研究者データベース

上野 洋路(ウエノ ヒロミチ)
水産科学研究院 海洋生物資源科学部門 海洋環境科学分野
准教授

基本情報

所属

  • 水産科学研究院 海洋生物資源科学部門 海洋環境科学分野

職名

  • 准教授

学位

  • 博士(理学)(東京大学)

ホームページURL

科研費研究者番号

  • 90421875

J-Global ID

研究キーワード

  • アラスカンストリーム   船舶   Argo   衛星   海洋生物生産   北太平洋亜寒帯域   海洋中規模渦   海洋物理   海洋観測   群集構造   高次捕食者   食物網   生態系   

研究分野

  • 自然科学一般 / 大気水圏科学

職歴

  • 2014年04月 - 現在 北海道大学 大学院水産科学研究院 准教授
  • 2009年04月 - 2014年03月 北海道大学 大学院水産科学研究院 助教
  • 2007年04月 - 2009年03月 独立行政法人海洋研究開発機構 研究員
  • 2004年04月 - 2007年03月 独立行政法人海洋研究開発機構 ポスドク研究員
  • 2003年04月 - 2004年03月 東京大学 日本学術振興会特別研究員

学歴

  • 2000年04月 - 2003年03月   東京大学   大学院理学系研究科   地球惑星科学専攻 博士課程
  • 1998年04月 - 2000年03月   東京大学   大学院理学系研究科   地球惑星物理学専攻 修士課程
  • 1994年04月 - 1998年03月   東京大学   理学部   地球惑星物理学科

所属学協会

  • 日本海洋学会   水産海洋学会   米国地球惑星科学連合学会   

研究活動情報

論文

  • Hiromichi Ueno, Mizuki Komatsu, Zhaoqianyi Ji, Ryo Dobashi, Miaki Muramatsu, Hiroto Abe, Keiri Imai, Atushi Ooki, Toru Hirawake
    Deep Sea Research Part II: Topical Studies in Oceanography 104820 - 104820 2020年06月 [査読有り][通常論文]
  • Toru Hirawake, Masaki Uchida, Hiroto Abe, Irene D. Alabia, Tamotsu Hoshino, Shota Masumoto, Akira S. Mori, Jun Nishioka, Bungo Nishizawa, Atsushi Ooki, Akinori Takahashi, Yukiko Tanabe, Motoaki Tojo, Masaharu Tsuji, Hiromichi Ueno, Hisatomo Waga, Yuuki Y. Watanabe, Atsushi Yamaguchi, Youhei Yamashita
    Polar Science 100533 - 100533 2020年05月 [査読有り][通常論文]
  • Yuka Karasawa, Hiromichi Ueno, Ryo Tanisugi, Ryo Dobashi, Seokjin Yoon, Akihide Kasai, Masashi Kiyota
    Deep Sea Research Part II: Topical Studies in Oceanography 175 104702 - 104702 2020年05月 [査読有り][通常論文]
  • Shota Katsura, Hiromichi Ueno, Humio Mitsudera, Shinya Kouketsu
    JOURNAL OF PHYSICAL OCEANOGRAPHY 50 1 95 - 109 2020年01月 [査読有り][通常論文]
     
    The spatial distribution and seasonality of halocline structures in the subarctic North Pacific (SNP) were investigated using Argo profiling float data and various surface flux data collected in 2003-17. The permanent halocline (PH) showed zonal patterns in the spatial distributions of its depth and intensity and tended to be shallow and strong in the eastern SNP but deep and weak in the west. Mean distributions of PH depth and intensity corresponded to the winter mixed layer depth and sea surface salinity, respectively, indicating that it forms in association with the development of the winter mixed layer. In the Western Subarctic Gyre and Alaskan Gyre, where a relatively strong PH formed, PH intensity and depth showed clear seasonal variations, and deepening of the mixed layer compressed the underlying PH during the cooling period, resulting in intensification and development of the PH in late winter. In both regions, upwelling of high-salinity water also contributed to PH intensification. The summer seasonal halocline (SH) showed distinct zonal differences in frequency and intensity, which were opposite to the PH distribution. While an SH formed in the western and central SNP and coastal regions, it was seldom present in the eastern area. This zonal contrast of SH corresponded to freshening of the mixed layer during the warming period, primarily reflecting freshwater flux. Geostrophic and Ekman advection play important roles in spatial differences in SH intensity and depth. SH development contributed to PH intensification in the following winter, by decreasing salinity above the PH through entrainment.
  • Hisatomo Waga, Toru Hirawake, Hiromichi Ueno
    GEOPHYSICAL RESEARCH LETTERS 46 22 13191 - 13198 2019年11月 [査読有り][通常論文]
     
    The impact of mesoscale eddies on phytoplankton communities attracts considerable research attention because phytoplankton play numerous roles in marine ecosystems. Using remote sensing techniques, this study considered a synoptic relationship between phytoplankton size structure, which is a determinant of energy transfer efficiency in marine ecosystems, and mesoscale eddies, which are ubiquitous ocean features. We found clear spatial variation in the impacts of mesoscale eddies on phytoplankton size structure; phytoplankton communities with larger cell sizes were supported by anticyclonic eddies in oligotrophic regions and by cyclonic eddies in eutrophic regions. Differences in the phytoplankton size structure within these two types of mesoscale eddies became greater, accompanied by interannual trends in the phytoplankton size structure for 2003-2014. Our findings are the first to demonstrate the important linkage between mesoscale eddies and phytoplankton size structure on a global scale; this new knowledge might help better predict variability in marine ecosystems.Plain Language Summary Mesoscale eddies are ubiquitous ocean features and they play a significant role in phytoplankton dynamics. This study used satellite remote sensing techniques to examine the impact of mesoscale eddies on phytoplankton size structure, an important factor of marine ecosystems. We found clear regional and temporal variations in the impacts of two types of mesoscale eddies: communities of larger-sized phytoplankton were observed in anticyclonic eddies in oligotrophic regions and in cyclonic eddies in eutrophic regions, and differences in the phytoplankton size structure inside these two eddy types increased during the period 2003-2014. Our findings are the first to demonstrate the important linkage between the cell-size composition of phytoplankton communities and mesoscale eddies on a global scale; this new knowledge might help us to better predict variability in marine ecosystems both now and in the future.
  • Youhei Yamashita, Yuki Yagi, Hiromichi Ueno, Atsushi Ooki, Toru Hirawake
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 124 11 7545 - 7556 2019年11月 [査読有り][通常論文]
     
    Pacific water is an important nutrient source for sustaining biological production in the Chukchi Sea, western Arctic Ocean, which is one of the productive regions in the world. Therefore, to understand the impacts of future environmental changes on biological production in the sea, it is crucial to understand the origins, modification processes, and spatiotemporal variations of the water masses from the Bering Sea with changes in nutrient concentrations. To improve water mass analysis in the shelf regions of the Bering and Chukchi Seas, we observed levels of humic-like fluorescent organic matter (FOMH) by using an in situ fluorometer directly connected to a temperature-salinity sensor during a cruise in the early summer of 2013 and evaluated the potential of FOMH as a third parameter of water mass analysis. The levels of FOMH were different among specific water masses in the region, and FOMH seemed to behave semiconservatively in the shelf regions of the Bering and Chukchi Seas during the early summer of 2013. The distributional pattern of FOMH implies that FOMH estimated by the in situ fluorometer has the potential to (1) separate warm water into riverine-affected Alaskan Coastal Water and historically photobleached summer Bering Basin Water; (2) distinguish the Anadyr Water, which has low FOMH levels and high nutrient concentrations, from the Bering Shelf Water; and (3) determine different formation/modification processes of dense shelf water that contains high nutrient concentrations.
  • Hiroto Abe, Naoto Ebuchi, Hiromichi Ueno, Hiromu Ishiyama, Yoshimasa Matsumura
    JOURNAL OF OCEANOGRAPHY 75 1 37 - 50 2019年02月 [査読有り][通常論文]
     
    This research presents a case study that examines an upper-ocean salinity response to intense rainfall using 4years of observed salinity data from the Aquarius and Argo floats. The Aquarius sea surface salinity (SSS) in the subtropical region of the North Pacific reveals a notable event in which SSS is locally freshened by intense rainfall. Although the SSS pattern shortly after the rainfall reflects the atmospheric pattern, its final form reflects the ocean's dynamic structure; low-salinity water distributes in the shape of an anticyclonic eddy. Observations using Argo profiling floats confirm that low-salinity water dominates the entire water column of the eddy above 70m. We found that an eddy stirring effect would play an important role in forming the eddy-shaped low-salinity water. As a precondition, intense rainfall on the tropical side enhances the meridional gradient of background SSS with freshened low-salinity water to the south and saline water to the north. The anticyclonic eddy located at the enhanced SSS front stirs the water in a clockwise direction. Specifically, northward flow in the western side of the eddy transports fresh water, whereas southward flow in the eastern side transports saline water. As this northward-southward flow moves the eddy to the west where the transported fresh water is dominant as a baroclinic Rossby wave, this dynamic process would form the eddy-shaped low-salinity water. This clear view of such eddy stirring is due to the inherent nature of the subtropical region that is characterized by less frequent precipitation.
  • Yushiro Tsukada, Hiromichi Ueno, Naoki Ohta, Motoyo Itoh, Eiji Watanabe, Takashi Kikuchi, Shigeto Nishino, Kohei Mizobata
    POLAR SCIENCE 17 33 - 39 2018年09月 [査読有り][通常論文]
     
    Solar heating in summer in the Chukchi Sea was estimated using satellite-derived sea-ice concentration data and reanalysis shortwave radiation data. The shortwave radiation was validated by in-situ data obtained by the R/V Mirai and NCEP-CFSR/CFSv2 was found to reproduce in-situ data accurately compared with NCEP/NCAR Reanalysis 1 and ERA-Interim. Solar heating integrated over the Chukchi Sea in summer varied interannually from 3.6 x 10(20) J in 2000 to 6.7 x 10(20) J in 2015, and was up to twice the northward heat flux through the Bering Strait. The total heating in the Chukchi Sea implies that the heat in the Chukchi Sea provided by northward heat flux through the Bering Strait is amplified by solar heating in the Chukchi Sea. We further compared these heat fluxes into the Chukchi Sea with the summertime northward heat flux through Barrow Canyon, an indicator of heat flux from the Chukchi Sea to the Arctic basin. The northward heat flux through Barrow Canyon was affected by the interannual variation of solar heating in the eastern Chukchi Sea. These results imply that modification of Pacific water in the Chukchi Sea by solar heating plays an important role in the interannual variation in heat transport from the Chukchi Sea to the western Arctic basin.
  • Hiromichi Ueno, Seokjin Yoon, Eiji Watanabe, Michio J. Kishi
    NIPPON SUISAN GAKKAISHI 84 5 931 - 931 2018年 [査読有り][通常論文]
  • 上野 洋路, 小埜 恒夫, 森岡 優志, 藤井 直紀, 藤井 賢彦, 轡田 邦夫, 原田 尚美
    沿岸海洋研究 = Bulletin on coastal oceanography 55 1 65 - 70 日本海洋学会沿岸海洋研究部会 2017年08月 [査読有り][通常論文]
  • 田中雄大, 安田一郎, 久万健志, 西岡純, 田中祐希, 大西広二, 上野洋路, 増島雅親
    月刊海洋 47‐55  2016年11月01日 [査読無し][通常論文]
  • Hiroko Sasaki, Kohei Matsuno, Amane Fujiwara, Misaki Onuka, Atsushi Yamaguchi, Hiromichi Ueno, Yutaka Watanuki, Takashi Kikuchi
    BIOGEOSCIENCES 13 15 4555 - 4567 2016年08月 [査読有り][通常論文]
     
    The advection of warm Pacific water and the reduction in sea ice in the western Arctic Ocean may influence the abundance and distribution of copepods, a key component of food webs. To quantify the factors affecting the abundance of copepods in the northern Bering and Chukchi seas, we constructed habitat models explaining the spatial patterns of large and small Arctic and Pacific copepods separately. Copepods were sampled using NORPAC (North Pacific Standard) nets. The structures of water masses indexed by principle component analysis scores, satellite-derived timing of sea ice retreat, bottom depth and chlorophyll a concentration were integrated into generalized additive models as explanatory variables. The adequate models for all copepods exhibited clear continuous relationships between the abundance of copepods and the indexed water masses. Large Arctic copepods were abundant at stations where the bottom layer was saline; however they were scarce at stations where warm fresh water formed the upper layer. Small Arctic copepods were abundant at stations where the upper layer was warm and saline and the bottom layer was cold and highly saline. In contrast, Pacific copepods were abundant at stations where the Pacific-origin water mass was predominant (i.e. a warm, saline upper layer and saline and a highly saline bottom layer). All copepod groups showed a positive relationship with early sea ice retreat. Early sea ice retreat has been reported to initiate spring blooms in open water, allowing copepods to utilize more food while maintaining their high activity in warm water without sea ice and cold water. This finding indicates that early sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic-benthic-type ecosystem to a pelagic-pelagic type.
  • Shinya Kouketsu, Hitoshi Kaneko, Takeshi Okunishi, Kosei Sasaoka, Sachihiko Itoh, Ryuichiro Inoue, Hiromichi Ueno
    JOURNAL OF OCEANOGRAPHY 72 3 439 - 451 2016年06月 [査読有り][通常論文]
     
    We investigated the relationship between chlorophyll a (Chl-a) concentrations estimated from satellite observations and the activity of eddies in the Kuroshio Extension region. High (low) area-averaged Chl-a concentrations were frequently observed in the core of cyclonic (anticyclonic) eddies. Such relationships between Chl-a concentrations and eddy cores were not frequently observed in the southern part of the recirculation gyre, and advection of background meridional gradient of Chl-a by eddy-edge currents accounted for Chl-a spatial variability. Decadal-scale changes of Chl-a concentrations around the Kuroshio Extension were strongly affected by eddy activity and transport but not by large-scale near-surface isopycnal heaving. We also found that decadal changes of nutrient concentrations near the main stream could affect Chl-a concentrations in the southern part of the recirculation gyre via southward transport of eddies and mean flow.
  • Rui Saito, Ichiro Yasuda, Kosei Komatsu, Hiromu Ishiyama, Hiromichi Ueno, Hiroji Onishi, Takeshi Setou, Manabu Shimizu
    OCEAN DYNAMICS 66 5 605 - 621 2016年05月 [査読有り][通常論文]
     
    Aleutian eddies are mesoscale anticyclonic eddies formed within the Alaskan Stream region between 180A degrees meridian and 170A degrees E south of the Aleutian Islands. They propagate southwestward after the isolation from the Alaskan Stream and pass through the Western Subarctic Gyre. We compared hydrographic structures of three Aleutian eddies observed during summer, west of 170A degrees E (Eddy A) and east of 170A degrees E (Eddies B and C). In each eddy, a subsurface dichothermal water (3.0-4.0 A degrees C) was observed above a subsurface mesothermal water (4.0-4.5 A degrees C). The minimum temperature in the dichothermal water at around a depth of 100 m was colder in Eddy A (2.8 A degrees C) than in Eddies B and C (3.0-3.2 A degrees C). This difference could be ascribed to wintertime cooling and influence of surrounding waters during spring warming period. The wintertime cooling makes the dichothermal water colder for eddies isolated from the Alaskan Stream region for a longer time. Particle-tracking experiments using re-analysis products from a data-assimilative eddy resolving ocean model suggested that the dichothermal water within Eddy A was cooled by the entrainment of surrounding colder water even during the spring warming period. The mesothermal waters at depth around 250 m demonstrated similarity among the observed eddies, and the maximum temperature in the mesothermal water within Eddy A (4.3 A degrees C) was close to that of Eddies B and C (4.2 A degrees C) in the in situ observations. These results indicated that the dichothermal water of Aleutian eddies modifies over time, whereas the mesothermal water maintains the original feature as they propagate southwestward from the Alaskan Stream region to the Western Subarctic Gyre.
  • Temporal and Spatial Variation in a Growth Condition of Pacific Salmon
    上野洋路
    North Pacific Anadromous Fish Commission (NPAFC) Bulletin No.6 181-187  2016年 [査読有り][通常論文]
  • 田中 雄大, 安田 一郎, 久万 健志, 西岡 純, 田中 祐希, 大西 広二, 上野 洋路, 増島 雅親
    海洋. 号外 = Kaiyo monthly : カラー版 58 47 - 55 海洋出版 2016年 [査読無し][通常論文]
  • Seokjin Yoon, Eiji Watanabe, Hiromichi Ueno, Michio J. Kishi
    PROGRESS IN OCEANOGRAPHY 131 146 - 158 2015年02月 [査読有り][通常論文]
     
    Chum salmon (Oncorhynchus keta) are predominantly located in the Bering Sea during summer and fall. However, several studies have recently reported a different tendency as follows. Observed densities of chum salmon were higher in the vicinity of the Bering Strait and the Chukchi Sea than the eastern Bering Sea in September 2007, and Japanese chum salmon migrated to northern areas in the Bering Sea during summer 2009. The sea surface temperature (SST) in the Arctic marginal seas has increased since the mid1960s, and especially since 2000. We speculated that the SST increase directly promoted salmon northing from the Bering Sea to the Western Arctic. In this study, we estimated the potential habitat for chum salmon in the Western Arctic using a bioenergetics model coupled with a three-dimensional lower trophic ecosystem model (3-D NEMURO). "Potential habitat" was defined as "an area where chum salmon could grow (i.e., the growth rate was positive)". In the bioenergetics model, the growth rate of an individual chum salmon was calculated as a function of water temperature, salinity, and prey density, which were obtained from the 3-D NEMURO model results. To evaluate the habitat responses under a global warming scenario, we used the modeled monthly change of water temperature between 2005 (averaged from 2001 to 2010) and 2095 (averaged from 2091 to 2100) under the IPCC SRES-A1 B scenario. Our calculations, following the global warming scenario, suggested that the potential habitat for chum salmon would expand to the north due to the increase in water temperature and prey density. In contrast, south of 71 degrees N during summer, the potential habitat would shrink regionally because the water temperature exceeded the optimal condition. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.
  • T. Tanaka, I. Yasuda, H. Onishi, H. Ueno, M. Masujima
    Journal of Oceanography 71 1 1 - 17 2015年 [査読有り][通常論文]
     
    Tide-induced vertical mixing along the shelf break in the eastern Bering Sea is considered one of the main physical processes that sustain local summertime high biological production. However, observations based on microstructure measurements that show enhanced tidal mixing are scarce. In this study, repeated casts of current and turbulence in the vicinity of the shelf break within Pribilof Canyon were conducted over a day in June 2012, enabling us to evaluate the representativeness of the vertical mixing intensity during one day and to detect the relationship between turbulence and tidal current. The cross-sectional distributions of the one-day averaged vertical diffusivity and the turbulent energy dissipation rate showed that strong vertical mixing occurred at the subsurface within about 15 km of the shelf break and near the seabed of the outer shelf. This result agrees with prior observations that were made by us and based on a single profile at each station, which indicated that the observed spatial pattern of turbulence is robust. Diurnal and semidiurnal tidal currents dominated the flow variations off the shelf break, and a statistically significant positive correlation was detected between the vertical shear of the horizontal tidal currents and the turbulent energy dissipation rate. This result suggests that the high turbulent energy dissipation and the enhanced vertical mixing off the shelf break were induced by the strong vertical shear of tidal currents.
  • Sachihiko Itoh, Ichiro Yasuda, Hiromichi Ueno, Toshio Suga, Shigeho Kakehi
    JOURNAL OF OCEANOGRAPHY 70 3 211 - 223 2014年06月 [査読有り][通常論文]
     
    Regeneration of a warm anticyclonic ring as a result of interaction with cold water masses was observed within the western subarctic gyre of the North Pacific. Satellite, profiling float, and shipboard observations revealed that a warm-core ring originated from the Kuroshio Extension, propagating northeastwards, entrained cold and fresh water masses from the coastal area of Hokkaido, which are typically recognized within the ring as water that is colder than 2.5 A degrees C. The potential temperature and planetary contribution of potential vorticity of the cold water in the coastal area of Hokkaido were < 2 A degrees C and 15 x 10(-11) m(-1)s(-1), respectively, suggesting that it originated from the Sea of Okhotsk. After the intrusion, the warm core of the ring cooled, freshened, and contracted, while the outer and lower parts became occupied by the cold and fresh water; however, even after the cooling, the positive surface elevation and downward depression of the main pycnocline, typical of an anticyclonic ring, were still evident. The ring continued to propagate northeastwards, with the main part of its structure occupied by the cold water, but changed its direction of travel from northwest to west-southwest 8 months after the cold-water event, and was finally absorbed into another warm-core ring. It is suggested that these anticyclonic rings, which transported and mixed warm and cold water masses, play important roles in the cross-gyre exchange of subtropical and subarctic waters in the North Pacific.
  • Atsushi Yamaguchi, Tomoe Homma, Rui Saito, Kohei Matsuno, Hiromichi Ueno, Toru Hirawake, Ichiro Imai
    Plankton and Benthos Research 8 3 116 - 123 2014年 [査読有り][通常論文]
     
    Stratified zooplankton sampling was conducted in the subarctic Pacific in June 2009 at four stations along 47°N from 0 to 3,000 m depth to evaluate longitudinal changes in population structure and vertical distribution of the dominant copepod species. At the westernmost station (160°E), the population structure of Eucalanus bungii and Metridia pacifica was dominated by early copepodid stages. In E. bungii, nauplii were abundant and adult females had developed ovaries at 160°E, while at the three stations to the east (167°E, 174°E and 179°W), no E. bungii nauplii were collected, and the resting stages were dominant. This suggests the species was reproducing near 160°E and in diapause in the east. In all three Neocalanus species analyzed (N. cristatus, N. flemingeri and N. plumchrus), late copepodid stages were dominant at the eastern three stations. Lipid accumulation in the fifth copepodid stage of Neocalanus spp. was greater in the west than in the east. This probably resulted from better food conditions and lower temperatures in the west, where copepods could consume more food during development than in the east.
  • Rui Saito, Atsushi Yamaguchi, Ichiro Yasuda, Hiromichi Ueno, Hiromu Ishiyama, Hiroji Onishi, Ichiro Imai
    JOURNAL OF PLANKTON RESEARCH 36 1 117 - 128 2014年01月 [査読有り][通常論文]
     
    Mesoscale anticyclonic eddies have been observed south of the Aleutian Islands. Eddies farther east, in the Gulf of Alaska, are known to transport coastal water and coastal zooplankton to the offshore open ocean. The impacts of mesoscale anticyclonic eddies formed south of the western Aleutian Islands (Aleutian eddies) on the zooplankton community are not fully understood. In the present study, we describe zooplankton population structures within an Aleutian eddy and outside the eddy during July 2010. Based on the sea-level anomaly, the Aleutian eddy was formed south of Attu Island (172 degrees 54'E) in February 2010, and it moved southeastward in the next 5 months. Large oceanic copepods, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were more abundant inside the eddy than the outside. Inside the eddy, the life stage distribution of N. cristatus was more advanced than that outside, and Neocalanus spp. had accumulated more lipids. These conditions probably reflect the greater primary production in the eddy, production enhanced by nutrients advected into the eddy. The Aleutian eddy contained mostly oceanic copepods because it was formed in the offshore water and/or eddy-eddy interaction occurred after its formation. The sufficient food condition in the eddy presumably resulted in higher growth and survival rates of these oceanic copepods, resulting in the greater abundance, advanced development stages and greater lipid accumulation.
  • Atsushi Yamaguchi, Tomoe Homma, Rui Saito, Kohei Matsuno, Hiromichi Ueno, Toru Hirawake, Ichiro Imai
    Plankton and Benthos Research 8 3 116 - 123 2014年 [査読有り][通常論文]
     
    Stratified zooplankton sampling was conducted in the subarctic Pacific in June 2009 at four stations along 47°N from 0 to 3,000 m depth to evaluate longitudinal changes in population structure and vertical distribution of the dominant copepod species. At the westernmost station (160°E), the population structure of Eucalanus bungii and Metridia pacifica was dominated by early copepodid stages. In E. bungii, nauplii were abundant and adult females had developed ovaries at 160°E, while at the three stations to the east (167°E, 174°E and 179°W), no E. bungii nauplii were collected, and the resting stages were dominant. This suggests the species was reproducing near 160°E and in diapause in the east. In all three Neocalanus species analyzed (N. cristatus, N. flemingeri and N. plumchrus), late copepodid stages were dominant at the eastern three stations. Lipid accumulation in the fifth copepodid stage of Neocalanus spp. was greater in the west than in the east. This probably resulted from better food conditions and lower temperatures in the west, where copepods could consume more food during development than in the east.
  • Hiromichi Ueno
    JOURNAL OF OCEANOGRAPHY 69 2 277 - 283 2013年04月 [査読有り][通常論文]
     
    Hydrographic data measured for 50 years along Line P between the North American west coast and mid Gulf of Alaska as well as data from profiling float observations were analyzed to study the formation and variation of temperature inversions in the eastern subarctic North Pacific. Remarkable decadal to inter-decadal variation was observed in the magnitude of temperature inversions. This variation was mostly attributed to the variation of southward Ekman transport, eastward geostrophic transport, and surface cooling.
  • Ren Uchida, Kenshi Kuma, Aya Omata, Satoko Ishikawa, Nanako Hioki, Hiromichi Ueno, Yutaka Isoda, Keiichiro Sakaoka, Yoshihiko Kamei, Shohgo Takagi
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 118 3 1257 - 1271 2013年03月 [査読有り][通常論文]
     
    We measured water-column iron concentrations from west to east along 47 degrees N in the subarctic North Pacific, and in the Bering Sea. In the North Pacific dissolved Fe (D-Fe) showed surface depletion, mid-depth maxima at 1000-1500 m (west, 1.3-1.6 nM; east, 0.9-1.1 nM), and a gradual decrease with depth below 3500-4000 m depth (west, 1.1-1.4 nM; east, 0.6-0.7 nM). D-Fe and total soluble Fe (T-Fe) in deep water showed a decreasing trend eastward. The higher iron concentrations in western deep waters probably result from higher inputs of dissolved Fe through atmospheric deposition or lateral transport. In contrast, D-Fe throughout the Bering Sea showed a consistent depth regime characterized by a rapid increase with depth to mid-depths, a gradual increase with depth in intermediate water to a maximum of 1.6-1.7 nM at 1500-2250 m, and a gradual decrease with depth to 1.3-1.4 nM at 3700 m. Higher iron concentrations and deeper D-Fe maxima in the Bering Sea are likely due to higher biological productivity and greater and deeper D-Fe input from the decomposition of sinking particulate organic matter in deep water. We suggest that the higher concentrations and deeper input of D-Fe as well as PO4 and humic-type fluorescent dissolved organic matter in the Bering Sea probably results from the longer time for the accumulation of decomposition products resulting from iron supply from the organic-rich downslope sediment along the steep continental slopes and slow replacement of the deep water in the Bering Sea Basin.
  • Ren Uchida, Kenshi Kuma, Aya Omata, Satoko Ishikawa, Nanako Hioki, Hiromichi Ueno, Yutaka Isoda, Keiichiro Sakaoka, Yoshihiko Kamei, Shohgo Takagi
    Journal of Geophysical Research: Oceans 118 3 1257 - 1271 2013年 [査読有り][通常論文]
     
    We measured water-column iron concentrations from west to east along 47°N in the subarctic North Pacific, and in the Bering Sea. In the North Pacific dissolved Fe (D-Fe) showed surface depletion, mid-depth maxima at 1000-1500 m (west, 1.3-1.6 nM east, 0.9-1.1 nM), and a gradual decrease with depth below 3500-4000 m depth (west, 1.1-1.4 nM east, 0.6-0.7 nM). D-Fe and total soluble Fe (T-Fe) in deep water showed a decreasing trend eastward. The higher iron concentrations in western deep waters probably result from higher inputs of dissolved Fe through atmospheric deposition or lateral transport. In contrast, D-Fe throughout the Bering Sea showed a consistent depth regime characterized by a rapid increase with depth to mid-depths, a gradual increase with depth in intermediate water to a maximum of 1.6-1.7 nM at 1500-2250 m, and a gradual decrease with depth to 1.3-1.4 nM at 3700 m. Higher iron concentrations and deeper D-Fe maxima in the Bering Sea are likely due to higher biological productivity and greater and deeper D-Fe input from the decomposition of sinking particulate organic matter in deep water. We suggest that the higher concentrations and deeper input of D-Fe as well as PO 4 and humic-type fluorescent dissolved organic matter in the Bering Sea probably results from the longer time for the accumulation of decomposition products resulting from iron supply from the organic-rich downslope sediment along the steep continental slopes and slow replacement of the deep water in the Bering Sea Basin. © 2013. American Geophysical Union. All Rights Reserved.
  • Takeshi Terui, Michio J. Kishi, Hiromichi Ueno
    JOURNAL OF OCEANOGRAPHY 68 5 727 - 741 2012年10月 [査読有り][通常論文]
     
    A Lagrangian ensemble model describing the population dynamics of Neocalanus cristatus was developed. To describe the ecology of N. cristatus, life stage must be included in the model. For this purpose, a new zooplankton compartment, divided into nine life stages, was added to the North Pacific ecosystem model for understanding regional oceanography. In addition, we introduced Lagrangian particles for the copepod population. Each Lagrangian particle represented a population of the same cohort of copepods with information on representative age, developmental stage, growth rate, structural weight, and food satiation. The new model revealed that surviving cohorts are only matched with the phytoplankton bloom after the nauplii stages. The model showed that the existing phytoplankton concentration when copepodites of N. cristatus appear in the surface water determines the development pattern of copepodite stages. The timing of the seasonal phytoplankton bloom depends on climate change, and a sensitivity analysis showed that the multiple spawning strategy through time has an important role in matching the unstable seasonal bloom cycle on a daily basis. The model including the cohorts can collaborate closely with weekly or monthly observations to reveal the rapid response of the marine ecosystem.
  • UENO Hiromichi, YASUDA Ichiro, ITOH Sachihiko, ONISHI Hiroji, HIROE Yutaka, SUGA Toshio, OKA Eitarou
    J Geophys Res 117 C8 C08032-C08032-11  2012年08月 [査読有り][通常論文]
  • Hiromichi Ueno, Ichiro Yasuda, Sachihiko Itoh, Hiroji Onishi, Yutaka Hiroe, Toshio Suga, Eitarou Oka
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 117 2012年08月 [査読有り][通常論文]
     
    A Kenai eddy was studied through analyses of satellite altimeter data and hydrographic data from shipboard and Argo float observations. This eddy formed in December 2006 south of the Kenai Peninsula and propagated southwestward along the Alaskan Stream. The eddy held horizontally uniform warm core water in January 2007. In late winter 2007, this core water was cooled from the top and a subsurface temperature maximum was formed around 26.5 sigma(theta). Two years later in summer 2009, warm and low-dissolved-oxygen (low- DO) water characterized by a temperature maximum around 26.5 sigma(theta) was observed again in the eddy core and was likely the remnant of original core water. At the same time, cold and high-DO water intrusions occurred in the eddy core, suggesting that strong modification of core water was ongoing. After summer 2009, the core water was fully changed through interaction with another eddy.
  • Takahito Ikenoue, Hiromichi Ueno, Kozo Takahashi
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 117 C4 C04001-C04001  2012年04月 [査読有り][通常論文]
     
    The impact of mesoscale eddies on the production of radiolarian species Rhizoplegma boreale in the central subarctic Pacific was investigated through analysis of sinking particle fluxes collected using sediment-trap and altimetry data from satellite observations. Altimetry observations provided the locations of mesoscale eddies in time and space and indicated that mesoscale eddies propagating around sediment trap Station SA were closely related to the high R. boreale fluxes at the station. The mesoscale eddies likely provided the deep-sea region of the central subarctic Pacific with coastal nutrient-rich waters derived from the region around the Aleutian Islands, and influenced the productivity of microzooplankton groups at Station SA.
  • Hiromichi Ueno, Ichiro Yasuda, Sachihiko Itoh, Hiroji Onishi, Yutaka Hiroe, Toshio Suga, Eitarou Oka
    Journal of Geophysical Research: Oceans 117 8 2012年 [査読有り][通常論文]
     
    A Kenai eddy was studied through analyses of satellite altimeter data and hydrographic data from shipboard and Argo float observations. This eddy formed in December 2006 south of the Kenai Peninsula and propagated southwestward along the Alaskan Stream. The eddy held horizontally uniform warm core water in January 2007. In late winter 2007, this core water was cooled from the top and a subsurface temperature maximum was formed around 26.5. Two years later in summer 2009, warm and low-dissolved-oxygen (low-DO) water characterized by a temperature maximum around 26.5 was observed again in the eddy core and was likely the remnant of original core water. At the same time, cold and high-DO water intrusions occurred in the eddy core, suggesting that strong modification of core water was ongoing. After summer 2009, the core water was fully changed through interaction with another eddy. © 2012. American Geophysical Union. All Rights Reserved.
  • Takahito Ikenoue, Hiromichi Ueno, Kozo Takahashi
    Journal of Geophysical Research: Oceans 117 4 2012年 [査読有り][通常論文]
     
    The impact of mesoscale eddies on the production of radiolarian species Rhizoplegma boreale in the central subarctic Pacific was investigated through analysis of sinking particle fluxes collected using sediment-trap and altimetry data from satellite observations. Altimetry observations provided the locations of mesoscale eddies in time and space and indicated that mesoscale eddies propagating around sediment trap Station SA were closely related to the high R. boreale fluxes at the station. The mesoscale eddies likely provided the deep-sea region of the central subarctic Pacific with coastal nutrient-rich waters derived from the region around the Aleutian Islands, and influenced the productivity of microzooplankton groups at Station SA. © 2012 by the American Geophysical Union.
  • 上野洋路, 安田一郎, 伊藤幸彦, 大西広二, 廣江豊, 廣江豊, 須賀利雄, 須賀利雄, 岡英太郎
    月刊海洋 43 12 756 - 762 2011年12月 [査読無し][通常論文]
  • Ken-Ichi Sato, Atsushi Yamaguchi, Hiromichi Ueno, Tsutomu Ikeda
    JOURNAL OF PLANKTON RESEARCH 33 8 1230 - 1238 2011年08月 [査読有り][通常論文]
     
    Fine-scale vertical distribution patterns of the calanoid copepods Neocalanus flemingeri, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were studied by stratified sampling (9 strata between 0 and 1000 m) with a vertical multiple plankton sampler (VMPS) every 3 h for 24 h during 21-22 March 2005 in the Oyashio region. Most C1-C5 stages of N. flemingeri and N. cristatus occurred in the 30-90 m and 70-200 m strata, respectively, both by day and night. Irrespective of day and night, C3-C6 E. bungii were distributed broadly in the 200-430 m stratum (C5 inhabiting the shallowest layer). Thus, these three copepods exhibited vertical partitioning of their habitats in the upper layers. The C1-C6 of M. pacifica were distributed broadly from 140 to 400 m during daytime and migrated up to the 100-180 m layer at night (except for non-migrant C1 and C6 males). The within-species zonation of copepodid stages was less marked, but older stages tended to occupy deeper zones (N. flemingeri, N. cristatus and M. pacifica) or shallower zones (E. bungii). Gut content analyses of N. flemingeri and N. cristatus revealed the predominance of diatoms in the guts of both species, but the proportion of broken cells was greater in the deep-dwelling N. cristatus than in the shallow-dwelling N. flemingeri, suggesting the importance of sinking phytoplankton aggregates as a food source for the former species.
  • 上野洋路
    海の研究 19 6 301 - 315 2010年11月05日 [査読有り][通常論文]
  • Michio J. Kishi, Masahide Kaeriyama, Hiromichi Ueno, Yasuko Kamezawa
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 57 13-14 1257 - 1265 2010年07月 [査読有り][通常論文]
     
    From the 1970s to 1990s, a reduction in the body size of Japanese chum salmon (Oncorhynchus keta) was observed. To investigate this body size reduction in the North Pacific, we developed a bioenergetics model for chum salmon coupled with the results from a lower trophic ecosystem model embedded into a three-dimensional global model. In the bioenergetics model, respiration and consumption terms are assumed to be functions of water temperature and prey zooplankton density, which are the determining factors of the reduction of body size. The model reproduced the body size of the 1972 and 1991 year classes of chum salmon. The reproduced body size of the 1972 year class was larger than that of 1991 year class, and this result agrees with observations from the Bering Sea. Our model also reproduced the body size trend from 1970 to 2000. The prey density, especially in the eastern North Pacific, had a greater influence on the change of body size than did the SST. This suggests that the size reduction of Japanese chum salmon in the 1990s was partly affected by changes in prey zooplankton density. In the context of the global warming scenario, we discuss changes in the migration route of chum salmon and predict that the population of Japanese chum salmon experience significant declines over this century. (C) 2010 Elsevier Ltd. All rights reserved.
  • Michio J. Kishi, Masahide Kaeriyama, Hiromichi Ueno, Yasuko Kamezawa
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 57 13-14 1257 - 1265 2010年07月 [査読有り][通常論文]
     
    From the 1970s to 1990s, a reduction in the body size of Japanese chum salmon (Oncorhynchus keta) was observed. To investigate this body size reduction in the North Pacific, we developed a bioenergetics model for chum salmon coupled with the results from a lower trophic ecosystem model embedded into a three-dimensional global model. In the bioenergetics model, respiration and consumption terms are assumed to be functions of water temperature and prey zooplankton density, which are the determining factors of the reduction of body size. The model reproduced the body size of the 1972 and 1991 year classes of chum salmon. The reproduced body size of the 1972 year class was larger than that of 1991 year class, and this result agrees with observations from the Bering Sea. Our model also reproduced the body size trend from 1970 to 2000. The prey density, especially in the eastern North Pacific, had a greater influence on the change of body size than did the SST. This suggests that the size reduction of Japanese chum salmon in the 1990s was partly affected by changes in prey zooplankton density. In the context of the global warming scenario, we discuss changes in the migration route of chum salmon and predict that the population of Japanese chum salmon experience significant declines over this century. (C) 2010 Elsevier Ltd. All rights reserved.
  • Hiromichi Ueno, William R. Crawford, Hiroji Onishi
    JOURNAL OF OCEANOGRAPHY 66 3 319 - 328 2010年06月 [査読有り][通常論文]
     
    The impact of the Alaskan Stream (AS) eddies on the chlorophyll a (chl-a) distribution in the central subarctic North Pacific was investigated through analysis of chl-a and altimetry data from satellite observations. Altimetry observations provided the locations of mesoscale eddies in time and space within the maps of chlorophyll distributions. The climatological chl-a distributions averaged in the area and time showing presence of AS eddies suggested that AS eddies contributed significantly to the chl-a distribution in the deep-sea region of the subarctic North Pacific. The chl-a distribution was closely related to the AS eddies regardless of whether the eddy was located in or detached from the AS. A combination of two or three AS eddies sometimes formed high chl-a concentration belts that injected chlorophyll and coastal nutrient-rich waters southward from the Aleutian Islands far into the deep-sea region of the subarctic North Pacific. These results indicate that chl-a distribution in the central subarctic North Pacific was strongly impacted by AS eddies.
  • Hiromichi Ueno, Howard J. Freeland, William R. Crawford, Hiroji Onishi, Eitarou Oka, Kanako Sato, Toshio Suga
    JOURNAL OF PHYSICAL OCEANOGRAPHY 39 4 934 - 951 2009年04月 [査読有り][通常論文]
     
    Anticyclonic eddies propagating southwestward in the Alaskan Stream (AS) were investigated through analysis of altimetry data from satellite observations during 1992-2006 and hydrographic data from profiling float observations during 2001-06. Fifteen long-lived eddies were identified and categorized based on their area of first appearance. Three eddies were present at the beginning of the satellite observations; another three formed in the eastern Gulf of Alaska off Sitka, Alaska; and four were first detected at the head of the Gulf of Alaska near Yakutat, Alaska. The other five eddies formed along the AS between 157 degrees and 169 degrees W, and were named AS eddies. While the eddies that formed in the Gulf of Alaska mainly decayed before exiting the Gulf of Alaska, the AS eddies mostly crossed the 180 degrees meridian and reached the western subarctic gyre. Four of five AS eddies formed under negative or weakly positive wind stress curls, which possibly caused AS separation from the coast. Comparison of eddy propagation speeds in the AS with the bottom slope showed that eddies propagated faster over steeper slopes, although eddy speeds were slower than those predicted by the topographic planetary wave dispersion relation. An AS eddy was observed by profiling floats in the western subarctic gyre after it detached from the AS. Intermediate-layer water near the eddy center had low potential vorticity compared with the surrounding water, suggesting that AS eddies provided the western subarctic gyre with water just south of the Aleutian Islands.
  • 須賀利雄, 須賀利雄, 上野洋路, 大西広二, 林和彦, 齋藤寛子, 鋤柄千穂, 遠山勝也
    月刊海洋 39 7 450 - 455 2007年07月01日 [査読無し][通常論文]
  • Hiromichi Ueno, Eitarou Oka, Toshio Suga, Hiroji Onishi, Dean Roemmich
    GEOPHYSICAL RESEARCH LETTERS 34 5 L05603-L05603  2007年03月 [査読有り][通常論文]
     
    Hydrographic data from profiling float observations for 2001 - 2005 and from expendable bathythermograph observations for 1993 - 2005 were analyzed to study the formation and variation of temperature inversions (T-inversions) in the eastern subarctic North Pacific ( SNP). The formation and variation of T-inversions differed significantly between the northern and southern regions of the eastern SNP. In the northern region, the temperature minimum (T-min) at the top of T-inversions outcropped to the sea surface and was cooled in the mixed layer nearly every winter. This process caused a seasonal cycle in the magnitude of T-inversions (DT), with a maximum in winter. In the southern region, the winter T-min outcropped relatively infrequently and the DT did not exhibit a significant maximum in winter during most years. The T-min in the southern region was likely to outcrop upstream near the date line roughly one year earlier and was then advected to the southern region.
  • H Ueno, Yasuda, I
    JOURNAL OF PHYSICAL OCEANOGRAPHY 35 12 2444 - 2456 2005年12月 [査読有り][通常論文]
     
    Hydrographic data from the World Ocean Database 2001 and Argo profiling floats were analyzed to study temperature inversions in the subarctic North Pacific Ocean. The frequency distribution of temperature inversions [F(t-inv)] at a resolution of 1 degrees ( latitude) x 3 degrees ( longitude) was calculated. Temperature inversions seldom occurred around 50 degrees N in the eastern subarctic North Pacific but were more common in the northern Gulf of Alaska and the southeastern subarctic North Pacific (42 degrees-48 degrees N, 140 degrees-170 degrees W). Large temperature inversions occurred throughout the year in the western and central subarctic North Pacific ( north of 42 N and west of 180) except near the Aleutian and Kuril Islands. Near those islands, F(t-inv) was characterized by pronounced seasonal variations forced by surface heating/cooling and strong tidal mixing.
  • H Ueno, E Oka, T Suga, H Onishi
    GEOPHYSICAL RESEARCH LETTERS 32 20 L20603-L20603  2005年10月 [査読有り][通常論文]
  • H Ueno, Yasuda, I
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 109 C2 2004年02月 [査読無し][通常論文]
  • H Ueno, Yasuda, I
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 108 C11 2003年11月 [査読有り][通常論文]
     
    [1] The intermediate water circulation in the North Pacific subarctic and northern subtropical regions is investigated through inverse analysis, focusing on the volume and heat transports from the subtropical to the subarctic regions. The inverse method we adopted is a hybrid method of beta- spiral and box inverse methods which permits diapycnal flux. The isopycnal velocities estimated through the inverse analysis are mostly consistent with the oxygen distribution and support the hypothesis that warm and saline intermediate water is transported from the transition domain east of Japan to the northern Gulf of Alaska. The northward volume transport across 46 degrees N between 158 degrees E and 130 degrees W is estimated to be - 0.2 to 5.3 Sv in the density range of 26.7 - 27.2sigma(theta). The upward diapycnal transports in the open subarctic North Pacific ( region N) across 26.7 and 27.2sq isopycnal surfaces are estimated to be 0.2 to 1.5 Sv and - 0.2 to 0.9 Sv, respectively. Part of the water transported upward across 26.7sigma(theta) might outcrop and be carried to the subtropical region by the southward Ekman drift. Through the examination of heat balance of the intermediate layer in the subarctic region, it is suggested quantitatively that the intermediate heat transport from the south plays an essential role in maintaining the heat of the mesothermal waters in the subarctic region.
  • H Ueno, Yasuda, I
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 108 C11 2003年11月 [査読有り][通常論文]
     
    [1] The intermediate water circulation in the North Pacific subarctic and northern subtropical regions is investigated through inverse analysis, focusing on the volume and heat transports from the subtropical to the subarctic regions. The inverse method we adopted is a hybrid method of beta- spiral and box inverse methods which permits diapycnal flux. The isopycnal velocities estimated through the inverse analysis are mostly consistent with the oxygen distribution and support the hypothesis that warm and saline intermediate water is transported from the transition domain east of Japan to the northern Gulf of Alaska. The northward volume transport across 46 degrees N between 158 degrees E and 130 degrees W is estimated to be - 0.2 to 5.3 Sv in the density range of 26.7 - 27.2sigma(theta). The upward diapycnal transports in the open subarctic North Pacific ( region N) across 26.7 and 27.2sq isopycnal surfaces are estimated to be 0.2 to 1.5 Sv and - 0.2 to 0.9 Sv, respectively. Part of the water transported upward across 26.7sigma(theta) might outcrop and be carried to the subtropical region by the southward Ekman drift. Through the examination of heat balance of the intermediate layer in the subarctic region, it is suggested quantitatively that the intermediate heat transport from the south plays an essential role in maintaining the heat of the mesothermal waters in the subarctic region.
  • H Ueno, Yasuda, I
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 106 C10 22131 - 22141 2001年10月 [査読有り][通常論文]
     
    A warm and saline water transport to the North Pacific subarctic region which could feed the mesothermal (intermediate temperature maximum) water is investigated through the analysis of World Ocean Circulation Experiment and Subarctic Gyre Experiment hydrographic data. The analysis of individual cruise data supports the hypothesis that warm and saline water is transported from the area east of Japan, to the Gulf of Alaska and also indicates that the isopycnal mixing is active in the area east of 165 degreesE. The transport route obtained from individual cruise data mostly agrees with that based on climatological data. As a whole, isopycnal potential temperature and potential vorticity are conserved along the transport route using both the climatological and individual data excepting that the potential vorticity at 26.8 sigma (theta) rapidly increases along streamlines in the Gulf of Alaska when the climatological data are used. This discrepancy might be attributed to the existence of the strong potential vorticity front in the Gulf of Alaska and excessive smoothing in the climatological data.
  • H Ueno, Yasuda, I
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 106 C10 22131 - 22141 2001年10月 [査読有り][通常論文]
     
    A warm and saline water transport to the North Pacific subarctic region which could feed the mesothermal (intermediate temperature maximum) water is investigated through the analysis of World Ocean Circulation Experiment and Subarctic Gyre Experiment hydrographic data. The analysis of individual cruise data supports the hypothesis that warm and saline water is transported from the area east of Japan, to the Gulf of Alaska and also indicates that the isopycnal mixing is active in the area east of 165 degreesE. The transport route obtained from individual cruise data mostly agrees with that based on climatological data. As a whole, isopycnal potential temperature and potential vorticity are conserved along the transport route using both the climatological and individual data excepting that the potential vorticity at 26.8 sigma (theta) rapidly increases along streamlines in the Gulf of Alaska when the climatological data are used. This discrepancy might be attributed to the existence of the strong potential vorticity front in the Gulf of Alaska and excessive smoothing in the climatological data.
  • H Ueno, Yasuda, I
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 105 C7 16885 - 16897 2000年07月 [査読有り][通常論文]
     
    The distribution and formation of mesothermal structure (temperature inversions) in the North Pacific subarctic region are investigated through analysis of climatological hydrographic data. It is suggested that the heat and salt that maintain the mesothermal water and thus the halocline in the density range of 26.7-27.2 sigma(theta) are transported as a cross-gyre flow from the transition domain just east of Japan, where the waters an influenced by the subtropical gyre water mass, to the eastern subarctic region. Along the transport route the isopycnal potential temperature and thus salinity are well conserved. In the western subarctic gyre, the Bering Sea, and the northern Gulf of Alaska, the temperature reaches its minimum at the surface in winter and the areal coverage agrees well with the distribution of the mesothermal structure. In the southeastern part of the zonally distributed mesothermal structure in the area of 170 degrees E-150 degrees W and 45 degrees-50 degrees N, where the winter sea surface temperature is higher than that in the deeper layer, dichothermal water is formed by subsurface intrusion of the low-temperature and low-salinity water that outcropped in the previous winter over the warm and saline water transported from the transition domain.
  • H Ueno, Yasuda, I
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 105 C7 16885 - 16897 2000年07月 [査読有り][通常論文]
     
    The distribution and formation of mesothermal structure (temperature inversions) in the North Pacific subarctic region are investigated through analysis of climatological hydrographic data. It is suggested that the heat and salt that maintain the mesothermal water and thus the halocline in the density range of 26.7-27.2 sigma(theta) are transported as a cross-gyre flow from the transition domain just east of Japan, where the waters an influenced by the subtropical gyre water mass, to the eastern subarctic region. Along the transport route the isopycnal potential temperature and thus salinity are well conserved. In the western subarctic gyre, the Bering Sea, and the northern Gulf of Alaska, the temperature reaches its minimum at the surface in winter and the areal coverage agrees well with the distribution of the mesothermal structure. In the southeastern part of the zonally distributed mesothermal structure in the area of 170 degrees E-150 degrees W and 45 degrees-50 degrees N, where the winter sea surface temperature is higher than that in the deeper layer, dichothermal water is formed by subsurface intrusion of the low-temperature and low-salinity water that outcropped in the previous winter over the warm and saline water transported from the transition domain.

書籍

講演・口頭発表等

受賞

  • 2010年度日本海洋学会岡田賞
     北太平洋亜寒帯の海洋構造と動態の解析研究 
    受賞者: 上野洋路

共同研究・競争的資金等の研究課題

  • 北太平洋における塩分躍層の時空間変動とその生物生産への影響
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 上野 洋路, 三寺 史夫
     
    海洋の塩分躍層は、塩分が深さとともに急激に増加する層のことであり、北太平洋亜寒帯域では、成層構造や混合層深度の決定に重要な役割を果たしている。2018年度では、冬季混合層下の塩分躍層に注目し、その全球分布と経年変動を明らかにすることを目的として研究をおこなった。 本研究ではまず、観測年や観測手法によって異なる水温、塩分プロファイルの鉛直解像度を均質化し、塩分躍層強度や深度の人為的変動を抑制する手法を開発、米国海洋大気庁World Ocean Databaseの水温、塩分データに適用した。また、塩分躍層強度として、各プロファイルの10-300m深における各層の塩分鉛直勾配の最大値を採用し、最大値をとる深度を塩分躍層深度と定義した。このデータ、定義を用いて塩分躍層強度、深度を計算したところ、明瞭な塩分躍層は、北太平洋亜寒帯域、北大西洋西部亜寒帯域、全球の熱帯海域、南極海域に分布していることが示された。また、塩分躍層強度と海面塩分の分布相関解析を行ったところ、有意な負の相関が得られ、強い塩分躍層は海面塩分が相対的に低い海域で発達していることが明らかになった。 塩分躍層は、その強度および深度において大きな振幅で年々変動していることも示された。また、ほとんどの海域において、塩分躍層強度の年々変動は、海面塩分の年々変動と負の相関を持つことが示された。これは、塩分躍層の空間分布と同様に、海面塩分が低い年に塩分躍層が強化されているという傾向であり、淡水フラックスの経年変動の塩分躍層強度への影響が示唆された。しかし、アラスカ湾では海面塩分が高い年に塩分躍層が強化されるという他の海域とは異なる結果が得られ、塩分躍層の経年変動には、複数のメカニズムが関与していることが示された。
  • 北太平洋西部亜寒域における海洋中規模渦の物質循環・低次生態系への影響の解明
    日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 上野 洋路
     
    本研究では、アリューシャン列島南岸で形成され、北太平洋西部亜寒域を南西に伝播、同海域の水平、鉛直混合に重要な役割を果たすと考えられているアリューシャン渦に注目し、同渦が北太平洋西部亜寒域における生産を左右する栄養物質の循環および低次生態系への影響を理解することを目的として研究を実施した。 今年度は、2016年度おしょろ丸60日航海において実施した乱流観測および鉄濃度観測によって得られたデータについて詳しい検討を行った。本観測は、海洋中規模渦内・縁辺付近では、乱流エネルギー散逸率、鉛直拡散係数が大きく、その結果、渦内・縁辺付近に高い生物生産をもたらしているのではないかとの予測に基づいて実施したものである。しかし、解析の結果、その予測とは異なる結果が得られた。まず、乱流データ解析の結果、渦内外で鉛直拡散係数に顕著な違いはなく、一般的な外洋域の値程度であることが示された。鉄濃度に関しても、渦内外で顕著な差は観測されず、一般的な北太平洋亜寒帯外洋域の値に近いものとなっていた。これらの結果は、クロロフィル蛍光度の分布、すなわち渦内外でクロロフィル蛍光度に顕著な差は観測されなかったという観測結果と整合的であった。以上の結果から、2016年度おしょろ丸60日航海において観測した中規模高気圧性渦内・外縁部付近では、鉛直混合、さらにそれに伴う下層から有光層への鉄供給が周辺海域と同様に弱く、結果として周辺海域と比べて高いクロロフィル蛍光度が観測されなかったと考えられる。 本研究ではさらに、北太平洋西部亜寒帯全域における中規模渦の性質も検討した。その結果、アリューシャン渦形成域では、その周辺海域と比べて特に多くの渦が形成されるわけではないことが示され、当該海域では、周辺海域よりも大きくて強い渦が形成され、寿命も長いという特徴を持つことで、西部亜寒帯外洋域に大きな影響を持つことが示唆された。
  • 日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2012年06月 -2017年03月 
    代表者 : 清田 雅史, 米崎 史郎, 酒井 光夫, 上野 洋路, 帰山 雅秀, 奥田 武弘, 加藤 慶樹, 帰山 雅秀, 村上 知里
     
    北西太平洋の表層高次捕食者の生活の場として海洋区を理解するため、4つの研究アプローチを進めた:1) 新開発したクラスター分析法を用いて高次捕食者群集を分類し、機械学習を応用して群集マップを作成した。2) 海洋区別の生態系モデルを構築し、海洋区の食物網特性の比較、鍵種・鍵プロセスの推定、漁業の影響評価を行った。3) 1年で再生産するアカイカの雌雄による南北回遊の違いが、成長と体サイズの性差をもたらす過程を、安定同位体分析により推定し数理モデル上で再現した。4) 川から放流された日本系サケが成魚として再び戻って来るまでの回遊と成長を支える各海洋区の生産量を推定し生態系基盤サービスとして定量化した。
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2010年04月 -2014年03月 
    代表者 : 上野 洋路
     
    舶、衛星、フロート観測データを用いることにより、北太平洋亜寒帯中西部における中規模渦の物理的性質および生物場への影響を調べた。その結果、アラスカ湾北部で形成される海洋中規模渦の一つであるキーナイ渦の中心付近の水塊が、形成直後から約4年間に冬季混合層過程、水平貫入、渦-渦相互作用などによって変質する様子が初めて明らかになった。また、中規模渦が動物プランクトンに大きな影響を与えていることが示された。
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2008年 -2009年 
    代表者 : 上野 洋路
     
    衛星観測データ等を用いて、アリューシャン列島南岸で形成された高気圧性渦(アラスカンストリーム渦)の形成・伝播および北太平洋亜寒帯外洋域の生物生産場に与える影響を調べた。その結果、形成・伝播には、形成域の風応力場、海底地形が効いていること、また栄養塩に富む海水をアリューシャン列島海域から外洋域への輸送すること等により、アラスカンストリーム渦が亜寒帯外洋域のクロロフィルa濃度分布に大きく寄与することが示唆された。
  • 北太平洋亜熱帯-亜寒帯循環系における中層水の形成と循環に関する研究
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2002年 -2003年 
    代表者 : 上野 洋路
     
    本研究ではまず、昨年度に引き続きインバース法を用いて亜熱帯-亜寒帯海水交換と等密度面を横切る流れの亜寒帯域水温極大水(中暖水)への影響の定量的評価を行った。本年度は特に、誤差の評価に重点を置いた解析を行ない、亜寒帯域中暖水の熱の維持には南からの中層熱輸送が本質的な役割を果たしていることを、より定量的に示すことができた。この成果に関しては、2003年4月にフランス・ニースで開催された国際学会「欧州地球物理学会-米国地球物理学連合学会-欧州地球科学会・合同大会」および2003年7月に札幌で開催された国際学会「第23回国際測地学・地球物理学連合総会」にてポスター発表を行い、2003年11月に国際学術誌「Journal of Geophysical Research」に掲載された。 本研究では更に、北太平洋中高緯度域の亜表層・中層の水温・塩分構造の更なる理解を目指し、過去に観測された海洋データ(北太平洋中高緯度域で約80万点)の直接解析を行なった。具体的には、北太平洋亜寒帯域に特徴的な構造である水温逆転構造の存在確率分布を推定、どの海域でどの程度の水温逆転が起こっているかを定量的に議論した。その結果、例えばアリューシャン列島、千島列島沿いでは、冬季に水温逆転が形成され、季節の進行と共に極小、極大水が共に昇温するが、極小水の昇温の方が大きい為、逆転水温及び水温逆転存在確率は秋にかけて減少することが分かった。また、上記水温上昇は、海面加熱と中層における暖水供給、及び強い潮汐混合によると推察される。この結果は、国際学術誌「Journal of Geophysical Research」に投稿中であり、2004年3月27日に筑波大学で開催される2004年度日本海洋学会春季大会にて口頭発表する予定である。

教育活動情報

主要な担当授業

  • 専門横断科目(一般科目):海外留学
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 専門横断科目
  • 海洋学入門
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : 海底地形、海洋大循環、熱/物質循環、プランクトン、海底資源、海洋観測、海洋法、海洋生物資源の保全
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 海洋環境、水圏生態、水産資源、海洋物理学、海洋化学、プランクトン、イカ、サバ
  • 海洋資源科学実験Ⅲ
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : 行動生態計測、衛星データ解析-マイクロ波リモートセンシング、衛星データ解析-海色リモートセンシング、海洋観測データ解析、魚類遊泳力学,魚類行動計測、水産海洋工学、数値流体解析
  • 応用物理学
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : ニュートン力学,常微分方程式の解法,流体の力学,流れの解析,数値計算法
  • 環境と人間
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 海洋物理,海洋化学、海洋生態系,気候変化,プランクトン,ベントス,カレイ,サケ、深海魚、イカ・タコ類,鯨類,海鳥類,海獣類,衛星海洋学,人間活動,地球温暖化,海洋動物の保全・保護

大学運営

委員歴

  • 2018年 - 現在   日本学術会議   環境学委員会・地球惑星科学委員会合同FE・WCRP合同分科会CLIVAR小委員会委員
  • 2016年11月 - 現在   Co-chair PICES/WG38 (Mesoscale and Submesoscale Processes)
  • 2016年 - 現在   日本海洋学会   教育問題研究会 海の出前授業担当
  • 2014年09月 - 現在   Member, PICES/POC (Physical Oceanography and Climate Committee)
  • 2013年04月 - 現在   日本海洋学会 教育問題研究会   サイエンスカフェ担当
  • 2019年 - 2020年   日本海洋学会   論文賞受賞候補者選考委員会委員長
  • 2018年 - 2019年   日本海洋学会   論文賞受賞候補者選考委員会委員
  • 2017年 - 2019年   水産海洋学会   評議員
  • 2015年04月 - 2017年03月   日本海洋学会   広報委員会 委員


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