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4. Rapidly changing glaciers, ocean and coastal environments, and their impact on human society in the Qaanaaq region, northwestern Greenland

Author

Sugiyama, Shin, Kanna, Naoya, Sakakibara, Daiki, Ando, Takuto, Asaji, Izumi, Kondo, Ken, Wang, Yefan, Fujishi, Yoshiki, Fukumoto, Shungo, Podolskiy, Evgeniy, Fukamachi, Yasushi, Takahashi, Minori, Matoba, Sumito, Iizuka, Yoshinori, Greve, Ralf, Furuya, Masato, Tateyama, Kazutaka, Watanabe, Tatsuya, Yamasaki, Shintaro, Yamaguchi, Atsushi, Nishizawa, Bungo, Matsuno, Kohei, Nomura, Daiki, Sakuragi, Yuta, Matsumura, Yoshimasa, Ohashi, Yoshihiko, Aoki, Teruo, Niwano, Masashi, Hayashi, Naotaka, Minowa, Masahiro, Jouvet, Guillaume, van Dongen, Eef, Bauder, Andreas, Funk, Martin, Bjørk, Anders Anker, and Oshima, Toku

Published
2021
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6. Age distribution of Antarctic Bottom Water off Cape Darnley, East Antarctica, estimated using chlorofluorocarbon and sulfur hexafluoride

Author

Ohashi, Yoshihiko, Kawai, Michiyo, Kusahara, Kazuya, Sasaki, Kenichi, and Ohshima, Kay I.

Subjects
Ocean sciences, Multidisciplinary, Age Distribution, Marine chemistry, Physical oceanography, Sulfur Hexafluoride, Antarctic Regions, Water, Chlorofluorocarbons
Abstract

Chlorofluorocarbon (CFC) and sulfur hexafluoride (SF6) were used to investigate the timescale of Antarctic Bottom Water (AABW) that spreads off Cape Darnley (CD) in East Antarctica. The age of the AABW was estimated based on the observed SF6/CFC-12 ratio while taking into account tracer dilution by Lower Circumpolar Deep Water. Along the western canyons off CD and the ~ 3000 to 3500 m isobaths, the bottom water age was 20 years in the northwestern offshore region indicate inflows of AABW through the Princess Elizabeth Trough and Weddell Sea Deep Water, respectively. This study determined the age distribution in the region off CD, where three different types of AABW spread.

Published
2021
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10. Recent ice mass loss in northwestern Greenland : Results of the GRENE Greenland project and overview of the ArCS project

Author

Sugiyama, Shin, Tsutaki, Shun, Sakakibara, Daiki, Saito, Jun, Ohashi, Yoshihiko, Katayama, Naoki, Podolskiy, Evgeny, Matoba, Sumito, Funk, Martin, and Genco, Riccardo

Subjects
glacier, Greenland, ice-ocean interaction, ice cap, ice sheet
Abstract

The Greenland ice sheet and peripheral ice caps are rapidly losing mass. This mass change has been captured by satellite remote sensing, but more detailed investigations are necessary to understand the spatiotemporal variations and mechanism of the ice loss. It has increased particularly in northwestern Greenland, but in-situ data for northern Greenland are generally sparse. To better understand the ice mass loss in northwestern Greenland, we studied the ice sheet, ice caps and calving glaciers in the Qaanaaq region, as a part of the Green Network of Excellence (GRENE) Arctic Climate Change Research Project. Field and satellite observations were performed to measure the mass loss of the ice caps and calving glaciers in the region. Detailed processes were investigated based on field measurements to understand mechanisms driving the ice loss. The field activities include mass balance monitoring on Qaanaaq Ice Cap since 2012, integrated field observations near the front of Bowdoin Glacier since 2013 and ocean measurements near the calving glaciers. In this contribution, we summarize the results of the GRENE Greenland project, and introduce an overview of the next project to be carried out under the framework of the Arctic Challenge for Sustainability Project (ArCS).

Published
2017

11. Modeling subglacial meltwater plumes and associated sediment transport

Author

Matsumura, Yoshimasa, Ohashi, Yoshihiko, Aoki, Shigeru, and Sugiyama, Shin

Subjects
粒子追跡法, 非静力学海洋モデル, 融解水プルーム, 懸濁物質輸送
Abstract

グリーンランド氷床の表面融解水は，氷河を貫通するムーランを通過して岩盤に到達し，陸上の堆積物を懸濁物質として取り込みながら氷河末端で海洋に流出する．淡水である融解水は海水より軽いため直ちに湧昇し，氷河末端で高濁度の融解水プルームを形成してフィヨルド内の鉛直循環を駆動する．本研究では粒子追跡法を組み込んだ非静力学海洋モデルによる理想化シミュレーションによってこの高濁度水プルームを再現し，特にフィヨルド内の懸濁物質輸送過程について解析した．, The surface meltwater of the Greenland ice sheet is drained through englacial channels called moulins that reach the bedrock, and hence it contains substantial amounts of terrestrial sediments. The meltwater runoff from marineterminating glaciers form an upwelling turbid plume at the glacier front and drives overturning circulation in the fjord. We perform idealized numerical experiments on the turbid meltwater plume and associated sediment transport by using a non-hydrostatic ocean model coupled with a Lagrangian particle tracking system that simulates the dynamics of suspended sediments.

Published
2017

17. グリーンランド北西部ボードウィンフィヨルドにおける係留観測

Author

Fukamachi, Yasushi, Kanna, Naoya, Sugiyama, Shin, Ohashi, Yoshihiko, Sakakibara, Daiki, and Nomura, Daiki

Abstract

第8回極域科学シンポジウム/個別セッション：[OM] 極域気水圏12月5日（火）国立極地研究所 1階交流アトリウムThe Eighth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and GlaciologyTue. 5 Dec./Entrance Hall (1st floor), National Institute of Polar Research

Published
2017

18. Contrasting assemblages of seabirds in the subglacial meltwater plume and oceanic water of Bowdoin Fjord, northwestern Greenland.

Author

Nishizawa, Bungo, Kanna, Naoya, Abe, Yoshiyuki, Ohashi, Yoshihiko, Sakakibara, Daiki, Asaji, Izumi, Sugiyama, Shin, Yamaguchi, Atsushi, and Watanuki, Yutaka

Subjects
MELTWATER, FJORDS, SURFACE segregation, CALANUS, TIDE-waters, WATER
Abstract

In Greenland, tidewater glaciers discharge turbid subglacial freshwater into fjords, forming plumes near the calving fronts, and these areas serve as an important foraging habitat for seabirds. To investigate the effect of subglacial discharge on the foraging assemblages of surface feeders and divers in a glacial fjord, we conducted boat-based seabird surveys, near-surface zooplankton samplings, and hydrographic measurements at Bowdoin Fjord, northwestern Greenland in July. Foraging surface feeders (black-legged kittiwake Rissa tridactyla , glaucous gull Larus hyperboreus , and northern fulmar Fulmarus glacialis) aggregated within a plume-affected area in front of Bowdoin Glacier. This area was characterized by highly turbid subglacial meltwater and abundant large-sized zooplankton including Calanus hyperboreus , chaetognaths, and ctenophores near the surface. Surface feeders fed on these aggregated prey presumably transported to the surface by strong upwelling of subglacial meltwater. In contrast, divers (little auk Alle alle , thick-billed murre Uria lomvia , and black guillemot Cepphus grylle) foraged outside the fjord, where turbidity was low and jellyfish and Calanus copepods dominated under the influence of Atlantic water. Our study indicates spatial segregation between surface feeders and divers in a glacial fjord; surface feeders are not hindered by turbidity if taking prey at the surface, whereas divers need clear water. [ABSTRACT FROM AUTHOR]

Published
2020
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20. Modeling subglacial meltwater runoff and associated sediment transport

Author

Matsumura, Yoshimasa, Ohashi, Yoshihiko, Aoki, Shigeru, and Sugiyama, Shin

Abstract

第7回極域科学シンポジウム/横断セッション:[IA] ニーオルスン観測拠点設立25周年記念横断セッション—北極域の科学（ニーオルスン、GRENE、ArCS)—12月2日（金）国立極地研究所1階交流アトリウム

Published
2016

21. Turbid water and chlorophyll a distributions near the interface of the ocean and a tidewater glacier in northwest Greenland

Author

Kanna, Naoya, Sugiyama, Shin, Ohashi, Yoshihiko, Sakakibara, Daiki, Nishizawa, Bungo, Asaji, Izumi, and Fukamachi, Yasushi

Abstract

第7回極域科学シンポジウム/横断セッション:[IA] ニーオルスン観測拠点設立25周年記念横断セッション—北極域の科学（ニーオルスン、GRENE、ArCS)—12月2日（金）国立極地研究所1階交流アトリウム

Published
2016

22. Changes in seabird density relative to oceanographic gradients in the glacial fjord in northwestern Greenland

Author

Nishizawa, Bungo, Kanna, Naoya, Ohashi, Yoshihiko, Sakakibara, Daiki, Asaji, Izumi, Sugiyama, Shin, Fukamachi, Yasushi, and Watanuki, Yutaka

Abstract

第7回極域科学シンポジウム/横断セッション:[IA] ニーオルスン観測拠点設立25周年記念横断セッション—北極域の科学（ニーオルスン、GRENE、ArCS)—12月2日（金）国立極地研究所1階交流アトリウム

Published
2016

23. グリーンランド氷床北西部Bowdoinフィヨルドにおける氷河融解水流出過程のモデリング

Author

Ohashi, Yoshihiko, Aoki, Shigeru, Matsumura, Yoshimasa, Sugiyama, Shin, Kanna, Naoya, Sakakibara, Daiki, and Fukamachi, Yasushi

Abstract

第7回極域科学シンポジウム/横断セッション:[IA] ニーオルスン観測拠点設立25周年記念横断セッション—北極域の科学（ニーオルスン、GRENE、ArCS)—12月2日（金）国立極地研究所1階交流アトリウム

Published
2016

25. Thermal structure of proglacial lakes in Patagonia

Author

Sugiyama, Shin, Minowa, Masahiro, Sakakibara, Daiki, Skvarca, Pedro, Sawagaki, Takanobu, Ohashi, Yoshihiko, Naito, Nozomu, Chikita, Kazuhisa, Sugiyama, Shin, Minowa, Masahiro, Sakakibara, Daiki, Skvarca, Pedro, Sawagaki, Takanobu, Ohashi, Yoshihiko, Naito, Nozomu, and Chikita, Kazuhisa

Abstract

Calving glaciers are rapidly retreating in many regions under the influence of ice-water interactions at the glacier front. In contrast to the numerous researches conducted on fjords in front of tidewater glaciers, very few studies have been reported on lakes in which freshwater calving glaciers terminate. To better understand ice-water interactions at the front of freshwater calving glaciers, we measured lakewater temperature, turbidity, and bathymetry near Glaciar Perito Moreno, Upsala, and Viedma, large calving glaciers of the Southern Patagonia Icefield. The thermal structures of these lakes were significantly different from those reported in glacial fjords. There was no indication of upwelling subglacial meltwater; instead, turbid and cold glacial water discharge filled the region near the lake bottom. This was because water density was controlled by suspended sediment concentrations rather than by water temperature. Near-surface wind-driven circulation reaches a depth of similar to 180 m, forming a relatively warm isothermal layer (mean temperature of similar to 5-6 degrees C at Perito Moreno, similar to 3-4 degrees C at Upsala, and similar to 6-7 degrees C at Viedma), which should convey heat energy to the ice-water interface. However, the deeper part of the glacier front is in contact with stratified cold water, implying a limited amount of melting there. In the lake in front of Glaciar Viedma, the region deeper than 120 m was filled entirely with turbid and very cold water at pressure melting temperature. Our results revealed a previously unexplored thermal structure of proglacial lakes in Patagonia, suggesting its importance in the subaqueous melting of freshwater calving glaciers.

Published
2016

26. Thermal structure of proglacial lakes in Patagonia

Author

1000020421951, Sugiyama, Shin, Minowa, Masahiro, Sakakibara, Daiki, Skvarca, Pedro, 1000070312410, Sawagaki, Takanobu, Ohashi, Yoshihiko, Naito, Nozomu, 1000070142685, Chikita, Kazuhisa, 1000020421951, Sugiyama, Shin, Minowa, Masahiro, Sakakibara, Daiki, Skvarca, Pedro, 1000070312410, Sawagaki, Takanobu, Ohashi, Yoshihiko, Naito, Nozomu, 1000070142685, and Chikita, Kazuhisa

Abstract

Calving glaciers are rapidly retreating in many regions under the influence of ice-water interactions at the glacier front. In contrast to the numerous researches conducted on fjords in front of tidewater glaciers, very few studies have been reported on lakes in which freshwater calving glaciers terminate. To better understand ice-water interactions at the front of freshwater calving glaciers, we measured lakewater temperature, turbidity, and bathymetry near Glaciar Perito Moreno, Upsala, and Viedma, large calving glaciers of the Southern Patagonia Icefield. The thermal structures of these lakes were significantly different from those reported in glacial fjords. There was no indication of upwelling subglacial meltwater; instead, turbid and cold glacial water discharge filled the region near the lake bottom. This was because water density was controlled by suspended sediment concentrations rather than by water temperature. Near-surface wind-driven circulation reaches a depth of similar to 180 m, forming a relatively warm isothermal layer (mean temperature of similar to 5-6 degrees C at Perito Moreno, similar to 3-4 degrees C at Upsala, and similar to 6-7 degrees C at Viedma), which should convey heat energy to the ice-water interface. However, the deeper part of the glacier front is in contact with stratified cold water, implying a limited amount of melting there. In the lake in front of Glaciar Viedma, the region deeper than 120 m was filled entirely with turbid and very cold water at pressure melting temperature. Our results revealed a previously unexplored thermal structure of proglacial lakes in Patagonia, suggesting its importance in the subaqueous melting of freshwater calving glaciers.

Published
2016

27. Thermal structure of proglacial lakes in Patagonia

Author

Sugiyama, Shin, primary, Minowa, Masahiro, additional, Sakakibara, Daiki, additional, Skvarca, Pedro, additional, Sawagaki, Takanobu, additional, Ohashi, Yoshihiko, additional, Naito, Nozomu, additional, and Chikita, Kazuhisa, additional

Published
2016
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39. Expression of the theta class GST isozyme, YdfYdf, in low GST dogs.

Author

Watanabe, Toshiyuki, Ohashi, Yoshihiko, Kosaka, Toshiyuki, Arakawa, Shingo, Shibaya, Yukari, Yamoto, Takashi, Manabe, Sunao, and Takasaki, Wataru

Subjects
*GLUTATHIONE transferase, *ISOENZYMES, *DOGS, *TRANSFERASES, *LIVER
Abstract

We have reported the existence of low glutathione S-transferase (GST) dogs whose GST activity to 1,2-dichloro-4-nitrobenzene (DCNB) as a substrate (GST-D activity) is quite low, and have also reported significant individual differences in dog liver GST-D activity. The dogs were classified as “low”, “middle”, or “high” GST dogs based on their GST-D activity. In the present study, in order to investigate the causes of quite low GST-D activity in low GST dogs and the individual differences in dog GST-D activity, glutathione (GSH) conjugation of DCNB was kinetically analyzed. Moreover, liver cytosolic proteins whose expression levels were significantly lower in low GST dogs than in high GST dogs were identified by two-dimensional difference gel electrophoresis (2D-DIGE) and LC tandem mass spectrometry (LC/MS/MS). Interestingly, Vmax values for this reaction well reflected their GST-D activities in all groups, i.e. they were 3.8, 80.6, and 169.2 nmol/min/mg protein in the low, middle, and high GST dogs, respectively. However, Km values were almost the same (260.0–283.7 μM) among these groups. These suggest that GSH conjugation of DCNB should be catalyzed by the same enzyme in all the dogs, and individual differences in the GST-D activity should be the result of individual differences in the expression level of the GST isozyme, which catalyzes conjugation of DCNB. In 2D-DIGE, the expression levels of the two protein spots were significantly lower in the low GST dogs than in the high GST dogs. Positive good correlation ( r>0.800) was observed between GST-D activity and expression levels of these two protein spots. Moreover, expression levels were quite low in low GST dogs. These two proteins were both identified as the theta class GST isozyme, YdfYdf, which specifically catalyzes GSH conjugation of DCNB in dog livers. In the present study, we present two novel findings based on an enzyme kinetic study and protein-expression analysis: (1) GSTYdfYdf is expressed at quite a low level in the liver of low GST dogs, and (2) individual differences in dog liver GST-D activity would be due to individual differences in the expression level of GSTYdfYdf. Considering these findings, low GST dogs might have high susceptibility, including an unexpected toxicity at abnormal exposure to chemicals metabolized by GSTYdfYdf. [ABSTRACT FROM AUTHOR]

Published
2006
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