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Yoshinori Iizuka
Institute of Low Temperature Science　Frontier Ice and Snow Science
Associate Professor
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Last Updated :2024/05/09

Researcher Profile and Settings

Affiliation

  • Institute of Low Temperature Science　Frontier Ice and Snow Science

Job Title

  • Associate Professor

URL

J-Global ID

Research Interests

  • 氷床コア   南極   第四紀   季節変動   エアロゾル   古環境復元   アイスコア   極地   環境変動   地球化学   古環境変動   イオン濃度   無機イオン濃度   塩微粒子   地球環境変動   氷床   時間スケール   陸域水循環・物質循環   フィルン   AIMイベント   D-0イベント   ドームふじ   高時間分解能解析   気候変動   ミランコビッチ理論   ダストフラックス   雪   結晶組織   地球規模環境変動   地球規模気候変動   

Research Areas

  • Environmental science/Agricultural science / Environmental dynamics
  • Natural sciences / Atmospheric and hydrospheric science

Educational Organization

Academic & Professional Experience

  • 2007 - 2012 Hokkaido University Institute of Low Temperature Science

Research Activities

Published Papers

  • Tomotaka Saruya, Atsushi Miyamoto, Shuji Fujita, Kumiko Goto-Azuma, Motohiro Hirabayashi, Akira Hori, Makoto Igarashi, Yoshinori Iizuka, Takao Kameda, Hiroshi Ohno, Wataru Shigeyama, Shun Tsutaki
    2024/01/05
  • Kaoru Kawakami, Yoshinori Iizuka, Mahiro Sasage, Mai Matsumoto, Takeshi Saito, Akira Hori, Sakiko Ishino, Shuji Fujita, Koji Fujita, Keita Takasugi, Takumi Hatakeyama, Saaya Hamamoto, Akihisa Watari, Nao Esashi, Miu Otsuka, Ryu Uemura, Kazuho Horiuchi, Masahiro Minowa, Shohei Hattori, Teruo Aoki, Motohiro Hirabayashi, Kenji Kawamura, Sumito Matoba
    Journal of Geophysical Research: Atmospheres 128 (20) 2169-897X 2023/10/13 
    Abstract Arctic warming has accelerated surface melting even in the highland areas of the Greenland ice sheet (GrIS). Understanding the relationship between climate and surface melting is essential for improving the estimates of ice‐sheet mass loss due to warming. Here we analyze a 250 m‐long ice core from the southeastern dome of GrIS (SE‐Dome site; 67°19′17″ N, 36°47′03″ W, 3,161 m a.s.l.), where the annual mean temperature is −20.9°C and the accumulation rate is high and there is a large discrepancy among climate models regarding snow accumulation estimates. A time scale was established for 1799–2020 with a half‐year uncertainty using annual counting of H2O2 concentration and five time horizons determined by electrical conductivity, melt events, and tritium concentration. The annual accumulation rate from the ice core shows no significant trend over 221 years and has an average of 1.04 ± 0.20 m w.e. year−1. In contrast, the frequency and thickness of refrozen melt layer (ML) have increased over 221 years, and are synchronized with temperature changes in the Arctic. The thickness of MLs correlates positively with the time‐integrated summer temperature anomaly using a reanalysis of air temperature. The in‐situ accumulation records in the southeastern GrIS provide an important basis for correcting reanalysis data such as ERA5, which in turn are valuable for improving regional climate models.
  • Yutaka Kurosaki, Sumito Matoba, Yoshinori Iizuka, Koji Fujita, Rigen Shimada
    Communications Earth & Environment 3 (1) 2022/12/26 
    Abstract Ocean phytoplankton are an important source of dimethyl sulfide, which influences marine cloud formation. Model studies suggest that declines in Arctic sea ice may lead to increased dimethyl sulfide emissions, however observational support is lacking. Here, we present a 55-year high-resolution ice core record of methane sulfonic acid flux, an oxidation product of dimethyl sulfide, from the southeast Greenland Ice Sheet. We infer temporal variations in ocean dimethyl sulfide emissions and find that springtime (April–June) fluxes of methane sulfonic acid correlate well with satellite-derived chlorophyll-a concentration in the Irminger Sea. Summertime (July–September) methane sulfonic acid fluxes were 3 to 6 times higher between 2002–2014 than 1972–2001. We attribute this to sea ice retreat day becoming earlier and a coincident increase in chlorophyll-a concentration in the adjacent open coastal waters.
  • Kaoru Kawakami, Yoshinori Iizuka, Sumito Matoba, Teruo Aoki, Takuto Ando
    Journal of Glaciology 1 - 13 0022-1430 2022/11/21 
    Abstract In recent decades, surface melting on the inland Greenland ice sheet has increased, leading to significant meltwater-refreezing in the snow and firn. Increased knowledge of the physical and chemical characteristics of these melt features (i.e., ice layers) is needed to help estimate future global sea-level rise. Here, using a combination of microscopy and spectroscopy, we investigate the size, shape, location, and chemical compositions of inclusions in 12 ice layers of the SIGMA-A ice core in the northwestern Greenland ice sheet (78°03′06″N, 67°37′42″W, 1490 m a.s.l.). In the ice layers, we found inclusions exceeding 30 μm diameter that could only be formed by melting–refreezing, which we classify into columnar-, particle-, and rod-like inclusions. We propose that the smaller columnar- and particle-like inclusions of solid Na2SO4⋅10H2O and CaSO4⋅2H2O form first, within the ice grains, followed by the larger rod-like inclusions of brines with mainly Na+ and Cl− in grain boundaries. Our results suggest a new proxy that may help identify past warm climates in deeper ice cores in Greenland and for studying future ice sheet melting behavior.
  • Y. Iizuka, R. Uemura, H. Matsui, N. Oshima, K. Kawakami, S. Hattori, H. Ohno, S. Matoba
    Journal of Geophysical Research: Atmospheres 2022/09/16 [Refereed][Not invited]
  • Tomotaka Saruya, Shuji Fujita, Yoshinori Iizuka, Atsushi Miyamoto, Hiroshi Ohno, Akira Hori, Wataru Shigeyama, Motohiro Hirabayashi, Kumiko Goto-Azuma
    The Cryosphere 16 (7) 2985 - 3003 2022/07/27 
    Abstract. The crystal orientation fabric (COF) of a polar ice sheethas a significant effect on the rheology of the ice sheet. With the aim ofbetter understanding the deformation regime of ice sheets, the workpresented here investigates the COF in the upper 80 % of the Dome FujiStation ice core in East Antarctica. Dielectric anisotropy (Δε) data were acquired as a novel indicator of the verticalclustering of COF resulting from vertical compressional strain within thedome. The Δε values were found to exhibit a generalincrease with depth, but with fluctuations over distances in the order of10–102 m. In addition, significant decreases in Δεwere found to be associated with depths corresponding to three major glacialto interglacial transitions. These changes in Δε areascribed to variations in the deformational history caused by dislocationmotion occurring from near-surface depths to deeper layers. Fluctuations inΔε over distances of less than 0.5 m exhibited a stronginverse correlation with Δε at depths greater thanapproximately 1200 m, indicating that they were enhanced during theglacial-interglacial transitions. The Δε data alsoexhibited a positive correlation with the concentration of chloride ions andan inverse correlation with the amount of dust particles in the ice core atgreater depths corresponding to decreases in the degree of c axis clustering.Finally, we found that fluctuations in Δε persisted toapproximately 80 % of the total depth of the ice sheet. These data suggestthat the factors determining the deformation of ice include theconcentration of chloride ions and the amount of dust particles, and thatthe layered contrast associated with the COF is preserved all the way fromthe near-surface to a depth corresponding to approximately 80 % of thethickness of the ice sheet. These findings provide important implicationsregarding further development of the COF under the various stress-strainconfigurations that the ice will experience in the deepest region,approximately 20 % of the total depth from the ice/bed interface.
  • Chihiro Miyamoto, Yoshinori Iizuka, Sumito Matoba, Shohei Hattori, Yoshio Takahashi
    Atmospheric Environment 278 119061 - 119061 1352-2310 2022/06
  • Ryu Uemura, Kosuke Masaka, Yoshinori Iizuka, Motohiro Hirabayashi, Hitoshi Matsui, Risei Matsumoto, Miki Uemura, Koji Fujita, Hideaki Motoyama
    Earth and Planetary Science Letters 578 117299 - 117299 0012-821X 2022/01
  • Hiroshi Ohno, Yoshinori Iizuka, Shuji Fujita
    Journal of Glaciology 67 (265) 903 - 908 0022-1430 2021/10 
    AbstractEarlier gas measurements of firn air (atmosphere in open pore channels) at polar sites have revealed the occurrence of gas fractionation phenomena during bubble close-off, in addition to well-known thermal and gravitational gas separation. Nevertheless, because of difficulties posed by measurement, little is known about the distribution of air constituents in already closed pores (bubbles) in firn. Herein, we describe the application of high-sensitivity pure rotational Raman spectroscopy, combined with sample immersion in the fluorocarbon-based inert fluid for removing the optical disturbance by diffused reflection. That application efficiently elicits information about nitrogen and oxygen composition ratios (N2/O2 or O2/N2) for each air bubble in firn. The developed methodology presents important implications for elucidating how gas records are formed and modified in the course of pore close-off in polar firn.
  • Koji Fujita, Sumito Matoba, Yoshinori Iizuka, Nozomu Takeuchi, Akane Tsushima, Yutaka Kurosaki, Teruo Aoki
    Earth and Space Science 8 (7) 2333-5084 2021/07/17
  • Shohei Hattori, Yoshinori Iizuka, Becky Alexander, Sakiko Ishino, Koji Fujita, Shuting Zhai, Tomás Sherwen, Naga Oshima, Ryu Uemura, Akinori Yamada, Nozomi Suzuki, Sumito Matoba, Asuka Tsuruta, Joel Savarino, Naohiro Yoshida
    Science Advances 7 (19) eabd4610 - eabd4610 2021/05 
    After the 1980s, atmospheric sulfate reduction is slower than the dramatic reductions in sulfur dioxide (SO2) emissions. However, a lack of observational evidence has hindered the identification of causal feedback mechanisms. Here, we report an increase in the oxygen isotopic composition of sulfate (Δ17OSO42−) in a Greenland ice core, implying an enhanced role of acidity-dependent in-cloud oxidation by ozone (up to 17 to 27%) in sulfate production since the 1960s. A global chemical transport model reproduces the magnitude of the increase in observed Δ17OSO42− with a 10 to 15% enhancement in the conversion efficiency from SO2 to sulfate in Eastern North America and Western Europe. With an expected continued decrease in atmospheric acidity, this feedback will continue in the future and partially hinder air quality improvements.
  • Tomomi Amino, Yoshinori Iizuka, Sumito Matoba, Rigen Shimada, Naga Oshima, Toshitaka Suzuki, Takuto Ando, Teruo Aoki, Koji Fujita
    Polar Science 27 100599 - 100599 1873-9652 2021/03 
    Mineral dust plays a key role in both local and global climates. At high latitudes, atmospheric dust can affect ice-nuclei formation, and surface dust can reduce the albedo as well as increase subsequent ice melting. As a proxy for past climate, mineral dust is preserved in ice cores, but few studies have examined deposited dust in ice cores during the Anthropocene, especially after 2000. We measured dust concentrations in an ice core at the southeastern dome in Greenland (SE-Dome), and reconstructed the annual and seasonal dust fluxes during 1960–2014. We find the annual average flux during 1960–2014 to be 34.8 ± 13.5 mg m yr , a value about twice that of ice cores further inland. The more recent part of that period, 2000–2014, has the higher annual flux of 46.6 ± 16.2 mg m yr . The annual and autumn dust fluxes highly correlate with air temperature in Tasiilaq (r = 0.61 and 0.50, respectively), a coastal location in southeastern Greenland. Our results suggest that the local dust emissions at the coastal region are increasing due to a decreasing seasonal snow-cover area arising from coastal Greenland warming after 2000. −2 −1 −2 −1
  • Kawakami Kaoru, Iizuka Yoshinori, Matoba Sumito, Aoki Teruo, Sugiyama Shin, Ando Takuto
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2021 34 - 34 1883-0870 2021
  • Esashi Nao, Tsushima Akane, Uemura Ryu, Iizuka Yoshinori, Matoba Sumito, Fujita Koji
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2021 21 - 21 1883-0870 2021
  • Hattori Shohei, Iizuka Yoshinori, Alexander Becky, Ishino Sakiko, Fujita Koji, Zhai Shuting, Sherwen Tomas, Oshima Naga, Uemura Ryu, Yamada Akinori, Suzuki Nozomi, Matoba Sumito, Tsuruta Asuka, Savarino Joel, Yoshida Naohiro
    Abstracts of Annual Meeting of the Geochemical Society of Japan 一般社団法人日本地球化学会 68 158  2021 
    大気中の硫酸の三酸素同位体組成は、大気中におけるSO2から硫酸への酸化過程における酸化剤の寄与率を反映して変動する。本研究では、グリーンランド南東ドームで採取された過去60年分のアイスコアを用い、その硫酸の三酸素同位体組成を分析することで、過去の大気化学反応の変化を復元した。硫酸の三酸素同位体組成は過去60年間で上昇し、SO2の液相O3酸化の寄与率が高くなっていたことを示した。硫酸の三酸素同位体組成の中和率やH+フラックスの変化とよく相関していた。SO2の液相O3酸化は酸性度が低いほど促進されることから、1980年代以降のSO2排出量の削減とアンモニア排出の増加による大気中酸性度の低下が促進の要因であると考えられる。このように、硫酸の三酸素同位体組成の分析によって、SO2排出規制にも関わらず硫酸エアロゾルの減少が鈍化するケミカルフィードバック機構の要因が、大気酸性度の低下によるSO2の液相O3酸化の促進であることが特定された。
  • Yoshinori IIZUKA, Sumito MATOBA, Masahiro MINOWA, Tetsuhide YAMASAKI, Kaoru KAWAKAMI, Ayako KAKUGO, Morihiro MIYAHARA, Akihiro HASHIMOTO, Masashi NIWANO, Tomonori TANIKAWA, Koji FUJITA, Teruo AOKI
    Bulletin of Glaciological Research 39 1 - 12 1345-3807 2021
  • 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 Bjørk, Toku Oshima
    Polar Science 27 1873-9652 2021 
    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.
  • Yutaka Kurosaki, Sumito Matoba, Yoshinori Iizuka, Masashi Niwano, Tomonori Tanikawa, Takuto Ando, Akira Hori, Atsushi Miyamoto, Shuji Fujita, Teruo Aoki
    Journal of Geophysical Research: Atmospheres 125 (16) 2169-897X 2020/08 [Refereed][Not invited]
  • I. Oyabu, Y. Iizuka, K. Kawamura, E. Wolff, M. Severi, R. Ohgaito, A. Abe‐Ouchi, M. Hansson
    Journal of Geophysical Research: Atmospheres 125 (4) 2020/02/27
  • Kawakami Kaoru, Iizuka Yoshinori, Matoba Sumito, Aoki Teruo, Sugiyama Shin, Ando Takuto
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2020 66 - 66 1883-0870 2020
  • Matoba Sumito, Iizuka Yoshinori, Miyazaki Yuzo, Suzuki Toshitaka, Hattori Shohei, Uemura Ryu, Hara Keiichiro, Oshima Naga, Yamasaki Tetsuhide, Aoki Teruo
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2020 111 - 111 1883-0870 2020
  • Iizuka Yoshinori, Uemura Ryu, Matsui Hitoshi, Oshima Naga, Matoba Sumito
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2020 67 - 67 1883-0870 2020
  • Kazuho Horiuchi, Hiroshi Ohno, Go Iwahana, Yoshinori Iizuka, Hiroyuki Matsuzaki
    Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Elsevier {BV} 459 64  2019/11 [Refereed][Not invited]
  • Goto-Azuma K, Hirabayashi M, Motoyama H, Miyake T, Kuramoto T, Uemura R, Igarashi M, Iizuka Y, Sakurai T, Horikawa S, Suzuki K, Suzuki T, Fujita K, Kondo Y, Hattori S, Fujii Y
    Nature Communications 10 (1) 324  2019/07 [Refereed][Not invited]
     
    © 2019, The Author(s). Marine biogenic sulphur affects Earth’s radiation budget and may be an indicator of primary productivity in the Southern Ocean, which is closely related to atmospheric CO2 variability through the biological pump. Previous ice-core studies in Antarctica show little climate dependence of marine biogenic sulphur emissions and hence primary productivity, contradictory to marine sediment records. Here we present new 720,000-year ice core records from Dome Fuji in East Antarctica and show that a large portion of non-sea-salt sulphate, which was traditionally used as a proxy for marine biogenic sulphate, likely originates from terrestrial dust during glacials. By correcting for this, we make a revised calculation of biogenic sulphate and find that its flux is reduced in glacial periods. Our results suggest reduced dimethylsulphide emissions in the Antarctic Zone of the Southern Ocean during glacials and provide new evidence for the coupling between climate and the Southern Ocean sulphur cycle.
  • Nishino Saori, Suzuki Toshitaka, Iizuka Yoshinori, Hirabayashi Motohiro, Kawamura Kenji, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2019 83 - 83 1883-0870 2019
  • Esashi Nao, Suzuki Toshitaka, Iizuka Yoshinori, Hirabayashi Motohiro, Kawamura Kenji, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2019 84 - 84 1883-0870 2019
  • Open-sea and sea-ice fluctuations in nearshore Beaufort Sea during the last deglaciation derived from ion concentrations in ice wedge
    Iizuka, Y, C. Miyamoto, S. Matoba, G. Iwahana, K. Horiuchi, Y. Takahashi, N. Kanna, K. Suzuki, H. Ohno
    Earth and Planetary Science Letter 515 58 - 66 2019 [Refereed][Not invited]
  • Iizuka Yoshinori, Miyamoto Chihiro, Matoba Sumito, Iwahana Go, Horiuchi Kazuho, Takahashi Yoshio, Kanna Naoya, Suzuki Koji, Ohno Hiroshi
    Earth and Planetary Science Letters 515 58 - 66 0012-821X 2019 [Refereed][Not invited]
     
    © 2019 Elsevier B.V. For atmospheric gases and aerosols, snow and ice provide a useful archive of paleoenvironmental history. In the northern hemisphere, this archive has been largely limited to Greenland ice, but promising pioneering work has been done recently using chronology of an ice wedge in Barrow, northern Alaska. Here, we investigate past aerosols at the same ice-wedge sampling site, reconstructing the sea-ice fluctuations in the adjacent Beaufort Sea during the Bølling/Allerød (BA) and Younger Dryas (YD) periods. We confirm the integrity of methanesulfonate ion (MS − ) concentrations in the BIWS as marine proxies, and then find that the ice wedge has a high MS − concentration through the beginning (coldest) YD periods. The high MS − concentration indicates that even during the coldest YD periods (12,900–12,700 yrBP), the near-shore region in the Alaskan Beaufort Sea near Barrow may not have been completely filled by permanent sea ice.
  • Parvin F, Seki O, Fujita K, Iizuka Y, Matoba S, Ando T, Sawada K
    Atmospheric Environment 196 86 - 94 1352-2310 2019/01 [Refereed][Not invited]
     
    We provide continuous records of biomass burning molecular tracers (levoglucosan and dehydroabietic acid) in a Greenland ice core collected from the Southeastern Dome (the SE-Dome ice core) over the past several decades to assess the paleoclimatic utility of these tracers in Greenland ice cores. An air mass backward-trajectory analysis indicates that eastern Canada is likely the primary source region of the biomass burning tracers. Comparisons of levoglucosan and dehydroabietic acid data in the SE-Dome ice core and area burned (vegetation fire) events in Canada suggests that the biomass burning tracers in the ice core document most of the pronounced biomass burning events in eastern Canada over the past several decades, confirming that analyses of biomass burning molecular tracers in Greenland ice cores are useful to reconstruct the frequency of significant biomass burning events in a local region. However, our study also highlights that the wind pattern when the biomass burning occurs is decisive for the registration of a biomass burning event in an ice core even though long-term changes in the wind regime associated with decadal-scale climate oscillations do not significantly influence the transport and deposition of biomass burning tracers on the Greenland ice sheet.
  • Ryu Uemura, Hideaki Motoyama, Valérie Masson-Delmotte, Jean Jouzel, Kenji Kawamura, Kumiko Goto-Azuma, Shuji Fujita, Takayuki Kuramoto, Motohiro Hirabayashi, Takayuki Miyake, Hiroshi Ohno, Koji Fujita, Ayako Abe-Ouchi, Yoshinori Iizuka, Shinichiro Horikawa, Makoto Igarashi, Keisuke Suzuki, Toshitaka Suzuki, Yoshiyuki Fujii
    Nature Communications 9 (1) 2041-1723 2018/12/01 [Refereed][Not invited]
     
    The δD temperature proxy in Antarctic ice cores varies in parallel with CO2 through glacial cycles. However, these variables display a puzzling asynchrony. Well-dated records of Southern Ocean temperature will provide crucial information because the Southern Ocean is likely key in regulating CO2 variations. Here, we perform multiple isotopic analyses on an Antarctic ice core and estimate temperature variations at this site and in the oceanic moisture source over the past 720,000 years, which extend the longest records by 300,000 years. Antarctic temperature is affected by large variations in local insolation that are induced by obliquity. At the obliquity periodicity, the Antarctic and ocean temperatures lag annual mean insolation. Further, the magnitude of the phase lag is minimal during low eccentricity periods, suggesting that secular changes in the global carbon cycle and the ocean circulation modulate the phase relationship among temperatures, CO2 and insolation in the obliquity frequency band.
  • Angel T. Bautista, Yasuto Miyake, Hiroyuki Matsuzaki, Yoshinori Iizuka, Kazuho Horiuchi
    Journal of Environmental Radioactivity 184-185 14 - 21 1879-1700 2018/04/01 [Refereed][Not invited]
     
    129I in natural archives, such as ice cores, can be used as a proxy for human nuclear activities, age marker, and environmental tracer. Currently, there is only one published record of 129I in ice core (i.e., from Fiescherhorn Glacier, Swiss Alps) and its limited time resolution (1–2 years) prevents the full use of 129I for the mentioned applications. Here we show 129I concentrations in an ice core from SE-Dome, Greenland, covering years 1956–1976 at a time resolution of ∼6 months, the most detailed record to date. Results revealed 129I bomb peaks in years 1959, 1962, and 1963, associated to tests performed by the former Soviet Union, one year prior, in its Novaya Zemlya test site. All 129I bomb peaks were observed in winter (1958.9, 1962.1, and 1963.0), while tritium bomb peaks, another prominent radionuclide associated with nuclear bomb testing, were observed in spring or summer (1959.3, and 1963.6 Iizuka et al., 2017). These results indicate that 129I bomb peaks can be used as annual and seasonal age markers for these years. Furthermore, we found that 129I recorded nuclear fuel reprocessing signals and that these can be potentially used to correct timing of estimated 129I releases during years 1964–1976. Comparisons with other published records of 129I in natural archives showed that 129I can be used as common age marker and tracer for different types of records. Most notably, the 1963 129I bomb peak can be used as common age marker for ice and coral cores, providing the means to reconcile age models and associated trends from the polar and tropical regions, respectively.
  • Masashi Niwano, Teruo Aoki, Akihiro Hashimoto, Sumito Matoba, Satoru Yamaguchi, Tomonori Tanikawa, Koji Fujita, Akane Tsushima, Yoshinori Iizuka, Rigen Shimada, Masahiro Hori
    Cryosphere 12 (2) 635 - 655 1994-0424 2018/02/23 [Refereed][Not invited]
     
    To improve surface mass balance (SMB) estimates for the Greenland Ice Sheet (GrIS), we developed a 5ĝ€̄km resolution regional climate model combining the Japan Meteorological Agency Non-Hydrostatic atmospheric Model and the Snow Metamorphism and Albedo Process model (NHM-SMAP) with an output interval of 1ĝ€̄h, forced by the Japanese 55-year reanalysis (JRA-55). We used in situ data to evaluate NHM-SMAP in the GrIS during the 2011-2014 mass balance years. We investigated two options for the lower boundary conditions of the atmosphere: an offline configuration using snow, firn, and ice albedo, surface temperature data from JRA-55, and an online configuration using values from SMAP. The online configuration improved model performance in simulating 2ĝ€̄m air temperature, suggesting that the surface analysis provided by JRA-55 is inadequate for the GrIS and that SMAP results can better simulate physical conditions of snow/firn/ice. It also reproduced the measured features of the GrIS climate, diurnal variations, and even a strong mesoscale wind event. In particular, it successfully reproduced the temporal evolution of the GrIS surface melt area extent as well as the record melt event around 12 July 2012, at which time the simulated melt area extent reached 92.4ĝ€̄%. Sensitivity tests showed that the choice of calculation schemes for vertical water movement in snow and firn has an effect as great as 200ĝ€̄Gtĝ€̄year-1 in the GrIS-wide accumulated SMB estimates a scheme based on the Richards equation provided the best performance.
  • Yoshinori Iizuka, Ryu Uemura, Koji Fujita, Shohei Hattori, Osamu Seki, Chihiro Miyamoto, Toshitaka Suzuki, Naohiro Yoshida, Hideaki Motoyama, Sumito Matoba
    Journal of Geophysical Research: Atmospheres Wiley-Blackwell 123 (1) 574 - 589 2169-897X 2018/01/16 [Refereed][Not invited]
     
    ©2017. American Geophysical Union. All Rights Reserved. The Southeastern Greenland Dome (SE-Dome) has both a high elevation and a high accumulation rate (1.01 m we yr−1), which are suitable properties for reconstructing past environmental changes with a high time resolution. For this study, we measured the major ion fluxes in a 90 m ice core drilled from the SE-Dome region in 2015 and present the records of annual ion fluxes from 1957 to 2014. From 1970 to 2010, the trend of nonsea-salt (nss) SO42− flux decreases, whereas that for NH4+ increases, tracking well with the anthropogenic SOx and NH3 emissions mainly from North America. The result suggests that these fluxes reflect histories of the anthropogenic SOx and NH3 emissions. In contrast, the decadal trend of NO3− flux differs from the decreasing trend of anthropogenic NOx emissions. Although the cause of this discrepancy remains unclear, it may be related to changes in particle formation processes and chemical scavenging rates caused by an increase in sea salt and dust and/or a decrease in nssSO42−. We also find a high average NO3− flux (1.13 mmol m−2 yr−1) in the ice core, which suggests a negligible effect from postdepositional NO3− loss. Thus, the SE-Dome region is an excellent location for reconstructing nitrate fluxes. Over a decadal time scale, our NO3− flux record is similar to those from other ice cores in Greenland high-elevation sites, suggesting that NO3− concentration records from these ice cores are reliable.
  • Matoba Sumito, Niwano Masashi, Tanikawa Tomonori, Iizuka Yoshinori, Yamasaki Tetsuhide, Kurosaki Yutaka, Aoki Teruo, Hashimoto Akihiro, Hosaka Masahiro, Sugiyama Shin
    Bulletin of Glaciological Research 36 (0) 15 - 22 1345-3807 2018 [Refereed][Not invited]
  • Hattori Shohei, Iizuka Yoshinori, Uemura Ryu, Suzuki Nozomi, Tsuruta Asuka, Ishino Sakiko, Fujita Koji, Matoba Sumito, Yoshida Naohiro
    Abstracts of Annual Meeting of the Geochemical Society of Japan 一般社団法人日本地球化学会 65 12  2018 
    グリーンランドの氷床コアは北アメリカやヨーロッパ由来の大気が由来し、過去のエアロゾル動態を復元する貴重な環境媒体である。産業革命以降の人間活動の増大に伴い、大気中に放出される硫黄及び窒素酸化物の濃度が上昇し、1970年以降に北アメリカ、ヨーロッパで排出が抑制された。事実、氷床コア中の硫酸濃度の減少がSO2排出量の減少と対応していることが知られている。本研究では、グリーンランド南東ドーム(SE-Dome)で採取された約90 m、60年分のアイスコアを用い、時間解像度3~6年で硫酸の三酸素同位体組成を分析した。
  • Nishino Saori, Arai Miho, Suzuki Toshitaka, Iizuka Yoshinori, Hirabayashi Motohiro, Kawamura Kenji, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2018 23 - 23 1883-0870 2018
  • Yonekura Ayaka, Suzuki Toshitaka, Iizuka Yoshinori, Hirabayashi Motohiro, Motoyama Hideaki, Kawamura Kenji
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2018 22 - 22 1883-0870 2018
  • 黒﨑豊, 的場澄人, 飯塚芳徳, 庭野匡思, 谷川朋範, 青木輝夫
    雪氷 80 (6) 515 - 529 2018 [Refereed][Not invited]
  • Ryoto Furukawa, Ryu Uemura, Koji Fujita, Jesper Sjolte, Kei Yoshimura, Sumito Matoba, Yoshinori Iizuka
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 122 (20) 10873 - 10887 2169-897X 2017/10 [Refereed][Not invited]
     
    A precise age scale based on annual layer counting is essential for investigating past environmental changes from ice core records. However, subannual scale dating is hampered by the irregular intraannual variabilities of oxygen isotope (delta O-18) records. Here we propose a dating method based on matching the delta O-18 variations between ice core records and records simulated by isotope-enabled climate models. We applied this method to a new delta O-18 record from an ice core obtained from a dome site in southeast Greenland. The close similarity between the delta O-18 records from the ice core and models enables correlation and the production of a precise age scale, with an accuracy of a few months. A missing delta O-18 minimum in the 1995/1996 winter is an example of an indistinct delta O-18 seasonal cycle. Our analysis suggests that the missing delta O-18 minimum is likely caused by a combination of warm air temperature, weak moisture transport, and cool ocean temperature. Based on the age scale, the average accumulation rate from 1960 to 2014 is reconstructed as 1.02 m yr(-1) in water equivalent. The annual accumulation rate shows an increasing trend with a slope of 3.6 mm yr(-1), which is mainly caused by the increase in the autumn accumulation rate of 2.6 mm yr(-1). This increase is likely linked to the enhanced hydrological cycle caused by the decrease in Arctic sea ice area. Unlike the strong seasonality of precipitation amount in the ERA reanalysis data in the southeast dome region, our reconstructed accumulation rate suggests a weak seasonality.
  • Overview of the chemical composition and characteristics of Na+ and Cl– distributions in samples from Antarctic ice core DF01 (Dome Fuji) drilled in 2001
    Yuko Motizuki, K. Takahashi, Y. Nakai, Y. Iizuka, K. Suzuki, H. Motoyama
    RIKEN Accel. Prog. Rep. 49 133  2017/03 [Refereed][Not invited]
  • Kenji Kawamura, Ayako Abe-Ouchi, Hideaki Motoyama, Yutaka Ageta, Shuji Aoki, Nobuhiko Azuma, Yoshiyuki Fujii, Koji Fujita, Shuji Fujita, Kotaro Fukui, Teruo Furukawa, Atsushi Furusaki, Kumiko Goto-Azuma, Ralf Greve, Motohiro Hirabayashi, Takeo Hondoh, Akira Hori, Shinichiro Horikawa, Kazuho Horiuchi, Makoto Igarashi, Yoshinori Iizuka, Takao Kameda, Hiroshi Kanda, Mika Kohno, Takayuki Kuramoto, Yuki Matsushi, Morihiro Miyahara, Takayuki Miyake, Atsushi Miyamoto, Yasuo Nagashima, Yoshiki Nakayama, Takakiyo Nakazawa, Fumio Nakazawa, Fumihiko Nishio, Ichio Obinata, Rumi Ohgaito, Akira Oka, Jun'ichi Okuno, Junichi Okuyama, Ikumi Oyabu, Frederic Parrenin, Frank Pattyn, Fuyuki Saito, Takashi Saito, Takeshi Saito, Toshimitsu Sakurai, Kimikazu Sasa, Hakime Seddik, Yasuyuki Shibata, Kunio Shinbori, Keisuke Suzuki, Toshitaka Suzuki, Akiyoshi Takahashi, Kunio Takahashi, Shuhei Takahashi, Morimasa Takata, Yoichi Tanaka, Ryu Uemura, Genta Watanabe, Okitsugu Watanabe, Tetsuhide Yamasaki, Kotaro Yokoyama, Masakazu Yoshimori, Takayasu Yoshimoto
    SCIENCE ADVANCES 3 (2) 2375-2548 2017/02 [Refereed][Not invited]
     
    Climatic variabilities on millennial and longer time scales with a bipolar seesaw pattern have been documented in paleoclimatic records, but their frequencies, relationships with mean climatic state, and mechanisms remain unclear. Understanding the processes and sensitivities that underlie these changes will underpin better understanding of the climate system and projections of its future change. We investigate the long-term characteristics of climatic variability using a new ice-core record from Dome Fuji, East Antarctica, combined with an existing long record from the Dome C ice core. Antarctic warming events over the past 720,000 years are most frequent when the Antarctic temperature is slightly below average on orbital time scales, equivalent to an intermediate climate during glacial periods, whereas interglacial and fully glaciated climates are unfavourable for a millennial-scale bipolar seesaw. Numerical experiments using a fully coupled atmosphere-ocean general circulation model with freshwater hosing in the northern North Atlantic showed that climate becomes most unstable in intermediate glacial conditions associated with large changes in sea ice and the Atlantic Meridional Overturning Circulation. Model sensitivity experiments suggest that the prerequisite for the most frequent climate instabilitywith bipolar seesaw pattern during the late Pleistocene era is associated with reduced atmospheric CO2 concentration via global cooling and sea ice formation in the North Atlantic, in addition to extended Northern Hemisphere ice sheets.
  • Yoshinori Iizuka, Atsushi Miyamoto, Akira Hori, Sumito Matoba, Ryoto Furukawa, Takeshi Saito, Shuji Fujita, Motohiro Hirabayashi, Satoru Yamaguchi, Koji Fujita, Nozomu Takeuchi
    ARCTIC ANTARCTIC AND ALPINE RESEARCH 49 (1) 13 - 27 1523-0430 2017/02 [Refereed][Not invited]
     
    We examine a firn core from a dome in southeast Greenland that exhibits distinct firn densification. The ice was-20.9 degrees C at 20 m depth, and the core gives an average accumulation rate of 1.0 m w.e. yr(-1) in water equivalent. However, the close-off density of 830 kg m(-3) occurs at 83.4-86.8 m depth, which is about 20-m shallower than that obtained from two empirical models. Where the density p > 750 kg m(-3), the densification appears faster than that from the empirical models. As a result, compared to the empirical coefficient, the actual compactive viscosity coefficient is nonlinear and decreases at p > 750 kg m(-3), indicating that the fun with a higher density is softer than that from the empirical result. We argue here that the high accumulation rate creates a high overburden pressure in a short time. Thus, the relative softness of the firn may arise from (1) there being not enough time to form bonds between grains as strong as those in a lower accumulation-rate area, and similarly, (2) the dislocation density in the firn being relatively high.
  • Furukawa Ryoto, Uemura Ryu, Fujita Koji, Sjolte Jesper, Yoshimura Kei, Matoba Sumito, Iizuka Yoshinori
    Abstracts of Annual Meeting of the Geochemical Society of Japan 一般社団法人日本地球化学会 64 18 - 18 2017 

  • Tsuruta Asuka, Hattori Shohei, Iizuka Yoshinori, Fujita Koji, Uemura Ryu, Matoba Sumito, Yoshida Naohiro
    Abstracts of Annual Meeting of the Geochemical Society of Japan 一般社団法人日本地球化学会 64 19 - 19 2017 

  • Amino Tomomi, Iizuka Yoshinori, Matoba Sumito
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2017 154 - 154 2017
  • Tsuruta Asuka, Hattori Shohei, Iizuka Yoshinori, Fujita Koji, Uemura Ryu, Matoba Sumito, Yoshida Naohiro
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2017 120 - 120 2017
  • Matoba Sumito, Niwano Masashi, Tanikawa Tomonori, Iizuka Yoshinori, Yamasaki Tetsuhide, Kurosaki Yutaka, Aoki Teruo, Hashimoto Akihiro, Hosaka Masahiro, Sugiyama Shin
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2017 288 - 288 2017
  • Yonekura Ayaka, Suzuki Toshitaka, Iizuka Yoshinori, Hirabayashi Motohiroi, Kawamura Kenji, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2017 30 - 30 2017
  • Suzuki Toshitaka, Shoji Airi, Shibata Mai, Iizuka Yoshinori, Hirabayashi Motohitro, Kawamura Kenji, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2017 29 - 29 2017
  • Sasaki Chiaki, Suzuki Toshitaka, Hirabayashi Motohiro, Iizuka Yoshinori
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2017 28 - 28 2017
  • Kurosaki Yutaka, Matoba Sumito, Iizuka Yoshinori, Aoki Teruo, Sugiyama Shin
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2017 191 - 191 2017
  • Characteristics of Na+ and Cl– distributions in shallow samples from an Antarctic ice core DF01 (Dome Fuji) drilled in 2001: Result of strong atmospheric high-pressure blocking events?
    Y. Motizuki, H. Motoyama, Y. Nakai, K. Suzuki, Y. Iizuka, K. Takahashi
    RIKEN Accel. Prog. Rep. 50 (144) 2017 [Refereed][Not invited]
  • Ikumi Oyabu, Sumito Matoba, Tetsuhide Yamasaki, Moe Kadota, Yoshinori Iizuka
    POLAR SCIENCE 10 (1) 36 - 42 1873-9652 2016/03 [Refereed][Not invited]
     
    We analyze snow-pit samples collected in May 2015 at the South East Dome (SE Dome) on the Greenland ice sheet. The analysis includes high-resolution records of delta D and delta O-18, as well as the major ions, CH3SO3-, Cl-, NO3-, SO42-, Na+, NH4+, K+, Ma(2+), and Ca2+. We find that the 3.55-m snow pit recorded temperature and aerosol proxies back to summer or autumn of 2014. This indicates a higher accumulation rate than those at other major drilling sites in Greenland. Due to this high accumulation rate, ion concentrations except Na+ are lower than those typical of the central Greenland ice sheet. Concerning seasonal variability, the Na+, Cl-, Ca2+, Mg2+, and NO3- vary similarly to other sites in Greenland, with the Na+ and Cl- peaking in winter to early spring, Ca2+ peaking in spring, Mg2+ peaking in winter to spring, and NO3- towards a peak in summer while showing smaller peaks in winter to spring. The NH4+ increased in spring, and SO42- increased in autumn to winter at SE Dome. On the other hand, the seasonal trend in the Cl-/Na+ ratio differs from those in the inland region. As we did not fully recover one seasonal cycle, some seasonal peaks may have been missed. (C) 2016 Elsevier B.V. and NIPR. All rights reserved.
  • Uemura Ryu, Masaka Kosuke, Matsumoto Risei, Uemura Miki, Iizuka Yoshinori, Hirabayashi Motohiro, Motoyama Hideaki
    Abstracts of Annual Meeting of the Geochemical Society of Japan 一般社団法人日本地球化学会 63 23  2016 
    硫酸エアロゾルは、直接・間接効果によって気候変動に影響を与える物質である。その硫黄安定同位体比(δ34S)は、起源ごとに特有の値を持つとともに、酸化過程による分別によって変動することも知られている。したがって、アイスコアのδ34S値から、過去数万年スケールの硫酸エアロゾルの変動メカニズムや起源推定が行える可能性がある。本研究では、最終氷期から完新世にかけてのドームふじアイスコアのδ34Sを測定し、変動メカニズムの解析を行った。DF1コアの完新世のδ34S値は、現在の東南極表面積雪の値と誤差範囲で一致していた。また、DF1コアのδ34Sは、最終氷期から完新世にかけての温暖化に対応して、高くなる傾向を示した。
  • Furukawa Ryoto, Iizuka Yoshinori, Matoba Sumito, Uemura Ryu
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2016 31  1883-0870 2016 [Not refereed]
  • Kawamura Kenji, Iizuka Y., Uemura R., Uchida T., Oono H., Kameda T., Suzuki T., Takata M., Hirabayashi M., Fujita K., Fukui K., Motoyama H., Hori A., Horiuchi K., Matoba S., Miyamoto A., Goto-Azuma K., Fujita S., Furukawa T., Nakazawa F., Aoki S., Azuma N., Abe-Ouchi A.
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2016 194 - 194 1883-0870 2016
  • Yoshinori Iizuka, Hiroshi Ohno, Ryu Uemura, Toshitaka Suzuki, Ikumi Oyabu, Yu Hoshina, Kotaro Fukui, Motohiro Hirabayashi, Hideaki Motoyama
    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY 68 1600-0889 2016 [Refereed][Not invited]
     
    To better understand how sea salt reacts in surface snow of Antarctica, we collected and identified non-volatile particles in surface snow along a traverse in East Antarctica. Samples were obtained during summer 2012/2013 from coastal to inland regions within 69 degrees S to 80 degrees S and 39 degrees E to 45 degrees E, a total distance exceeding 800 km. The spatial resolution of samples is about one sample per latitude between 1500 and 3800m altitude. Here, we obtain the atomic ratios of Na, S and Cl, and calculate the masses of sodium sulphate and sodium chloride. The results show that, even in the coast snow sample (69 degrees S), sea salt is highly modified by acid (HNO3 or H2SO4). The fraction of sea salt that reacts with acid increases in the region from 70 degrees S to 74 degrees S below 3000m a.s.l., where some NaCl remains. At the higher altitudes (above 3300m a.s.l.) in the inland region (74 degrees S to 80 degrees S), the reaction uses almost all of the available NaCl.
  • Oyabu Ikumi, Iizuka Yoshinori, Matoba Sumito, Yamasaki Tetsuhide, Kadota Moe
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2015 73 - 73 2015
  • Arai Miho, Suzuki Toshitaka, Iizuka Yoshinori, Hirabayashi Motohiro, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2015 208 - 208 2015
  • Kumagai Kohei, Suzuki Toshitaka, Iizuka Yoshinori, Hirabayashi Motohiro, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2015 209 - 209 2015
  • Ikumi Oyabu, Yoshinori Iizuka, Hubertus Fischer, Simon Schüpbach, Gideon Gfeller, Anders Svensson, Manabu Fukui, Jørgen Peder Steffensen, Margareta Hansson
    Journal of Geophysical Research 120 (18) 9789 - 9813 2156-2202 2015 [Refereed][Not invited]
     
    This study reports the chemical composition of particles present along Greenland’s North Greenland Eemian Ice Drilling (NEEM) ice core, back to 110,000 years before present. Insoluble and soluble particles larger than 0.45 µm were extracted from the ice core by ice sublimation, and their chemical composition was analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy and micro-Raman spectroscopy. We show that the dominant insoluble components are silicates, whereas NaCl, Na2SO4, CaSO4, and CaCO3 represent major soluble salts. For the first time, particles of CaMg(CO3)2 and Ca(NO3)2•4H2O are identified in a Greenland ice core. The chemical speciation of salts varies with past climatic conditions. Whereas the fraction of Na salts (NaCl + Na2SO4) exceeds that of Ca salts (CaSO4 + CaCO3) during the Holocene (0.6-11.7 kyr B.P.), the two fractions are similar during the Bølling-Allerød period (12.9-14.6 kyr B.P.). During cold climate such as over the Younger Dryas (12.0-12.6 kyr B.P.) and the Last Glacial Maximum (15.0-26.9 kyr B.P.), the fraction of Ca salts exceeds that of Na salts, showing that the most abundant ion generally controls the salt budget in each period. High-resolution analyses reveal changing particle compositions: those in Holocene ice show seasonal changes, and those in LGM ice show a difference between cloudy bands and clear layers, which again can be largely explained by the availability of ionic components in the atmospheric aerosol body of air masses reaching Greenland.
  • Ikumi Oyabu, Yoshinori Iizuka, Ryu Uemura, Takayuki Miyake, Motohiro Hirabayashi, Hideaki Motoyama, Toshimitsu Sakurai, Toshitaka Suzuki, Takeo Hondoh
    Journal of Geophysical Research 119 (24) 14 - 058 2156-2202 2014/12/27 [Refereed][Not invited]
     
    The flux and chemical composition of aerosols impact the climate. Antarctic ice cores preserve the record of past atmospheric aerosols, providing useful information about past atmospheric environments. However, few studies have directly measured the chemical composition of aerosol particles preserved in ice cores. Here we present the chemical compositions of sulfate and chloride salts from aerosol particles in the Dome Fuji ice core. The analysis method involves ice sublimation, and the period covers the last termination, 25.0–11.0 thousand years before present (kyr B.P.), with a 350 year resolution. The major components of the soluble particles are CaSO4, Na2SO4, and NaCl. The dominant sulfate salt changes at 16.8 kyr B.P. from CaSO4, a glacial type, to Na2SO4, an interglacial type. The sulfate salt flux (CaSO4 plus Na2SO4) inversely correlates with δ18O in Dome Fuji over millennial timescales. This correlation is consistent with the idea that sulfate salt aerosols contributed to the last deglacial warming of inland Antarctica by reducing the aerosol indirect effect. Between 16.3 and 11.0 kyr B.P., the presence of NaCl suggests that winter atmospheric aerosols are preserved. A high NaCl/Na2SO4 fraction between 12.3 and 11.0 kyr B.P. indicates that the contribution from the transport of winter atmospheric aerosols increased during this period.
  • Ikumi Oyabu, Yoshinori Iizuka, Ryu Uemura, Takayuki Miyake, Motohiro Hirabayashi, Hideaki Motoyama, Toshimitsu Sakurai, Toshitaka Suzuki, Takeo Hondoh
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 119 (24) 14045 - 14058 2169-897X 2014/12 [Refereed][Not invited]
     
    The flux and chemical composition of aerosols impact the climate. Antarctic ice cores preserve the record of past atmospheric aerosols, providing useful information about past atmospheric environments. However, few studies have directly measured the chemical composition of aerosol particles preserved in ice cores. Here we present the chemical compositions of sulfate and chloride salts from aerosol particles in the Dome Fuji ice core. The analysis method involves ice sublimation, and the period covers the last termination, 25.0-11.0 thousand years before present (kyr B.P.), with a 350 year resolution. The major components of the soluble particles are CaSO4, Na2SO4, and NaCl. The dominant sulfate salt changes at 16.8 kyr B.P. from CaSO4, a glacial type, to Na2SO4, an interglacial type. The sulfate salt flux (CaSO4 plus Na2SO4) inversely correlates with delta O-18 in Dome Fuji over millennial timescales. This correlation is consistent with the idea that sulfate salt aerosols contributed to the last deglacial warming of inland Antarctica by reducing the aerosol indirect effect. Between 16.3 and 11.0 kyr B.P., the presence of NaCl suggests that winter atmospheric aerosols are preserved. A high NaCl/Na2SO4 fraction between 12.3 and 11.0 kyr B.P. indicates that the contribution from the transport of winter atmospheric aerosols increased during this period.
  • Yu Hoshina, Koji Fujita, Fumio Nakazawa, Yoshinori Iizuka, Takayuki Miyake, Motohiro Hirabayashi, Takayuki Kuramoto, Shuji Fujita, Hideaki Motoyama
    Journal of Geophysical Research 119 (1) 274 - 283 2156-2202 2014/01/16 [Refereed][Not invited]
     
    Postdepositional changes in water stable isotopes in polar firn were investigated at three sites characterized by different accumulation rates along the East Antarctic ice divide near Dome Fuji. Water stable isotopes, major ion concentrations, and tritium contents of three 2–4 m deep pits were measured at high resolution (2 cm). Temporally, the snow pits cover the past 50 years with snow accumulation rates in the range of 29–41 kg m2 a1 around Dome Fuji. Oxygen isotopic profiles in the three pits do not show annual fluctuations, but instead exhibit multiyear cycles. These multiyear cycles are lower in frequency at Dome Fuji as compared with the other two sites. Peaks of water stable isotopes in the multiyear cycles correspond to some ion concentration minima in the pits, although such relationships are not observed in coastal regions. We propose that the extremely low accumulation environment keeps the snow layer at the near surface, which result in postdepositional modifications of isotopic signals by processes such as ventilation and vapor condensation-sublimation. We estimate that oxygen isotopic ratios could be modified by > 10‰ and that the original seasonal cycle could be completely overprinted under the accumulation conditions at Dome Fuji. Moreover, stake measurements at Dome Fuji suggest that the large variability in snow accumulation rate is the cause of the multiyear cycles.
  • 藤田 秀二, 福井 幸太郎, 中澤 文男, 榎本 浩之, 杉山 慎, 藤井 理行, 藤田 耕史, 古川 晶雄, 原 圭一郎, 保科 優, 五十嵐 誠, 飯塚 芳徳, 伊村 智, 本山 秀明, Surdyk Sylviane, 植村 立, Shuji Fujita, Kotaro Fukui, Fumio Nakazawa, Hiroyuki Enomoto, Shin Sugiyama, Yoshiyuki Fujii, Koji Fujita, Teruo Furukawa, Keiichiro Hara, Yu Hoshina, Makoto Igarashi, Yoshinori Iizuka, Satoshi Imura, Hideaki Motoyama, Sylviane Surdyk, Ryu Uemura
    南極資料 国立極地研究所 58 (3) 352 - 392 0085-7289 2014 [Refereed][Not invited]
     
    南極地域観測第Ⅶ期5か年計画に基づき，2007/2008 年の南極の夏期シーズンに，国立極地研究所を中心とした研究グループは，スウェーデンの研究者グループと共同で，東南極内陸域のドロンイングモードランド地域の内陸部の氷床環境調査を実施した．本報告は，現地調査前に5年間を費やした研究計画の企画検討の経過や行った事前準備と，現地野外観測を終了した後の6年間に得られた研究成果の概要をまとめるものである．本プロジェクトの調査により，南極内陸高原部の氷床環境の時空間分布について，多くの科学的知見が明らかになった．本報告はその概要を報告する．現地調査の実行の経過は別途の報告に記述する．In the seventh five-year plan of the Japanese Antarctic Research Expedition, a group of Japanese scientists (led by the National Institute of Polar Research) together with a group of Swedish scientists, conducted field surveys to better understand the glaciology of the ice sheet in Dronning Maud Land, East Antarctica, during the 2007/2008 austral summer season. This paper reports on the planning and field preparations, and outlines the scientific achievements of the field expedition. We have gained numerous new scientific insights on the spatio-temporal distribution of the ice sheet environment in the inland plateau. Here, we provide an overview of the new knowledge gained.
  • Yu Hoshina, Koji Fujita, Fumio Nakazawa, Yoshinori Iizuka, Takayuki Miyake, Motohiro Hirabayashi, Takayuki Kuramoto, Shuji Fujita, Hideaki Motoyama
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 119 (1) 274 - 283 2169-897X 2014/01 [Refereed][Not invited]
     
    Postdepositional changes in water stable isotopes in polar firn were investigated at three sites characterized by different accumulation rates along the East Antarctic ice divide near Dome Fuji. Water stable isotopes, major ion concentrations, and tritium contents of three 2-4m deep pits were measured at high resolution (2cm). Temporally, the snow pits cover the past 50years with snow accumulation rates in the range of 29-41kgm(-2) a(-1) around Dome Fuji. Oxygen isotopic profiles in the three pits do not show annual fluctuations, but instead exhibit multiyearcycles. These multiyearcycles are lower in frequency at Dome Fuji as compared with the other two sites. Peaks of water stable isotopes in the multiyearcycles correspond to some ion concentration minima in the pits, although such relationships are not observed in coastal regions. We propose that the extremely low accumulation environment keeps the snow layer at the near surface, which result in postdepositional modifications of isotopic signals by processes such as ventilation and vapor condensation-sublimation. We estimate that oxygen isotopic ratios could be modified by >10 and that the original seasonal cycle could be completely overprinted under the accumulation conditions at Dome Fuji. Moreover, stake measurements at Dome Fuji suggest that the large variability in snow accumulation rate is the cause of the multiyearcycles.
  • SatoH, SuzukiT, HirabayashiM, MotoyamaH, IizukaY, FujiiY
    Atmospheric and Climate Sciences 3 186 - 192 2013 [Refereed][Not invited]
  • Yoshinori Iizuka, Akira Tsuchimoto, Yu Hoshina, Toshimitsu Sakurai, Margareta Hansson, Torbjorn Karlin, Koji Fujita, Fumio Nakazawa, Hideaki Motoyama, Shuji Fujita
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 117 2169-897X 2012/02 [Refereed][Not invited]
     
    Most of the aerosol particles present in the surface snow and ice of inland Antarctica come from primary sea salt (sodium chloride) and marine biological activity (methansulfonic and sulfuric acids). Melted water from surface snow, firn, and Holocene ice contains mainly sodium, chloride, and sulfate ions. Although it is well known that sea salt aerosols react rapidly with sulfuric acid, a process known as sulfatization, it is not known when this process takes place. In this research we undertake to measure the proportion of sea salt aerosols that undergo sulfatization in the atmosphere and surface snow, as opposed to deeper ice, in order to understand the suitability of sea salt aerosols as a proxy for past climates in deep ice cores. We directly measure the sulfatization rates in recently fallen snow (0-4 m in depth) collected at the Dome Fuji station, using X-ray dispersion spectroscopy to determine the constituent elements of soluble particles and computing the molar ratios of sodium chloride and sodium sulfate. We estimate that about 90% of the initial sea salt aerosols sulfatize as they are taken up by precipitation over Dome Fuji or in the snowpack within one year after being deposited on the ice sheet.
  • Motoyama Hideaki, Furusaki Atsushi, Takahashi Hiromu, Takata Morimasa, Takahashi Akiyoshi, Miyahara Morihiro, Motoba Sumito, Sugiyama Shin, Iizuka Yoshinori, Shinbori Kunio
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2012 161 - 161 2012
  • Ohno Hiroshi, Iizuka Yoshinori, Hondoh Takeo, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2012 159 - 159 2012
  • Hoshina Yu, Fujita Koji, Nakazawa Fumio, Iizuka Yoshinori, Miyake Takayuki, Hirabayashi Motohiro, Kuramoto Takayuki, Motoyama Hideaki, Fujita Shuji
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2012 121 - 121 2012
  • Fujita, S, Enomoto, H, Fukui, K, Iizuka, Y, Motoyama, H, Nakazawa, F, Sugiyama, S, Surdyk, S
    The Cryosphere Discussions 6 (2) 1205-1267  2012 [Not refereed][Not invited]
     
    Abstract. The initial stage of postdepositional metamorphism in polar firn was investigated at sites located under spatial variations of accumulation rate and wind speed along the East Antarctic ice divide near Dome Fuji. A better understanding of this process is important for interpreting local insolation proxies used for astronomical dating of deep ice cores. Three 2–4 m deep pits were excavated and physical properties, including density ρ, grain size D, reflectance R of near infrared light and microwave dielectric anisotropy Δε, were investigated at high spatial resolution. We found that Δε ranges between 0.028 and 0.067 and that such high values occur in the surface ~0.1 m. In addition, short scale variations of ρ are correlated with those of Δε, and inversely correlated with those of D, confirming contrasting development of initially higher density layers and initially lower density layers. Moreover, postdepositional metamorphism makes these contrasts more distinct with increasing depths. Both the contrasts and Δε for given values of ρ are higher under lower accumulation rate conditions and under less windy conditions. Insolation efficiently causes evolution of strata of firn at the ice sheet surface under such conditions. Under more windy conditions, the strata contain more wind-driven hard layers with higher ρ and Δε and thus have larger fluctuations of ρ and Δε. We suggest that the initial variability of ρ at the surface and the duration of exposure to diurnal and seasonal temperature gradients play sequential roles in determining the physical/mechanical properties of firn, which is retained throughout the densification process.
  • S. Fujita, P. Holmlund, I. Andersson, I. Brown, H. Enomoto, Y. Fujii, K. Fujita, K. Fukui, T. Furukawa, M. Hansson, K. Hara, Y. Hoshina, M. Igarashi, Y. Iizuka, S. Imura, S. Ingvander, T. Karlin, H. Motoyama, F. Nakazawa, H. Oerter, L. E. Sjöberg, S. Sugiyama, S. Surdyk, J. Ström, R. Uemura, F. Wilhelms
    The Cryosphere 5 (4) 1057 - 1081 0260-3055 2011/11/28 [Refereed][Not invited]
     
    Abstract. To better understand the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML), East Antarctica, a 2800-km-long Japanese-Swedish traverse was carried out. The route includes ice divides between two ice-coring sites at Dome Fuji and EPICA DML. We determined the surface mass balance (SMB) averaged over various time scales in the late Holocene based on studies of snow pits and firn cores, in addition to radar data. We find that the large-scale distribution of the SMB depends on the surface elevation and continentality, and that the SMB differs between the windward and leeward sides of ice divides for strong-wind events. We suggest that the SMB is highly influenced by interactions between the large-scale surface topography of ice divides and the wind field of strong-wind events that are often associated with high-precipitation events. Local variations in the SMB are governed by the local surface topography, which is influenced by the bedrock topography. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by ~15 % than averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar increasing trend has been reported for many inland plateau sites in Antarctica with the exception of several sites on the leeward side of the ice divides.
  • Hiroshi Ohno, Ikumi Oyabu, Yoshinori Iizuka, Takeo Hondoh, Hideo Narita, Jiro Nagao
    JOURNAL OF PHYSICAL CHEMISTRY A 115 (32) 8889 - 8894 1089-5639 2011/08 [Refereed][Not invited]
     
    The dissociation of C2H6 hydrate particles by slow depressurization at temperatures slightly below the ice melting point was studied using optical microscopy and Raman spectroscopy. Visual observations and Raman measurements revealed that ethane hydrates can be present as a metastable state at pressures lower than the dissociation pressures of the three components: ice, hydrate, and free gas. However, they decompose into liquid water and gas phases once the system pressure drops to the equilibrium boundary for supercooled water, hydrate, and free gas. Structural analyses of obtained Raman spectra indicate that structures of the metastable hydrates and liquid water from the hydrate decay are fundamentally identical to those of the stable hydrates and supercooled water without experience of the hydration. These results imply a considerably high energy barrier for the direct hydrate-to-ice transition. Water solidification, probably induced by dynamic nucleation, was also observed during melting.
  • Toshimitsu Sakurai, Hiroshi Ohno, Shinichiro Horikawa, Yoshinori Iizuka, Tsutomu Uchida, Kazuomi Hirakawa, Takeo Hondoh
    JOURNAL OF GLACIOLOGY 57 (206) 1027 - 1032 0022-1430 2011 [Refereed][Not invited]
     
    This study clarifies changes in the chemical forms of microparticles during Termination I, the period of drastic climate change between the Last Glacial Maximum (LGM) and the Holocene. We determine the chemical forms of individual water-soluble microparticles through micro-Raman spectroscopy and compare the relative frequencies of different types with the ion concentrations in melted ice. Micro-Raman spectroscopy shows that Na2SO4 center dot 10H(2)O and MgSO4 center dot 11H(2)O are abundant in Holocene ice, while CaSO4 center dot 2H(2)O and other salts are abundant in LGM ice. Further, the number of CaSO4 center dot 2H(2)O particles is strongly correlated with the concentration of Ca2+ during Termination I. Taken together, the evidence strongly suggests that most of the Ca2+ exists as CaSO4 center dot 2H(2)O. The different compositions of microparticles from the Holocene and LGM can be explained by ion balance arguments.
  • The behavior of sulfate and chloride ions in ice sheets as a function of increasing depth
    Toshimitsu Sakurai, Shinichiro Horikawa, Yoshinori Iizuka, Takayuki Miyake, Tsutomu Uchida, Takeo Hondoh
    Physics and Chemistry of Ice 2010 [Y. Furukawa, G. Sazaki, T. Uchida, N. Watanabe (Eds)], Institute of Low Temperature Science, Hokkaido University press, Hokkaido, Japan 37 - 44 2011 [Refereed][Not invited]
  • Hiroshi Ohno, Masato Kida, Toshimitsu Sakurai, Yoshinori Iizuka, Takeo Hondoh, Hideo Narita, Jiro Nagao
    CHEMPHYSCHEM 11 (14) 3070 - 3073 1439-4235 2010/10 [Refereed][Not invited]
  • Toshimitsu Sakurai, Hiroshi Ohno, F. Elif Genceli, Shinichirou Horikawa, Yoshinori Iizuka, Tsutomu Uchida, Takeo Hondoh
    JOURNAL OF GLACIOLOGY 56 (199) 837 - 842 0022-1430 2010 [Refereed][Not invited]
     
    Using micro-Raman spectroscopy, we identified the chemical forms of methanesulfonate salt particles in reference samples of the Dome Fuji (Antarctica) ice core. We found only (CH3SO3)2Mg center dot nH(2)O among methanesulfonate salts, and this salt particle is most prevalent in the Last Glacial Maximum (LGM) ice. We suggest that during the LGM, (CH3SO3)(2)Mg center dot nH(2)O may have formed in the atmosphere through the chemical reaction of CH3SO3H with sea salts, but probably not in the firn and ice due to the neutralization of acid in LGM ice of inland Antarctica.
  • Yoshinori Iizuka, Hideki Miura, Shogo Iwasaki, Hideaki Maemoku, Takanobu Sawagaki, Ralf Greve, Hiroshi Satake, Kimikazu Sasa, Yuki Matsushi
    JOURNAL OF GLACIOLOGY 56 (197) 395 - 404 0022-1430 2010 [Refereed][Not invited]
     
    Ice originating near the inland ice divide of the ice sheet can reappear as marginal ice at the surface near the ice terminal in the ablation area. We have analyzed delta(18)O values and ion concentrations of the Skallen, Skarvsnes and Hamna terminal ice sections, located along the estuary line in the Soya drainage basin, East Antarctica. The data suggest that the upper part of the Skallen terminal ice section could have originated from inland precipitation on the Shirase drainage basin during marine isotope stage (MIS) 5e, while the upper part of Skarvsnes and Hamna terminal ice sections could have originated from inland precipitation on the Soya drainage basin. We calculate past elevation maps for the Antarctic ice sheet using the three-dimensional model, SICOPOLIS. This model suggests that the upstream portion of the Soya drainage basin during the glacial period (MIS 2, 3 or 4) was located to the northeast of its present location. A flow history is proposed wherein ice from the inland Shirase drainage area flowed over the present ice-divide line from the Shirase to the Soya drainage basin during the glacial period. The ice in the Soya drainage basin then flowed to the marginal part of the sheet after the ice divide had assumed its present position.
  • T. Sakurai, H. Ohno, S. Horikawa, Y. Iizuka, T. Uchida, T. Hondoh
    International Journal of Spectroscopy Hindawi Publishing Corporation 2010 384956-1 - 384956-7 1687-9449 2010 [Refereed][Not invited]
     
    We describe in detail our method of measuring the chemical forms of microparticles in polar ice samples through micro-Raman spectroscopy. The method is intended for solid ice samples, an important point because melting the ice can result in dissociation, contamination, and chemical reactions prior to or during a measurement. We demonstrate the technique of measuring the chemical forms of these microparticles and show that the reference spectra of those salts expected to be common in polar ice are unambiguously detected. From our measurements, Raman intensity of sulfate salts is relatively higher than insoluble dust due to the specific Raman scattering cross-section of chemical forms of microparticles in ice.
  • F. Elif Genceli, Shinichirou Horikawa, Yoshinori Iizuka, Toshimitsu Sakurai, Takeo Hondoh, Toshiyuki Kawamura, Geert-Jan Witkamp
    JOURNAL OF GLACIOLOGY 55 (189) 117 - 122 0022-1430 2009 [Refereed][Not invited]
     
    Inclusions affect the behavior of ice, and their characteristics help us understand the formation history of the ice. Recently, a low-temperature magnesium sulfate salt was discovered. This paper describes this naturally occurring MgSO4 center dot 11H(2)O mineral, meridianiite, derived from salt inclusions in sea ice of Lake Saroma, Japan and in Antarctic continental core ice. Its occurrence is confirmed by using micro-Raman spectroscopy to compare Raman spectra of synthetic MgSO4 center dot 11H(2)O with those of the inclusions.
  • Toshimitsu Sakurai, Yoshinori Iizuka, Shinichiro Horikawa, Sigfus Johnsen, Dorthe Dahl-Jensen, Jorgen Peder Steffensen, Takeo Hondoh
    JOURNAL OF GLACIOLOGY 55 (193) 777 - 783 0022-1430 2009 [Refereed][Not invited]
     
    We provide the first direct evidence that a number of water-soluble compounds, in particular calcium sulfate (CaSO4 center dot 2H(2)O) and calcium carbonate (CaCO3), are present as solid, micron-sized inclusions within the Greenland GRIP ice core. The compounds are detected by two independent methods: micro-Raman spectroscopy of a solid ice sample, and energy-dispersive X-ray spectroscopy of individual inclusions remaining after sublimation. CaSO4 center dot 2H(2)O is found in abundance throughout the Holocene and the last glacial period, while CaCO3 exists mainly in the glacial period ice. We also present size and spatial distributions of the micro-inclusions. These results suggest that water-soluble aerosols in the GRIP ice core are dependable proxies for past atmospheric conditions.
  • Yoshinori Iizuka, Takayuki Miyake, Motohiro Hirabayashi, Toshitaka Suzuki, Sumito Matoba, Hideaki Motoyama, Yoshiyuki Fujii, Takeo Hondoh
    JOURNAL OF GLACIOLOGY 55 (191) 552 - 562 0022-1430 2009 [Refereed][Not invited]
     
    In order to find environmental signals based on the dust and calcium-ion concentrations in ice cores, we determine the constituent elements of residue particles obtained after melting ice samples. We have designed a sublimating system that operates at -45 degrees C, below the eutectic temperatures of major salts. This system permits us to obtain a great many non-volatile particles. After studying the nonvolatile particles, we immersed them in water to remove soluble particles and compounds. We thereby analyzed a total of 1272 residue particles (from the melted sample), 2418 non-volatile particles (after sublimation) and 1463 insoluble particles taken from five sections of Last Glacial Maximum ice from the Dome Fuji (Antarctica) ice core. Their constituent elements were determined by scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM-EDS) and compared to the dust, calcium-ion and sodium-ion concentrations measured by ion chromatography. Our results indicate that >99.9% of the insoluble particles contain silicon but no sulfur, nitrogen or chlorine. A significant number of the non-volatile particles, however, contain sulfur and chlorine. We conclude that insoluble dust consists mostly of silicate, that almost all calcium ions originate from calcium sulfate and that almost all sodium ions originate from sodium sulfate and sodium chloride.
  • Iizuka Yoshinori, Ohno Hiroshi, Sakurai Toshimitsu
    低温科学 北海道大学低温科学研究所 68 273 - 285 1880-7593 2009 [Refereed][Not invited]
     
    The amounts of water-soluble impurities in ice cores have been widely discussed in past research on prehistoric climates; in those studies, the analysis of the soluble-aerosol signals of several ion concentrations took place after the ice cores were melted. However, the chemical compounds of the impurities being studied were unclear, due to the ionization of the impurities being caused by the melting of the ice cores. In this paper, the chemical compounds of water-soluble impurities in Dome Fuji ice core are discussed and analyzed using micro-Raman spectroscopy and ion chromatography. Raman spectroscopy helped identify micro-inclusions within ice grains as water-soluble impurities made up primarily of sodium sulfate formed in warm periods and calcium sulfate in cold periods. The major chemical compounds of the water-soluble impurities (sodium sulfate and calcium sulfate) were deduced by examining ion concentrations and the stability of chemical compounds. The amounts of impurities reflect the differences in climatic time periods, as the environment was acidic during warm times and reductive during cold.Physics of Ice Core Records II : Papers collected after the 2nd International Workshop on Physics of Ice Core Records, held in Sapporo, Japan, 2-6 February 2007. Edited by Takeo Hondoh
  • 飯塚 芳徳, 鈴木 利孝, 平林 幹啓, 三宅 隆之, 本山 秀明, 藤井 理行, 本堂 武夫
    日本地球化学会年会要旨集 日本地球化学会 56 39 - 39 2009 
    年平均気温が-50℃以下になる南極内陸地域はほぼすべての主要な水溶性エアロゾル塩が固体として存在するため、南極内陸の氷床コアは水溶性エアロゾルの良い保存媒体となる。発表者らは南極ドームふじで採取された氷コアを-50℃環境で昇華させ、残渣の不揮発性粒子の元素組成を分析した。その結果、不溶性粒子の99％にはSiが含まれ、主にシリカ鉱物であること、水溶性粒子のほとんどにはS、Clが含まれ、それぞれ硫酸塩や塩化物塩であることが示唆された。また、最近の氷期-間氷期サイクルにおける水溶性エアロゾルは、1)間氷期や氷期初期の硫酸ナトリウムが水溶性エアロゾルの主成分でエアロゾル濃度の低い時期、2)氷期中期の硫酸カルシウムが主成分で濃度の低い時期、3)氷期末期の硫酸カルシウムが主成分で濃度の高い時期という周期的な変遷をしていることが示唆された。
  • Hoshina Yu, Fujita Koji, Nakazawa Fumio, Iizuka Yoshinori, Miyake Takayuki, Hirabayashi Motohiro, Kuramoto Takayuki, Motoyama Hideaki
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2009 84 - 84 1883-0870 2009
  • Iizuka Yoshinori, Suzuki Toshitaka, Sakurai Toshimitsu, Hirabayashi Motohiro, Miyake Takayuki, Motoyama Hideaki, Fujii Yoshiyuki, Hondoh Takeo
    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research 公益社団法人 日本雪氷学会／日本雪工学会 2009 83 - 83 1883-0870 2009
  • Yoshinori Iizuka, Takeo Hondoh, Yoshiyuki Fujii
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 113 (D15) 2169-897X 2008/08 [Refereed][Not invited]
     
    Interannual fluctuations in the Antarctic sea ice extent (SIE) affect the global albedo and heat balance, and they may affect global CO2 levels. We found that the annual trend of sodium ion fluxes in the snowpack in the Dome Fuji region of East Antarctica can serve as a proxy for the present-day SIE in the southern Indian Ocean and Weddell Sea sectors. We then used sodium ion profiles obtained from the Dome Fuji ice core to reconstruct the SIE during the Holocene. We observed that (1) the beginnings of both the climatic optimum (12.0 ka BP) and neoglaciation (5.4 ka BP) in the Southern Ocean, indicated by siliceous microfossil records, are consistent with decreases (11.8 ka BP) and increases (5.4 ka BP) in the sodium ion fluxes in the Dome Fuji ice core, and (2) the interannual fluctuation in the SIE during some periods of the neoglaciation was greater than the interannual fluctuation during the climatic optimum.
  • Yoshinori Iizuka, Shinichiro Horikawa, Toshimitsu Sakurai, Sigfus Johnson, Dorthe Dahl-Jensen, Jørgen Peder Steffensen, Takeo Hondoh
    Journal of Geophysical Research Atmospheres 113 (7) 0148-0227 2008/04/16 [Refereed][Not invited]
     
    We have proposed a method of deducing the chemical compounds found in deep polar ice cores by analyzing the balance between six major ions (C1< sup> -< /sup> , NO< inf> 3< /inf> < sup> -< /sup> , SO< inf> 4< /inf> < sup> 2-< /sup> , Na< sup> +< /sup> , Mg< sup> 2+< /sup> , and Ca< sup> 2+< /sup> ). The method is demonstrated for the Holocene and last glacial maximum regions of the Dome Fuji and GRIP ice cores. The dominant compounds depend only on the ion balance and the sequence of chemical reactions. In priority order, the principle salts are calcium sulfate, other sulfates, nitrate, chloride, and carbonate. The chemical abundances deduced by this method agree well with the results of Raman spectroscopy on individual salt inclusions. The abundances in the ice cores are shown to reflect differences in climatic periods (the acidic envirom-nent of the Holocene versus the reductive environment of the last glacial maximum) and regional conditions (the marine environment of Antarctica versus the continental environment of Greenland). Copyright 2008 by the American Geophysical Union.
  • Yoshinori Iizuka, Shinichiro Horikawa, Toshimitsu Sakurai, Sigfus Johnson, Dorthe Dahl-Jensen, Jorgen Peder Steffensen, Takeo Hondoh
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 113 (D7) 2169-897X 2008/04 [Refereed][Not invited]
     
    We have proposed a method of deducing the chemical compounds found in deep polar ice cores by analyzing the balance between six major ions (Cl-, NO3-, SO42-, Na+, Mg2+, and Ca2+). The method is demonstrated for the Holocene and last glacial maximum regions of the Dome Fuji and GRIP ice cores. The dominant compounds depend only on the ion balance and the sequence of chemical reactions. In priority order, the principle salts are calcium sulfate, other sulfates, nitrate, chloride, and carbonate. The chemical abundances deduced by this method agree well with the results of Raman spectroscopy on individual salt inclusions. The abundances in the ice cores are shown to reflect differences in climatic periods (the acidic environment of the Holocene versus the reductive environment of the last glacial maximum) and regional conditions (the marine environment of Antarctica versus the continental environment of Greenland).
  • Sakurai Toshimitsu, Ohno Hiroshi, Iizuka Yoshinori, Horikawa Shinichirou, Aoki Teruo, Johnsen Sigfus, Dahl-Jensen Dorthe, Steffensen J.P., Hondoh Takeo
    Abstracts of Annual Meeting of the Geochemical Society of Japan 日本地球化学会 55 422 - 422 2008 
    過去数十万年間における氷期・間氷期サイクルの詳細な情報は、南極やグリーンランド氷床の頂上で鉛直に掘られた氷床コアから復元できる。氷期から間氷期へ気候が急激に変化する引き金は、北半球の日射量の増加であると考えられた。しかし、日射量の変化が、地球の気候に影響を与えることは間違いないが、地球システムの複雑な現象が絡み合っているため、日射量の変化に応答する地表面の気候変動を詳細に見積もることは難しい。それを見積もるためにはまず、過去の大気成分を氷コアから復元して、日射量が地表面まで伝達する過程を氷期と間氷期について計算する（放射強制力）必要がある。本研究は、氷コアに含まれる微粒子の数密度・化学組成を融かさずに測定し、氷期・間氷期における水溶性エアロゾルの詳細を復元することを目的とし、エアロゾルによる氷期・間氷期の放射強制力を明らかにすることを目指すものである。
  • Yoshinori Iizuka, Takeo Hondoh, Yoshiyuki Fujii
    Journal of Geophysical Research Atmospheres 113 (15) 0148-0227 2008 [Refereed][Not invited]
     
    Interannual fluctuations in the Antarctic sea ice extent (SIE) affect the global albedo and heat balance, and they may affect global CO< inf> 2< /inf> levels. We found that the annual trend of sodium ion fluxes in the snowpack in the Dome Fuji region of East Antarctica can serve as a proxy for the present-day SIE in the southern Indian Ocean and Weddell Sea sectors. We then used sodium ion profiles obtained from the Dome Fuji ice core to reconstruct the SIE during the Holocene. We observed that (1) the beginnings of both the climatic optimum (12.0 ka BP) and neoglaciation (5.4 ka BP) in the Southern Ocean, indicated by siliceous microfossil records, are consistent with decreases (11.8 ka BP) and increases (5.4 ka BP) in the sodium ion fluxes in the Dome Fuji ice core, and (2) the interannual fluctuation in the SIE during some periods of the neoglaciation was greater than the interannual fluctuation during the climatic optimum. Copyright 2008 by the American Geophysical Union.
  • Goto-Azuma Kumiko, Hirabayashi Motohiro, Miyake Takayuki, Uemura Ryu, Kohno Mika, Motoyama Hideaki, Fujii Yoshiyuki, Iizuka Yoshinori, Horikawa Shinichiro, Suzuki Toshitaka, Igarashi Makoto, Satow Kazuhide, Suzuki Keisuke, Fukuoka Takaaki, Fujita Koji, Yoshida Naohiro, Watanabe Okitsugu
    Preprints of the Annual Conference, Japanese Society of Snow and Ice 公益社団法人 日本雪氷学会 2007 18 - 18 0919-7346 2007
  • Miyake Takayuki, Iizuka Yoshinori, Tatenuma Takuya, Yanagisawa Takahiro, Sano Kiyofumi, Uemura Ryu, Hondoh Takeo, Fujii Yoshiyuki
    Preprints of the Annual Conference, Japanese Society of Snow and Ice 公益社団法人 日本雪氷学会 2007 177 - 177 0919-7346 2007
  • Miyake Takayuki, Fujii Yoshiyuki, Goto-Azuma Kumiko, Iizuka Yoshinori, Igarashi Makoto, Uemura Ryu, Kohno Mika, Satow Kazuhide, Suzuki Keisuke, Suzuki Toshitaka, Hirabayashi Motohiro, Fukuoka Takaaki, Fujita Koji, Horikawa Shinichiro, Motoyama Hideaki, Yoshida Naohiro, Watanabe Okitsugu
    Preprints of the Annual Conference, Japanese Society of Snow and Ice 公益社団法人 日本雪氷学会 2007 101 - 101 0919-7346 2007
  • Yoshinori Iizuka, Takeo Hondoh, Yoshiyuki Fujii
    JOURNAL OF GLACIOLOGY 52 (176) 58 - 64 0022-1430 2006 [Refereed][Not invited]
     
    We analyzed the profiles of ionic chemical species in three 500 mm sections of an ice core from Dome Fuji, Antarctica, dated 3.0, 8.9 and 13.3 kyr BP (before present), and compared the profiles to those in the surface snow. The 3.0 and 8.9 kyr sections are from the Holocene and the 13.3 kyr section slightly predates the Holocene. The analyses were done on 2 mm thick slices within each section. At each depth, the primary ionic species were Na+, H+, Cl- and SO42-. The SO42-, Na+ and Mg2+ levels varied with depth in each section over distances ranging from several millimeters to several centimeters. Also, the correlation coefficients between Na+ and SO42- and between Mg2+ and SO42- for each depth were 0.90 or greater, in contrast to the value of 0.59 or less in the surface snow (defined here as 0-3.4 m from the surface). These results suggest that almost all Na+ and Mg2+ in the Holocene ice exists as Na2SO4 and MgSO4 salts, and the formation of these salts occurs not only in the atmosphere during transport, but also in the firn layer.
  • Iizuka Yoshinori, Hondoh Takeo, Fujii Yoshiyuki
    Preprints of the Annual Conference, Japanese Society of Snow and Ice 公益社団法人 日本雪氷学会 2006 211 - 211 0919-7346 2006
  • FUJITA SHUJI, AZUMA KUMIKO, IGARASHI MAKOTO, AZUMA NOBUHIKO, KAMEDA TAKAO, IIZUKA YOSHINORI, SAITO TAKESHI, SHOJI HITOSHI, TAKATA MORIMASA, TANAKA YOICHI, SUZUKI KEISUKE, SUZUKI TOSHITAKA, FUJII YOSHIYUKI, FUJITA KOJI, FURUSAKI ATSUSI, HONDOH TAKEO, MOTOYAMA HIDEAKI, WATANABE OKITSUGU
    Preprints of the Annual Conference, Japanese Society of Snow and Ice 公益社団法人 日本雪氷学会 2006 210 - 210 0919-7346 2006
  • Fluctuations in Antarctic sea-ice extent during the past 30 kyr.
    Iizuka, Y, Hondoh, T, Fujii, Y
    Earth and Planetary Science Letters. 2006 [Refereed][Not invited]
  • Y Iizuka, Y Fujii, N Hirasawa, T Suzuki, H Motoyama, T Furukawa, T Hondoh
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 109 (D4) 2169-897X 2004/02 [Refereed][Not invited]
     
    By chemically analyzing snow samples at Dome Fuji, Antarctica, we found that the snowdrift deposited just after snowfall and the snow layer down to 3.4 m have summer minima in the non-sea-salt (nss)-SO42- and Na+ concentrations and summer maxima of Cl-/Na+. Such a summer nss-SO42- minimum in either snowdrift or the snow layer has not been reported at any other site in Antarctica and arises in spite of the known maximum in the nss-SO42- concentration in aerosol at Dome Fuji in summer. We then did laboratory experiments to better understand the phenomenon. The results supported the following mechanism for the summer nss-SO42- minimum in the snowdrift and snow layer. In summer, water vapor sublimates from within the snow in the daytime and condenses on the surface as frost in the nighttime, resulting in a dilution of the nss-SO42- concentration. This sublimation-condensation process likely occurs at other cold inland regions. In addition, the results might be useful for obtaining a high-resolution dating method for Dome Fuji deep ice cores by counting the number of layers with low nss-SO42- concentration.
  • M Takata, Y Iizuka, T Hondoh, S Fujita, Y Fujii, H Shoji
    ANNALS OF GLACIOLOGY, VOL 39, 2004 39 467 - 472 0260-3055 2004 [Refereed][Not invited]
     
    Long-term changes of snow-accumulation rate in Antarctica are a major uncertainty in our understanding of past climate. Because the visible strata in polar ice are due to variations in the sizes and concentrations of air inclusions and microparticles, the scattered light intensity from an ice core yields valuable information on the stratification, which is likely to provide estimates of the annual accumulation rates. Identification of each layer is therefore necessary, and we developed an optical scanner apparatus to record detailed visible strata of ice cores. The apparatus records the two-dimensional distribution of light-scattering intensity along ice-core samples and produces an image of the whole ice-core sample by an image analysis process. These images showed that ice from Dome Fuji ice core contained a large number of layers. Volcanic layers were also well identified. We processed the scattering intensity on the enhanced intensity images to produce an intensity profile. This profile showed that the period of the intensity variations is consistent with a core-dating model applied to the Dome Fuji ice core. We also found that the intensity peaks are closely correlated to peaks in Ca2+ ion concentrations. Thus, our scanning method is a promising approach to measuring annual-layer thickness and, as a result, may be used to infer past accumulation rates in Antarctica.
  • Y Iizuka, M Takata, T Hondoh, Y Fujii
    ANNALS OF GLACIOLOGY, VOL 39, 2004 39 452 - 456 0260-3055 2004 [Refereed][Not invited]
     
    We measured the depth profiles of soluble ions in the Dome Fuji (Antarctica) ice core to search for possible paleoclimate indications of seasonal climate variations in the last glacial period. A 523 mm long core section between 587.65 and 588.18 m depth was selected for this pilot study, and the high-resolution chemical analysis was done on 2mm thick samples. Our results indicate that anion-cation trapping in ice affects the profiles of the soluble ions and [Na+] in the core may preserve its seasonal signal. Correlation coefficients and the equivalent balances of the soluble ions suggest the following selective coexistences: (1) [Cl-] = [Na+], (2) [NO3-] = 1/2[Ca2+] + [K+], and (3) [SO42-] = 1/2[Ca2+] + [H+] + [Mg2+]. These coexistences are probably due to (1) a sea-salt source of Na+ and Cl-, (2) reaction of NO3- with dust for Ca2+ and NO3-, and (3) anion-cation trapping in ice for SO42- and Ca2+ (Mg2+), respectively.
  • Iizuka Yoshinori, Fujita Koji, Matoba Sumito, Fujii Yoshiyuki, Matsuki Kenichiro, Kohno Mika, Aizen Vladimir B
    Polar meteorology and glaciology 国立極地研究所 18 114 - 120 1344-3437 2004 [Refereed][Not invited]
     
    To better understand how the chemical composition of a glacier in an inland continental region relates to the local climate, we collected ice core samples from the Belukha Glacier, Russia, in July 2001. We analyzed the samples for pH, anions, and cations. The primary soluble ions were SO42-, NO3-, NH4+, Ca2+, and HCOO-. Moreover, we argue the following. 1) Ca2+ and its equivalent SO42-+ NO3- likely originated from terrestrial dust such as soil. 2) HCOO- and its equivalent NH4+ likely originated from vegetation and/or biomass burning. 3) The remaining SO42-+NO3- and NH4+ likely originated from livestock, commercial fertilizers, and natural fertilizers. 4) The NH4+ concentration was low when there was no contribution from vegetation and/or biomass burning.
  • Regional characteristics of surface snow chemistry at East Dronning Maud Land, Antarctica
    Motoyama, H, K. Kamiyama, T. Shiraiwa, T. Saito, T. Kameda, N. Azuma, S. Fujita, Y. Fujii, K. Suzuki, T. Yamada, T. Suzuki, Y. Iizuka, T. Furukawa, K. Nishimura, S. Kanamori, O. Watanabe
    Seventh International Symposium on Antarctic Glaciology 11  2003/08/01 [Not refereed][Not invited]
  • 高田 守昌, 飯塚 芳徳, 庄子 仁, 宮本 淳, 本堂 武夫, 藤田 秀二, 藤井 理行, Morimasa Takata, Yoshinori Iizuka, Hitoshi Shoji, Atsushi Miyamoto, Sepp Kipfstuhl, Takeo Hondoh, Shuji Fujita, Yoshiyuki Fujii
    南極資料 = Antarctic Record 47 (3) 328 - 337 0085-7289 2003 [Refereed][Not invited]
     
    第二期ドームふじ氷床コアプロジェクトの現場解析において,簡便に光学層位を記録するため,専用装置を開発した.この装置は,二次元的な光の散乱強度を氷床コアサンプルの深さ方向に沿って連続的に測定する.我々は,この装置のハードウェアおよび制御ソフトウェアを開発した.この結果,経験のないオペレーターでも容易に測定可能な,自動測定装置が完成した.測定速度は5mm/sを想定しており,この場合,現場処理解析の基本長である1.5mのサンプルを約6分間で測定可能である.この装置は第44次越冬隊が南極ドームふじ観測拠点に搬入し,第45次夏隊から始まる深層コア掘削の現場解析処理に使用される予定である.An optical scanner for stratigraphical study was developed for the Dome Fuji ice core project II. The optical scanner measures two-dimensional light scattering intensities and records optical structures of ice cores. We developed the scanner hardware and control software. The line scanner is controlled by a personal computer and is constructed for automatic measurement. The sliding speed of the scanner is about 5mm per second and, therefore, one ice core sample with a standard length for our sample processes (1.5m long) can be measured within about six minutes. The line scanner was transported to Dome Fuji Station, Antarctica, by the wintering party of the 44th Japanese Antarctic Research Expedition (JARE-44), and will be used for Dome Fuji II ice core measurement by the JARE-45 summer party and successive parties.
  • Spatial distribution of chemical tracers in snow along the route from the coast to 1000km inland at east Dronning Maud Land, Antarctica
    Suzuki, T, Y. Iizuka, T. Furukawa, K. Matsuoka, K. Kamiyama, O. Watanabe
    Chinese Journal of Polar Science 14, 48-56  2003 [Refereed][Not invited]
  • T Suzuki, Y Iizuka, K Matsuoka, T Furukawa, K Kamiyama, O Watanabe
    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY 54 (4) 407 - 411 0280-6509 2002/09 [Refereed][Not invited]
     
    We show and discuss the results of the regional distribution of Cl- and Na+ concentrations in snow cover along the study route from the coast to Dome Fuji station, 1000 km inland, in east Dronning Maud Land, Antarctica. The concentrations of Cl- and Na+ at the coast exponentially decreased with distance from the coast up to 200 km inland. Between 200-1000 km inland, the concentrations of Na+ were nearly constant. On the other hand, the concentrations of Cl- increased with distance beyond 750 km inland. Furthermore, the contribution factors between Cl- and Na+ decreased and the Cl-/Na+ ratio and the nssCl(-)/Cl- ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl- other than sea salt exists in the inland plateau of Antarctica.
  • Glaciological data collected by the 39th and 40th Japanese Antarctic Research Expedition during 1998-2000
    Furukawa, T, T. Yamada, K. Suzuki, T. Suzuki, K. Matsuoka, K. Horikawa, E. Murakata, K. Yasugahira, Y. Iizuka
    JARE Data Reports, No. 267 (Glaciology 29) 2002/04/01 [Not refereed][Not invited]
  • 飯塚 芳徳, 渡辺 興亜
    Bulletin of glaciological research 19 59 - 62 2002 [Refereed][Not invited]
  • Y Iizuka, M Igarashi, K Kamiyama, H Motoyama, O Watanabe
    JOURNAL OF GLACIOLOGY 48 (162) 452 - 460 0022-1430 2002 [Refereed][Not invited]
     
    Snowpack and ice-core samples were collected from the dome of Austfonna ice cap, Svalbard, in the spring of both 1998 and 1999. The samples were analyzed for anions, cations, pH, liquid electrical conductivity and oxygen isotopes. Concentrations of chemical components in snowpack with a history of melting were much lower than those in unmelted snowpack. There was a clear difference between Mg2+/Na+ ratios previously in melted snowpack (0.03+/-0.02) and in unmelted snowpack (0.11+/-0.02). We propose that the Mg2+/Na+ ratio can be used as an indicator of whether or not firn or bubbly ice in the Austfonna ice core has experienced melt percolation. The Mg2+/Na+ ratio indicates that firn or bubbly ice prior to AD 1920 was much less affected by melt percolation than firn or bubbly ice formed after 1920.
  • Iizuka Yoshinori, Satake Hiroshi, Watanabe Okitsugu
    Polar meteorology and glaciology 16 53 - 60 2002 [Refereed][Not invited]
     
    To clarify the basal hydrology of Soya drainage, East Antarctica, we studied the formation processes of a pocket consisting of bubble-free ice in Hamna ice cliff, Soya Coast by using stable isotope ratios (δ^<18>O andδD). The stable isotopes of this bubble-free ice are almost the same values withoutδ-value fluctuations as those from Rayleigh-type fractionation; isotopically, the bubble-free ice was heavier by 3.8 and 27‰ for δ^<18>O and δD, respectively, than the neighboring bubbly ice. These results suggest that the pocket was formed by meltwater refreezing during the discharge of water to the lower reach under the Soya drainage. Meltwater under the Soya drainage is considered to have flowed through R-channels.
  • 松元 高峰, 飯塚 芳徳, 兒玉 裕二, Muravyev Yaroslav D, 鈴木 啓助
    Bulletin of glaciological research 19 71 - 80 2002 [Refereed][Not invited]
  • 神山 孝吉, 飯塚 芳徳, Kokichi Kamiyama, Yoshinori Iizuka, Bernhard Stauffer
    南極資料 = Antarctic Record 45 (2) 171 - 184 0085-7289 2001 [Refereed][Not invited]
     
    雪氷コアの解析には, 初期に様々な処理作業を必要とする。特に化学解析の場合には試料を解析機器に導入する前の処理作業が不可欠であり汚染除去の方法など従来から検討されてきた。ここでは低温実験室で行っていた作業の一部を常温実験室で行い, 処理作業環境の向上を目指した。極地研究所の低温実験室に冷凍保管していた雪氷コアの切断作業を常温実験室に設置した温度コントロールチェンバーを利用して行った。チェンバー内部に小型のコア切断機器を設置し試料を整形した後, 直ちにコア密度を測定した。融解後試料の電気伝導度などを測定し, ラベルを記載した専用容器に保管し, その後トリチウム濃度などの計測に供した。コア試料の切断・密度測定・融解・電気伝導度測定・融解保存容器への保管整理で5m/6時間/一人の作業量効率であることを確認した。また冷凍状態での雪氷コア試料を, 常温実験室で深さ方向の連続融解と試料のサンプル容器への自動分注方法について検討した。実際のコア試料を連続融解しイオン分析用に専用の容器への分注を行ったが, 10試料/15cm/30分/一人の作業量を必要とした。なお作業については複数の人間が携わる必要はなく処理作業効率が上昇し, 測定結果は十分満足できる精度であった。Ice core analyses start with the processing of ice cores. Especially for chemical analyses, pre-treatments for introducing the samples to the measuring instruments without contamination is essential. Part of processing can be carried out under a normal laboratory instead of the cold one to improve the efficiency of processing the core samples. The ice core cutting was carried out in a small chamber, with temperature control, installed in a normal laboratory. The ice core sample was cut with a small instrument in the chamber and melted after the determination of solid bulk density. The melted samples were stored after labeling for the planned measurements, such as HTO measurements. The core processing including cutting in the chamber, measurement of bulk density and electrical conductivity before the storage of melted samples with labeling, were carried out at the rate of 5m/(6 hours・person). The continuous melting and sampling procedures for the ice core sample toward the depth direction are also discussed. Continuous melting with continuous sampling for measurement of ion chromatography was carried out on 10 samples/(15cm・30min・person). The processing was efficient for the delicate sampling, and the data obtained in the procedure was supported by those obtained with normal procedure.
  • Iizuka Yoshinori, Satake Hiroshi, Watanabe Okitsugu
    Polar meteorology and glaciology 国立極地研究所 15 107 - 113 1344-3437 2001 [Refereed][Not invited]
     
    The present paper mainly discusses chloride ions (Cl^-) in debris-laden basal ice near Hamna Icefall, Queen Maud Land, East Antarctica. The basal ice consists of alternating layers of bubble-free and bubbly ice of the order of mm to cm in thickness. Detailed analyses of Cl^- and stable isotopes (δ^<18>O and δD) on the alternating layers were performed. The Cl^- concentrations in the bubble-free ice layers and in the bubbly ice layers whose isotopic fluctuations decrease from neighboring bubble-free ice layers are reduced compared to those in the bubbly ice layers having quasi-neutral values on the isotopic profile. The reduction of Cl concentration in frozen ice compared to that in pre-freezing water was also observed from an experiment on ion fractionation by freezing. These results suggest that the bubble-free ice layers and the bubbly ice layers whose isotopic fluctuation is decreased from that in neighboring bubble-free ice layers were formed by melt-refreezing processes. The reduction of Cl concentration in the basal ice is considered to be an indicator to distinguish whether the basal ice has experienced melt-refreezing or not.
  • Suzuki Toshitaka, Iizuka Yoshinori, Furukawa Teruo, Matsuoka Kenichi, Kamiyama Kokichi, Watanabe Okitsugu
    Polar meteorology and glaciology 国立極地研究所 15 133 - 140 1344-3437 2001 [Refereed][Not invited]
     
    We show and discuss the regional distributions of Cl^-, Na^+, SO_4^2,NO_3 and ^7Be concentrations in snow cover along the route from S16 to Dome Fuji Station in east Dronning Maud Land, Antarctica. The concentrations of Cl and Na^+ at the coast exponentially decreased with distance from the coast up to 200km inland. Between 200-1000km inland, the concentrations of Na^+ were nearly constant. On the other hand, the concentrations of Cl increased with distance beyond 750km inland. Furthermore, the contribution factors between Cl and Na^+ decreased and the Cl/Na^+ ratio and the nssCl^-/Cl^- ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl other than sea salt exists in the inland plateau of Antarctica. The concentrations of SO_4^2,NO_3 and ^7Be in snow were relatively high in the coastal region and the inland plateau region compared with those in the katabatic-wind region.
  • Motoyama Hideaki, Watanabe Okitsugu, Kamiyama Kokichi, Igarashi Makoto, Azuma Kumiko, Fujii Yoshiyuki, Iizuka Yoshinori, Matoba Sumito, Narita Hideki, Kameda Takao
    Polar meteorology and glaciology 国立極地研究所 15 55 - 66 1344-3437 2001 [Refereed][Not invited]
     
    Surface snow observations were carried out on many glaciers in the Arctic. The observational sites were in Svalbard, Severnaya Zemlya, Greenland and arctic Canada. The seasonal variations of chemical constituents in snowfall remained in the surface snow on the central Greenland ice sheet where the effect of snowmelt was weak. Conversely, the chemical constituents in the snow layer changed with infiltration of melt water on the Svalbard glacier where strong snowmelt occurred, even in high latitudes. But in general, specific regional characteristics remained in all the glaciers. The concentrations of ions in snow were significantly decreased, because of percolation of melt water. But the ratio of NO_3 to Cl still had unique regional characteristic values.
  • 内陸旅行：夏期ドーム旅行
    古川晶雄, 鈴木利孝, 松岡健一, 五十嵐賢二, 草谷洋光, 飯塚芳徳
    日本南極地域観測隊第40次隊報告 369 - 386 2000/04/01 [Not refereed][Not invited]
  • 飯塚 芳徳, 五十嵐 誠, 渡辺 幸一, 神山 孝吉, 渡辺 興亜
    雪氷 The Japanese Society of Snow and Ice 62 (3) 245 - 254 0373-1006 2000 [Refereed][Not invited]
     
    Snowpack samples were collected from the dome of Austfonna ice cap, Svalbard, in the spring of 1998. Snowpack samples were analyzed for anions, cations, pH, EC and δ18O. The results showed that the concentration levels in melted and refrozen snowpack were much lower than those in non-melted snowpack. It is suggested that the ions were flushed out from the snowpack during the thaw. A clear difference of Mg2+/Na+ ratio between the melting experienced snowpack (0.03±0.02) and the non-melted snowpack (0.11±0.02) was detected. We propose that the Mg2+/Na+ ratio become an indicator to distinguish whether firn in the ice core has experienced of melting or not.
  • Iizuka Yoshinori, Igarashi Makoto, Shiraiwa Takayuki, Naruse Renji, Yamada Tomomi, Watanabe Okitsugu
    Polar meteorology and glaciology 国立極地研究所 14 8 - 15 1344-3437 2000 [Refereed][Not invited]
     
    Debris-laden basal ice is exposed along an ice cliff (about 30m high) near Hamna Icefall, Soya Coast, East Antarctica. The basal ice about 6.8m thick can be divided into an upper part (5.5m) and a lower part (1.3m) based on stratigraphic features. Major dissolved ions of the basal ice are probably composed of eight species (Na^+, K^+, Mg^<2+>, Ca^<2+>, Cl, SO_4^2,NO_3 and HCO_3). Almost all Na^+, K^+, Mg^<2+>, Ca^<2+>, SO_4^2 and HCO_3 in the basal ice are considered to have originated from chemical erosion of rock minerals at the base of the ice sheet. According to a calculation of ion composition, the primary rock mineral dissolved in the basal ice is considered to be carbonate.

Books etc

  • アイスコア 地球環境のタイムカプセル
    飯塚芳徳 (Joint work)
    2010/03
  • なぞの宝庫 南極大陸
    飯塚芳徳 (Joint work)
    2008

MISC

  • 青木 輝夫, 的場 澄人, 庭野 匡思, 朽木 勝幸, 谷川 朋範, 竹内 望, 山口 悟, 本山 秀明, 藤田 耕史, 山崎 哲秀, 飯塚 芳徳, 堀 雅裕, 島田 利元, 植竹 淳, 永塚 尚子, 大沼 友貴彦, 橋本 明弘, 石元 裕史, 田中 泰宙, 大島 長, 梶野 瑞王, 足立 光司, 黒﨑 豊, 杉山 慎, 津滝 俊, 東 久美子, 八久保 晶弘, 川上 薫, 木名瀨 健  雪氷 : journal of the Japanese Society of Snow and Ice  83-  (2)  169  -191  2021/03
  • 川上薫, 川上薫, 飯塚芳徳, 的場澄人, 青木輝夫, 杉山慎, 安藤卓人  雪氷研究大会講演要旨集(Web)  2020-  2020
  • OYABU Ikumi, OYABU Ikumi, IIZUKA Yoshinori, KAWAMURA Kenji, KAWAMURA Kenji, KAWAMURA Kenji, WOLFF Eric, SEVERI Mirko, HANSSON Margareta  日本地球惑星科学連合大会予稿集(Web)  2019-  2019
  • 安藤卓人, 飯塚芳徳, 柴田麻衣, 的場澄人, 杉山慎, 飯塚芳徳, 柴田麻衣, 的場澄人, 杉山慎, 安達聖, 山口悟, 藤田耕史, 堀彰, 青木輝夫, 藤田秀二  日本地球惑星科学連合大会予稿集(Web)  2019-  ROMBUNNO.ACC26‐03 (WEB ONLY)  2019  [Not refereed][Not invited]
  • S. Schüpbach, H. Fischer, M. Bigler, T. Erhardt, G. Gfeller, D. Leuenberger, O. Mini, R. Mulvaney, N. J. Abram, L. Fleet, M. M. Frey, E. Thomas, A. Svensson, D. Dahl-Jensen, E. Kettner, H. Kjaer, I. Seierstad, J. P. Steffensen, S. O. Rasmussen, P. Vallelonga, M. Winstrup, A. Wegner, B. Twarloh, K. Wolff, K. Schmidt, K. Goto-Azuma, T. Kuramoto, M. Hirabayashi, J. Uetake, J. Zheng, J. Bourgeois, D. Fisher, D. Zhiheng, C. Xiao, M. Legrand, A. Spolaor, J. Gabrieli, C. Barbante, J. H. Kang, S. D. Hur, S. B. Hong, H. J. Hwang, S. Hong, M. Hansson, Y. Iizuka, I. Oyabu, R. Muscheler, F. Adolphi, O. Maselli, J. McConnell, E. W. Wolff  Nature Communications  9-  (1)  2018/12/01  [Not refereed][Not invited]
     
    The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.
  • Yutaka Kurosaki, Sumito Matoba, Yoshinori Iizuka, Shin Sugiyama, Takuto Ando, Teruo Aoki  Annual Report on Snow and Ice Studies in Hokkaido  37-  91  -94  2018/09  [Not refereed][Not invited]
  • 安藤卓人, 飯塚芳徳, 的場澄人, 杉山慎, 柴田麻衣, 黒崎豊, 堀彰, 八久保晶弘, 藤田秀二, 青木輝夫  雪氷研究大会講演要旨集(Web)  2018-  113(J‐STAGE)  2018  [Not refereed][Not invited]
  • 川村賢二, 川村賢二, 川村賢二, 植村立, 本山秀明, 本山秀明, 飯塚芳徳, 堀内一穂, 青木周司, 東久美子, 東久美子, 藤田秀二, 藤田秀二, 関宰, 平林幹啓, 中澤文男, 中澤文男, 大藪幾美, 大野浩, 津滝俊, 阿部彩子  日本地球惑星科学連合大会予稿集(Web)  2018-  ROMBUNNO.MIS06‐P12 (WEB ONLY)  2018  [Not refereed][Not invited]
  • 柴田麻衣, 山口悟, 藤田耕史, 安達聖, 安藤卓人, 藤田秀二, 堀彰, 青木輝夫, 飯塚芳徳  日本地球惑星科学連合大会予稿集(Web)  2018-  ROMBUNNO.ACC29‐P04 (WEB ONLY)  2018  [Not refereed][Not invited]
  • Sumito Matoba, Masashi Niwano, Tomonori Tanikawa, Yoshinori Iizuka, Tetsuhide Yamasaki, Tetsuhide Yamasaki, Yutaka Kurosaki, Yutaka Kurosaki, Teruo Aoki, Akihiro Hashimoto, Masahiro Hosaka, Shin Sugiyama  Bulletin of Glaciological Research  36-  (0)  15  -22  2018/01/01  [Not refereed][Not invited]
     
    © 2018 Japanese Society of Snow and Ice. During spring 2017, we conducted research expeditions to the SIGMA-A site, which is located on the northwestern Greenland Ice Sheet. We maintained an automated weather station (AWS) to enable continuous meteorological observations. We extended 1.5-m long poles of the AWS and replaced two aerovane sensors, two thermo-hydrometers and an ultrasonic snow gauge. We also drilled an ice core and recovered a core with a total length of 60.06m, conducted stratigraphic observations, and measured the density of the ice core. In addition, we conducted snow-pit observations and snow sampling, measured the specific surface area of snow using near-infrared reflectance, performed sunphotometry observations, and measured the spectral albedo. To schedule research activities in the field camp and helicopter pick-up flights, we received weather forecasts from the Meteorological Research Institute of Japan through the Internet using a satellite phone every day. We took a male dog to the field camp to alert us to approaching animals.
  • 庭野匡思, 青木輝夫, 青木輝夫, 橋本明弘, 的場澄人, 山口悟, 谷川朋範, 藤田耕史, 對馬あかね, 飯塚芳徳, 島田利元, 堀雅裕  日本気象学会大会講演予稿集  (112)  79  2017/09/30  [Not refereed][Not invited]
  • Hashimoto, A, M. Niwano, T. Aoki, S. Tsutaki, S. Sugiyama, T. Yamasaki, Y. Iizuka, S. Matoba  Low Temperature Science  75-  91  -104  2017/03  [Not refereed][Not invited]
     
    As part of a research project titled, "Snow Impurity and Glacial Microbe effects on abruptwarming in the Arctic" (SIGMA), numerous observation campaigns were conducted on the Greenlandice sheet (GrIS) from FY2011 to FY2015. To support research activities in the field, the JapanMeteorological Agency Non-Hydrostatic Model (JMA-NHM) was applied to form a numerical weatherprediction system covering all of Greenland. Before executing our numerical simulation using thismodel, however, we modified the model to better represent the meteorological processes over theGrIS, since the original model was adjusted to fit mid-latitude environments. Using our modifiedmodel, we performed numerical weather prediction twice per day such that expedition crews in thefield could access the resulting prediction information in the morning and evening, which helped themplan and execute their daily missions. Further, we improved our model during these campaigns byreferencing the daily reports obtained from the observation site on the GrIS. In this paper, wedescribe our weather prediction system and evaluate its performance in reference to surfacemeteorological observation data.
  • グリーンランド南東ドームにおける浅層掘削と初期物理解析
    飯塚芳徳, 的場澄人, 藤田秀二, 新堀邦夫, 山崎哲秀, 宮本淳, 堀彰, 斉藤健, 古川崚仁, 杉山慎, 青木輝夫  低温科学  75-  45  -52  2017/03  [Not refereed][Not invited]
  • Yoshinori Iizuka, Atsushi Miyamoto, Akira Hori, Sumito Matoba, Ryoto Furukawa, Takeshi Saito, Shuji Fujita, Motohiro Hirabayashi, Satoru Yamaguchi, Koji Fujita, Nozomu Takeuchi  ARCTIC ANTARCTIC AND ALPINE RESEARCH  49-  (1)  13  -27  2017/02  [Not refereed][Not invited]
     
    We examine a firn core from a dome in southeast Greenland that exhibits distinct firn densification. The ice was-20.9 degrees C at 20 m depth, and the core gives an average accumulation rate of 1.0 m w.e. yr(-1) in water equivalent. However, the close-off density of 830 kg m(-3) occurs at 83.4-86.8 m depth, which is about 20-m shallower than that obtained from two empirical models. Where the density p > 750 kg m(-3), the densification appears faster than that from the empirical models. As a result, compared to the empirical coefficient, the actual compactive viscosity coefficient is nonlinear and decreases at p > 750 kg m(-3), indicating that the fun with a higher density is softer than that from the empirical result. We argue here that the high accumulation rate creates a high overburden pressure in a short time. Thus, the relative softness of the firn may arise from (1) there being not enough time to form bonds between grains as strong as those in a lower accumulation-rate area, and similarly, (2) the dislocation density in the firn being relatively high.
  • Niwano Masashi, Aoki Teruo, Hashimoto Akihiro, Matoba Sumito, Yamaguchi Satoru, Tanikawa Tomonori, Fujita Koji, Tsushima Akane, Iizuka Yoshinori, Shimada Rigen, Hori Masahiro  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2017-  118  2017
  • 安藤卓人, 飯塚芳徳, 飯塚芳徳, 大野浩, 杉山慎, 杉山慎  日本地球化学会年会要旨集(Web)  64th-  ROMBUNNO.1A20(J‐STAGE)  2017  [Not refereed][Not invited]
  • 川村賢二, 川村賢二, 川村賢二, 杉山慎, 植村立, 本山秀明, 本山秀明, 澤柿教伸, 飯塚芳徳, 堀内一穂, 青木周司, 東久美子, 東久美子, 藤田秀二, 藤田秀二, 関宰, 平林幹啓, 大藪幾美  日本地球惑星科学連合大会予稿集(Web)  2017-  ROMBUNNO.MIS10‐12 (WEB ONLY)  2017  [Not refereed][Not invited]
  • 庭野匡思, 青木輝夫, 青木輝夫, 橋本明弘, 的場澄人, 山口悟, 谷川朋範, 藤田耕史, 對馬あかね, 飯塚芳徳, 島田利元, 堀雅裕  雪氷研究大会講演要旨集(Web)  2017-  118(J‐STAGE)  2017  [Not refereed][Not invited]
  • Yuko Motizuki, Hideaki Motoyama, Yoichi Nakai, Keisuke Suzuki, Yoshinori Iizuka, Kazuya Takahashi  GEOCHEMICAL JOURNAL  51-  (3)  293  -298  2017  [Not refereed][Not invited]
     
    Ice core samples record information about the geological history of the Earth, including past climate changes. Dome Fuji, situated at the highest point of Queen Maud Land, is considered one of the best drilling locations for procuring samples to reconstruct past climates and environments. We present here fundamental data on the concentrations of dissolved ions in shallow samples, between 7.7 m and 65.0 m depth, from the Dome Fuji ice core drilled in 2001. The measured anions were HCOO-, CH3COO-, CH3SO3-, F-, Cl-, NO2-, NO3-, SO42-, C2O42-, and PO43-, and the cations were Na+, K+, Mg2+, Ca2+, and NH4+. The temporal resolution of the depth profiles of the ion concentrations was less than one year. No significant correlations were observed among the ions except between Na+ and Cl-. The ion balance in the core, based on the averaged ion concentrations of the samples, was different to that of sea salt, a result consistent with the findings of previous studies. In several samples, however, synchronous concentration peaks of Na+ and Cl- were identified, and the Cl-/Na+ ratios of the corresponding samples were close to the sea salt ratio. This observation indicates the possibility that climate conditions were such that precipitation containing sea salt occurred in the Dome Fuji area. The Cl-/Na+ ratio of samples that did not exhibit Na+ and Cl- peaks in the depth profile differed from that previously reported for the covering snow. This result implies that Cl-, but not Na+, was redistributed after deposition. High concentrations of SO42- in some samples may account for this alteration of Cl-/Na+ ratios. To interpret these observations and elucidate the climatic conditions, further studies, such as isotopic analyses of delta O-18 and delta D, are required.
  • Hiroshi Ohno, Yoshinori Iizuka, Akira Hori, Atsushi Miyamoto, Motohiro Hirabayashi, Takayuki Miyake, Takayuki Kuramoto, Shuji Fujita, Takahiro Segawa, Ryu Uemura, Toshimitsu Sakurai, Toshitaka Suzuki, Hideaki Motoyama  JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE  121-  (7)  1230  -1250  2016/07  [Not refereed][Not invited]
     
    The deepest ice in inland Antarctica is expected to preserve the oldest ice records and to potentially contain microorganisms. However, little is known about the physicochemical conditions in the deepest part of ice sheets. This study investigates the physicochemical properties of the bottom section (3000-3035m) of the Dome Fuji inland ice core, which is located immediately above unfrozen bedrock. The ubiquitous presence of air hydrates and the water isotope composition of ice comparable to the upper main ice core show that the bottom ice is meteoric. However, ion concentrations exhibit abnormal drops at the greatest depths (approximately below 3033m). In the same depth range, microscopic investigations reveal that considerable relocation of air hydrates and microinclusions (water-soluble impurities) occurs, suggesting that the observed reduction in ion concentration results from the segregation of inclusions to ice grain boundaries and the subsequent discharge of chemicals through liquid-water veins. Principal component analysis of ion data supports the meteoric-ice hypothesis, suggesting that the bottom ice had similar original chemistry through all depths. Statistical analyses of chemical data suggest that the water-soluble impurities attached to hydrates or dust (water-insoluble), the ice-soluble chemical species (such as chlorine), and solid particles are less affected by this chemical displacement phenomenon. It is also noteworthy that in the bottom ice, impurity chemicals, which are limiting nutrients for ice-dwelling microorganisms, are concentrated largely to ice-hydrate interfaces, where oxygen, another vital matter for aerobic microorganisms, is also enriched.
  • Ryu Uemura, Kosuke Masaka, Kotaro Fukui, Yoshinori Iizuka, Motohiro Hirabayashi, Hideaki Motoyama  GEOPHYSICAL RESEARCH LETTERS  43-  (11)  5878  -5885  2016/06  [Not refereed][Not invited]
     
    The sulfur stable isotopic values (S-34) of sulfate aerosols can be used to assess oxidation pathways and contributions from various sources, such as marine biogenic sulfur, volcanoes, and sea salt. However, because of a lack of observations, the spatial distribution of S-34 values in Antarctic sulfate aerosols remains unclear. Here we present the first sulfur isotopic values from surface snow samples along a latitudinal transect in eastern Dronning Maud Land, East Antarctica. The S-34 values of sulfate showed remarkably uniform values, in the range of 14.8-16.9, and no significant decrease toward the inland part of the transect was noted. These results suggest that net isotopic fractionation during long-range transport is insignificant. Thus, the S-34 values can be used to infer source contributions. The S-34 values suggest that marine biogenic sulfur is the dominant source of sulfate aerosols, with a fractional contribution of 8416%.
  • Yu Hoshina, Koji Fujita, Yoshinori Iizuka, Hideaki Motoyama  POLAR SCIENCE  10-  (1)  1  -10  2016/03  [Not refereed][Not invited]
     
    Major ions, stable oxygen isotopes (delta O-18), and accumulation rates are analyzed using high temporal resolution data from shallow ice cores and snow pits from East and West Antarctica. Seasonal cycles of major ions and delta O-18 are well preserved at sites with an accumulation rate threshold of >100 kg m(-2) a(-1) and calm wind conditions. The seasonal cycle is unclear at sites with high wind speeds, even if the accumulation rate is greater than the threshold. To eliminate the influences of different source regions on major ion and delta O-18 signals in ice cores, we calculate correlation coefficients between annually averaged major ion concentrations and delta O-18, and then compare these with accumulation rates and other geographical variables such as latitude, elevation, and distance from the coast. We find that accumulation rates are highly correlated with elevation and the 10-m snow temperature, and that major ions and delta O-18 are negatively correlated at low accumulation sites in inland Antarctica. Negative correlations could reflect inconsistent accumulation due to a large inter-annual variability in the accumulation rate. The results show that the relationships between major ions and delta O-18 may not reflect climatic signatures, and could be a result of the unique characteristics of this arid environment. (C) 2015 Elsevier B.V. and NIPR. All rights reserved.
  • 川村賢二, 川村賢二, 川村賢二, 本山秀明, 本山秀明, 東久美子, 東久美子, 藤田秀二, 藤田秀二, 古川晶雄, 古川晶雄, 中澤文男, 中澤文男, 青木周司, 東信彦, 阿部彩子, 阿部彩子, 飯塚芳徳, 植村立, 内田努, 大野浩, 亀田貴雄, 鈴木利孝, 高田守昌, 平林幹啓, 藤田耕史, 福井幸太郎, 堀彰, 堀内一穂, 的場澄人, 宮本淳  雪氷研究大会講演要旨集(Web)  2016-  2016
  • 植村立, 眞坂昂佑, 福井幸太郎, 飯塚芳徳, 平林幹啓, 本山秀明  日本地球惑星科学連合大会予稿集(Web)  2016-  2016
  • 藤田秀二, 藤田秀二, 東久美子, 東久美子, 榎本浩之, 榎本浩之, 榎本浩之, 福井幸太郎, 福井幸太郎, 平林幹啓, 堀彰, 保科優, 保科優, 飯塚芳徳, 望月優子, 本山秀明, 本山秀明, 中澤文男, 杉山慎, SURDYK Sylviane, 高橋和也  日本地球惑星科学連合大会予稿集(Web)  2016-  2016
  • Yoshinori Iizuka, Hiroshi Ohno, Ryu Uemura, Toshitaka Suzuki, Ikumi Oyabu, Yu Hoshina, Kotaro Fukui, Motohiro Hirabayashi, Hideaki Motoyama  Tellus, Series B: Chemical and Physical Meteorology  68-  (1)  2016  [Not refereed][Not invited]
     
    To better understand how sea salt reacts in surface snow of Antarctica, we collected and identified non-volatile particles in surface snow along a traverse in East Antarctica. Samples were obtained during summer 2012/2013 from coastal to inland regions within 69°S to 80°S and 39°E to 45°E, a total distance exceeding 800 km. The spatial resolution of samples is about one sample per latitude between 1500 and 3800m altitude. Here, we obtain the atomic ratios of Na, S and Cl, and calculate the masses of sodium sulphate and sodium chloride. The results show that, even in the coast snow sample (698S), sea salt is highly modified by acid (HNO3 or H2SO4). The fraction of sea salt that reacts with acid increases in the region from 70°S to 74°S below 3000m a.s.l., where some NaCl remains. At the higher altitudes (above 3300m a.s.l.) in the inland region (74°S to 80°S), the reaction uses almost all of the available NaCl.
  • Yoshinori Iizuka, Sumito Matoba, Tetsuhide Yamasaki, Ikumi Oyabu, Moe Kadota, Teruo Aoki  Bulletin of Glaciological Research  34-  (1)  1  -10  2016  [Not refereed][Not invited]
     
    In order to understand 1) temporal variations of anthropogenic aerosols from European regions under the Icelandic low with high time resolution, and 2) the snow densification mechanism at the high accumulation dome in Greenland, we drilled a 90.45m ice core in a high accumulation area of the southeastern Greenland Ice Sheet. The drilling site (SE-Dome 67.18°N, 36.37°W, 3170m a.s.l.) is located 185km north of the town of Tasiilaq in southeastern Greenland. We also conducted borehole temperature measurements. The temperature in the borehole was -20.9°C at a depth of 20m. In addition, we did snow-pit observations, aerosol sampling, snow sampling for chemical and physical analyses and meteorological observation. Air temperature and air pressure were on average -16.8°C and 667hPa during our stay. The aerosol concentration in the top surface 0.1m snow at SE-Dome in the spring of 2015 was lower than those of the other regions in Greenland, likely due to a highland dome of the ice sheet and/or dilution of mass flux by high snow accumulation.
  • Shuji Fujita, Kumiko Goto-Azuma, Motohiro Hirabayashi, Akira Hori, Yoshinori Iizuka, Yuko Motizuki, Hideaki Motoyama, Kazuya Takahashi  JOURNAL OF GLACIOLOGY  62-  (231)  103  -123  2016  [Not refereed][Not invited]
     
    In order to better understand the densification of polar firn, firn cores from the three sites within similar to 10 km of Dome Fuji, Antarctica, were investigated using surrogates of density: dielectric permittivities epsilon(v) and epsilon(h) at microwave frequencies with electrical fields in the vertical and horizontal planes respectively. Dielectric anisotropy Delta epsilon (=epsilon(v) - epsilon(h)) was then examined as a surrogate of the anisotropic geometry of firn. We find that layered densification is explained as a result of complex effects of two phenomena that commonly occur at the three sites. Basically, layers with initially smaller density and smaller geometrical anisotropy deform preferentially throughout the densification process due to textural effects. Second, layers having a higher concentration of Cl- ions deform preferentially during a limited period from the near surface depths until smoothing out of layered Cl- ions by diffusion. We hypothesize that Cl- ions dissociated from sea salts soften firn due to modulation of dislocation movement. Moreover, firn differs markedly across the three sites in terms of strength of geometrical anisotropy, mean rate of densification and density fluctuation. We hypothesize that these differences are caused by textural effects resulting from differences in depositional conditions within various spatial scales.
  • Ikumi Oyabu, Yoshinori Iizuka, Hubertus Fischer, Simon Schuepbach, Gideon Gfeller, Anders Svensson, Manabu Fukui, Jorgen Peder Steffensen, Margareta Hansson  JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES  120-  (18)  9789  -9813  2015/09  [Not refereed][Not invited]
     
    This study reports the chemical composition of particles present along Greenland's North Greenland Eemian Ice Drilling (NEEM) ice core, back to 110,000years before present. Insoluble and soluble particles larger than 0.45 mu m were extracted from the ice core by ice sublimation, and their chemical composition was analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy and micro-Raman spectroscopy. We show that the dominant insoluble components are silicates, whereas NaCl, Na2SO4, CaSO4, and CaCO3 represent major soluble salts. For the first time, particles of CaMg(CO3)(2) and Ca(NO3)(2)center dot 4H(2)O are identified in a Greenland ice core. The chemical speciation of salts varies with past climatic conditions. Whereas the fraction of Na salts (NaCl+Na2SO4) exceeds that of Ca salts (CaSO4+CaCO3) during the Holocene (0.6-11.7kyr B.P.), the two fractions are similar during the BOlling-AllerOd period (12.9-14.6kyr B.P.). During cold climate such as over the Younger Dryas (12.0-12.6kyr B.P.) and the Last Glacial Maximum (15.0-26.9kyr B.P.), the fraction of Ca salts exceeds that of Na salts, showing that the most abundant ion generally controls the salt budget in each period. High-resolution analyses reveal changing particle compositions: those in Holocene ice show seasonal changes, and those in LGM ice show a difference between cloudy bands and clear layers, which again can be largely explained by the availability of ionic components in the atmospheric aerosol body of air masses reaching Greenland.
  • Iizuka Yoshinori, Matoba Sumito, Oyabu Ikumi, Yamasaki Tetsuhide, Kadota Moe, Shinbori Kunio, Aoki Teruo, Saito Takeshi, Miyamoto Atsushi, Furukawa Ryoto, Fujita Shuji, Hori Akira, Yamaguchi Satoru, Ohno Hiroshi, Suzuki Toshitaka, Uemura Ryu, Seki Osamu, Motoyama Hideaki  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2015-  190  2015
  • 眞坂昂佑, 植村立, 福井幸太郎, 飯塚芳徳, 松本理誠, 植村美希, 平林幹啓, 本山秀明  日本地球化学会年会講演要旨集  62nd-  2015
  • 鈴木香寿恵, 本山秀明, 本山秀明, 山内恭, 山内恭, 平沢尚彦, 平沢尚彦, 榎本浩之, 榎本浩之, 田村岳史, 田村岳史, 飯塚芳徳, 的場澄人, 樋口知之, 樋口知之  雪氷研究大会講演要旨集(Web)  2015-  63(J‐STAGE)  2015  [Not refereed][Not invited]
  • 飯塚芳徳, 的場澄人, 大藪幾美, 山崎哲秀, 門田萌, 新堀邦夫, 青木輝夫, 斉藤健, 宮本淳, 古川崚仁, 藤田秀二, 堀彰, 山口悟, 大野浩, 鈴木利孝, 植村立, 関宰, 本山秀明  雪氷研究大会講演要旨集(Web)  2015-  190(J‐STAGE)  2015  [Not refereed][Not invited]
  • Ikumi Oyabu, Yoshinori Iizuka, Ryu Uemura, Takayuki Miyake, Motohiro Hirabayashi, Hideaki Motoyama, Toshimitsu Sakurai, Toshitaka Suzuki, Takeo Hondoh  JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES  119-  (24)  14045  -14058  2014/12  [Not refereed][Not invited]
     
    The flux and chemical composition of aerosols impact the climate. Antarctic ice cores preserve the record of past atmospheric aerosols, providing useful information about past atmospheric environments. However, few studies have directly measured the chemical composition of aerosol particles preserved in ice cores. Here we present the chemical compositions of sulfate and chloride salts from aerosol particles in the Dome Fuji ice core. The analysis method involves ice sublimation, and the period covers the last termination, 25.0-11.0 thousand years before present (kyr B.P.), with a 350 year resolution. The major components of the soluble particles are CaSO4, Na2SO4, and NaCl. The dominant sulfate salt changes at 16.8 kyr B.P. from CaSO4, a glacial type, to Na2SO4, an interglacial type. The sulfate salt flux (CaSO4 plus Na2SO4) inversely correlates with delta O-18 in Dome Fuji over millennial timescales. This correlation is consistent with the idea that sulfate salt aerosols contributed to the last deglacial warming of inland Antarctica by reducing the aerosol indirect effect. Between 16.3 and 11.0 kyr B.P., the presence of NaCl suggests that winter atmospheric aerosols are preserved. A high NaCl/Na2SO4 fraction between 12.3 and 11.0 kyr B.P. indicates that the contribution from the transport of winter atmospheric aerosols increased during this period.
  • Ikumi Oyabu, Ikumi Oyabu, Yoshinori Iizuka, Ryu Uemura, Takayuki Miyake, Motohiro Hirabayashi, Hideaki Motoyama, Toshimitsu Sakurai, Toshimitsu Sakurai, Toshimitsu Sakurai, Toshitaka Suzuki, Takeo Hondoh  Journal of Geophysical Research  119-  (24)  45  -14  2014/11/27  [Not refereed][Not invited]
     
    © 2014. American Geophysical Union. All Rights Reserved. The flux and chemical composition of aerosols impact the climate. Antarctic ice cores preserve the record of past atmospheric aerosols, providing useful information about past atmospheric environments. However, few studies have directly measured the chemical composition of aerosol particles preserved in ice cores. Here we present the chemical compositions of sulfate and chloride salts from aerosol particles in the Dome Fuji ice core. The analysis method involves ice sublimation, and the period covers the last termination, 25.0–11.0 thousand years before present (kyr B.P.), with a 350 year resolution. The major components of the soluble particles are CaSO 4 , Na 2 SO 4 , and NaCl. The dominant sulfate salt changes at 16.8 kyr B.P. from CaSO 4 , a glacial type, to Na 2 SO 4 , an interglacial type. The sulfate salt flux (CaSO 4 plus Na 2 SO 4 ) inversely correlates with δ 18 O in Dome Fuji over millennial timescales. This correlation is consistent with the idea that sulfate salt aerosols contributed to the last deglacial warming of inland Antarctica by reducing the aerosol indirect effect. Between 16.3 and 11.0 kyr B.P., the presence of NaCl suggests that winter atmospheric aerosols are preserved. A high NaCl/Na 2 SO 4 fraction between 12.3 and 11.0 kyr B.P. indicates that the contribution from the transport of winter atmospheric aerosols increased during this period.
  • Shuji Fujita, Shuji Fujita, Kotaro Fukui, Fumio Nakazawa, Hiroyuki Enomoto, Hiroyuki Enomoto, Hiroyuki Enomoto, Shin Sugiyama, Yoshiyuki Fujii, Koji Fujita, Teruo Furukawa, Teruo Furukawa, Keiichiro Hara, Yu Hoshina, Makoto Igarashi, Yoshinori Iizuka, Satoshi Imura, Satoshi Imura, Hideaki Motoyama, Hideaki Motoyama, Sylviane Surdyk, Ryu Uemura  Antarctic Record  58-  352  -392  2014/11/01  [Not refereed][Not invited]
     
    © 2014 National Institute of Polar Research. In the seventh five-year plan of the Japanese Antarctic Research Expedition, a group of Japanese scientists (led by the National Institute of Polar Research) together with a group of Swedish scientists, conducted field surveys to better understand the glaciology of the ice sheet in Dronning Maud Land, East Antarctica, during the 2007/2008 austral summer season. This paper reports on the planning and field preparations, and outlines the scientific achievements of the field expedition. We have gained numerous new scientific insights on the spatio-temporal distribution of the ice sheet environment in the inland plateau. Here, we provide an overview of the new knowledge gained.
  • 鈴木香寿恵, 本山秀明, 山内恭, 榎本浩之, 田村岳史, 飯塚芳徳, 樋口知之  雪氷研究大会講演要旨集  2014-  235  2014/09/05  [Not refereed][Not invited]
  • Hiroshi Ohno, Yoshinori Iizuka, Shinichiro Horikawa, Toshimitsu Sakurai, Takeo Hondoh, Hideaki Motoyama  POLAR SCIENCE  8-  (1)  1  -9  2014/03  [Not refereed][Not invited]
     
    Water-soluble trace constituents affect the physicochemical properties of polar ice. Their structural distribution provides important insights into the formation history of ice and inclusions. We report the first finding of KAl(SO4)(2)center dot 12H(2)O (potassium alum) and Al-2(SO4)(3)center dot nH(2)O (aluminum sulfate) micro-inclusions in the Dome Fuji ice core, East Antartica, using a micro-Raman technique. Eutectic temperatures of these water-soluble species determined using thermal analysis were -0.4 degrees C for potassium alum and -8.0 degrees C for aluminum sulfate. Although the formation process of the aluminum-bearing sulfates remains unclear, the occurrence of these salts largely depends on ice depth. (C) 2013 Elsevier B.V. and NIPR. All rights reserved.
  • 飯塚芳徳, 保科優, 植村立, 大野浩, 平林幹啓, 福井幸太郎, 鈴木利孝, 本山秀明  雪氷研究大会講演要旨集  2014-  2014
  • 鈴木利孝, 関口絢子, 飯塚芳徳, 平林幹啓, 保科優, 大野浩, 福井幸太郎, 本山秀明  雪氷研究大会講演要旨集  2014-  2014
  • 鈴木香寿恵, 本山秀明, 平沢尚彦, 山内恭, 榎本浩之, 田村岳史, 飯塚芳徳, 的場澄人, 樋口知之  極域科学シンポジウム講演予稿集(CD-ROM)  5th-  ROMBUNNO.OM,12GATSU2NICHI,11:15  2014  [Not refereed][Not invited]
  • Yu Hoshina, Koji Fujita, Fumio Nakazawa, Yoshinori Iizuka, Takayuki Miyake, Motohiro Hirabayashi, Takayuki Kuramoto, Shuji Fujita, Hideaki Motoyama  JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES  119-  (1)  274  -283  2014/01  [Not refereed][Not invited]
     
    Postdepositional changes in water stable isotopes in polar firn were investigated at three sites characterized by different accumulation rates along the East Antarctic ice divide near Dome Fuji. Water stable isotopes, major ion concentrations, and tritium contents of three 2-4m deep pits were measured at high resolution (2cm). Temporally, the snow pits cover the past 50years with snow accumulation rates in the range of 29-41kgm(-2) a(-1) around Dome Fuji. Oxygen isotopic profiles in the three pits do not show annual fluctuations, but instead exhibit multiyearcycles. These multiyearcycles are lower in frequency at Dome Fuji as compared with the other two sites. Peaks of water stable isotopes in the multiyearcycles correspond to some ion concentration minima in the pits, although such relationships are not observed in coastal regions. We propose that the extremely low accumulation environment keeps the snow layer at the near surface, which result in postdepositional modifications of isotopic signals by processes such as ventilation and vapor condensation-sublimation. We estimate that oxygen isotopic ratios could be modified by >10 and that the original seasonal cycle could be completely overprinted under the accumulation conditions at Dome Fuji. Moreover, stake measurements at Dome Fuji suggest that the large variability in snow accumulation rate is the cause of the multiyearcycles.
  • D. Dahl-Jensen, M. R. Albert, A. Aldahan, N. Azuma, D. Balslev-Clausen, M. Baumgartner, A. M. Berggren, M. Bigler, T. Binder, T. Blunier, J. C. Bourgeois, E. J. Brook, S. L. Buchardt, C. Buizert, E. Capron, J. Chappellaz, J. Chung, H. B. Clausen, I. Cvijanovic, S. M. Davies, P. Ditlevsen, O. Eicher, H. Fischer, D. A. Fisher, L. G. Fleet, G. Gfeller, V. Gkinis, S. Gogineni, K. Goto-Azuma, A. Grinsted, H. Gudlaugsdottir, M. Guillevic, S. B. Hansen, M. Hansson, M. Hirabayashi, S. Hong, S. D. Hur, P. Huybrechts, C. S. Hvidberg, Y. Iizuka, T. Jenk, S. J. Johnsen, T. R. Jones, J. Jouzel, N. B. Karlsson, K. Kawamura, K. Keegan, E. Kettner, S. Kipfstuhl, H. A. Kjær, M. Koutnik, T. Kuramoto, P. Köhler, T. Laepple, A. Landais, P. L. Langen, L. B. Larsen, D. Leuenberger, M. Leuenberger, C. Leuschen, J. Li, V. Lipenkov, P. Martinerie, O. J. Maselli, V. Masson-Delmotte, J. R. McConnell, H. Miller, O. Mini, A. Miyamoto, M. Montagnat-Rentier, R. Mulvaney, R. Muscheler, A. J. Orsi, J. Paden, C. Panton, F. Pattyn, J. R. Petit, K. Pol, T. Popp, G. Possnert, F. Prié, M. Prokopiou, A. Quiquet, S. O. Rasmussen, D. Raynaud, J. Ren, C. Reutenauer, C. Ritz, T. Röckmann, J. L. Rosen, M. Rubino, O. Rybak, D. Samyn, C. J. Sapart, A. Schilt, A. M.Z. Schmidt, J. Schwander, S. Schüpbach, I. Seierstad, J. P. Severinghaus, S. Sheldon, S. B. Simonsen, J. Sjolte, A. M. Solgaard, T. Sowers, P. Sperlich, H. C. Steen-Larsen, K. Steffen, J. P. Steffensen, D. Steinhage, T. F. Stocker, C. Stowasser, A. S. Sturevik, W. T. Sturges, A. Sveinbjörnsdottir, A. Svensson, J. L. Tison, J. Uetake, P. Vallelonga, R. S.W. Van De Wal, G. Van Der Wel, B. H. Vaughn, B. Vinther, E. Waddington, A. Wegner, I. Weikusat, J. W.C. White, F. Wilhelms, M. Winstrup, E. Witrant, E. W. Wolff, C. Xiao, J. Zheng  Nature  493-  (7433)  489  -494  2013/01/24  [Not refereed][Not invited]
     
    Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 ± 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 ± 250 metres, reaching surface elevations 122,000 years ago of 130 ± 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future. © 2013 Macmillan Publishers Limited. All rights reserved.
  • 保科優, 藤田耕史, 中澤文男, 飯塚芳徳, 三宅隆之, 平林啓幹, 倉元隆之, 本山秀明, 藤田秀二  雪氷研究大会講演要旨集  2013-  2013
  • 三宅隆之, 藤井理行, 平林幹啓, 東久美子, 植村立, 植村立, 倉元隆之, 倉元隆之, 本山秀明, 藤田耕史, 堀川信一郎, 飯塚芳徳, 五十嵐誠, 河野美香, 鈴木啓助, 鈴木利孝  極域科学シンポジウム講演予稿集(CD-ROM)  4th-  2013
  • 植村立, 植村立, 本山秀明, MASSON-DELMOTTE V., JOUZEL J., 三宅隆之, 平林幹啓, 倉元隆之, 大野浩, 河野美香, 東久美子, 藤井理行, 藤田耕史, 堀川信一郎, 飯塚芳徳, 五十嵐誠, 鈴木啓助, 鈴木利孝  極域科学シンポジウム講演予稿集(CD-ROM)  4th-  2013
  • 飯塚芳徳, 保科優, 植村立, 大野浩, 平林幹啓, 福井幸太郎, 鈴木利孝, 本山秀明  雪氷研究大会講演要旨集  2013-  2013
  • 大野浩, 飯塚芳徳, 保科優, 福井幸太郎, 鈴木利孝, 本山秀明  雪氷研究大会講演要旨集  2013-  2013
  • 飯塚芳徳, 保科優, 植村立, 大野浩, 平林幹啓, 福井幸太郎, 鈴木利孝, 本山秀明  極域科学シンポジウム講演予稿集(CD-ROM)  4th-  2013
  • 東久美子, 平林幹啓, 本山秀明, 三宅隆之, 倉元隆之, 植村立, 川村賢二, PARRENIN Frederic, 鈴木香寿恵, 飯塚芳徳, 鈴木啓助, 五十嵐誠, 藤井理行, 鈴木利孝, 堀川信一郎, 河野美香, 藤田耕史, 櫻井俊光, 小端拓郎  極域科学シンポジウム講演予稿集(CD-ROM)  4th-  ROMBUNNO.IC,GOTOAZUMAKUMIKO,1,V3  2013  [Not refereed][Not invited]
  • Yoshinori Iizuka, Barbara Delmonte, Ikumi Oyabu, Torbjörn Karlin, Valter Maggi, Samuel Albani, Manabu Fukui, Takeo Hondoh, Margareta Hansson  Tellus, Series B: Chemical and Physical Meteorology  65-  (1)  1  -9  2013  [Not refereed][Not invited]
     
    Antarctic ice cores preserve the record of past aerosols, an important proxy of past atmospheric chemistry. Here we present the aerosol compositions of sulphate and chloride particles in the Talos Dome (TD) ice core from the Holocene and Last Glacial Period. We find that the main salt types of both periods are NaCl,Na2SO4 and CaSO4, indicating that TD ice contains relatively abundant sea salt (NaCl) from marine primary particles. By evaluating the molar ratio of NaCl toNa2SO4, we show that about half of the sea salt does not undergo sulphatisation during late Holocene. Compared to in inland Antarctica, the lower sulphatisation rate at TD is probably due to relatively little contact between sea salt and sulphuric acid. This low contact rate can be related to a reduced time of reaction for marine-sourced aerosol before reaching TD and/or to a reduced post-depositional effect from the higher accumulation rate at TD. Many sulphate and chloride salts are adhered to silicate minerals. The ratio of sulphate-adhered mineral to particle mass and the corresponding ratio of chloride-adhered mineral both increase with increasing dust concentration. Also, the TD ice appears to contain Ca(NO3)2 or CaCO3 particles, thus differing from aerosol compositions in inland Antarctica, and indicating the proximity of peripheral regions to marine aerosols. © 2013 Y. Iizuka et al.
  • Yoshinori Iizuka, Ryu Uemura, Hideaki Motoyama, Toshitaka Suzuki, Takayuki Miyake, Motohiro Hirabayashi, Takeo Hondoh  NATURE  490-  (7418)  81  -84  2012/10  [Not refereed][Not invited]
     
    Sulphate aerosols, particularly micrometre-sized particles of sulphate salt and sulphate-adhered dust, can act as cloud condensation nuclei, leading to increased solar scattering that cools Earth's climate(1,2). Evidence for such a coupling may lie in the sulphate record from polar ice cores, but previous analyses of melted ice-core samples have provided only sulphate ion concentrations, which may be due to sulphuric acid(3). Here we present profiles of sulphate salt and sulphate-adhered dust fluxes over the past 300,000 years from the Dome Fuji ice core in inland Antarctica. Our results show a nearly constant flux of sulphate-adhered dust through glacial and interglacial periods despite the large increases in total dust flux during glacial maxima(4). The sulphate salt flux, however, correlates inversely with temperature, suggesting a climatic coupling between particulate sulphur and temperature. For example, the total sulphate salt flux during the Last Glacial Maximum averages 5.78 mg m(-2) yr(-1), which is almost twice the Holocene value. Although it is based on a modern analogue with considerable uncertainties when applied to the ice-core record, this analysis indicates that the glacial-to-interglacial decrease in sulphate would lessen the aerosol indirect effects on cloud lifetime and albedo, leading to an Antarctic warming of 0.1 to 5 kelvin.
  • 飯塚 芳徳  雪氷 : 日本雪氷協會雜誌  74-  (1)  78  -79  2012/01/15  [Not refereed][Not invited]
  • Yoshinori Iizuka, Akira Tsuchimoto, Yu Hoshina, Toshimitsu Sakurai, Margareta Hansson, Torbjörn Karlin, Koji Fujita, Fumio Nakazawa, Hideaki Motoyama, Shuji Fujita  Journal of Geophysical Research Atmospheres  117-  (4)  2012  [Not refereed][Not invited]
     
    Most of the aerosol particles present in the surface snow and ice of inland Antarctica come from primary sea salt (sodium chloride) and marine biological activity (methansulfonic and sulfuric acids). Melted water from surface snow, firn, and Holocene ice contains mainly sodium, chloride, and sulfate ions. Although it is well known that sea salt aerosols react rapidly with sulfuric acid, a process known as sulfatization, it is not known when this process takes place. In this research we undertake to measure the proportion of sea salt aerosols that undergo sulfatization in the atmosphere and surface snow, as opposed to deeper ice, in order to understand the suitability of sea salt aerosols as a proxy for past climates in deep ice cores. We directly measure the sulfatization rates in recently fallen snow (0-4 m in depth) collected at the Dome Fuji station, using X-ray dispersion spectroscopy to determine the constituent elements of soluble particles and computing the molar ratios of sodium chloride and sodium sulfate. We estimate that about 90% of the initial sea salt aerosols sulfatize as they are taken up by precipitation over Dome Fuji or in the snowpack within one year after being deposited on the ice sheet. Copyright © 2012 by the American Geophysical Union.
  • 保科優, 藤田耕史, 中澤文男, 飯塚芳徳, 三宅隆之, 平林幹啓, 倉元隆之, 本山秀明, 藤田秀二  雪氷研究大会講演要旨集  2011-  2011
  • 本山秀明, 本山秀明, 新堀邦夫, 倉元隆之, 飯塚芳徳, 三宅隆之, 平林幹啓, 的場澄人  雪氷研究大会講演要旨集  2011-  2011
  • 植村立, 植村立, 本山秀明, MASSON-DELMOTTE V., JOUZEL J., 三宅隆之, 三宅隆之, 平林幹啓, 倉元隆之, 河野美香, 河野美香, 東久美子, 藤井理行, 藤田耕史, 堀川信一郎, 飯塚芳徳, 五十嵐誠, 鈴木啓助, 鈴木利孝  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2011-  2011
  • 本山秀明, 本山秀明, 新堀邦夫, 倉元隆之, 飯塚芳徳, 三宅隆之, 平林幹啓, 的場澄人  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2011-  2011
  • 東久美子, 青木周司, 東信彦, 飯塚芳徳, 植竹淳, 川村賢二, 神田啓史, 倉元隆之, 小端拓郎, 笹公和, 佐藤基之, 瀬川高弘, 高村近子, 中澤高清, 平林幹啓, 藤井理行, 藤田秀二, 堀彰, 堀内一穂, 三宅隆之, 三宅隆之, 宮本淳, 本山秀明  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2011-  2011
  • 保科優, 藤田耕史, 中澤文男, 飯塚芳徳, 三宅隆之, 平林幹啓, 倉元隆之, 本山秀明, 藤田秀二  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2011-  2011
  • 三宅隆之, 三宅隆之, 藤井理行, 平林幹啓, 植村立, 倉元隆之, 東久美子, 本山秀明, 藤田耕史, 堀川信一郎, 飯塚芳徳, 五十嵐誠, 河野美香, 河野美香, 鈴木啓助, 鈴木利孝  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2011-  2011
  • 藤田秀二, HOLMLUND P., ANDERSSON I., BROWN I., 榎本浩之, 榎本浩之, 藤井理行, 藤田耕史, 福井幸太郎, 福井幸太郎, 古川晶雄, HANSSON M., 原圭一郎, 保科優, 五十嵐誠, 飯塚芳徳, 伊村智, INGVANDER S., KARLIN T., 本山秀明, 中澤文男, OERTER H., SJOEBERG L.E, 杉山慎, SURDYK S., STROEM J., 植村立, WILHELMS F.  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2011-  2011
  • 藤田秀二, 榎本浩之, 榎本浩之, 福井幸太郎, 福井幸太郎, 藤田耕史, 保科優, 飯塚芳徳, 中澤文男, 杉山慎  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2011-  2011
  • Hideaki Motoyama, Kunio Shinbori, Yoshinori Iizuka, Sumito Matoba, Takayuki Kuramoto, Motohiro Hirabayashi, Takayuki Miyake  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2011-  22  2011  [Not refereed][Not invited]
  • Shuji Fujita, P. Holmlund, I. Andersson, I. Brown, H. I. Enomoto, Y. Fujii, K. Fujita, K. Fukui, T. Furukawa, M. Hansson, K. Hara, Y. Hoshina, M. Igarashi, Y. Iizuka, S. Imura, S. Ingvander, T. Kameda, T. Karlin, H. Motoyama, F. Nakazawa, H. Oerter, L. Sjöberg, S. Sugiyama, S. Surdyk, J. Ström, R. Uemura, F. Wilhelms  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2011-  162  2011  [Not refereed][Not invited]
     
    To form a clearer understanding of the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML), East Antarctica, glaciological investigations were carried out along the 2800-km-long Japanese-Swedish IPY 2007/2008 traverse. The traverse route covers ice sheet ridges and two deep ice coring sites at Dome Fuji and EPICA DML. The surface mass balance (SMB) distribution was derived based on analysis of isochrones within snow pit samples, fim core samples and subsurface radar signals. The SMB averaged over various time scales in the Holocene was determined. This was then compared with various data such as surface elevation, surface slope, prevailing windfield, ice thickness, polarization ratio of satellite-based microwave emissivity and normal backscattered strength of VHF radio waves from within the ice. We find that the large-scale distribution of the SMB depends on the surface elevation, continentality and interactions between ice sheet ridges and the prevailing counterclockwise windfield in DML. A different SMB is found for the windward and leeward sides of the ridges. Local-scale variability in the SMB is essentially governed by bedrock topography which determines the local surface topography and the probability of snow deposition. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by ~15% compared to averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar trend has been reported for many inland plateau sites in East Antarctica. © 2011, The Japanese Society of Snow and Ice / Japan Society for Snow Engineering. All rights reserved.
  • Y. Hoshina, Koji Fujita, Fumio Nakazawa, Motohiro Hirabayashi, Takayuki Kuramoto, Hideaki Motoyama, Shuji Fujita, Yoshinori Iizuka, Takayuki Miyake  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2011-  161  2011  [Not refereed][Not invited]
  • Hirokazu Imai, Toshitaka Suzuki, Yoshinori Iizuka, Hideaki Motoyama, Yoshiyuki Fujii  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2011-  208  2011  [Not refereed][Not invited]
  • S. Fujita, P. Holmlund, I. Andersson, I. Brown, H. Enomoto, Y. Fujii, K. Fujita, K. Fukui, T. Furukawa, M. Hansson, K. Hara, Y. Hoshina, M. Igarashi, Y. Iizuka, S. Imura, S. Ingvander, T. Karlin, H. Motoyama, F. Nakazawa, H. Oerter, L. E. Sjoberg, S. Sugiyama, S. Surdyk, J. Strom, R. Uemura, F. Wilhelms  CRYOSPHERE  5-  (4)  1057  -1081  2011  [Not refereed][Not invited]
     
    To better understand the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML), East Antarctica, a 2800-km-long Japanese-Swedish traverse was carried out. The route includes ice divides between two ice-coring sites at Dome Fuji and EPICA DML. We determined the surface mass balance (SMB) averaged over various time scales in the late Holocene based on studies of snow pits and firn cores, in addition to radar data. We find that the large-scale distribution of the SMB depends on the surface elevation and continentality, and that the SMB differs between the windward and leeward sides of ice divides for strong-wind events. We suggest that the SMB is highly influenced by interactions between the large-scale surface topography of ice divides and the wind field of strong-wind events that are often associated with high-precipitation events. Local variations in the SMB are governed by the local surface topography, which is influenced by the bedrock topography. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by similar to 15% than averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar increasing trend has been reported for many inland plateau sites in Antarctica with the exception of several sites on the leeward side of the ice divides.
  • 三宅隆之, 藤井理行, 平林幹啓, 植村立, 植村立, 倉元隆之, 東久美子, 本山秀明, 藤田耕史, 堀川信一郎, 飯塚芳徳, 五十嵐誠, 河野美香, 河野美香, 鈴木啓助, 鈴木利孝  雪氷研究大会講演要旨集  2010-  2010
  • 東久美子, 青木周司, 東信彦, 飯塚芳徳, 植竹淳, 川村賢二, 神田啓史, 倉元隆之, 小端拓郎, 笹公和, 佐藤基之, 瀬川高弘, 高村近子, 中澤高清, 平林幹啓, 藤井理行, 藤田秀二, 堀彰, 堀内一穂, 三宅隆之, 宮本淳, 本山秀明  雪氷研究大会講演要旨集  2010-  2010
  • 東久美子, 青木周司, 東信彦, 飯塚芳徳, 植竹淳, 川村賢二, 神田啓史, 倉元隆之, 小端拓郎, 笹公和, 佐藤基之, 瀬川高弘, 高村近子, 中澤高清, 平林幹啓, 藤井理行, 藤田秀二, 堀彰, 堀内一穂, 三宅隆之, 宮本淳, 本山秀明  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2010-  2010
  • 保科優, 藤田耕史, 中澤文男, 飯塚芳徳, 三宅隆之, 平林幹啓, 倉元隆之, 本山秀明  雪氷研究大会講演要旨集  2010-  2010
  • 保科優, 藤田耕史, 中澤文男, 飯塚芳徳, 三宅隆之, 平林幹啓, 倉元隆之, 本山秀明  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2010-  2010
  • 藤田秀二, HOLMLUND P., ANDERSSON I., BROWN I., 榎本浩之, 藤井理行, 藤田耕史, 福井幸太郎, 古川晶雄, HANSSON M., 原圭一郎, 飯塚芳徳, 伊村智, INGVANDER S., KARLIN T., 本山秀明, 中澤文男, SJOEBERG L., 杉山慎, SURDYK S., STROEM J.  極域科学・宙空圏・気水圏・生物・地学シンポジウム講演予稿集(CD-ROM)  2010-  2010
  • T. Sakurai, A. Miyamoto, Y. Iizuka, T. Hondoh, T. Uchida, S. Fujita  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2010-  109  2010  [Not refereed][Not invited]
  • Katsunari Matsushima, Toshitaka Suzuki, Hironori Sato, Yoshinori Iizuka, Motohiro Hirabayashi, Hideaki Motoyama, Yoshiyuki Fujii  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2010-  98  2010  [Not refereed][Not invited]
  • Hirokazu Imai, Saeko Yui, Toshitaka Suzuki, Yoshinori Iizuka, Hideaki Motoyama, Yoshiyuki Fujii  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2010-  97  2010  [Not refereed][Not invited]
  • Kumiko Goto-Azuma, Jun Uetake, Kenji Kawamura, Hiroshi Kanda, Takayuki Kuramoto, Takuro Kobashi, Takahiro Segawa, Chiikako Takamura, Motohiro Hirabayashi, Yoshiyuki Fujii, Shuji Fujita, Takayuki Miyake, Hideaki Motoyama, Shuji Aoki, Takakiyo Nakazawa, Nobuhiko Azuma, Motoyuki Sato, Yoshinori Iizuka, Atsushi Miyamoto, Kimikazu Sasa, Akira Hori, Kazuho Horiuchi  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2010-  4  2010  [Not refereed][Not invited]
  • Yu Hoshina, Koji Fujita, Fumio Nakazawa, Takayuki Miyake, Motohiro Hirabayashi, Takayuki Kuramoto, Hideaki Motoyama, Yoshinori Iizuka  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2010-  146  2010  [Not refereed][Not invited]
  • Takayuki Miyake, Yoshiyuki Fujii, Motohiro Hirabayashi, Ryu Uemura, Takayuki Kuramoto, Kumiko Goto-Azuma, Hideaki Motoyama, Makoto Igarashi, Mika Kohno, Ryu Uemura, Koji Fujita, Shinichiro Horikawa, Yoshinori Iizuka, Mika Kohno, Keisuke Suzuki, Toshitaka Suzuki  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2010-  144  2010  [Not refereed][Not invited]
  • 本山秀明, 本山秀明, 東久美子, 東久美子, 植村立, 三宅隆之, 平林幹啓, 倉元隆之, 飯塚芳徳, 鈴木啓助, 藤田秀二, 藤田秀二  雪氷研究大会講演要旨集  2009-  2009
  • Hideaki Motoyama, Takayuki Miyake, Motohiro Hirabayashi, Takayuki Kuramoto, Kumiko Goto-Azuma, Shuji Fujita, Ryu Uemura, Hideaki Motoyama, Kumiko Goto-Azuma, Takayuki Kuramoto, Ryu Uemura, Yoshinori Iizuka, Keisuke Suzuki  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2009-  24  2009  [Not refereed][Not invited]
  • 東久美子, 平林幹啓, 三宅隆之, 植村立, 植村立, 倉元隆之, 本山秀明, 五十嵐誠, 飯塚芳徳, 鈴木啓助, 鈴木利孝, 藤田耕史, 堀川信一郎, 河野美香, 河野美香, 藤井理行, 川村賢二, 青木周司, 中澤高清  極域気水圏シンポジウムプログラム・講演要旨  31st-  2008
  • 三宅隆之, 藤井理行, 平林幹啓, 植村立, 植村立, 倉元隆之, 東久美子, 本山秀明, 飯塚芳徳, 五十嵐誠, 河野美香, 河野美香, 鈴木啓助, 鈴木利孝, 藤田耕史, 堀川信一郎  極域気水圏シンポジウムプログラム・講演要旨  31st-  2008
  • Analyses of Ice Core Data from Various Sites in Svalbard Glaciers from 1987 to 1999.
    Motoyama, H, Watanabe, O, Fujii, Y, Kamiyama, K, Igarashi, M, Matoba, S, Kameda, T, Goto-Azuma, K, Izumi, K, Narita, H, Iizuka, Y, Isaksson, E  NIPR Arctic Data Report  7, 1-79.  2008  [Not refereed][Not invited]
  • T. Sakurai, Y. Iizuka, S. Horikawa, T. Hondoh, T. Uchida  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2008-  79  2008  [Not refereed][Not invited]
  • Takayuki Miyake, Ryu Uemura, Yoshiyuki Fujii, Yoshinori Iizuka, Takeo Hondoh, Kiyofumi Sano, Takuya Tatenuma  Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research  2008-  77  2008  [Not refereed][Not invited]
  • Yoshinori Iizuka, Yoshiyuki Fujii, Naohiko Hirasawa, Toshitaka Suzuki, Hideaki Motoyama, Teruo Furukawa, Takeo Hondoh  Journal of Geophysical Research D: Atmospheres  109-  2004/02/27  [Not refereed][Not invited]
     
    By chemically analyzing snow samples at Dome Fuji, Antarctica, we found that the snowdrift deposited just after snowfall and the snow layer down to 3.4 m have summer minima in the non-sea-salt (nss -SO 2- 4 and Na + concentrations and summer maxima of Cl - /Na + . Such a summer nss-SO 2- 4 minimum in either snowdrift or the snow layer has not been reported at any other site in Antarctica and arises in spite of the known maximum in the nss-SO 2- 4 concentration in aerosol at Dome Fuji in summer. We then did laboratory experiments to better understand the phenomenon. The results supported the following mechanism for the summer nss-SO 2- 4 minimum in the snowdrift and snow layer. In summer, water vapor sublimates from within the snow in the daytime and condenses on the surface as frost in the nighttime, resulting in a dilution of the nss-SO 2- 4 concentration. This sublimation-condensation process likely occurs at other cold inland regions. In addition, the results might be useful for obtaining a high-resolution dating method for Dome Fuji deep ice cores by counting the number of layers with low nss-SO 2- 4 concentration. Copyright 2004 by the American Geophysical Union.
  • 第7回国際南極雪氷シンポジウム報告
    堀彰, 藤井理行, 河村俊行, 前野英生, 宮本淳, 飯塚芳徳  雪氷  66巻1号、69-72  2004  [Not refereed][Not invited]
  • Y Iizuka, M Takata, T Hondoh, Y Fujii  ANNALS OF GLACIOLOGY, VOL 39, 2004  39-  452  -456  2004  [Not refereed][Not invited]
     
    We measured the depth profiles of soluble ions in the Dome Fuji (Antarctica) ice core to search for possible paleoclimate indications of seasonal climate variations in the last glacial period. A 523 mm long core section between 587.65 and 588.18 m depth was selected for this pilot study, and the high-resolution chemical analysis was done on 2mm thick samples. Our results indicate that anion-cation trapping in ice affects the profiles of the soluble ions and [Na+] in the core may preserve its seasonal signal. Correlation coefficients and the equivalent balances of the soluble ions suggest the following selective coexistences: (1) [Cl-] = [Na+], (2) [NO3-] = 1/2[Ca2+] + [K+], and (3) [SO42-] = 1/2[Ca2+] + [H+] + [Mg2+]. These coexistences are probably due to (1) a sea-salt source of Na+ and Cl-, (2) reaction of NO3- with dust for Ca2+ and NO3-, and (3) anion-cation trapping in ice for SO42- and Ca2+ (Mg2+), respectively.
  • Morimasa Takata, Yoshinori Iizuka, Hitoshi Shoji, Atsushi Miyamoto, Sepp Kipfstuhl, Takeo Hondoh, Shuji Fujita, Yoshiyuki Fujii  Antarctic Record  47-  328  -337  2003/11/01  [Not refereed][Not invited]
     
    An optical scanner for stratigraphical study was developed for the Dome Fuji ice core project II. The optical scanner measures two-dimensional light scattering intensities and records optical structures of ice cores. We developed the scanner hardware and control software. The line scanner is controlled by a personal computer and is constructed for automatic measurement. The sliding speed of the scanner is about 5 mm per second and, therefore, one ice core sample with a standard length for our sample processes (1.5 m long) can be measured within about six minutes. The line scanner was transported to Dome Fuji Station, Antarctica, by the wintering party of the 44th Japanese Antarctic Research Expedition (JARE-44), and will be used for Dome Fuji II ice core measurement by the JARE-45 summer party and successive parties. © 2003 National Institute of Polar Research.
  • Y Iizuka, M Igarashi, K Kamiyama, H Motoyama, O Watanabe  JOURNAL OF GLACIOLOGY  48-  (162)  452  -460  2002  [Not refereed][Not invited]
     
    Snowpack and ice-core samples were collected from the dome of Austfonna ice cap, Svalbard, in the spring of both 1998 and 1999. The samples were analyzed for anions, cations, pH, liquid electrical conductivity and oxygen isotopes. Concentrations of chemical components in snowpack with a history of melting were much lower than those in unmelted snowpack. There was a clear difference between Mg2+/Na+ ratios previously in melted snowpack (0.03+/-0.02) and in unmelted snowpack (0.11+/-0.02). We propose that the Mg2+/Na+ ratio can be used as an indicator of whether or not firn or bubbly ice in the Austfonna ice core has experienced melt percolation. The Mg2+/Na+ ratio indicates that firn or bubbly ice prior to AD 1920 was much less affected by melt percolation than firn or bubbly ice formed after 1920.
  • Y Iizuka, H Satake, T Shiraiwa, R Naruse  JOURNAL OF GLACIOLOGY  47-  (157)  223  -231  2001  [Not refereed][Not invited]
     
    Debris-laden basal ice is exposed along an ice cliff near Hamna Glacier, Soya Coast, East Antarctica. The basal ice is about 6.8 in thick and shows conspicuous stratigraphic features. The upper 5.5 in consists of alternating layers of bubble-free and bubbly ice. delta values of the bubble-free ice layers are enriched by 2.4 +/- 1.0 parts per thousand (standard deviation) for delta O-18 compared to values of neighboring bubbly ice layers above, and slopes of delta O-18 vs deltaD are close to 8. Such layers are suggested to have been formed by refreezing of meltwater in an open system. In contrast, part of the bubbly ice layers shows neutral profiles for stable isotopes, suggesting that these ice masses are undisturbed ice-sheet ice which was not affected by melting and freezing. The massive alternating layers are thus considered to have been formed by folding of refrozen and non-melted layers. The lower 1.3 m consists predominantly of bubble-free massive ice. The profile of co-isotopic values shows a change of about 3.0 parts per thousand for delta O-18 at the interface between bubble-free and bubbly ice. Since the isotopic change occurred over a wider thickness than the upper 5.5 in, the basal ice is suggested to have been formed by refreezing of meltwater on a larger scale than the upper 5.5 m.
  • 藤田 秀二, 東 久美子, 飯塚 芳徳, 堀 彰, 宮本 淳  雪氷  61-  (1)  51  -54  1999/01/15  [Not refereed][Not invited]
  • 飯塚 芳徳  雪氷  59-  (4)  268  -270  1997/07/15  [Not refereed][Not invited]

Awards & Honors

  • 2011/09 日本雪氷学会 平田賞
     
    受賞者: 飯塚芳徳

Research Grants & Projects

  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2023/04 -2027/03 
    Author : 石野 咲子, 飯塚 芳徳
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2018/06 -2023/03 
    Author : 藤田 秀二, 平林 幹啓, 飯塚 芳徳, 大野 浩
     
    当初計画に従い、以下の項目の研究を遂行した。 Ⅰ．アイスコアの物理層位の計測：①ミリ波誘電率テンソルの計測を2400m深から深い側に延伸した。② ①とあわせ、結晶Ｃ軸方位の直接計測とを実施し比較を実施した。③水平面内での誘電テンソルの主軸２成分の差を明らかにする分析を実施した。④ミリ波誘電テンソルにかかる研究成果の論文化を開始し、2021年4月と11月にそれぞれ投稿し、前者は出版に至った。後者は公開査読論文として出版され、本報告執筆時には公開査読が継続されている。 Ⅱ．連続融解計測装置系（CFA）を用いたアイスコアの化学層位計測：①2019年度までに開発した小型融解ヘッドの試験を重ねている。ただし、ドームふじアイスコアの分析・消費については、他研究分野との調整の必要が生じ、この計測実施を最終年度に延期した。②ドームふじアイスコアの中層のアイスコアとしては、約570m深～600m深の試料についての連続解析を実施した。また同様に、ドームふじ近傍で2017/2018年に新たに掘削された152m長の浅層コアについて、約75m深よりも浅い深度区間の計測を完了した。 Ⅲ. 塩微粒子の層位にかかる研究：不純物の存在状態の検知計測を、ラマン分光散乱を用いて継続した。 Ⅳ. アイスコアの信号形成にかかるプロセスにかかる研究：2020年度は、以下の２点についての研究を推進した。氷床に閉じ込められてから数百年程度以内の深度約100-120m深の気泡をラマン分光散乱で解析し、気泡中の酸素と窒素の分別比を実測した。 このほか、ドームふじアイスコアの固体電気伝導度解析として前年度まで実施してきたDEPデータの解析、氷床探査用レーダの観測データとアイスコアデータとの比較、アイスコア間の気候変動イベントの年代差の抽出作業を、同期進捗に応じ随時実施した。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2018/06 -2023/03 
    Author : 飯塚 芳徳, 植村 立, 関 宰, 的場 澄人, 大島 長, 藤田 耕史, 大野 浩, 服部 祥平
     
    本プロジェクトの目的は産業革命から現在までの高確度エアロゾルデータベースの構築とアイスコアの新規分析手法から人新世の大気環境復元を高度化することである。最初の目的のために、グリーンランド南東ドームでの250mのアイスコア掘削した。2020年度では、コロナ禍でデンマークやグリーンランドは通年レベル3の渡航禁止下であり、2021年度（本年度）に計画を延期していた。2021年度もデンマークやグリーンランドは通年レベル3の渡航禁止下であり続けたが、4―7月に困難な状況のもとで掘削を決行し、250mのアイスコアの取得に成功した。11月にアイスコアが輸入され、2021年度末現在、そのアイスコアの初期解析を実施している。 第2の目的達成のために、すでに本プロジェクトで公開済のエアロゾルデータを参考にしつつ、1)衛星による近過去の雲量との統計的解析（主担当：藤田）、2)氷晶核能測定装置の開発、3)ダストデータの高精度解読、4)電子顕微鏡による硝酸塩組成の復元（主担当：大野）、5）過酸化水素分析法の確立（主担当：服部）、6）硫酸エアロゾル中の酸素同位体比を用いた大気酸化力の復元（主担当：服部）、7）メタンスルホン酸による海氷面積・海洋生物活動の復元（主担当：的場）、8）過去の硫酸エアロゾルの粒径復元、9）ラマン分析によるアンモニウム塩・硝酸塩の組成復元、10）放射光によるカルシウムエアロゾルの化合物同定のなどの分析に着手してきた。 このうち、硫酸エアロゾル中の酸素同位体比を用いた大気酸化力の復元から、1980年以降の二酸化硫黄排出規制にもかかわらず、硫酸エアロゾルの減少が鈍化しているメカニズムを解明し、論文にまとめた。アンモニアなどのアルカリ性物質の増加による大気の酸性度低下が原因で、大気化学過程が変化し、結果的に硫酸生成効率が上昇することを突きとめた。今後の北極域の環境変動予測に重要な成果である。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2016/04 -2020/03 
    Author : Aoki Teruo
     
    In order to clarify the recent surface melting of the Greenland ice sheet, in-situ field observations, satellite remote sensing and numerical modelling were conducted. In the field observations, existing automatic weather station observations were continued and the data were published. Ice core samples were analyzed to characterize water vapor and mineral dust transport. In satellite remote sensing, we developed an algorithm to retrieve the snow and ice physical parameters using a non-spherical snow particle shape model and quantified the causes of ice sheet surface darkening. In numerical modelling, a regional meteorological model including the detailed processes of light-absorbing aerosols (LAA) was developed. A regional meteorological model including snow metamorphism was used to simulate the time and spatial variation of ice sheet surface melting. In addition, the radiative forcing due to LAA in the atmosphere and snow/ice was estimated by an earth system model.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2016/04 -2019/03 
    Author : Iizuka Yoshinori, Uemura Ryu, Sano Yuji, Kagoshima Shogo, Ando Takuto
     
    In order to measure sulfur and nitrogen isotopes in a single particle of sulfate and nitrate aerosols in polar ice cores, we collected particles on a mesh from ice cores. Then, we measured sulfur isotopes of the single particles. As a result, the average isotope values are about 22 ‰, which is reasonable result for natural sulfate aerosols, however with large error of about 10 ‰.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2016/04 -2019/03 
    Author : Ohno Hiroshi
     
    This study has attempted paleoenvironmental reconstruction using Alaskan ancient permafrost ground ice (14000 to 12300 B.P.). It has become evident that methane concentration and stable carbon isotope ratio of methane in the ground ice co-vary with temperature (stable oxygen isotope ratio of ice), indicating relation between methane productivity (formation pathway) and climate changes. Also, significantly high methanesulfonic acid concentrations were found even in the cold period (Younger Dryas) ice, indicating that near-shore region in the Alaskan Beaufort Sea may not have been completely filled by permanent sea ice at that time.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2019/03 
    Author : Iizuka Yoshinori
     
    The Southeastern Greenland Dome (SE-Dome) has both a high elevation and a high accumulation rate (1.01 m w.e. yr-1), which are suitable properties for reconstructing past environmental changes with a high time resolution. For this study, we measured the major ion fluxes in a 90-m ice core drilled from the SE-Dome region in 2015, and present the records of annual ion fluxes from 1957 to 2014. From 1970 to 2010, the trend of non-sea-salt (nss) SO42- flux decreases, whereas that for NH4+ increases, tracking well with the anthropogenic SOx and NH3 emissions mainly from North America. The result suggests that these fluxes reflect histories of the anthropogenic SOx and NH3 emissions. In contrast, the decadal trend of NO3- flux differs from the decreasing trend of anthropogenic NOx emissions.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2018/03 
    Author : UEMURA Ryu, HIRABAYASHI Motohiro, IIZUKA Yoshinori
     
    Sulfate aerosols affect Earth’s radiative forcing through direct and indirect effects. Ice core data suggest minor changes in sulfate aerosols over the glacial cycles. However, the variations of source contributions of sulfate aerosols remain unclear. In this project, to estimate the changes in source contributions of sulfate aerosols in Antarctica, we analyzed sulfur isotopic ratios of surface snow and ice core. Sulfur isotope ratio of present-day surface snow over East Antarctica shows that the effects of the transport process are small, and major source of present-day sulfate aerosol is marine biogenic activity. The ice core data show that the sulfur isotopic ratio increased from the last glacial period to Holocene.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2016/03 
    Author : Iizuka Yoshinori, NAKAMURA Kazuki, Sato Tomonori
     
    In this study, we had aerosol and snow precipitation sampling at same time in Tomamu basin, and then measured chemical compositions of solid particles both of insoluble and soluble materials. This study produce a first approach that direct comparison of chemical components between dry and wet depositions at same time in same place. We will discuss the difference of chemical components between dry and wet depositions. As a result, the chemical components between inclusions in snow and aerosols are diffrent. Especially, inclusions in snow have many NaCl not but aerosols have less NaCl particles. Also, inclusions in diamond dust have less NaCl. These diffrences are probably due to the diffrence of origins of inclusion.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2010/04 -2016/03 
    Author : Azuma Kumiko, KAWAMURA Kenji, FUJITA Shuji, UETAKE Jun, MOTOYAMA Hideaki, HIRABAYASHI Motohiro, KOBASHI Takuro, TAKAMURA Chikako, KURAMOTO Takayuki, SEGAWA Takahiro, AOKI Shuji, AZUMA Nobuhiko, IIZUKA Yoshinori
     
    We analyzed the ice core drilled under the international project North Greenland Eemian Ice Drilling. The air temperature during the warmest period of Eemian interglacial was warmer than the present by 8℃±４℃, which caused extensive surface melt in north Greenland. The thickness of the northwest Greenland ice sheet decreased by 400±250ｍ during 6000 years, which was much smaller than that had been expected. Mass loss of Antarctic ice sheet should have played a role in sea-level rise during the Eemian. Variations of methane, nitrous oxide, noble gases in the air extracted from the ice core, and those of ionic species and bacterial cell concentrations in ice provided us with valuable information on changes in atmospheric circulation, vegetation, microbial activities, mean ocean temperature etc during the warm periods and abrupt warming events.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2012/04 -2015/03 
    Author : FUJITA Shuji, HACHIKUBO Akihiro, IIZUKA Yoshinori, HORI Akira, KAWAMURA Kenji, KOBASHI Takuro, KIM Koui, KIPFSTUHL Josef
     
    In order to better understand the physical processes of formation of climate signals in deposited snow in inland plateau of the Antarctic Ice Sheet of polar firn, firn cores from Dome Fuji, Antarctica and NEEM Camp, Greenland, were investigated. Layers with initially smaller density and smaller geometrical anisotropy deform preferentially throughout the densification process due to textural effects. Second, layers having a higher concentration of chloride and/or fluoride ions deform preferentially during a limited period from the ice sheet surface until smoothing out of layered ions by diffusion. We hypothesize that these ions softened firn due to modulation of dislocation movement. Moreover, firn differs markedly between the sites in terms of strength of geometrical anisotropy, mean rate of densification, and density fluctuation. We hypothesize that these differences are caused by textural effects resulting from differences in depositional conditions within various spatial scales.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011 -2012 
    Author : IIZUKA Yoshinori
     
    Sulphate aerosols, particularly micron-sized particles of sulphate salt and sulphate-adhered dust, can act as cloud condensation nuclei, leading to increased solar scattering. Evidence for sulphate-climate coupling in the current era has not been found, but may be revealed in the long-term sulphate record from polar ice cores. Melted ice-core samples have previously provided only sulphate-ion concentrations, which may be due to sulphuric acid. We present profiles of sulphate-salt fluxes over the past 300,000 years from the Dome Fuji ice core in inland Antarctica. Results show the sulphate-salt flux correlates inversely with temperature, suggesting a climatic coupling between particulate sulphur and temperature. Although based on a model with serious uncertainties when applied to the ice core record, this analysis indicates that the glacial-to-interglacial decrease in sulphate would lessen the aerosol indirect effects on cloud albedo, leading to an Antarctic warming of 0.1 to 5.2 K.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2009 -2012 
    Author : MOTOYAMA Hideaki, AZUMA Kumiko, IIZUKA Yoshinori, UEMURA Ryu, SUZUKI Kazue, OHNO Hiroshi, KAWAMURA Kenji, FUJITA Shuji, MIYAKE Takayuki, HIRABAYASHI Motohiro, KURAMOTO Takayuki
     
    An ice core was drilled to a depth of 3035 m at the Dome Fuji station in Antarctica. Ice cores contain records of global environmental changes dating back to 720,000 years into the past. The age of the ice core was estimated with high accuracy, and a global standard record of climate and environmental changes was soon published. Further, a study of the mechanism of global environmental changes was developed. Results indicate that sulfate aerosol contributed to temperature change during the glacial-interglacial period. In addition, we clarified that the origin of the sulfate was not only the sea biological activity but also dust.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(若手研究(B))
    Date (from‐to) : 2009 -2010 
    Author : Yoshinori IIZUKA
     
    we reconstructed past aerosol components recent 720kyrBP by using Dome Fuji ice core. As a result, primary components in soluble aerosols were calcium sulfate and sodium chloride during glacial maximums ; on the other hand, primary components were sodium sulfate during interglacials.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2008 -2010 
    Author : FUJITA Shuji, FUKUI Kotaro, KAWAMURA Kenji, AZUMA Kumiko, SURDYK Sylviane, ENOMOTO Horoyuki, NAKAZAWA Fumio, SUGIYAMA Shin, MIYAMOTO Atsushi, IIZUKA Yoshinori, HORI Akira, NISHIMURA Daisuke
     
    Using the snow/firn samples and data obtained by traversing the interior of the Antarctic ice sheet, we studied physical mechanisms of the formation of the strata within snow and firn. Major findings include spatial distribution of the depositional environment in Antarctica, seasonal effects on firn density and spatial distribution of the subglacial environment. In addition, we found that polarization ratio of the microwave emissivity from the ice sheet surface is well correlated to accumulation rate observed by radar sounding.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2007 -2009 
    Author : SHIRAIWA Takayuki, MATOBA Sumito, YAMATAGA Kotaro, SUGIYAMA Shin, IIZUKA Yoshinori, YOSHIKAWA Kenji, SASAKI Hirotaka, FUKUDA Takehiro, TSUSHIMA Akane
     
    In order to study the relationship between the North Pacific climate regime shift and ocean primary production, we analyzed iron concentrations in an ice core drilled at Aurora Peak, Alaskan Range. It was found that the averaged iron deposition was 8.8mg m^2yr^<-1> for the last 10 years, but it was 29 and 19mg m^2yr^<-1> for 2001 and 2002 when there were significant Kosa events. The results suggest that the atmospheric iron deposition to the upper 30-m mixed layer will not affect the biomass production in average but the amounts as recorded in 2001 and 2002 will be high enough to affect the ocean primary production.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(若手研究(B))
    Date (from‐to) : 2007 -2008 
    Author : Yoshinori IIZUKA
     
    南極ドームふじ氷床コアの溶存イオン濃度を数mm 分解能の深さ分解能で分析し、おもな溶存イオン濃度の短周期変動が季節変動に起因していることを示唆した。完新世のナトリウムイオン濃度の短周期変動が南極海の海氷面積の季節変動と対応していることを提唱し、南極のヒプシサーマルの時期はそれ以後のやや寒冷な時期に比べて、海氷の季節変動幅が小さく、冬季に現在ほど北上していない可能性を示唆した。
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(S))
    Date (from‐to) : 2003 -2007 
    Author : Yoshiyuki FUJII, 神山 孝吉, 吉田 尚弘, 古川 晶雄, 藤田 秀二, 本山 秀明, 東 久美子, 三宅 隆之, 青木 周司, 吉田 尚弘, 飯塚 芳徳, 川村 賢二
     
    (Objects) The two deep ice cores from Dome Fuji, Antarctica showed the occurrences of a number of abrupt climate and environment changes during the glacial cycles. Objectives of the research project are 1. to establish high time resolution analysis of the deep ice core from Dome Fuji, 2. to reconstruct detailed climatic and environment changes with yearly time scale, and 3. to study scenarios caused the abrupt changes in climate and environment(Results) The high time resolution analyses of ice core in various climate stages (Holocene, LGM, interstadial and glacial stages) were done and the ...
  • 文部科学省：科学研究費補助金(若手研究(B))
    Date (from‐to) : 2004 -2006 
    Author : 飯塚 芳徳
     
    フィルンのイオン濃度プロファイルをこれまでにない高い時間分解能で測定した。その結果、主要なイオン種間の反応が表面から約8mの範囲(反応層)で生じていることを明らかにした。例えば、硫酸塩について、表面積雪の[Na^+]+[Mg^<2+>]のプロファイルと[SO_4^<2->]プロファイルの相関を調べると、部分的な相関は認められるが相関係数としては0.6程度であるのに対して、深度8mで0.8を越えて両者のプロファイルは酷似するようになる。すなわち、大気中でも硫酸塩は形成されるが、フィルン内部でもNaCl、MgCl_2(固)とH_2SO_4(液)の反応によって、硫酸塩が生成されることを意味している。また、この反応は、液体であるH_2SO_4が氷粒子の表面に広がって固体粒子であるNaCl等と接触することによって生ずると考えられるから、反応層以深のSO_4^<2->の濃度プロファイルは各深度の[Na^+]+[Mg^<2+>]プロファイルをなぞっているに他ならない。この例のように、生成される塩微粒子や液相で残る酸等の量や分布には、その深度のコアに含まれるイオン濃度のバランスによって様々な違いが生ずるが、[Na^+]や[Mg^<2+>]などのカチオンは堆積後移動しにくいため良い古気候シグナルになることがわかった。現在、カチオンを用いて季節変動による化学物質の存在状態の違いから完新世・最終氷...
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(学術創成研究費)
    Date (from‐to) : 2002 -2006 
    Author : Takeo HONDOH, 成田 英器, 白岩 孝行, 堀 彰, 藤田 秀二, 飯塚 芳徳, GREVE R・G, 亀田 貴雄
     
    The aim of the present study is to develop a new research field, Nanoglaciology, for better understanding the ice sheet processes on a macroscopic scale on the basis of various microphysical mechanisms involved in the processes, and to clarify the meaning of paleoclimate-and paleoenvironment-signals and their reliabilities. The main results obtained are summarized as ;1. A mass transfer in the firn and the formation process of layer structures : We revealed structural changes of the layering formed at the surface with depth by the use of various experimental methods. Using SEM-EDS and micro...

Educational Activities

Teaching Experience

  • Advanced Course in Glacier/Ice Sheet Science
    開講年度 : 2021
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 氷河、氷床、地球環境、雪、氷、永久凍土、古環境 glacier, ice sheet, earth environment, snow, ice, permafrost, paleoenvironment
  • Inter-Graduate School Classes(Educational Program):Antarctic Science
    開講年度 : 2021
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 野外観測、降雪、積雪、気象、水文
  • Fundamental Course in Paleoenvironmental Science
    開講年度 : 2021
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 古環境，古気候，古海洋，地球温暖化 Paleoenvironment, Paleoclimatology, Paleoceanography, Global warming
  • Fundamental Course in Cold Region Sciences
    開講年度 : 2021
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 雪氷・寒冷圏、雪、氷、極地 cryosphere, snow, ice, polar regions
  • Freshman Seminar
    開講年度 : 2021
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 南極、雪氷、地球環境、氷床、アイスコア、気象、海洋、海氷

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