes in Greenland. Trajectory analysis shows that the minerals were transported mainly from the western coast of Greenland in the two warming periods, which was likely due to an increase in dust sourced from local icefree areas as a result of shorter snow/ice cover duration in the Greenland coastal region during the melt season caused by recent warming. Meanwhile, ancient deposits in northern Canada, which were formed in past warmer climates, seem to be the best candidate during the colder period (1950-2004). Our results suggest that SEM-EDS analysis can detect variations in ice core dust sources during recent periods of low dust concentration.
  • Masahiro Minowa, Marius Schaefer, Shin Sugiyama, Daiki Sakakibara, Pedro Skvarca
    EARTH AND PLANETARY SCIENCE LETTERS 561 2021年05月 [査読有り]
     
    The complex dynamics of calving glaciers is a major uncertainty in projecting global glacial mass loss. We present frontal ablation and ice mass change for the 38 major calving glaciers in the Patagonian icefields based on remote-sensing observations of ice-front positions, surface speeds and elevation changes. The frontal ablation from 2000 to 2019 was -24.1 +/- 1.7 Gt a(-1), which represents 34 +/- 6% of the total ablation of the icefields. The fraction of frontal ablation was close to half in the southern icefield and about one fifth in the northern icefield. The rate of the mass loss from the icefields during the period of study was 15.2 +/- 3.5 Gt a(-1), which is generally explained by surface mass balance but was accelerated as a result of increasing frontal ablation. The frontal ablation and mass change values suggest surface mass balance to be -1.5 +/- 0.9 Gt a(-1) for the northern icefield and +11.5 +/- 2.7 Gt a(-1) for the southern icefield during this period. Our study demonstrates that a strong increase in frontal ablation at several glaciers drives the mass loss in the southern icefield, whereas increasingly negative surface mass balance drives the mass loss in the northern icefield. (C) 2021 Elsevier B.V. All rights reserved.
  • Shin Sugiyama, Naoya Kanna, Daiki Sakakibara, Takuto Ando, Izumi Asaji, Ken Kondo, Yefan Wang, Yoshiki Fujishi, Shungo Fukumoto, Evgeniy Podolskiy, Yasushi Fukamachi, Minori Takahashi, Sumito Matoba, Yoshinori Iizuka, Ralf Greve, Masato Furuya, Kazutaka Tateyama, Tatsuya Watanabe, Shintaro Yamasaki, Atsushi Yamaguchi, Bungo Nishizawa, Kohei Matsuno, Daiki Nomura, Yuta Sakuragi, Yoshimasa Matsumura, Yoshihiko Ohashi, Teruo Aoki, Masashi Niwano, Naotaka Hayashi, Masahiro Minowa, Guillaume Jouvet, Eef van Dongen, Andreas Bauder, Martin Funk, Anders Anker Bjork, Toku Oshima
    POLAR SCIENCE 27 2021年03月 [査読有り]
     
    Environments along the coast of Greenland are rapidly changing under the influence of a warming climate in the Arctic. To better understand the changes in the coastal environments, we performed researches in the Qaanaaq region in northwestern Greenland as a part of the ArCS (Arctic Challenge for Sustainability) Project. Mass loss of ice caps and marine-terminating outlet glaciers were quantified by field and satellite observations. Measurements and sampling in fjords revealed the important role of glacial meltwater discharge in marine ecosystems. Flooding of a glacial stream in Qaanaaq and landslides in a nearby settlement were investigated to identify the drivers of the incidents. Our study observed rapid changes in the coastal environments, and their critical impact on the society in Qaanaaq. We organized workshops with the residents to absorb local and indigenous knowledge, as well as to share the results and data obtained in the project. Continuous effort towards obtaining long-term observations requiring involvement of local communities is crucial to contribute to a sustainable future in Greenland.
  • Masahiro Minowa, Evgeny A. Podolskiy, Shin Sugiyama
    ANNALS OF GLACIOLOGY 60 79 57 - 67 2019年09月 [査読有り]
     
    We recorded the ice motion and icequakes on the floating part of Langhovde Glacier in East Antarctica to better understand the dynamic behavior of ice shelves and floating tongues. Diurnal and semi-diurnal variations in ice motion and seismicity were simultaneously observed at all four global navigation satellite system and three seismic stations over 2 weeks. The short-term along-flow ice motion is explained by the elastic response of the glacier to ocean tide-induced hydrostatic stress variations, which decayed at a rate of 0.8 km(-1) toward the grounding line. We observed a large number of icequakes during mid-rising and high tides that covered a broad frequency range and formed two major groups of events centered at 10 and 120 Hz, respectively. The hourly occurrence rates were similar to 500 events h(-1), with the observed seismicity consistent with fracture due to floating tongue bending. We also observed minor secondary peaks at high ice speeds, which could reflect surface cracking due to stretching or basal friction. Our observation demonstrates that tidal-modulation was the main factor to fracture the floating tongue of Langhovde Glacier.
  • Shin Sugiyama, Francisco J. Navarro, Takanobu Sawagaki, Masahiro Minowa, Takahiro Segawa, Yukihiko Onuma, Jaime Otero, Evgeny V. Vasilenko
    JOURNAL OF GLACIOLOGY 65 252 689 - 699 2019年08月 [査読有り]
     
    To study subglacial hydrological condition and its influence on the glacier dynamics, we drilled Johnsons Glacier on Livingston Island in the Antarctic Peninsula region. Subglacial water pressure was recorded in boreholes at two locations over 2 years, accompanied by high-frequency ice-speed measurements during two summer melt seasons. Water pressure showed two different regimes, namely high frequency and large amplitude variations during the melt season (January-April) and small fluctuations near the overburden pressure the rest of the year. Speed-up events were observed several times in each summer measurement period. Ice motion during these events substantially contributed to total glacier motion, for example, fast ice flow over 1 week accounted for similar to 70% of the total displacement over a 25-day long measurement period. We did not find a clear relationship between subglacial water pressure and ice speed. This was probably because subglacial hydraulic conditions were spatially inhomogeneous and thus our borehole data did not always represent a large-scale subglacial condition. Ice temperature measurements in the boreholes confirmed the existence of a cold ice layer near the glacier surface. Our data provide a basis to better understand the dynamic and hydrological conditions of relatively unstudied glaciers in the Antarctic Peninsula region.
  • Masahiro Minowa, Evgeny A. Podolskiy, Guillaume Jouvet, Yvo Weidmann, Daiki Sakakibara, Shun Tsutaki, Riccardo Genco, Shin Sugiyama
    EARTH AND PLANETARY SCIENCE LETTERS 515 283 - 290 2019年06月 [査読有り]
     
    Measuring glacier calving magnitude, frequency and location in high temporal resolution is necessary to understand mass loss mechanisms of ocean-terminating glaciers. We utilized calving-generated tsunami signals recorded with a pressure sensor for estimating the calving flux of Bowdoin Glacier in northwestern Greenland. We find a relationship between calving ice volume and wave amplitude. This relationship was used to compute calving flux variation. The calving flux showed large spatial and temporal fluctuations in July 2015 and in July 2016, with a mean flux of 2.3 +/- 0.15 x 10(5) m(3) d(-1). Calving flux was greater during periods of fast ice flow, high air temperature, and at low/falling tide, indicating the importance of increased longitudinal strain due to glacier acceleration and/or submarine melting at the calving front. Long-term measurements with the method introduced here are promising for understanding the complex interplay of ice dynamics, melting and calving at glacier fronts. (C) 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
  • Hakime Seddik, Ralf Greve, Daiki Sakakibara, Shun Tsutaki, Masahiro Minowa, Shin Sugiyama
    JOURNAL OF GLACIOLOGY 65 250 225 - 238 2019年04月 [査読有り]
     
    We use the full-Stokes model Elmer/Ice to investigate the present dynamics of Bowdoin Glacier, a marine-terminating outlet glacier in northwestern Greenland. Short-term speed variations of the glacier were observed, correlating with air temperature and precipitation, and with the semi-diurnal ocean tides. We use a control inverse method to determine the distribution of basal friction. This reveals that most of the glacier area is characterized by near-plug-flow conditions, while some sticky spots are also identified. We then conduct experiments to test the sensitivity of the glacier flow to basal lubrication and tidal forcing at the calving front. Reduction of the basal drag by 10-40% produces speed-ups that agree approximately with the observed range of speed-ups that result from warm weather and precipitation events. In agreement with the observations, tidal forcing and surface speed near the calving front are found to be in anti-phase (high tide corresponds to low speed, and vice versa). However, the amplitude of the semi-diurnal variability is underpredicted by a factor similar to 3, which is likely related to either inaccuracies in the surface and bedrock topographies or mechanical weakening due to crevassing.
  • Shin Sugiyama, Masahiro Minowa, Marius Schaefer
    GEOPHYSICAL RESEARCH LETTERS 46 5 2602 - 2609 2019年03月 [査読有り]
     
    Underwater ice geometry at the front of calving glaciers provides crucial information for calving and underwater melting. In this study, we present ice geometry captured by operating a side-scanning sonar near the front of Glaciar Grey, a freshwater calving glacier in Patagonia. The observations revealed ice projecting into the lake with a substantially different structure from that of known tidewater glaciers. Terrace-like ice structures were found at several tens of meters below the water surface and extended up to 100m from the aerial ice front. The structure depicted by the sonar was confirmed when the ice front was exposed by flotation during a major calving event. We infer that buoyant force acting on the submerged ice terrace acted as a driver of the calving event. Our study demonstrates the importance of the underwater ice geometry, which affects sizable calving at the front of freshwater calving glaciers.Plain Language Summary Glaciers terminating in lakes and the ocean are in general retreating more rapidly than glaciers on land. This is because such glaciers lose ice by discharging icebergs and melting in water. The shape of the submerged part of the ice front provides important information for understanding iceberg production and melting, but measurements near the glacier front are difficult to obtain. In this study, we used a side-scanning sonar to visualize underwater ice of a lake terminating glacier in Patagonia. The observations revealed ice jutting into the lake, forming terrace-like structures several tens of meters below the water surface. The structure was significantly different from that of ocean terminating glaciers. The observation was confirmed when the ice front was detached from the glacier and exposed by flotation. Our study demonstrates that buoyant force acting on the ice terrace plays a key role in the production of large icebergs at the front of freshwater calving glaciers.
  • Masahiro Minowa, Marius Schaefer, Pedro Skvarca, Sumito Matoba, GuiseIla Gacitua
    BULLETIN OF GLACIOLOGICAL RESEARCH 37 47 - 56 2019年 [査読有り]
     
    To better understand the temporal variation of the ice surface elevation and the spatio-temporal variation of snow accumulation in the accumulation area of the Southern Patagonian Icefield, we carried out a glaciological traverse in October 2018. This included measurements of surface elevation, firn layers, and sampling of snow in the accumulation areas of Glaciar Viedma and Glaciar Pio XI. The main results from the traverse are: i) during the period of 2000-2018 the surface elevation in the accumulation area of Glaciar Viedma decreased by 1.7 m a(-1), but increased at Glaciar Pio XI by 0.4 m a(-1), ii) ground-penetrating radar revealed numerous firn layers with a continuous water aquifer at 20-40 m depth, iii) the water isotope ratio of surface snow samples varied with wind direction. Repeating the traverse in the area will provide an opportunity to answer questions about the contrasting glacier behavior and the snow accumulation rate, a necessary step to make reliable projections of future glacier behavior in Patagonia.
  • Masahiro Minowa, Evgeny A. Podolskiy, Shin Sugiyama, Daiki Sakakibara, Pedro Skvarca
    JOURNAL OF GLACIOLOGY 64 245 362 - 376 2018年06月 [査読有り]
     
    Calving plays a key role in the recent rapid retreat of glaciers around the world. However, many processes related to calving are poorly understood since direct observations are scarce and challenging to obtain. When calving occurs at a glacier front, surface-water waves arise over the ocean or a lake in front of glaciers. To study calving processes from these surface waves, we performed field observations at Glaciar Perito Moreno, Patagonia. We synchronized time-lapse photography and surface waves record to confirm that glacier calving produces distinct waves compared with local noise. A total of 1074 calving events were observed over the course of 39 d. During austral summer, calving occurred twice more frequently than in spring. The cumulative distribution of calving-interevent time interval followed exponential model, implying random occurrence of events in time. We further investigated wave properties and found that source-to-sensor distance can be estimated from wave dispersion within similar to 20% error. We also found that waves produced by different calving types showed similar spectra in the same frequency range between 0.05-0.2 Hz, and that the amplitude of surface waves increased with the size of calving. This study demonstrates the potential of surface-wave monitoring for understanding calving processes.
  • 永塚 尚子, 東 久美子, 對馬 あかね, 本山 秀明, 的場 澄人, 藤田 耕史, 山崎 哲秀, 大沼 友貴彦, 箕輪 昌紘, 青木 輝夫
    雪氷研究大会講演要旨集 2017 119 - 119 公益社団法人 日本雪氷学会/日本雪工学会 2017年
  • Podolskiy Evgeny A., Genco Riccardo, Sugiyama Shin, Walter Fabian, Funk Martin, Minowa Masahiro, Tsutaki Shun, Ripepe Maurizio
    低温科学 75 15 - 36 低温科学第75巻編集委員会 2017年 
    Outlet glaciers in Greenland have retreated and lost mass over the past decade. Understandingthe dynamics of tidewater glaciers is crucial for forecasting sea-level rise and for understanding thefuture of the Greenland Ice Sheet, given the buttressing support that tidewater glaciers provide toinland ice. However, the mechanisms controlling glacier-front location and the role played byexternal forcings (e.g., meltwater input and tidal oscillation) in basal motion and fracture formationleading to iceberg calving are poorly understood. Today it is known that glaciers generate seismicand infrasound signals that are detectable at local and teleseismic distances and can be used to monitorglacier dynamics. Here, we present examples of data recorded by a temporary network of seismicand infrasound instruments deployed at a tidewater glacier (Bowdoin Glacier, Greenland) in July 2015.Some stations were installed on ice at distances as close as ~ 250 m from the calving front,representing the closest deployments to the calving front that have been made to date. Multipleseismic and infrasound events were recorded by five seismic and six infrasound sensors, and linked tosurface crevassing, calving, and ice-cliff collapses, and presumably also hydrofracturing, icebergrotations, teleseismic earthquakes, and helicopter-induced tremors. Using classic seismological andarray analysis approaches (e.g., "short-term averaging/long-term averaging" and "f-k" analysis), as wellas image processing techniques, we explore this unique dataset to understand the glacial response toexternal forcings. Our observations, supported by GPS measurements of ice velocity, local weatherstationrecords, and time-lapse photography, provide a valuable resource for studying seismogenicglacial processes and their dependence on ocean tides and other environmental factors.
  • Masahiro Minowa, Shin Sugiyama, Daiki Sakakibara, Pedro Skvarca
    FRONTIERS IN EARTH SCIENCE 5 2017年01月 [査読有り]
     
    The front position of calving glaciers is controlled by ice speed and frontal ablation which consists of the two processes of calving and subaqueous melting. However, the relative importance of these processes in frontal variation is difficult to assess and poorly understood, particularly for freshwater calving glaciers. To better understand the mechanism of seasonal variations involved in the ice front variations of freshwater calving glaciers, we measured front position, ice surface speed, air temperature, and proglacial lakewater temperature of Glaciar Perito Moreno in Patagonia. No substantial fluctuations in front position and ice speed occurred during the 15-year period studied (1999-2013), despite a warming trend in air temperature (0.059 degrees C a(-1)). Seasonal variations were observed both in the ice-front position (+/- 50 m) and ice speed (+/- 15%). The frontal ablation rate, computed from the frontal displacement rate and the ice speed, varied in a seasonal manner with an amplitude approximately five times greater than that in the ice speed. The frontal ablation correlated well with seasonal lakewater temperature variations (r = 0.96) rather than with air temperature (r = 0.86). Our findings indicate that the seasonal ice front variations of Glaciar Perito Moreno are primarily due to frontal ablation, which is controlled through subaqueous melting by the thermal conditions of the lake.
  • Shin Sugiyama, Masahiro Minowa, Daiki Sakakibara, Pedro Skvarca, Takanobu Sawagaki, Yoshihiko Ohashi, Nozomu Naito, Kazuhisa Chikita
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 121 12 2270 - 2286 2016年12月 [査読有り]
     
    Calving glaciers are rapidly retreating in many regions under the influence of ice-water interactions at the glacier front. In contrast to the numerous researches conducted on fjords in front of tidewater glaciers, very few studies have been reported on lakes in which freshwater calving glaciers terminate. To better understand ice-water interactions at the front of freshwater calving glaciers, we measured lakewater temperature, turbidity, and bathymetry near Glaciar Perito Moreno, Upsala, and Viedma, large calving glaciers of the Southern Patagonia Icefield. The thermal structures of these lakes were significantly different from those reported in glacial fjords. There was no indication of upwelling subglacial meltwater; instead, turbid and cold glacial water discharge filled the region near the lake bottom. This was because water density was controlled by suspended sediment concentrations rather than by water temperature. Near-surface wind-driven circulation reaches a depth of similar to 180 m, forming a relatively warm isothermal layer (mean temperature of similar to 5-6 degrees C at Perito Moreno, similar to 3-4 degrees C at Upsala, and similar to 6-7 degrees C at Viedma), which should convey heat energy to the ice-water interface. However, the deeper part of the glacier front is in contact with stratified cold water, implying a limited amount of melting there. In the lake in front of Glaciar Viedma, the region deeper than 120 m was filled entirely with turbid and very cold water at pressure melting temperature. Our results revealed a previously unexplored thermal structure of proglacial lakes in Patagonia, suggesting its importance in the subaqueous melting of freshwater calving glaciers.
  • Evgeny A. Podolskiy, Shin Sugiyama, Martin Funk, Fabian Walter, Riccardo Genco, Shun Tsutaki, Masahiro Minowa, Maurizio Ripepe
    GEOPHYSICAL RESEARCH LETTERS 43 5 2036 - 2044 2016年03月 [査読有り]
     
    Glacier microseismicity is a promising tool to study glacier dynamics. However, physical processes connecting seismic signals and ice dynamics are not clearly understood at present. Particularly, the relationship between tide-modulated seismicity and dynamics of calving glaciers remains elusive. Here we analyze records from an on-ice seismometer placed 250m from the calving front of Bowdoin Glacier, Greenland. Using high-frequency glacier flow speed measurements, we show that the microseismic activity is related to strain rate variations. The seismic activity correlates with longitudinal stretching measured at the glacier surface. Both higher melt rates and falling tides accelerate glacier motion and increase longitudinal stretching. Long-term microseismic monitoring could therefore provide insights on how a calving glacier's force balance and flow regime react to changes at the ice-ocean interface.
  • 門田 萌, 的場 澄人, 本山 秀明, 藤田 耕史, 山崎 哲秀, 大沼 友貴彦, 箕輪 昌紘, 小室 悠紀, 青木 輝夫
    雪氷研究大会講演要旨集 2015 191 - 191 公益社団法人 日本雪氷学会/日本雪工学会 2015年
  • 小室 悠紀, 鈴木 利孝, 大沼 友貴彦, 箕輪 昌紘, 山崎 哲秀, 的場 澄人, 藤田 耕史, 平林 幹啓, 本山 秀明, 青木 輝夫
    雪氷研究大会講演要旨集 2015 166 - 166 公益社団法人 日本雪氷学会/日本雪工学会 2015年
  • Sumito Matoba, Hideaki Motoyama, Koji Fujita, Tetsuhide Yamasaki, Masahiro Minowa, Yukihiko Onuma, Yuki Komuro, Teruo Aoki, Satoru Yamaguchi, Shin Sugiyama, Hiroyuki Enomoto
    BULLETIN OF GLACIOLOGICAL RESEARCH 33 7 - 14 2015年 [査読有り]
     
    During spring 2014, we drilled an ice core on the northwestern Greenland Ice Sheet, recovering a core of total length 225 m. We also conducted stratigraphic observations, measurements of the density of the ice core, near-infrared photography of the ice core, preparation of liquid samples for chemical analysis, and measurements of borehole temperature. The pore close-off depth was 60 m, and the temperature in the borehole was -25.6 degrees C. at a depth of 10 m. In addition, we conducted snow-pit observations, ice-velocity and surface-elevation measurements using the global positioning system (GPS), meteorological observations, and installation of an automated weather station (AWS).
  • Masahiro Minowa, Shin Sugiyama, Daiki Sakakibara, Takanobu Sawagaki
    ANNALS OF GLACIOLOGY 56 70 26 - 32 2015年 [査読有り]
     
    Glaciar Perito Moreno (GPM) and Glaciar Ameghino (GA), Southern Patagonia Icefield, are in contact in the accumulation area, but have shown contrasting frontal variations in the past few decades. To investigate recent changes of the two glaciers and processes controlling the different responses to similar climate conditions, we measured surface elevation change from 2000 to 2008 and terminus positions from 1999 to 2012 using several types of satellite data. GPM shows no significant changes in terminus position and 0.4 +/- 0.3 m a(-1) thickening over the period, whereas GA retreated 55 +/- 2 m a(-1) and thinned 2.6 +/- 0.3 m a(-1). Mass-balance measurements over the period 1999/2000 show that accumulation at GPM was ten times greater than that at GA, but ablation was only three times greater. The mass-balance-altitude profile is similar for the two glaciers; differences in the mass-balance distribution are caused by differences in the accumulation-area ratio (AAR). Our results suggest that the AAR and the calving flux exert strong control on the evolution of glaciers in the region.

その他活動・業績

共同研究・競争的資金等の研究課題

  • カービングの発生機構と氷河氷床の変動に与える影響の解明
    日本学術振興会:科学研究費助成事業 若手研究
    研究期間 : 2022年04月 -2025年03月 
    代表者 : 箕輪 昌紘
  • グリーンランド氷床におけるフィルン構造と氷河流出水の実態把握
    北極圏研究加速プロジェクト:
    研究期間 : 2022年04月 -2024年03月
  • カービング氷河の急速な質量損失メカニズム:現地データに基づいた数値モデリング
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 箕輪 昌紘
  • 淡水性カービング氷河の後退に末端消耗が果たす役割の解明
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 箕輪 昌紘
  • 急速に後退する氷河・氷床の変動に海・湖が果たす役割の解明
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 箕輪 昌紘
     
    パタゴニアのペリート・モレノ氷河においてカービングの測定手法の提案とカービング発生メカニズムについて解析を行った.これまでほとんど用いられていなかった水面波を使うことでカービングの頻度や氷山の体積を定量的に推定できることが提案した.またカービングの発生メカニズムについてはデータの測定期間が短期であったことから十分に考察できなかったが,平均気温と平均カービング発生回数はよく一致しており,今後長期の観測をすることが発生メカニズムを明らかにする上で重要であることが示唆された.これらの研究成果は,Journal of Glaciology誌に投稿し受理された.同様の解析はグリーンランドのボードイン氷河やアラスカのルコンテ氷河でも実施しており,現在研究成果の発表に向け準備中である. 氷河末端の水中融解の重要性についてパタゴニアの氷河湖で他時期に測定をした水温や濁度を解析することで考察を行った.解析・考察の結果,同じ気候条件であるにも関わらず氷河湖によって水温構造は大きく異なることが明らかとなった.またこの違いには,氷河融解水流出量と湖の深度が重要な影響を持つことが明らかになった.これらの結果は同地域に存在する氷河でも水中融解の重要性は大きく異なる可能性を示唆している.現在研究成果を国際誌への出版に向け準備中である. パタゴニアの氷河での一連の研究成果については2017年7月にベルリンで開催された国際シンポジウムで発表を行った.
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 杉山 慎, 澤柿 教伸, 山崎 新太郎, 箕輪 昌紘, 榊原 大貴, シェーファ マリウス, スクヴァルカ ペドロ
     
    カービング氷河(海や湖に流入する氷河)の水中融解は観測が困難で、その定量化とプロセスの理解が急務となっている。そこで本研究では、サイドスキャンソナーを使って氷河末端の水中形状を測定し、融解速度の測定を試みた。パタゴニア、グリーンランド、南極で観測を行った結果、パタゴニアの湖に流入するグレイ氷河にて、水中で前方に突出した氷河形状が明らかになった。水温の測定結果と合わせて、湖面付近でより著しい氷融解が示された。当初計画した手法では融解の定量化には至らなかったものの、水温、濁度、水同位体の測定から融解速度の推定に成功した。以上の成果は、淡水カービング氷河の消耗機構に新しい知見を与えるものである。

大学運営

委員歴

  • 2022年04月 - 現在   日本雪氷学会 北海道支部   雪氷教育担当理事
  • 2021年09月 - 現在   日本雪氷学会   氷河情報センター広報幹事

その他

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