研究者データベース

野村 大樹(ノムラ ダイキ)
北方生物圏フィールド科学センター
准教授

基本情報

所属

  • 北方生物圏フィールド科学センター

職名

  • 准教授

学位

  • 博士 (環境科学)(2008年03月 北海道大学)

ホームページURL

科研費研究者番号

  • 70550739

J-Global ID

研究キーワード

  • 極域   気体交換   二酸化炭素   海氷   海洋   

研究分野

  • 環境・農学 / 環境動態解析

職歴

  • 2020年04月 - 現在 北海道大学 北方生物圏フィールド科学センター 准教授
  • 2015年10月 - 2020年03月 北海道大学大学院水産科学研究院 助教
  • 2015年04月 - 2015年09月 北海道大学低温科学研究所 非常勤研究員
  • 2013年04月 - 2015年03月 日本学術振興会 特別研究員PD(北海道大学低温科学研究所)
  • 2012年04月 - 2013年03月 日本学術振興会 特別研究員PD(ノルウェー極地研究所)
  • 2011年04月 - 2012年03月 日本学術振興会 海外特別研究員(ノルウェー極地研究所)
  • 2009年04月 - 2011年03月 国立極地研究所 特任研究員
  • 2008年04月 - 2009年03月 日本学術振興会 特別研究員PD(北海道大学低温科学研究所) (DC2採用後PDに変更)
  • 2007年04月 - 2008年03月 日本学術振興会 特別研究員DC2(北海道大学大学院環境科学院)

研究活動情報

論文

  • Delphine Lannuzel, Letizia Tedesco, Maria van Leeuwe, Karley Campbell, Hauke Flores, Bruno Delille, Lisa Miller, Jacqueline Stefels, Philipp Assmy, Jeff Bowman, Kristina Brown, Giulia Castellani, Melissa Chierici, Odile Crabeck, Ellen Damm, Brent Else, Agneta Fransson, François Fripiat, Nicolas-Xavier Geilfus, Caroline Jacques, Elizabeth Jones, Hermanni Kaartokallio, Marie Kotovitch, Klaus Meiners, Sébastien Moreau, Daiki Nomura, Ilka Peeken, Janne-Markus Rintala, Nadja Steiner, Jean-Louis Tison, Martin Vancoppenolle, Fanny Van der Linden, Marcello Vichi, Pat Wongpan
    Nature Climate Change 10 11 983 - 992 2020年11月 [査読有り]
  • Naoya Kanna, Shin Sugiyama, Yasushi Fukamachi, Daiki Nomura, Jun Nishioka
    Global Biogeochemical Cycles 34 10 2020年10月 [査読有り][通常論文]
  • Lisa Miller, Francois Fripiat, Sebastien Moreau, Daiki Nomura, Jacqueline Stefels, Nadja Steiner, Letizia Tedesco, Martin Vancoppenolle
    Eos 101 2020年09月30日 [査読有り]
     
    Geoengineering strategies to slow sea ice melting would affect not only Earth's climate but also the biology and chemistry of the oceans, atmosphere, and ice.
  • Pat Wongpan, Daiki Nomura, Takenobu Toyota, Tomonori Tanikawa, Klaus M. Meiners, Tomomi Ishino, Tetsuya P. Tamura, Manami Tozawa, Yuichi Nosaka, Toru Hirawake, Atsushi Ooki, Shigeru Aoki
    Annals of Glaciology 1 - 10 2020年09月24日 [査読有り][通常論文]
     
    Abstract Sea ice, which forms in polar and nonpolar areas, transmits light to ice-associated (sympagic) algal communities. To noninvasively study the distribution of sea-ice algae, empirical relations to estimate its biomass from under-ice hyperspectral irradiance have been developed in the Arctic and Antarctica but lack for nonpolar regions. This study examines relationships between normalised difference indices (NDI) calculated from hyperspectral transmittance and sympagic algal biomass in the nonpolar Saroma-ko Lagoon. We analysed physico-biogeochemical properties of snow and land-fast sea ice supporting 27 paired bio-optical measurements along three transects covering an area of over 250 m × 250 m in February 2019. Snow depth (0.08 ± 0.01 m) and ice-bottom brine volume fraction (0.21 ± 0.02) showed low (0.06) and high (0.58) correlations with sea-ice core bottom section chlorophyll a (Chl. a), respectively. Spatial analyses unveiled the patch size of sea-ice Chl. a to be ~65 m, which is in the same range reported from previous studies. A selected NDI (669, 596 nm) explained 63% of algal biomass variability. This reflects the bio-optical properties and environmental conditions of the lagoon that favour the wavelength pair in the orange/red part of the spectrum and suggests the necessity of a specific bio-optical relationship for Saroma-ko Lagoon.
  • Kan Murakami, Daiki Nomura, Gen Hashida, Shin ichiro Nakaoka, Yujiro Kitade, Daisuke Hirano, Toru Hirawake, Kay I. Ohshima
    Marine Chemistry 225 103842 - 103842 2020年09月10日 [査読有り][通常論文]
     
    © 2020 Elsevier B.V. Formation of dense shelf water (DSW) in coastal polynyas (open water or thin sea-ice cover) in the sea-ice zone around Antarctica supplies Antarctic Bottom Water (AABW) through overflow down the continental slope. In coastal polynyas, atmospheric carbon dioxide (CO2) is absorbed by the ocean in the early spring because of active primary production, and DSW formation is an important process for transporting this carbon from the sea surface to the deep ocean. However, there have been few quantitative evaluations of carbon consumption by active primary production and transport in coastal polynyas. Here, we examined the carbon dynamics in the Cape Darnley polynya (CDP), East Antarctica during austral summer 2009, by using carbonate system parameters combined with oceanographic mooring data. The partial pressure of CO2 in the CDP surface water was lower than that of the atmosphere and the mean and standard deviation of sea−air CO2 flux was estimated as −6.5 ± 6.9 mmol C m−2 d−1 (a negative value indicates absorption of atmospheric CO2 by the ocean). Vertical profiles of dissolved inorganic carbon (DIC) concentration showed that concentrations in the bottom layer near the ocean floor were lower (by about 20 μmol kg−1) than those in the ambient water (e.g., modified Circumpolar Deep Water, mCDW). The low-DIC in the shelf water was maintained by the strong biological uptake of carbon imported from high-DIC mCDW within the water column. Therefore, low-DIC DSW overflowed down the continental slope, and low-DIC concentrations were maintained through an export pathway to the continental shelf. The annual production of dissolved organic carbon and particulate organic carbon on the shelf was estimated as 0.7 × 1011–1.5 × 1011 mol C using the data for the DIC of DSW and current velocity data from a mooring in the CDP. Our results provide quantitative estimates for the potential role of carbon consumption by the active primary production and carbon transport by dense water formation in Antarctic coastal polynyas.
  • Agneta Fransson, Melissa Chierici, Daiki Nomura, Mats A. Granskog, Svein Kristiansen, Tõnu Martma, Gernot Nehrke
    Annals of Glaciology 1 - 21 2020年08月13日 [査読有り][通常論文]
     
    Abstract The effect of freshwater sources on wintertime sea-ice CO2 processes was studied from the glacier front to the outer Tempelfjorden, Svalbard, in sea ice, glacier ice, brine and snow. March–April 2012 was mild, and the fjord was mainly covered with drift ice, in contrast to the observed thicker fast ice in the colder April 2013. This resulted in different physical and chemical properties of the sea ice and under-ice water. Data from stable oxygen isotopic ratios and salinity showed that the sea ice at the glacier front in April 2012 contained on average 54% of frozen-in glacial meltwater. This was five times higher than in April 2013, where the ice was frozen seawater. In April 2012, the largest excess of sea-ice total alkalinity (AT), carbonate ion ([CO32−]) and bicarbonate ion concentrations ([HCO3]) relative to salinity was mainly related to dissolved dolomite and calcite incorporated during freezing of mineral-enriched glacial water. In April 2013, the excess of these variables was mainly due to ikaite dissolution as a result of sea-ice processes. Dolomite dissolution increased sea-ice AT twice as much as ikaite and calcite dissolution, implying different buffering capacity and potential for ocean CO2 uptake in a changing climate.
  • Takenobu Toyota, Takashi Ono, Tomonori Tanikawa, Pat Wongpan, Daiki Nomura
    Annals of Glaciology 1 - 10 2020年07月14日 [査読有り][通常論文]
     
    Abstract Although the effects of snow during sea-ice growth have been investigated for sea ice which is thick enough to accommodate dry snow, those for thin sea ice have not been paid much attention due to the difficulty in observing them. Observations are complicated by the presence of slush and its subsequent freeze-up, and the surface heat budget might be sensitive to the additional ice thickness. An onsite short-term land fast sea-ice freeze-up experiment in the Saroma-ko Lagoon, Hokkaido, Japan was carried out to examine the effects of snowfall on the structure and surface heat budget of thin sea ice, based on observational results and a 1-D thermodynamic model. We found that snowfall contributes to the solidification of the surface slush layer, contributing ice thickness that is comparable to the snowfall amount and affecting the crystal texture significantly. On the other hand, the basal ice growth rate and turbulent heat flux were not significantly affected, being <3.1 × 10−8 m s−1 and 3 W m−2, respectively. This finding may validate the omission in past studies of snow effect in estimating ice production rates in polynyas and has implications about the reconstruction of growth history from sample analysis.
  • Jean-Louis Tison, Ted Maksym, Alexander D. Fraser, Matthew Corkill, Noriaki Kimura, Yuichi Nosaka, Daiki Nomura, Martin Vancoppenolle, Steve Ackley, Sharon Stammerjohn, Sarah Wauthy, Fanny Van der Linden, Gauthier Carnat, Célia Sapart, Jeroen de Jong, François Fripiat, Bruno Delille
    Annals of Glaciology 1 - 19 2020年06月24日 [査読有り][通常論文]
     
    Abstract This work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.
  • Snow property controls on modelled Ku-band altimeter estimates of first-year sea ice thickness: Case studies from the Canadian and Norwegian Arctic
    Nandan V, Scharien R. K, Geldsetzer T, Kwok R, Yackel J. J, Mahmud M. S, Rösel A, Tonboe R, Granskog M, Willatt R, Stroeve J, Nomura D, Frey M.
    IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 13 1082 - 1096 2020年 [査読有り][通常論文]
  • Daiki NOMURA, Pat WONGPAN, Takenobu TOYOTA, Tomonori TANIKAWA, Yusuke KAWAGUCHI, Takashi ONO, Tomomi ISHINO, Manami TOZAWA, Tetsuya P. TAMURA, Itsuka S. YABE, Eun Yae SON, Frederic VIVIER, Antonio LOURENCO, Marion LEBRUN, Yuichi NOSAKA, Toru HIRAWAKE, Atsushi OOKI, Shigeru AOKI, Brent ELSE, Francois FRIPIAT, Jun INOUE, Martin VANCOPPENOLLE
    Bulletin of Glaciological Research 38 0 1 - 12 2020年 [査読有り][通常論文]
  • Jennie L. Thomas, Jochen Stutz, Markus M. Frey, Thorsten Bartels-Rausch, Katye Altieri, Foteini Baladima, Jo Browse, Manuel Dall’Osto, Louis Marelle, Jeremie Mouginot, Jennifer G. Murphy, Daiki Nomura, Kerri A. Pratt, Megan D. Willis, Paul Zieger, Jon Abbatt, Thomas A. Douglas, Maria Cristina Facchini, James France, Anna E. Jones, Kitae Kim, Patricia A. Matrai, V. Faye McNeill, Alfonso Saiz-Lopez, Paul Shepson, Nadja Steiner, Kathy S. Law, Steve R. Arnold, Bruno Delille, Julia Schmale, Jeroen E. Sonke, Aurélien Dommergue, Didier Voisin, Megan L. Melamed, Jessica Gier
    Elem Sci Anth 7 1 58 - 58 2019年12月30日 [査読有り][通常論文]
  • Atsushi Ooki, Ryuta Shida, Masashi Otsu, Hiroji Onishi, Naoto Kobayashi, Takahiro Iida, Daiki Nomura, Kota Suzuki, Hideyoshi Yamaoka, Tetsuya Takatsu
    Journal of Oceanography 75 6 485 - 501 2019年12月 [査読有り][通常論文]
  • The effect of melting treatments on the assessment of biomass and nutrients in sea ice (Saroma-ko lagoon, Hokkaido, Japan)
    Roukaerts A, Nomura D, Deman F, Hattori H, Dehairs F, Fripiat F
    Polar Biology, 42, 347–356, 2019. 2019年 [査読有り][通常論文]
  • Takafumi Kataoka, Atsushi Ooki, Daiki Nomura
    Microbes and Environments 34 2 215 - 218 2019年 [査読有り][通常論文]
  • Effects of glacier and sea ice melting on the biogeochemical cycles in the surface water of the Arctic Ocean
    Nomura D, Kanna N, Ooki A
    Chikyu-Kagaku (Geochemistry), In Japanese with English abstract, figures, and table, 53, 149-158, doi:10.14934/chikyukagaku.53.149, 2019. 2019年 [査読有り][通常論文]
  • Biogeochemistry of bromine and organic sulfur compounds in the Arctic region
    Kameyama S, Ooki A, Nomura D
    Chikyu-Kagaku (Geochemistry), In Japanese with English abstract, and figures. 53, 159-171, doi:10.14934/chikyukagaku.53.159, 2019. 2019年 [査読有り][通常論文]
  • K. M. Meiners, M. Vancoppenolle, G. Carnat, G. Castellani, B. Delille, D. Delille, G. S. Dieckmann, H. Flores, F. Fripiat, M. Grotti, B. A. Lange, D. Lannuzel, A. Martin, A. McMinn, D. Nomura, I. Peeken, P. Rivaro, K. G. Ryan, J. Stefels, K. M. Swadling, D. N. Thomas, J.-L. Tison, P. van der Merwe, M. A. van Leeuwe, C. Weldrick, E. J. Yang
    Journal of Geophysical Research: Oceans 123 11 8444 - 8459 2018年11月 [査読有り][通常論文]
  • Daiki Nomura, Mats A. Granskog, Agneta Fransson, Melissa Chierici, Anna Silyakova, Kay I. Ohshima, Lana Cohen, Bruno Delille, Stephen R. Hudson, Gerhard S. Dieckmann
    Biogeosciences 15 11 3331 - 3343 2018年06月05日 [査読有り][通常論文]
     
    Abstract. Rare CO2 flux measurements from Arctic pack ice show that two types of ice contribute to the release of CO2 from the ice to the atmosphere during winter and spring: young, thin ice with a thin layer of snow and older (several weeks), thicker ice with thick snow cover. Young, thin sea ice is characterized by high salinity and high porosity, and snow-covered thick ice remains relatively warm ( >  −7.5 °C) due to the insulating snow cover despite air temperatures as low as −40 °C. Therefore, brine volume fractions of these two ice types are high enough to provide favorable conditions for gas exchange between sea ice and the atmosphere even in mid-winter. Although the potential CO2 flux from sea ice decreased due to the presence of the snow, the snow surface is still a CO2 source to the atmosphere for low snow density and thin snow conditions. We found that young sea ice that is formed in leads without snow cover produces CO2 fluxes an order of magnitude higher than those in snow-covered older ice (+1.0 ± 0.6 mmol C m−2 day−1 for young ice and +0.2 ± 0.2 mmol C m−2 day−1 for older ice).
  • Naoya Kanna, Shin Sugiyama, Yoshihiko Ohashi, Daiki Sakakibara, Yasushi Fukamachi, Daiki Nomura
    Journal of Geophysical Research: Biogeosciences 123 5 1666 - 1682 2018年05月 [査読有り][通常論文]
  • Daiki Nomura, Shigeru Aoki, Daisuke Simizu, Takahiro Iida
    Journal of Geophysical Research: Oceans 123 2 939 - 951 2018年02月 [査読有り][通常論文]
  • Effects of sea ice freezing and melting on air-sea CO2 exchange
    Nomura D
    Archives of Atmospheric Chemistry Research, In Japanese, 38, 038A03, 2018. 2018年 [査読有り][通常論文]
  • J.‐L. Tison, S. Schwegmann, G. Dieckmann, J.‐M. Rintala, H. Meyer, S. Moreau, M. Vancoppenolle, D. Nomura, S. Engberg, L. J. Blomster, S. Hendricks, C. Uhlig, A.‐M. Luhtanen, J. de Jong, J. Janssens, G. Carnat, J. Zhou, B. Delille
    Journal of Geophysical Research: Oceans 122 12 9548 - 9571 2017年12月 [査読有り][通常論文]
  • François Fripiat, Klaus M. Meiners, Martin Vancoppenolle, Stathys Papadimitriou, David N. Thomas, Stephen F. Ackley, Kevin R. Arrigo, Gauthier Carnat, Stefano Cozzi, Bruno Delille, Gerhard S. Dieckmann, Robert B. Dunbar, Agneta Fransson, Gerhard Kattner, Hilary Kennedy, Delphine Lannuzel, David R. Munro, Daiki Nomura, Janne-Markus Rintala, Véronique Schoemann, Jacqueline Stefels, Nadja Steiner, Jean-Louis Tison
    Elem Sci Anth 5 0 13 - 13 2017年03月29日 [査読有り][通常論文]
  • Thomas Coad, Andrew McMinn, Daiki Nomura, Andrew Martin
    Deep Sea Research Part II: Topical Studies in Oceanography 131 160 - 169 2016年09月
  • E. Damm, D. Nomura, A. Martin, G. S. Dieckmann, K. M. Meiners
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 131 150 - 159 2016年09月 [査読有り][通常論文]
     
    This study describes within-ice concentrations of dimethylsulfoniopropionate (DMSP), its degradation product dimethylsulphide (DMS), as well as nutrients and chlorophyll a, that were sampled during the Sea Ice Physics and Ecosystems eXperiment-2 (SIPEX-2) in 2012. DMSP is a methylated substrate produced in large amounts annually by ice-associated microalgae, while DMS plays a significant role in carbon and sulphur cycling in the Southern Ocean. In the East Antarctic study area between 115-125 degrees E and 64-66 degrees S, ice and slush cores, brine, under-ice seawater and zooplankton (Antarctic krill) samples were collected at 6 ice stations. The pack-ice was characterised by high snow loading which initiated flooding events and triggered nutrient supply to the sea-ice surface, while variation in ice conditions influenced sea-ice permeability. This ranged from impermeable surface and middle sections of the sea ice, to completely permeable ice cores at some stations. Chlorophyll a maxima shifted from the sea-ice surface horizon at the first station to the sea ice bottom layer at the last station. Highest DMSP concentrations were detected in brine samples at the sea-ice surface, reflecting a mismatch with respect to the distribution of chlorophyll a. Our data suggest enhanced DMSP production by sea-ice surface algal communities and its release into brine during freezing and melting, which in turn is coupled to flooding events early in the season. A time-cycle of DMS production by DMSP degradation and DMS efflux is evident at the sea ice-snow interface when slush is formed during melt. Seawater under the ice contained only low concentrations of DMSP and DMS, even when brine drainage was evident and the sea ice became permeable. We postulate that in situ grazing by zooplankton may act as sink for the DMSP produced early in the season. (C) 2016 Elsevier Ltd. All rights reserved.
  • Takenobu Toyota, Robert Massom, Olivier Lecomte, Daiki Nomura, Petra Heil, Takeshi Tamura, Alexander D. Fraser
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 131 53 - 67 2016年09月 [査読有り][通常論文]
     
    In late winter-early spring 2012, the second Sea Ice Physics and Ecosystems Experiment (SIPEX II) was conducted off Wilkes Land, East Antarctica, onboard R/V Aurora Australis. The sea-ice conditions were characterized by significantly thick first-year ice and snow, trapping the ship for about 10 days in the near coastal region. The deep snow cover was particularly remarkable, in that its average value of 0.45 m was almost three times that observed between 1992 and 2007 in the region. To reveal factors responsible, we used in situ observations and ERA-Interim reanalysis (1990-2012) to examine the relative contribution of the different components of the local-regional snow mass balance equation i.e., snow accumulation on sea ice, precipitation minus evaporation (P-E), and loss by (i) snow-ice formation and (ii) entering into leads due to drifting snow. Results show no evidence for significantly high P-E in the winter of 2012. Ice core analysis has shown that although the snow-ice layer was relatively thin, indicating less transformation from snow to snow-ice in 2012 as compared to measurements from 2007, the difference was not enough to explain the extraordinarily deep snow. Based on these results, we deduce that lower loss of snow into leads was probably responsible for the extraordinary snow in 2012. Statistical analysis and satellite images suggest that the reduction in loss of snow into leads is attributed to rough ice surface associated with active deformation processes and larger floe size due to sea-ice expansion. This highlights the importance of snow-sea ice interaction in determining the mean snow depth on Antarctic sea ice. (C) 2016 Elsevier Ltd. All rights reserved.
  • Suchana Chavanich, Voranop Viyakarn, Daiki Nomura, Kentaro Watanabe
    POLAR SCIENCE 9 4 389 - 392 2015年12月 [査読有り][通常論文]
     
    The feeding habits of the Antarctic fish Pseudotrematomus bernacchii (Previous name: Trematomus bernacchii) under the fast ice around Japanese Syowa Station were investigated in the summers of 2004/2005 and 2009/2010. The results showed that amphipods and krill were the major prey. However, there was a significant difference in the proportions of larger invertebrates such as squids, octopus and other crustaceans found in the fish stomachs between 2009/2010 and the previous years. Moreover, the percentage of amphipods and krill in fish stomachs declined over the 5-year period in all fish size classes. Several factors including sea ice melting, habitat and environmental changes might have influenced the pattern of feeding behavior. (C) 2015 Elsevier B.V. and NIPR. All rights reserved.
  • Atsushi Ooki, Daiki Nomura, Shigeto Nishino, Takashi Kikuchi, Yoko Yokouchi
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 120 6 4108 - 4128 2015年06月 [査読有り][通常論文]
     
    Isoprene (C5H8) and three volatile organic iodine compounds (VOIs: CH3I, C2H5I, and CH2ClI) in surface seawater were measured in the western Arctic, Northwest Pacific, Indian, and Southern Oceans during the period 2008-2012. These compounds are believed to play an important role in the marine atmospheric chemistry after their emission. The measurements were performed with high time-resolution (1-6 h intervals) using an online equilibrator gas chromatography mass spectrometer. C5H8 was most abundant in high-productivity transitional waters and eutrophic tropical waters. The chlorophyll-a normalized production rates of C5H8 were high in the warm subtropical and tropical waters, suggesting the existence of a high emitter of C5H8 in the biological community of the warm waters. High concentrations of the three VOIs in highly productive transitional water were attributed to biological productions. For CH3I, the highest concentrations were widely distributed in the basin area of the oligotrophic subtropical NW Pacific, probably due to photochemical production and/or high emission rates from phytoplankton. In contrast, the lowest concentrations of C2H5I in subtropical waters were attributed to photochemical removal. Enhancement of CH2ClI concentrations in the shelf-slope areas of the Chukchi Sea and the transitional waters of the NW Pacific in winter suggested that vertical mixing with subsurface waters by regional upwelling or winter cooling acts to increase the CH2ClI concentrations in surface layer. Sea-air flux calculations revealed that the fluxes of CH2ClI were the highest among the three VOIs in shelf-slope areas; the CH3I flux was highest in basin areas.
  • Agneta Fransson, Melissa Chierici, Daiki Nomura, Mats A. Granskog, Svein Kristiansen, Tonu Martma, Gernot Nehrke
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 120 4 2413 - 2429 2015年04月 [査読有り][通常論文]
     
    In order to investigate the effect of glacial water on the CO2 system in the fjord, we studied the variability of the total alkalinity (A(T)), total dissolved inorganic carbon (C-T), dissolved inorganic nutrients, oxygen isotopic ratio (O-18), and freshwater fractions from the glacier front to the outer Tempelfjorden on Spitsbergen in winter 2012 (January, March, and April) and 2013 (April) and summer/fall 2013 (September). The two contrasting years clearly showed that the influence of freshwater, mixing, and haline convection affected the chemical and physical characteristics of the fjord. The seasonal variability showed the lowest calcium carbonate saturation state () and pH values in March 2012 coinciding with the highest freshwater fractions. The highest and pH were found in September 2013, mostly due to CO2 uptake during primary production. Overall, we found that increased freshwater supply decreased , pH, and A(T). On the other hand, we observed higher A(T) relative to salinity in the freshwater end-member in the mild and rainy winter of 2012 (1142 mol kg(-1)) compared to A(T) in 2013 (526 mol kg(-1)). Observations of calcite and dolomite crystals in the glacial ice suggested supply of carbonate-rich glacial drainage water to the fjord. This implies that winters with a large amount of glacial drainage water partly provide a lessening of further ocean acidification, which will also affect the air-sea CO2 exchange.
  • Lisa A. Miller, Francois Fripiat, Brent G.T. Else, Jeff S. Bowman, Kristina A. Brown, R. Eric Collins, Marcela Ewert, Agneta Fransson, Michel Gosselin, Delphine Lannuzel, Klaus M. Meiners, Christine Michel, Jun Nishioka, Daiki Nomura, Stathys Papadimitriou, Lynn M. Russell, Lise Lotte Sørensen, David N. Thomas, Jean-Louis Tison, Maria A. van Leeuwe, Martin Vancoppenolle, Eric W. Wolff, Jiayun Zhou
    Elementa: Science of the Anthropocene 3 000038 - 000038 2015年01月23日 [査読有り][通常論文]
  • Mats A. Granskog, Daiki Nomura, Susann Muller, Andreas Krell, Takenobu Toyota, Hiroshi Hattori
    ANNALS OF GLACIOLOGY 56 69 1 - 8 2015年 [査読有り][通常論文]
     
    Absorption and fluorescence of chromophoric dissolved organic matter (CDOM) in sea ice and surface waters in the southern Sea of Okhotsk was examined. Sea-water CDOM had featureless absorption increasing exponentially with shorter wavelengths. Sea ice showed distinct absorption peaks in the ultraviolet, especially in younger ice. Older first-year sea ice had relatively flat absorption spectra in the ultraviolet range. Parallel factor analysis (PARAFAC) identified five fluorescent CDOM components, two humic-like and three protein-like. Sea water was largely governed by humic-like fluorescence. In sea ice, protein-like fluorescence was found in considerable excess relative to sea water. The accumulation of protein-like CDOM fluorescence in sea ice is likely a result of biological activity within the ice. Nevertheless, sea ice does not contribute excess CDOM during melt, but the material released will be of different composition than that present in the underlying waters. Thus, at least transiently, the CDOM introduced during sea-ice melt might provide a more labile source of fresher protein-like DOM to surface waters in the southern Sea of Okhotsk.
  • Effects of sea-ice growth and decay processes on the biogeochemical cycles in the polar oceans
    Nomura D
    Umi no Kenkyu (Oceanography in Japan), In Japanese with English abstract and figures, 24, 2, 2015. 2015年 [査読有り][通常論文]
  • Takeshi Tamura, Kay I. Ohshima, Jan L. Lieser, Takenobu Toyota, Kazutaka Tateyama, Daiki Nomura, Kazuki Nakata, Alexander D. Fraser, Peter W. Jansen, Kym B. Newbery, Robert A. Massom, Shuki Ushio
    ANNALS OF GLACIOLOGY 56 69 436 - 444 2015年 [査読有り][通常論文]
     
    Accurately measuring and monitoring the thickness distribution of thin ice is crucial for accurate estimation of ocean atmosphere heat fluxes and rates of ice production and salt flux in ice-affected oceans. Here we present results from helicopter-borne brightness temperature (TB) measurements in the Southern Ocean in October 2012 and in the Sea of Okhotsk in February 2009 carried out with a portable passive microwave (PMW) radiometer operating at a frequency of 36 GHz. The goal of these measurements is to aid evaluation of a satellite thin-ice thickness algorithm which uses data from the spaceborne Advanced Microwave Scanning Radiometer Earth Observing System AMSR-E) or the Advanced Microwave Scanning Radiometer-II (AMSR-II). AMSR-E and AMSR-II TB agree with the spatially collocated mean TB from the helicopter-borne measurements within the radiometers' precision. In the Sea of Okhotsk in February 2009, the AMSR-E 36 GHz TB values are closer to the mean than the modal TB values measured by the helicopter-borne radiometer. In an Antarctic coastal polynya in October 2012, the polarization ratio of 36 GHz vertical and horizontal TB is estimated to be 0.137 on average. Our measurements of the TB at 36 GHz over an iceberg tongue suggest a way to discriminate it from sea ice by its unique PMW signature.
  • Koga S, Nomura D, Wada M
    Polar Science, 8 (3), 306–313, 2014. 8 3 306 - 313 2014年09月 [査読有り][通常論文]
  • D. Nomura, H. Yoshikawa-Inoue, S. Kobayashi, S. Nakaoka, K. Nakata, G. Hashida
    BIOGEOSCIENCES 11 20 5749 - 5761 2014年 [査読有り][通常論文]
     
    Partial pressure of CO2 (pCO(2)) in surface water and vertical profiles of the carbonate system parameters were measured during austral summer in the Indian sector of the Southern Ocean (64-67 degrees S, 32-58 degrees E) in January 2006 to understand the CO2 dynamics of seawater in the seasonal ice zone. Surface-water pCO(2) ranged from 275 to 400 mu atm, and longitudinal variations reflected the dominant influence of water temperature and dilution by sea ice meltwater between 32 and 40 degrees E and biological productivity between 40 and 58 degrees E. Using carbonate system data from the temperature minimum layer (-1.9 degrees C < T <-1.5 degrees C, 34.2 < S < 34.5), we examined the winter-to-summer evolution of surface-water pCO(2) and the factors affecting it. Our results indicate that pCO(2) increased by as much as 32 mu atm, resulting mainly from the increase in water temperature. At the same time as changes in sea ice concentration and surface-water pCO(2), the air-sea CO2 flux, which consists of the exchange of CO2 between sea ice and atmosphere, changed from -1.1 to +0.9 mmol C m(-2) day(-1) between winter and summer. These results suggest that, for the atmosphere, the seasonal ice zone acts as a CO2 sink in winter and a temporary CO2 source in summer immediately after the retreat of sea ice. Subsequent biological productivity likely decreases surface-water pCO(2) and the air-sea CO2 flux becomes negative, such that in summer the study area is again a CO2 sink with respect to the atmosphere.
  • Daiki Nomura, Mats A. Granskog, Philipp Assmy, Daisuke Simizu, Gen Hashida
    Journal of Geophysical Research: Oceans 118 12 6511 - 6524 2013年12月 [査読有り]
  • Daiki Nomura, Philipp Assmy, Gernot Nehrke, Mats A. Granskog, Michael Fischer, Gerhard S. Dieckmann, Agneta Fransson, Yubin Hu, Bernhard Schnetger
    Annals of Glaciology 54 62 125 - 131 2013年 [査読有り][通常論文]
     
    AbstractWe identified ikaite crystals (CaCO3·6H2O) and examined their shape and size distribution in first-year Arctic pack ice, overlying snow and slush layers during the spring melt onset north of Svalbard. Additional measurements of total alkalinity (TA) were made for melted snow and sea-ice samples. Ikaite crystals were mainly found in the bottom of the snowpack, in slush and the surface layers of the sea ice where the temperature was generally lower and salinity higher than in the ice below. Image analysis showed that ikaite crystals were characterized by a roughly elliptical shape and a maximum caliper diameter of 201.0±115.9 μm (n = 918). Since the ice-melting season had already started, ikaite crystals may already have begun to dissolve, which might explain the lack of a relationship between ikaite crystal size and sea-ice parameters (temperature, salinity, and thickness of snow and ice). Comparisons of salinity and TA profiles for melted ice samples suggest that the precipitation/dissolution of ikaite crystals occurred at the top of the sea ice and the bottom of the snowpack during ice formation/melting processes.
  • Daiki Nomura, Daisuke Simizu, Suchana Chavanich, Hideo Shinagawa, Mitsuo Fukuchi
    ANTARCTIC SCIENCE 24 5 536 - 544 2012年10月 [査読有り][通常論文]
     
    We performed an artificial pool experiment in the Antarctic multi-year land-fast ice to examine and simulate the effect of sea ice melting on physical and biogeochemical components of the sea ice field. The input of snow and ice meltwater resulted in warmer, low salinity water at the surface of the pool and probably stratification of the less dense water. Current speed measurements also pointed to water stratification within the pool. Rapid phytoplankton growth in the pool resulted in drastic decreases in concentrations of dissolved inorganic carbon and nutrients (NO3- and Si(OH)(4)) in the surface waters of the pool, particularly depleted for NO3-. There was high correlation between variations of dissolved inorganic carbon and nutrient concentrations, but the apparent uptake ratios of these components deviated from that generally applied to marine phytoplankton. The sequence of changes in the physical and biogeochemical components of the pool water suggests that the onset of rapid phytoplankton growth was closely related to the water stratification, which provided stable conditions for phytoplankton bloom even though the supply of nutrients from under-ice water would have declined.
  • Daiki Nomura, Seizi Koga, Nobue Kasamatsu, Hideo Shinagawa, Daisuke Simizu, Makoto Wada, Mitsuo Fukuchi
    Journal of Geophysical Research: Oceans 117 4 2012年 [査読有り][通常論文]
     
    We present the first direct measurements of dimethylsulfide (DMS) emissions from Antarctic sea ice to the atmosphere during the seasonal warming period obtained using a chamber technique. Estimated DMS fluxes measured over the snow and superimposed ice (ice formed by the freezing of snow meltwater) were from 0.1 to 0.3 μmol m-2 d-1. The DMS fluxes measured directly over the sea-ice slush layer after removal of the snow and superimposed ice, ranged from 0.1 to 5.3 μmol m-2 d-1, were large compared to those measured over the snow and superimposed ice. The DMS concentrations in slush water ranged from 1.0 to 103.7 nM. The DMS fluxes increased with increasing DMS concentrations in slush water. Our results indicate that the potential DMS flux measured over the slush layer occurred originally from the slush layer, and was dependent on the DMS concentrations in slush water. However, snow accumulation and the formation of superimposed ice over the slush layer significantly blocks the diffusion of DMS to the atmosphere, with the result that DMS tends to accumulate in the slush layer although the removal process of DMS by photolysis reaction can modify the DMS flux from the slush layer. Hence, the slush layer has the potential to release the DMS to the atmosphere and ocean when the snow and superimposed ice melts.
  • Daiki Nomura, Atsushi Ooki, Daisuke Simizu, Mitsuo Fukuchi
    ANTARCTIC SCIENCE 23 6 623 - 628 2011年12月 [査読有り][通常論文]
     
    Bromoform concentrations in water of the slush layer that developed at the interface between snow and sea ice were measured during the seasonal warming in Lutzow-Holm Bay, East Antarctica. Mean bromoform concentration was 5.5 +/- 2.4 pmol l(-1), which was lower than that of the under-ice water (10.9 +/- 3.5 pmol l(-1)). Temporal decrease in bromoform concentrations and salinity with increasing temperature of the slush water suggest that the bromoform concentrations were reduced through dilution with meltwater input from the upper surface of sea ice. In contrast, bromoform concentrations in the under-ice water increased during this period while the salinity of the under-ice water decreased. It is speculated that the sea ice meltwater input contained high bromoform concentrations from the brine channels within the sea ice and from the bottom of the ice that were contributed to the increased bromoform concentrations in the under-ice water.
  • Daiki Nomura, Andrew McMinn, Hiroshi Hattori, Shigeru Aoki, Mitsuo Fukuchi
    MARINE CHEMISTRY 127 1-4 90 - 99 2011年12月 [査読有り][通常論文]
     
    Temporal measurements of temperature, salinity, water-oxygen isotopic ratio and nutrient concentrations at Saroma-ko Lagoon, southern Sea of Okhotsk, were made in February-March 2008 to examine the processes by which nitrogen compounds from the atmosphere were incorporated via snowfall into sea ice. Granular ice made up more than half the ice thickness, and the mass fraction of snow in the snow-ice layer on top of the ice ranged from 0.8% to 46.9%. The high concentrations of NO(3)(-) + NO(2)(-) and NH(4)(+) observed in the snow and snow-ice throughout the study period were likely due to the proximity of the study site, in northern Japan, to the east coast of the Asian continent. Pollutants containing high NO(3)(-) and NH(4)(+) concentrations are transported from East Asia and deposited in snowfall over the sea ice in the southern part of the Sea of Okhotsk. Compared with NO(3)(-) + NO(2)(-) and NH(4)(+) concentrations, PO(4)(3-) concentrations in the snow and snow-ice were low. The strong correlation between the NO(3)(-) + NO(2)(-) and NH(4)(+) concentrations in the snow-ice and the mass fraction of snow indicates that the nitrogen compounds on top of the sea ice were controlled mainly by the snow contribution to the sea ice when snow-ice predominated. Our results indicate that chemical cycles in sea ice can be affected by polluted precipitation (snow) originating from a nonpolar sea. (C) 2011 Elsevier B.V. All rights reserved.
  • Nomura D, Kasamatsu N, Tateyama K, Kudoh S, Fukuchi M
    Continental Shelf Research, 31, pp1377–1383, 2011. 31 13 1377 - 1383 2011年09月 [査読有り][通常論文]
     
    The combined concentration of total dimethylsulfoniopropionate and dimethylsulfide (DMSP+DMS) were measured in Antarctic fast ice on the coast of Lutzow-Holm Bay, eastern Antarctica. High bulk-ice DMSP+DMS and chlorophyll a concentrations were found at the bottom of the sea ice, and these concentrations were higher than those in the under-ice water. The bulk-ice DMSP+DMS and chlorophyll a concentrations were highly correlated (r(2)=0.68, P < 0.001), suggesting that the high bulk-ice DMSP+DMS concentrations were caused mainly by the presence of algae assemblages in the ice. The calculated brine DMSP+DMS concentrations were as high as 1100 nM in the bottom ice layer, and the vertical profile patterns of brine DMSP+DMS concentrations were almost the same as for the bulk ice, mainly because of the small amount of variability in the vertical brine volume fraction. DMSP+DMS and chlorophyll a concentrations in the under-ice water increased, whereas the salinity of the under-ice water decreased, during the sampling period. These results reflect the supply of freshwater containing high levels of DMSP+DMS to the water just under the ice as the ice melted. These results suggest that sea-ice melting could be important to sulfur cycling in coastal ice-covered regions of the polar oceans. (C) 2011 Elsevier Ltd. All rights reserved.
  • Daiki Nomura, Daisuke Simizu, Hideo Shinagawa, Chinatsu Ouchida, Mitsuo Fukuchi
    JOURNAL OF GLACIOLOGY 57 205 848 - 856 2011年 [査読有り][通常論文]
     
    Surface ponds on Antarctic fast ice were examined by measuring temperature, salinity and concentrations of chlorophyll a (Chl-a), dissolved inorganic carbon (DIC) and nutrients (NO(3) + NO(2), PO(4), and SiO(2)) in the surface pond water and under-ice water. Sea-ice cores were also collected from the bottom of a surface pond (pond-ice core) and from a site away from the pond (bare-ice core). Time-series measurements of surface pond water temperature showed that it varied with solar radiation rather than with air temperature. Comparison of water properties between surface pond water and under-ice water suggested that DIC and nutrients were consumed by biological productivity during pond formation. Depth profiles of nutrient concentrations in the pond-ice core suggested the remineralization of organic matter at the bottom of the surface pond. The Chl-a concentration was lower at the bottom of the pond-ice core than in the bare-ice core, suggesting that surface pond formation reduces ice algae abundance in sea ice because meltwater flushes algae from the porous sea ice into the under-ice water.
  • Sachiko Oguma, Tsuneo Ono, Yutaka W. Watanabe, Hiromi Kasai, Shuichi Watanabe, Daiki Nomura, Humio Mitsudera
    ESTUARINE COASTAL AND SHELF SCIENCE 91 1 24 - 32 2011年01月 [査読有り][通常論文]
     
    In this study, we examined the relationship between the low salinity water in the shelf region of the southern Okhotsk Sea which was seasonally sampled (0-200 m), and fluxes of low salinity water from Aniva Bay. To express the source of freshwater mixing in the surface layer, we applied normalized total alkalinity (NTA) and stable isotopes of seawater as chemical tracers. NTA-S diagrams indicate that NTA of low salinity water in the upper 30 m layer just off the Soya Warm Current is clearly higher than in the far offshore region in summer and autumn. Using NTA-S regression lines, we could deduce that the low salinity and high NTA water in the upper layer originates from Aniva Bay. For convenience, we defined this water as the Aniva Surface Water (ASW) with values S < 32, NTA > 2450 umol kg(-1). Formation and transport processes of ASW are discussed using historical data. The interaction between the maximum core of high NTA water on the bottom slope of eastern Aniva Bay and an anticyclonic eddy at the mouth of Aniva Bay are concluded to control ASW formation. Upwelling of the Cold Water Belt water at the tip of Cape Krillion is considered to cause ASW outflow from Aniva Bay. (C) 2010 Elsevier Ltd. All rights reserved.
  • Report on a portable laboratory, made from a modified cargo container, aboard the RV Shirase during the 2009-2010 Antarctic cruise of the 51st Japanese Antarctic Research Expedition (JARE-51)
    Wada M, Koga S, Nomura D, Odate T, Fukuchi M
    Antarctic Record, 55, 3, 269–286, 2011. 2011年 [査読有り][通常論文]
  • Daiki Nomura, Hajo Eicken, Rolf Gradinger, Kunio Shirasawa
    CONTINENTAL SHELF RESEARCH 30 19 1998 - 2004 2010年11月 [査読有り][通常論文]
     
    The air-sea ice CO2 flux was measured over landfast sea ice in the Chukchi Sea, off Barrow, Alaska in late May 2008 with a chamber technique. The ice cover transitioned from a cold early spring to a warm late spring state, with an increase in air temperature and incipient surface melt. During melt, brine salinity and brine dissolved inorganic carbon concentration (DIC) decreased from 67.3 to 18.7 and 3977.6 to 1163.5 mu mol kg(-1), respectively. In contrast, the salinity and DIC of under-ice water at depths of 3 and 5 m below the ice surface remained almost constant with average values of 32.4 +/- 0.3 (standard deviation) and 2163.1 +/- 16.8 mu mol kg(-1), respectively. The air-sea ice CO2 flux decreased from +0.7 to -1.0 mmol m(-2) day(-1) (where a positive value indicates CO2 being released to the atmosphere from the ice surface). During this early to late spring transition, brought on by surface melt, sea ice shifted from a source to a sink for atmospheric CO2, with a rapid decrease of brine DIC likely associated with a decrease in the partial pressure of CO2 of brine from a supersaturated to an undersaturated state compared to the atmosphere. Formation of superimposed ice coincident with melt was not sufficient to shut down ice-air gas exchange. (C) 2010 Elsevier Ltd. All rights reserved.
  • Daiki Nomura, Jun Nishioka, Mats A. Granskog, Andreas Krell, Sumito Matoba, Takenobu Toyota, Hiroshi Hattori, Kunio Shirasawa
    MARINE CHEMISTRY 119 1-4 1 - 8 2010年04月 [査読有り][通常論文]
     
    Samples of first-year sea ice, snow and under-ice water were collected in the southern Sea of Okhotsk in mid-February 2007 and 2008 to elucidate the processes controlling nutrient concentrations in sea ice. Temperature, salinity, oxygen isotopic ratio (delta O-18) and inorganic nutrient concentrations (NO3, NH4, NO2, PO4 and SiO2) were measured. Sea ice was categorized into four types; snow-ice, frazil ice, columnar ice and a mixture of granular and columnar ice, based on delta O-18 composition and ice texture. Frazil ice dominated the total ice thickness (52.8%), and columnar ice was sandwiched between frazil ice layers, indicating dynamic ice-growth processes such as rafting and ridging. Furthermore, the ice was banded by layers of particulate materials (sediment layers), which were frequently encountered during cruises. High NO3 and NH4 concentrations were found in snow and snow-ice implying that these were supplied from the atmosphere with snowfall and incorporated into the sea ice through snow-ice formation. In the sediment-laden layers, which were categorized as frazil ice, NO2, PO4 and SiO2 concentrations were highest of all the ice types and considerably enriched compared to parent seawater, suggesting the remineralization of the particulate organic matter. On the other hand, NO3 concentrations in sediment layers were low (depleted), leading to extremely low N (NO3 + NH4 + NO2): P ratios in sediment layers, from 0.2 to 0.8, with respect to that of under-ice water or Redfield ratio. These results suggest that in part of sediment-laden layers fixed-nitrogen was removed partially as molecular nitrogen (N-2) from the sea ice environment by anaerobic nitrate reduction processes (denitrification) by denitrifying bacteria while adding phosphate from associated remineralization of organic phosphorus. The effect of melting of snow and sea ice is dilution for salinity, NO3 and SiO2, no change in NO2 and PO4, and a minor enrichment for NH4 in the mixed layer in spring and early summer. This suggests that snow/ice meltwater with different nutrient ratios than in under-ice water/Redfield ratio is supplied to under-ice water during melt season in April/May in southern Sea of Okhotsk. However, the impact of sediment-laden sea ice cannot be assessed at this point. (C) 2009 Elsevier B.V. All rights reserved.
  • Nomura D, Yoshikawa-Inoue H, Toyota T, Shirasawa K
    Journal of Glaciology, 56, 196, pp262–270, 2010. 56 196 262 - 270 2010年 [査読有り][通常論文]
     
    The air-sea-ice CO2 flux was measured in the ice-covered Saroma-ko, a lagoon on the northeastern coast of Hokkaido, Japan, using a chamber technique. The air-sea-ice CO2 flux ranged from -1.8 to +0.5 mg C m(-2) h(-1) (where negative values indicate a sink for atmospheric CO2). The partial pressure of CO2 (pCO(2)) in the brine of sea ice was substantially lower than that of the atmosphere, primarily because of the influence of the under-ice plume from the Saromabetsu river located in the southeastern part of the lagoon. This suggests that the brine had the ability to take up atmospheric CO2 into the sea ice. However, the snow deposited over the sea ice and the superimposed ice that formed from snowmelting and refreezing partially blocked CO2 diffusion, acting as an impermeable medium for CO2 transfer. Our results suggest that the air-sea-ice CO2 flux was dependent not only on the difference in pCO(2) between the brine and the overlying air, but also on the status of the ice surface. These results provide the necessary evidence for evaluation of the gas exchange processes in ice-covered seas.
  • Biogeochemical Properties of Sea Ice
    McMinn A, Gradinger R, Nomura D
    Field Techniques for Sea Ice Research, pp259–282, 2009. 2009年 [査読無し][通常論文]
  • Daiki Nomura, Toru Takatsuka, Masao Ishikawa, Toshiyuki Kawamura, Kunio Shirasawa, Hisayuki Yoshikawa-Inoue
    ESTUARINE COASTAL AND SHELF SCIENCE 81 2 201 - 209 2009年01月 [査読有り][通常論文]
     
    Physico-chemical properties in the brine and under-ice water were measured in Saroma-ko Lagoon on the northeastern coast of Hokkaido, Japan, which is connected to the Sea of Okhotsk, during the period from mid-February through mid-March 2006. The brine within brine channels of the sea ice was collected with a new sampling method examined in this study. Salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), dissolved oxygen (DO), nutrients and oxygen isotopic ratio (8180) contained in the brine within brine channels of the sea ice and in the under-ice water varied largely in both time and space during the ice melt period, when discharge from Saromabetsu River located on the southeast of the lagoon increased markedly due to the onset of snow melting. The under-ice plume expands as far as 4.5 km from the river mouth at mid-March 2006, transporting chemical components supplied from the river into the lagoon. The under-ice river water was likely transported into the sea ice through well-developed brine channels in the sea ice due to upward flushing of water through brine channels occurred by loading of snowfalls deposited over the sea ice. These results suggest that the river water plume plays an important role in supplying chemical components into the sea ice, which may be a key process influencing the biogeochemical cycle in the seasonally ice-covered Saroma-ko Lagoon. (C) 2008 Elsevier Ltd. All rights reserved.
  • Daiki Nomura, Hisayuki Yoshikawa-Inoue, Takenobu Toyota
    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY 58 5 418 - 426 2006年11月 [査読有り][通常論文]
     
    In order to clarify the CO2 exchange between the seawater and the overlying air during the sea-ice formation, we have carried out tank experiments in a low-temperature room. CO2 concentration above the sea-ice began to increase since the beginning of the sea-ice formation, and increased at larger rates with time and the decrease in air temperature. This increase of CO2 concentration in air was mainly caused by the increase in dissolved inorganic carbon concentration in the brine of the upper part of sea-ice, changes in CO2 solubility and dissociation constants of carbonic acid. The CO2 flux increased logarithmically with time, and reached a level of 2 x 10(-4) to 5 x 10(-4) g-C m(-2) hr(-1) at 50 mm ice thickness. We found that the CO2 flux was correlated well with the salinity and negatively with the volume of the brine in the upper part of the sea-ice. These suggested the larger role of the difference in partial pressure of CO2 between brine and air as compared to that of competitive change in the brine volume. Present results suggest the necessity to examine the CO2 exchange between the seawater and air in seasonal sea-ice areas.

共同研究・競争的資金等の研究課題

  • 海氷表面に見られる有機臭素ガスの高濃度現象―低温化学反応チャンバー実験による検証 研究代表者 野村大樹 研究期間 (年度) 2020 – 2022 研究種目 基盤研究(B)
    研究期間 : 2020年
  • 日独共同観測による「北極の湿潤化」の追究 研究代表者 猪上 淳 研究期間 (年度) 2018 – 2020 研究種目 国際共同研究加速基金(国際共同研究強化(B))
    研究期間 : 2018年
  • 海洋炭酸系物質の時空間高解像度マッピング技術の南大洋への展開 研究代表者 渡辺 豊 研究期間 (年度) 2018 – 2020 研究種目 基盤研究(A)
    研究期間 : 2018年
  • 北極漂流横断観測による「新しい北極海」の探究 研究代表者 猪上 淳 研究期間 (年度) 2018 – 2021 研究種目 基盤研究(A)
    研究期間 : 2018年
  • 極域雪氷の融解現象が海洋表層の二酸化炭素濃度と大気との気体交換過程に与える影響 研究代表者 野村 大樹 研究期間 (年度) 2017 – 2019 研究種目 若手研究(A)
    研究期間 : 2017年
  • 海洋沿岸におけるヨウ素循環の解明-有機物分解に伴うヨウ素の化学形態変化- 研究代表者 大木 淳之 研究期間 (年度) 2016 – 2020 研究種目 基盤研究(B)
    研究期間 : 2016年
  • 海洋の炭酸系物質の準リアルタイムな時空間高解像度マッピングの展開に関する研究 研究代表者 渡辺 豊 研究期間 (年度) 2015 – 2017 研究種目 基盤研究(B)
    研究期間 : 2015年
  • 海氷内部における炭酸カルシウム結晶の生成メカニズムの解明 研究代表者 野村 大樹 研究期間 (年度) 2015 – 2016 研究種目 若手研究(B)
    研究期間 : 2015年
  • 海氷融解による生態系の変化が物質循環に与える影響ー豪州砕氷船による国際南極観測ー 研究代表者 飯田 高大 研究期間 (年度) 2015 – 2017 研究種目 基盤研究(B)
    研究期間 : 2015年
  • 南極海における海氷の生成と融解が大気-海洋間の二酸化炭素交換過程に及ぼす影響 研究代表者 野村 大樹 研究期間 (年度) 2009 – 2010 研究種目 研究活動スタート支援
    研究期間 : 2009年

教育活動情報

主要な担当授業

  • 海洋生物科学基礎実験
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 水産学部
  • 海洋生物地球化学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : 地球化学、化学海洋学、生物生産、環境化学
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : フィールド,海洋環境,自然,グループ学習,課題発見,問題解決,プレゼンテーション,おしょろ丸
  • 化学海洋学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : 栄養塩、基礎生産、物質循環、炭素循環、窒素循環、植物プランクトン、微量金属
  • 海洋生物科学実験Ⅰ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : 分析化学,環境分析,基礎?産,岩礁海岸の生物相


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