研究者データベース

飯塚 芳徳(イイヅカ ヨシノリ)
低温科学研究所 雪氷新領域部門
准教授

基本情報

所属

  • 低温科学研究所 雪氷新領域部門

職名

    准教授

学位

  • 博士(理学) (総合研究大学院大学)

ホームページURL

研究キーワード

  • 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   

研究分野

  • 環境学 / 環境動態解析
  • 地球惑星科学 / 気象・海洋物理・陸水学

職歴

  • 2007年 - 2012年  北海道大学 低温科学研究所助教

研究活動情報

論文

書籍

  • アイスコア 地球環境のタイムカプセル
    飯塚芳徳 (担当:共著)
    2010年03月
  • なぞの宝庫 南極大陸
    飯塚芳徳 (担当:共著)
    2008年

その他活動・業績

  • 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 13 -27 2017年02月 [査読無し][通常論文]
     
    © 2017 Regents of the University of Colorado. We examine a firn core from a dome in southeast Greenland that exhibits distinct firn densification. The ice was-20.9 °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 ρ > 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 ρ > 750 kg m -3 , indicating that the firn 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.
  • S. Schüpbach, H. Fischer, M. Bigler, T. Erhardt, G. Gfeller, D. Leuenberger, O. Mini, R. Mulvaney, N. J. Abram, 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, T. Kuramoto, M. Hirabayashi, J. Uetake, 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, F. Adolphi, O. Maselli, J. McConnell, E. W. Wolff Nature Communications 9 2018年12月 [査読無し][通常論文]
     
    © 2018 The Author(s). 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.
  • Yuko Motizuki, Hideaki Motoyama, Yoichi Nakai, Keisuke Suzuki, Yoshinori Iizuka, Kazuya Takahashi Geochemical Journal 51 293 -298 2017年01月 [査読無し][通常論文]
     
    © Copyright 2017 by The Geochemical Society of Japan. 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 d18O and dD, are required.
  • 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 15 -22 2018年01月 [査読無し][通常論文]
     
    © 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.
  • Hiroshi Ohno, Hiroshi Ohno, Yoshinori Iizuka, Akira Hori, Atsushi Miyamoto, Motohiro Hirabayashi, Takayuki Miyake, Takayuki Kuramoto, Shuji Fujita, Shuji Fujita, Takahiro Segawa, Takahiro Segawa, Takahiro Segawa, Ryu Uemura, Toshimitsu Sakurai, Toshitaka Suzuki, Hideaki Motoyama, Hideaki Motoyama Journal of Geophysical Research: Earth Surface 121 (7) 1230 -1250 2016年07月 [査読無し][通常論文]
     
    ©2016. American Geophysical Union. All Rights Reserved. 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 (3000–3035 m) 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 3033 m). In the same depth range, microscopic investigations reveal that considerable relocatio n 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年06月 [査読無し][通常論文]
     
    ©2016. The Authors. The sulfur stable isotopic values (δ 34 S) 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 δ 34 S 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 δ 34 S 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 δ 34 S values can be used to infer source contributions. The δ 34 S values suggest that marine biogenic sulfur is the dominant source of sulfate aerosols, with a fractional contribution of 84 ± 16%.
  • Yu Hoshina, Yu Hoshina, Koji Fujita, Yoshinori Iizuka, Hideaki Motoyama, Hideaki Motoyama Polar Science 10 (1) 10 -10 2016年03月 [査読無し][通常論文]
     
    © 2015 Elsevier B.V. and NIPR. Major ions, stable oxygen isotopes (δ 18 O), 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 δ 18 O 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 δ 18 O signals in ice cores, we calculate correlation coefficients between annually averaged major ion concentrations and δ 18 O, 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 δ 18 O 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 δ 18 O may not reflect climatic signatures, and could be a result of the unique characteristics of this arid environment.
  • Shuji Fujita, Shuji Fujita, Kumiko Goto-Azuma, Kumiko Goto-Azuma, Motohiro Hirabayashi, Akira Hori, Yoshinori Iizuka, Yuko Motizuki, Hideaki Motoyama, Hideaki Motoyama, Kazuya Takahashi Journal of Glaciology 62 (231) 103 -123 2016年02月 [査読無し][通常論文]
     
    © The Author(s) 2016. In order to better understand the densification of polar firn, firn cores from the three sites within ∼10 km of Dome Fuji, Antarctica, were investigated using surrogates of density: dielectric permittivities ε v and ε h at microwave frequencies with electrical fields in the vertical and horizontal planes respectively. Dielectric anisotropy Δε (=ε v - ε 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.
  • Yoshinori Iizuka, Hiroshi Ohno, Ryu Uemura, Toshitaka Suzuki, Ikumi Oyabu, Yu Hoshina, Kotaro Fukui, Motohiro Hirabayashi, Hideaki Motoyama, Hideaki Motoyama Tellus, Series B: Chemical and Physical Meteorology 68 2016年01月 [査読無し][通常論文]
     
    © 2016 Y. Iizuka et al. 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 (HNO 3 or H 2 SO 4 ). 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, Moe Kadota, Teruo Aoki Bulletin of Glaciological Research 34 10 -10 2016年01月 [査読無し][通常論文]
     
    © Japanese Society of Snow and Ice. 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.
  • Ikumi Oyabu, Ikumi Oyabu, 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 2015年01月 [査読無し][通常論文]
     
    © 2015. American Geophysical Union. All Rights Reserved. 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, Na 2 SO 4 , CaSO 4 , and CaCO 3 represent major soluble salts. For the first time, particles of CaMg(CO 3 ) 2 and Ca(NO 3 ) 2 •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 + Na 2 SO 4 ) exceeds that of Ca salts (CaSO 4 + CaCO 3 ) 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, 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年12月 [査読無し][通常論文]
     
    © 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.
  • 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年11月 [査読無し][通常論文]
     
    © 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年11月 [査読無し][通常論文]
     
    © 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.
  • Hiroshi Ohno, Hiroshi Ohno, Yoshinori Iizuka, Shinichiro Horikawa, Shinichiro Horikawa, Toshimitsu Sakurai, Toshimitsu Sakurai, Takeo Hondoh, Hideaki Motoyama Polar Science 8 (1) 1 -9 2014年03月 [査読無し][通常論文]
     
    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(SO 4 ) 2 ·12H 2 O (potassium alum) and Al 2 (SO 4 ) 3 ·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°C for potassium alum and -8.0°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. © 2013 Elsevier B.V. and NIPR.
  • Yu Hoshina, Koji Fujita, Fumio Nakazawa, Yoshinori Iizuka, Takayuki Miyake, Motohiro Hirabayashi, Takayuki Kuramoto, Takayuki Kuramoto, Shuji Fujita, Hideaki Motoyama Journal of Geophysical Research 119 (1) 274 -283 2014年01月 [査読無し][通常論文]
     
    © 2013. The Authors. 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 m 2 a 1 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.
  • 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年08月 [査読無し][通常論文]
     
    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,Na 2 SO 4 and CaSO 4 , indicating that TD ice contains relatively abundant sea salt (NaCl) from marine primary particles. By evaluating the molar ratio of NaCl toNa 2 SO 4 , 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(NO 3 ) 2 or CaCO 3 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, Takayuki Miyake, Motohiro Hirabayashi, Takeo Hondoh Nature 490 (7418) 81 -84 2012年10月 [査読無し][通常論文]
     
    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. 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. 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. 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 5.78â €‰mgâ €‰m -2 â €‰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 5â €‰kelvin. © 2012 Macmillan Publishers Limited. All rights reserved.
  • 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 Nature 493 489 -494 2013年01月 [査読無し][通常論文]
     
    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.
  • 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年01月 [査読無し][通常論文]
  • 飯塚 芳徳 雪氷 : 日本雪氷協會雜誌 74 (1) 78 -79 2012年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
     
    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 20 th 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.
  • 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 2012年01月 [査読無し][通常論文]
     
    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.
  • 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年01月 [査読無し][通常論文]
  • S. Fujita, P. Holmlund, I. Andersson, I. Brown, H. Enomoto, H. Enomoto, Y. Fujii, K. Fujita, K. Fukui, 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 Cryosphere 5 1057 -1081 2011年12月 [査読無し][通常論文]
     
    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. © Author(s) 2011.
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • 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年01月 [査読無し][通常論文]
  • Takayuki Miyake, Ryu Uemura, 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年01月 [査読無し][通常論文]
  • Yoshinori Iizuka, Morimasa Takata, Takeo Hondoh, Yoshiyuki Fujii Annals of Glaciology 39 452 -456 2004年12月 [査読無し][通常論文]
     
    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 2 mm 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) [NO 3 - ] = 1/2[Ca 2+ ] + [K + ], and (3) [SO 4 2- ] = 1/2[Ca 2+ ] + [H + ] + [Mg 2+ ]. These coexistences are probably due to (1) a sea-salt source of Na + and Cl - , (2) reaction of NO 3 - with dust for Ca 2+ and NO 3 - , and (3) anion-cation trapping in ice for SO 4 2- and Ca 2+ (Mg 2+ ), respectively.
  • Yoshinori Iizuka, Yoshiyuki Fujii, Naohiko Hirasawa, Toshitaka Suzuki, Hideaki Motoyama, Teruo Furukawa, Takeo Hondoh Journal of Geophysical Research D: Atmospheres 109 2004年02月 [査読無し][通常論文]
     
    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.
  • Morimasa Takata, Yoshinori Iizuka, Hitoshi Shoji, Atsushi Miyamoto, Sepp Kipfstuhl, Takeo Hondoh, Shuji Fujita, Yoshiyuki Fujii Antarctic Record 47 328 -337 2003年11月 [査読無し][通常論文]
     
    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, H. Satake, T. Shiraiwa, R. Naruse Journal of Glaciology 47 223 -231 2001年12月 [査読無し][通常論文]
     
    Debris-laden basal ice is exposed along an ice cliff near Hamna Glacier, Sôya Coast, East Antarctica. The basal ice is about 6.8 m thick and shows conspicuous stratigraphic features. The upper 5.5 m consists of alternating layers of bubble-free and bubbly ice. δ values of the bubble-free ice layers are enriched by 2.4 ± 1.0‰ (standard deviation) for δ 18 O compared to values of neighboring bubbly ice layers above, and slopes of δ 18 O vs δD 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‰ for δ 18 O at the interface between bubble-free and bubbly ice. Since the isotopic change occurred over a wider thickness than the upper 5.5 m, the basal ice is suggested to have been formed by refreezing of meltwater on a larger scale than the upper 5.5 m.
  • Yoshinori Iizuka, Makoto Igarashi, Kokichi Kamiyama, Hideaki Motoyama, Okitsugu Watanabe Journal of Glaciology 48 452 -460 2002年12月 [査読無し][通常論文]
     
    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.
  • 藤田 秀二, 東 久美子, 飯塚 芳徳, 堀 彰, 宮本 淳 雪氷 61 (1) 51 -54 1999年01月 [査読無し][通常論文]
  • 飯塚 芳徳 雪氷 59 (4) 268 -270 1997年07月 [査読無し][通常論文]

受賞

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

競争的資金等の研究課題

  • 文部科学省:科学研究費補助金(若手研究(A))
    研究期間 : 2011年 -2012年 
    代表者 : 飯塚 芳徳
  • 文部科学省:科学研究費補助金(基盤研究(S))
    研究期間 : 2009年 -2012年 
    代表者 : 本山 秀明
     
    ・南極氷床上の沿岸から内陸に至る約1000kmの輸送ルートがあり、10km毎に採取した表面積雪のイオン、水同位体、ダストの分析を行った。過去の研究結果をふまえて、環境指標物質の輸送過程と堆積環境の変動を調べている。特に最近の大雪との関連に注目して学会発表した。・新たな浅層コアの分析は出来なかったが、すでにある複数コアのデータセットを用いて近年の地球環境変動についての研究を進めた。・南極の最終氷期中の数千年スケールの温暖化イベントであるAIMについて、10年以内の時間分解能でコア解析を進めた。イオンが2.5万年前から3.9万年前まで、水同位体が2.7万年から3.9万年、ダストが2.3万年から3.9万年までで、6つのAIMイベントが含まれる。平成23年度から重点的に研究を進める。・ドームふじコアの72万年間の基本データセット作成と高精度年代決定については研究を継続中。・ダスト分析法については、さまざまな検討をして、一応の解決をした。平成23年度にその経過をまとめて発表する予定である。・補助金にて購入した水同位体分析装置は立ち上げ中で、まだ定常的な運用には至っていない。・氷床コアから気温変動復元を高精度化するために、同位体モデルを用いた気温復元実験について詳細な再検討を行った。とくに、水分子の「水素」と「酸素」安定同位体比を両方とも解析に組み入れることで、水蒸気起源海域の水温復元の...
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2009年 -2010年 
    代表者 : 飯塚 芳徳
     
    本研究の目的は過去72万年間における大気エアロゾルの組成を復元することである。南極ドームふじ氷床コアから、-50℃の環境で不揮発性粒子を集める方法を確立した。その後、不揮発性粒子の組成をエネルギー分散型X線分析で分析した。2万年分解能で大気エアロゾル組成を分析したところ、氷期間氷期スケールの気温変動に対応するように温暖期では硫酸ナトリウムが寒冷期には硫酸カルシウム、塩化ナトリウムが主成分であることが明らかとなり、南極上空に存在していた水溶性の大気エアロゾルはその組成が気候ステージで異なっていることが分かった。
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2007年 -2008年 
    代表者 : 飯塚 芳徳
     
    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。
  • 文部科学省:科学研究費補助金(基盤研究(S))
    研究期間 : 2003年 -2007年 
    代表者 : 藤井 理行
     
    本研究の目的は、南極氷床で得られたドームふじ深層コアの氷期サイクルにおける1年スケールの高時間分解能解析法を確立するとともに、コアに記録された急激な気候・環境変動の詳細を解読し、地球規模の変動シナリオの検証を踏まえ、南極域あるいは南半球固有の新たな変動シナリオを解明することである。完新世,LGM,亜氷期,亜間氷期,氷期(MIS7c→7d)のコアの高時間分解解析を行い、ダスト濃度及び非海塩性カルシウムイオンの関係を調べた。両者は時間分解能1年程度でも変動が残存しており、寒冷な気候ステージでは、いずれも濃度が高く両者の相関が高かった。一方、温暖な気候ステージでは、いずれも濃度が低く、かつ両者の相関は悪い。両者の比は温暖な気候ステージの方が大きい。気候ステージによりダストのカルシウム鉱物の組成が異なりかつ比較的短周期で変動している可能性が示唆された。コア中の気体組成(酸素と窒素の存在比)の変動が、過去の大気組成でなく現地の夏期日射量を記録していることを見いだし、地球の軌道要素の摂動による日射量の変動から、氷床コアの年代を正確に求めた。この年代に基づくことで、氷床コアから復元された気候変動や二酸化炭素などの温室効果気体の濃度変動を、地球軌道要素と詳細に比較することぶ初めて可能になった。これから北半球高緯度の夏期日射量の変動が氷期一間氷期の気候変動のきっかけであるという、ミランコビッチ...
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2004年 -2006年 
    代表者 : 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...
  • 文部科学省:科学研究費補助金(学術創成研究費)
    研究期間 : 2002年 -2006年 
    代表者 : 本堂 武夫
     
    本研究は、氷床における様々な微物理過程と巨視的な氷床過程を融合する新たな研究領域として、Nanoglaciologyを創成すると共に、各地で採取された氷コアの高分解能解析を実施し、種々のシグナルの意味と信頼性を明らかにすることを目的として行われた。当初設定した研究課題をほぼすべて達成し、課題によっては当初想定以上の成果を挙げることができた。研究成果の要点は以下の通りである。1.表層における物質移動と成層構造の形成過程:種々の手法を複合的に駆使して、フィルンにおける圧密過程と表層の層構造が深部に伝搬するメカニズムを明らかにした。また、SEM-EDSおよび顕微RAMANを用いて、イオン種の大部分が硫酸塩などの塩として固体微粒子の状態で存在し、塩生成反応の最終生成物とイオンバランスの関係を反応生成ダイヤグラムとしてまとめて表現できることを示した。2.気泡-ハイドレート遷移過程と気体分別:深部で気泡からクラスレート・ハイドレートに遷移する過程で、ハイドレートの新たな核生成過程を明らかにし、ハイドレートの層状分布が堆積微粒子の季節変動を反映することを示した。また、ハイドレートの成長過程と気体分別およびそれらが大気組成データに与える影響を明らかにした。3.結晶組織の発達過程と氷床流動:これまでの流動モデルで無視されてきた結晶方位分布の異方性を取り込んだ流動モデルの定式化を行った。このモデ...

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