Updated on 2024/10/10

写真a

 
TSUTSUMI Eisuke
 
Organization
Research Field in Fisheries, Agriculture, Fisheries and Veterinary Medicine Area Faculty of Fisheries Assistant Professor
Title
Assistant Professor

Degree

  • Ph. D ( 2012.3   Kyushu University )

Research Interests

  • Ocean mixing, Interaction between western boundary current region and coastal seas, Ocean environments

Research Areas

  • Natural Science / Atmospheric and hydrospheric sciences  / Physical Oceanography

Education

  • Kyushu University   Interdisciplinary Graduate School of Engineering Sciences   Ph.D course, Department of Earth System Science and Technology

    2009.4 - 2012.3

Research History

  • Kagoshima University   Assistant Professor

    2022.10

  • The University of Tokyo   Atmosphere and Ocean Research Institute   Project Assistant Professor

    2019.4 - 2022.9

  • Kyushu University   Research Institute for Applied Mechanics   Postdoctoral Fellow

    2015.4 - 2019.3

  • Ehime University   Center for Marine Environmental Studies   Postdoctoral Fellow

    2012.4 - 2015.3

 

Papers

  • Shuya Wang, Xinyu Guo, Akihiko Morimoto, Anzhou Cao, Eisuke Tsutsumi, Yasumasa Miyazawa, Sergey M. Varlamov .  Semidiurnal Internal Tides in a Shelf Sea South of Japan: Characteristics, Energetics, and Temporal variations .  Progress in Oceanography222   2024.3Semidiurnal Internal Tides in a Shelf Sea South of Japan: Characteristics, Energetics, and Temporal variations

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    Publishing type:Research paper (scientific journal)  

    Tidal mixing in a shelf sea south of Japan (Bungo Channel) plays an important role in modulating the water exchange between the Seto Inland Sea and Pacific Ocean. In this study, based on moored observations and model results from the Japan Coastal Ocean Predictability Experiment—Tides (JCOPE-T), the generation, propagation, and dissipation of semidiurnal internal tides in the Bungo Channel are investigated. Observational results indicate that semidiurnal internal tides induce strong baroclinic currents reaching 0.3 m/s. Their energy shows obvious spring-neap tidal cycles, generally coinciding with the local barotropic tidal forcing. By conducting the empirical orthogonal function analysis, we find that the observed semidiurnal internal tides are mainly dominated by the first two baroclinic modes. The JCOPE-T results suggest two main generation sites for semidiurnal internal tides in the region: one is located at a narrow strait north of the Bungo Channel, while the other is at the shelf break south of the Bungo Channel. The latter makes a major contribution to the observed semidiurnal internal tides. Northward internal tides generated at the shelf break are superposed with those generated at the narrow strait, causing a complex interference pattern in the channel. The temporal variation of semidiurnal internal tides in the Bungo Channel is affected by several factors. The intraseasonal variation of semidiurnal internal tides can be modulated by the Kuroshio warm water intrusion (Kyucho) because the occurrence of Kyucho changes the stratification in the channel and hence affects the energy conversion. The seasonal variation of semidiurnal internal tides in the Bungo Channel is determined mainly by the seasonally varying stratification; while those generated at the shelf break are under the combined influence of seasonal stratification and background currents. Southward internal tides from the shelf break are refracted due to the spatially varying stratification and background currents. The varying Kuroshio path and strength modulate the refraction of internal tides.

    DOI: 10.1016/j.pocean.2024.103229

    Scopus

  • Anne Takahashi, Ren-Chieh Lien, Eric Kunze, Barry Ma, Hirohiko Nakamura, Ayako Nishina, Eisuke Tsutsumi, Ryuichiro Inoue, Takeyoshi Nagai, Takahiro Endoh .  Energetic Stratified Turbulence Generated by Kuroshio–Seamount Interactions in Tokara Strait .  Journal of Physical Oceanography54 ( 2 ) 461 - 484   2024.2

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    Publishing type:Research paper (scientific journal)   Publisher:American Meteorological Society  

    Abstract

    Generating mechanisms and parameterizations for enhanced turbulence in the wake of a seamount in the path of the Kuroshio are investigated. Full-depth profiles of finescale temperature, salinity, horizontal velocity, and microscale thermal-variance dissipation rate up- and downstream of the ∼10-km-wide seamount were measured with EM-APEX profiling floats and ADCP moorings. Energetic turbulent kinetic energy dissipation rates and diapycnal diffusivities above the seamount flanks extend at least 20 km downstream. This extended turbulent wake length is inconsistent with isotropic turbulence, which is expected to decay in less than 100 m based on turbulence decay time of N<sup>−1</sup> ∼ 100 s and the 0.5 m s<sup>−1</sup> Kuroshio flow speed. Thus, the turbulent wake must be maintained by continuous replenishment which might arise from (i) nonlinear instability of a marginally unstable vortex wake, (ii) anisotropic stratified turbulence with expected downstream decay scales of 10–100 km, and/or (iii) lee-wave critical-layer trapping at the base of the Kuroshio. Three turbulence parameterizations operating on different scales, (i) finescale, (ii) large-eddy, and (iii) reduced-shear, are tested. Average ε vertical profiles are well reproduced by all three parameterizations. Vertical wavenumber spectra for shear and strain are saturated over 10–100 m vertical wavelengths comparable to water depth with spectral levels independent of ε and spectral slopes of −1, indicating that the wake flows are strongly nonlinear. In contrast, vertical divergence spectral levels increase with ε.

    DOI: 10.1175/jpo-d-22-0242.1

    Other Link: https://journals.ametsoc.org/downloadpdf/journals/phoc/54/2/JPO-D-22-0242.1.xml

  • Ryuichiro Inoue, Eisuke Tsutsumi, Hirohiko Nakamura .  Numerical Simulation of the Kuroshio Flowing over the Hirase Seamount in the Tokara Strait in Autumn: Tidal Vortex Shedding in a Baroclinic Jet .  Journal of Physical Oceanography54 ( 1 ) 153 - 172   2024.1

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    Publishing type:Research paper (scientific journal)   Publisher:American Meteorological Society  

    Abstract

    Idealized numerical simulations of the Kuroshio western boundary current flowing over the Hirase seamount were conducted to examine the mechanisms of phenomena observed by shipboard and mooring measurements. Along the Kuroshio, enhanced mixing [vertical diffusivity, K<sub>ρ</sub> = O(10<sup>−2</sup>) m<sup>2</sup> s<sup>−1</sup>] was observed in a low-stratification layer between high-shear layers around low tide, and a V-shaped band of the negative vertical component of relative vorticity (ζ<sub>z</sub>) was also observed. Those features were reproduced in simulations of the Kuroshio that included the D2 tide. In the simulation, a streak of negative ζ<sub>z</sub> detached from the Hirase turned into vertically tilted 10-km-scale vortices. The buoyancy frequency squared (N<sup>2</sup>) budget at the mooring position showed that the low stratification was caused by vertical and horizontal advection and horizontal tilting. The K<sub>ρ</sub> tended to increase when the Ertel potential vorticity (PV) &lt; 0, as expected given the inertial instability. However, the magnitude of K<sub>ρ</sub> also depended on the tidal phase near Hirase, and K<sub>ρ</sub> was increased in the high vertical shear zones at the periphery of vortices where a strain motion is large. These results indicate that not only inertial instability but also tidal and vertical shear effects are important for driving turbulent mixing.

    Significance Statement

    A basin-scale distribution of wind stress drives a strong surface-intensified current in the western part of each ocean basin, such as the Gulf Stream and the Kuroshio. This western boundary current is regarded as a place where the kinetic energy and vorticity generated by winds are dissipated, allowing the basin-scale circulation to keep a steady state, but its dissipation mechanisms are not well understood. To understand the mechanisms, we conducted idealized numerical simulations that isolate the interactions between a seamount and the current as well as tidal currents, and compared results with observations. Our findings provide insights into how the current transfers kinetic energy to smaller scales when it flows over a seamount.

    DOI: 10.1175/jpo-d-23-0050.1

    Other Link: https://journals.ametsoc.org/downloadpdf/journals/phoc/54/1/JPO-D-23-0050.1.xml

  • Siteng Justin Zhu, Jing Zhang, Takeshi Matsuno, Eisuke Tsutsumi, Shota Kambayashi, Keiji Horikawa, Katsumi Takayama, Mutsuo Inoue, Seiya Nagao .  Quantifying the Water Contribution of Subtropical Mode Water and Related Isopycnal/Diapycnal Water Mixing in the Western Pacific Boundary Current Area Using Radiocesium: A Significant Nutrient Contribution From Subtropical Pacific Gyre to the Marginal Region .  Journal of Geophysical Research: Oceans128 ( 4 )   2023.4

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    Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union (AGU)  

    DOI: 10.1029/2022jc018975

  • Ming-Huei Chang, Yu-Hsin Cheng, Yu-Yu Yeh, Yiing Jang Yang, Sen Jan, Chih-Lun Liu, Takeshi Matsuno, Takahiro Endoh, Eisuke Tsutsumi, Jia-Lin Chen, Xinyu Guo .  Internal Hydraulic Transition and Turbulent Mixing Observed in the Kuroshio over the I-Lan Ridge off Northeastern Taiwan .  Journal of Physical Oceanography52 ( 12 ) 3179 - 3198   2022.12Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Meteorological Society  

    Abstract

    Complex small-scale processes and energetic turbulence are observed at a sill located on the I-Lan Ridge that spans across the strong Kuroshio off Taiwan. The current speed above the sill is strong (1.5 m s<sup>−1</sup>) and unsteady (±0.5 m s<sup>−1</sup>) due to the Kuroshio being modulated by the semidiurnal tide. Above the sill crest, isothermal domes, with vertical scales of ∼20 and ∼50 m during the low and high tides, respectively, are generated by turbulent mixing as a result of shear instability in the bottom boundary layer. Tidally modulated hydraulic character modifies the small-scale processes occurring on the leeward side of the sill. Criticality analysis, performed by solving the Taylor–Goldstein equation, suggests that the observed lee waves and intermediate layer sandwiched by two free shear layers are related to the mode-1 and mode-2 critical control between the sill crest and immediate lee, respectively. Around high tide, lee waves are advected further downstream, and only mode-1 critical control can occur, leading to a warm water depression. The shear instabilities ensuing from the hydraulic transition processes continuously mediate flow kinetic energy to turbulence such that the status of marginal instability where the Richardson number converges at approximately 0.25 is reached. The resultant eddy diffusivity K<sub>ρ</sub> is concentrated from O(10<sup>−4</sup>) to O(10<sup>−3</sup>) m<sup>2</sup> s<sup>−1</sup> and has a maximum value of 10 m<sup>2</sup> s<sup>−1</sup>. The sill on the western flank of the Kuroshio is a hotspot for energetic mixing of Kuroshio waters and South China Sea waters.

    DOI: 10.1175/jpo-d-21-0245.1

    Scopus

    Other Link: https://journals.ametsoc.org/downloadpdf/journals/phoc/52/12/JPO-D-21-0245.1.xml

  • S. Itoh, E. Tsutsumi, E. Masunaga, T. T. Sakamoto, K. Ishikawa, D. Yanagimoto, Y. Hoshiba, H. Kaneko, D. Hasegawa, K. Tanaka, H. Fukuda, T. Nagata .  Seasonal cycle of the confluence of the Tsugaru Warm, Oyashio, and Kuroshio currents east of Japan .  Journal of Geophysical Research: Oceans127 ( 8 )   2022.8

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    Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union (AGU)  

    DOI: 10.1029/2022JC018556

    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2022JC018556

  • Takahiro Endoh, Eisuke Tsutsumi, Chang-Su Hong, Gyu-Nam Baek, Ming-Huei Chang, Yiing Jang Yang, Takeshi Matsuno, Jae Hak Lee .  Estimating propagation speed and direction, and vertical displacement of second-mode nonlinear internal waves from ADCP measurements .  Continental Shelf Research   104644 - 104644   2022.1Estimating propagation speed and direction, and vertical displacement of second-mode nonlinear internal waves from ADCP measurements

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.csr.2021.104644

  • Takeyoshi Nagai, Daisuke Hasegawa, Eisuke Tsutsumi, Hirohiko Nakamura, Ayako Nishina, Tomoharu Senjyu, Takahiro Endoh, Takeshi Matsuno, Ryuichiro Inoue, Amit Tandon .  The Kuroshio flowing over seamounts and associated submesoscale flows drive 100-km-wide 100-1000-fold enhancement of turbulence .  COMMUNICATIONS EARTH & ENVIRONMENT2 ( 1 )   2021.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:SPRINGERNATURE  

    Although previous studies reported that currents over topographic features, such as seamounts and ridges, cause strong turbulence in close proximity, it has been elusive how far intense turbulence spreads toward the downstream. Here, we conducted a series of intensive in-situ turbulence observations using a state-of-the-art tow-yo microstructure profiler in the Kuroshio flowing over the seamounts of the Tokara Strait, south of Kyusyu Japan, in November 2017, June 2018, and November 2019, and employed a high-resolution numerical model to elucidate the turbulence generation mechanisms. We find that the Kuroshio flowing over seamounts generates streaks of negative potential vorticity and near-inertial waves. With these long-persisting mechanisms in addition to other near-field mixing processes, intense mixing hotspots are formed over a 100-km scale with the elevated energy dissipation by 100- to 1000-fold. The observed turbulence could supply nutrients to sunlit layers, promoting phytoplankton primary production and CO2 uptake.Persistent and intense mixing hotspots are generated where the Kuroshio flows over steep seamounts, with an increase in energy dissipation by two to three orders of magnitude, according to tow-yo microstructure measurements combined with numerical simulations.

    DOI: 10.1038/s43247-021-00230-7

    Web of Science

    Scopus

  • Akie Sakai, Tomoharu Senjyu, Takeshi Matsuno, Eisuke Tsutsumi, Takahiro Endoh .  Internal waves with high vertical wavenumber structure generated by diurnal tidal flow over the eastern ridge of Luzon Strait .  JOURNAL OF OCEANOGRAPHY   2021.8Internal waves with high vertical wavenumber structure generated by diurnal tidal flow over the eastern ridge of Luzon Strait

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    Internal waves with high vertical wavenumber structures on the northern part of the eastern ridge in Luzon Strait were investigated using shipboard observations and a wave propagation model. Detailed repeat observations across the ridge revealed complex undulations of isopycnals near the ridge that were characterized by vertically alternating concave and convex structures. In addition, strong eastward and westward flow areas with horizontal and vertical scales of 3-5 km and 150-250 m, respectively, occurred alternately on the downstream side of the ridge. These high-wavenumber structures in flow and density fields were associated with internal waves generated by interactions between diurnal tidal flow and the meridional submarine ridge in the strait; an acoustic Doppler current profiler recorded no signals of the Kuroshio Current and semi-diurnal tides in the zonal flow on the western slope of the eastern ridge. Many temperature inversions around the ridge exhibited vertical scales of predominantly similar to 30 m. Simple calculations of internal wave motion reveal that each internal wave mode tends to stagnate near the summits of the ridge depending on the direction and strength of the background tidal flow. This suggests that the observed high-wavenumber structure in the flow profiles near the ridge is ascribed to the superposition of transient internal wave modes, although this is not the main cause of the temperature inversions. As a possible mechanism to explain the temperature inversions, we propose that higher-mode internal waves emanating from the unresolved topographic undulations are trapped by the observed high-wavenumber structures, resulting in turbulent mixing.Y

    DOI: 10.1007/s10872-021-00615-4

    Web of Science

  • D. Hasegawa, T. Matsuno, E. Tsutsumi, T. Senjyu, T. Endoh, T. Tanaka, N. Yoshie, H. Nakamura, A. Nishina, T. Kobari, T. Nagai, X. Guo .  How a Small Reef in the Kuroshio Cultivates the Ocean .  Geophysical Research Letters48 ( 7 )   2021.4Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union (AGU)  

    Vertical nitrate fluxes associated with turbulent mixing and upwelling around a small reef in the Kuroshio are quantified by continuously deploying a turbulence microstructure profiler with an attached submersible ultraviolet nitrate analyzer while drifting from the upstream to the downstream of the reef. Flow separations and trains of Kelvin-Helmholtz billows (thickness = 60 m) are identified using a shipboard ADCP and an echo-sounder. The turbulence diffusivity associated with the vigorous turbulent mixing reaches up to O(10−1 m2 s−1), resulting in strong nitrate fluxes of O(1–103 mmol m−2 day−1). In addition, large differences between the upstream and downstream density profiles suggest a strong upwelling velocity of O(10−3 m s−1), as well as an upwelling nitrate flux of O(102 mmol m−2 day−1) in the entire subsurface layer.

    DOI: 10.1029/2020GL092063

    Scopus

    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020GL092063

  • S. Itoh, H. Kaneko, S. Kouketsu, T. Okunishi, E. Tsutsumi, H. Ogawa, I. Yasuda .  Vertical eddy diffusivity in the subsurface pycnocline across the Pacific .  Journal of Oceanography   2021.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    <title>Abstract</title>In the stratified ocean, vertical eddy diffusivity in the subsurface pycnocline plays a major role in new production through transporting nutrients upwards from the darker/nutrient-rich layer. In order to evaluate the diffusivity that was less available in the subsurface layers where indirect estimations are difficult, we conducted direct microstructure measurements in the upper 300 m of the open Pacific during summer, from 40°S to 50°N along 170°W and from 137°E to 120°W across the subtropical North Pacific (21°30′N–23°N). The subsurface pycnocline in the mid- and low-latitude regions was occupied primarily by the Subtropical Underwaters characterized by high salinity, and the Subtropical Mode Waters appeared with an increasing depth and latitude. In the North Pacific, low-salinity subarctic water with shallow seasonal pycnocline was observed in the high-latitude region. The base level of the diffusivity was 0.14–0.47 × 10<sup>–5</sup> m<sup>2</sup> s<sup>–1</sup>, while elevations up to 0.51–13 × 10<sup>–5</sup> m<sup>2</sup> s<sup>–1</sup> were observed at the equator where the Equatorial Undercurrents formed the strong shear in the subsurface layer, and in areas high internal tide energy such as the Hawaiian Ridge. The effect of wind on the diffusivity was less clear, probably because the wind energy is generally low during summer. The shear-to-strain ratio showed dome-shaped profiles with respect to latitude and an increasing trend from west to east in the subtropical North Pacific. The geographical distributions of the diffusivity presented in this study will contribute to better understanding biogeochemical cycles in the stratified upper ocean through improving estimations of the material transport.

    DOI: 10.1007/s10872-020-00589-9

    Scopus

    Other Link: http://link.springer.com/article/10.1007/s10872-020-00589-9/fulltext.html

  • Eisuke Tsutsumi, Takeshi Matsuno, Sachihiko Itoh, Jing Zhang, Tomoharu Senjyu, Akie Sakai, Keunjong Lee, Daigo Yanagimoto, Ichiro Yasuda, Hiroshi Ogawa, Cesar Villanoy .  Vertical fluxes of nutrients enhanced by strong turbulence and phytoplankton bloom around the ocean ridge in the Luzon Strait .  Scientific Reports10 ( 1 )   2020.12Reviewed

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    <title>Abstract</title>
    Steep oceanic ridges and tidal currents in the Luzon Strait generate some of the world’s strongest turbulent mixing. To evaluate the impacts of the turbulence intensity on the marine ecosystem, we carried out measurements of microstructure turbulence and biogeochemical hydrography along 21°N in the Luzon Strait during the R/V <italic>Hakuho Maru</italic> cruise, KH-17-5-2, in November 2017. We found a turbulent kinetic energy dissipation rate exceeding <italic>O</italic>(10<sup>−7</sup>) W kg<sup>−1</sup> and vertical eddy diffusivity exceeding <italic>O</italic>(10<sup>−3</sup>) m<sup>2</sup> s<sup>−1</sup>, two orders of magnitude larger than those in the open ocean, above a shallow sub-ridge on the eastern ridge of the Luzon Strait. In addition, a clear chlorophyll <italic>a</italic> bloom was identified in the surface layer above the sub-ridge from in situ measurements and satellite observations. High values of nitrate (4.7 mmol N m<sup>−2</sup> d<sup>−1</sup>) and phosphate (0.33 mmol P m<sup>−2</sup> d<sup>−1</sup>) fluxes estimated near the base of the surface chlorophyll <italic>a</italic> bloom strongly suggest that enhanced turbulent mixing promotes nutrient supply to the euphotic zone and generates new production within the surface layer, contributing to the formation of a quasi-permanent local chlorophyll <italic>a</italic> bloom north of Itbayat Island on the eastern ridge.

    DOI: 10.1038/s41598-020-74938-5

    Scopus

    PubMed

    Other Link: http://www.nature.com/articles/s41598-020-74938-5

  • Toru Kobari, Taiga Honma, Daisuke Hasegawa, Naoki Yoshie, Eisuke Tsutsumi, Takeshi Matsuno, Takeyoshi Nagai, Takeru Kanayama, Fukutaro Karu, Koji Suzuki, Takahiro Tanaka, Xinyu Guo, Gen Kume, Ayako Nishina, Hirohiko Nakamura .  Phytoplankton growth and consumption by microzooplankton stimulated by turbulent nitrate flux suggest rapid trophic transfer in the oligotrophic Kuroshio .  Biogeosciences17 ( 9 ) 2441 - 2452   2020.5Reviewed

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    Publishing type:Research paper (scientific journal)   Publisher:Copernicus GmbH  

    Abstract. The Kuroshio Current has been thought to be biologically
    unproductive because of its oligotrophic conditions and low plankton
    standing stocks. Even though vulnerable life stages of major foraging fishes
    risk being entrapped by frontal eddies and meanders and encountering low
    food availability, they have life cycle strategies that include growing and
    recruiting around the Kuroshio Current. Here we report that phytoplankton
    growth and consumption by microzooplankton are stimulated by turbulent
    nitrate flux amplified by the Kuroshio Current. Oceanographic observations
    demonstrate that the Kuroshio Current topographically enhances significant
    turbulent mixing and nitrate influx to the euphotic zone. Graduated nutrient
    enrichment experiments show that growth rates of phytoplankton and
    microheterotroph communities were stimulated within the range of the
    turbulent nitrate flux. Results of dilution experiments imply significant
    microzooplankton grazing on phytoplankton. We propose that these rapid and
    systematic trophodynamics enhance biological productivity in the Kuroshio.

    DOI: 10.5194/bg-17-2441-2020

    Scopus

  • Takashi Mano, Xinyo Guo, Naoki Fujii, Naoki Yoshie, Eisuke Tsutsumi, Rui Saito .  Moon jellyfish aggregations observed by a scientific echo sounder and an underwater video camera and their relation to internal waves .  Journal of Oceanography75 ( 4 ) 359 - 374   2019.8Reviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

    © 2019, The Oceanographic Society of Japan and Springer Nature Singapore Pte Ltd. We found a good linear relation between the mean volume backscattering strength measured using a scientific echo sounder and the distribution density of moon jellyfish recorded simultaneously by an underwater video camera in small bays (Hokezu Bay and Mikame Bay) in Japan. This relation held in all of the surveys carried out in recent years (2013–2016), although the regression coefficient varied slightly from year to year due to the existence of ambient organisms. Using this relation and high-resolution echo sounder scan surveys across the bay, we obtained the spatial structures of moon jellyfish aggregations and categorized them into either patchy, layered, or wavy aggregations. We also examined possible physical mechanisms responsible for the moon jellyfish aggregations. In particular, passive particle tracking simulations of several idealized internal wave fields suggest that the formation of wavy aggregations is closely related to the presence of internal waves. However, internal waves alone cannot induce patchy and layered aggregations, indicating that particular biological processes (e.g., swimming behavior) are also necessary for such aggregations to form.

    DOI: 10.1007/s10872-019-00507-8

    Scopus

  • Hasegawa Daisuke, Tanaka Takahiro, Matsuno Takeshi, Senjyu Tomoharu, Tsutsumi Eisuke, Nakamura Hirohiko, Nishina Ayako, Kobari Toru, Yoshie Naoki, Guo Xinyu, Nagai Takeyoshi, Okunishi Takeshi, Yasuda Ichiro .  Measuring the Vertical Turbulent Nitrate Flux Using Sensors .  Bulletin on Coastal Oceanography57 ( 1 ) 59 - 64   2019Reviewed

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    Language:Japanese   Publisher:Coastal Oceanography Research Committee, the Oceanographic Society of Japan  

    Under the Grants-in-Aid for Scientific Research in Innovative Areas(MEXT)project “Ocean Mixing Study(OMIX)”, we
    established a system to measure the turbulent nitrate flux by attaching a small nitrate sensor on a turbulence profiler. In this
    paper, we explain the instrument setup, the data processing method considering measurement errors, and then demonstrate the
    capability of the developed observational system.

    DOI: 10.32142/engankaiyo.2019.8.008

    CiNii Books

    Other Link: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17H01860/

  • Takeyoshi Nagai, Daisuke Hasegawa, Takahiro Tanaka, Hirohiko Nakamura, Eisuke Tsutsumi, Ryuichiro Inoue, Toru Yamashiro .  First Evidence of Coherent Bands of Strong Turbulent Layers Associated with High-Wavenumber Internal-Wave Shear in the Upstream Kuroshio .  SCIENTIFIC REPORTS7   14555   2017.11First Evidence of Coherent Bands of Strong Turbulent Layers Associated with High-Wavenumber Internal-Wave Shear in the Upstream KuroshioReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE PUBLISHING GROUP  

    The upstream Kuroshio flows through Okinawa Trough and the Tokara island chain, the region near the continental shelf of the East China Sea and shallow seamounts, where the Kuroshio can induce strong mixing over the shallow topography. Also, tidal currents over the rough topography may produce internal tides, and associated turbulence. The previous observations show energetic high vertical wavenumber near-inertial wave shear in the Kuroshio thermocline, which implies strong turbulent mixing. However, direct turbulence measurements in this region are very scarce. Using high lateral resolution (1-2 km) direct turbulence measurements, we show here, for the first time, that strong turbulent layers form spatially coherent banded structures with lateral scales of &gt;O(10 km), associated with bands of near-inertial wave/diurnal internal tide shear of high vertical wavenumber in the upstream Kuroshio. The turbulent kinetic energy dissipation rates within these turbulent layers are &gt;O(10-7 W kg(-1)), and estimated vertical eddy diffusivity shows &gt;O(10(-4) m(2) s(-1)) on average. These results suggest that the high vertical wavenumber near-inertial waves propagating in the upstream Kuroshio could have large impacts on the watermass modifications, momentum mixing, nutrient supply, and associated biogeochemical responses in its downstream.

    DOI: 10.1038/s41598-017-15167-1

    Web of Science

  • Eisuke Tsutsumi, Takeshi Matsuno, Ren-Chieh Lien, Hirohiko Nakamura, Tomoharu Senjyu, Xinyu Guo .  Turbulent mixing within the Kuroshio in the Tokara Strait .  JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS122 ( 9 ) 7082 - 7094   2017.9Turbulent mixing within the Kuroshio in the Tokara StraitReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER GEOPHYSICAL UNION  

    Turbulent mixing and background current were observed using a microstructure profiler and acoustic Doppler current profilers in the Tokara Strait, where many seamounts and small islands exist within the route of the Kuroshio in the East China Sea. Vertical structure and water properties of the Kuroshio were greatly modified downstream from shallow seamounts. In the lee of a seamount crest at 200 m depth, the modification made the flow tend to shear instability, and the vertical eddy diffusivity is enhanced by nearly 100 times that of the upstream site, to K-p similar to O(10(-3))-O(10(-2)) m(2) s(-1). A one-dimensional diffusion model using the observed eddy diffusivity reproduced the observed downstream evolution of the temperature-salinity profile. However, the estimated diffusion time-scale is at least 10 times longer than the observed advection time-scale. This suggests that the eddy diffusivity reaches to O(10(-1)) m(2) s(-1) in the vicinity of the seamount. At a site away from the abrupt topography, eddy diffusivity was also elevated to O(10(-3)) m(2) s(-1), and was associated with shear instability presumably induced by the Kuroshio shear and near-inertial internal-wave shear. Our study suggests that a better prediction of current, water-mass properties, and nutrients within the Kuroshio requires accurate understanding and parameterization of flow-topography interaction such as internal hydraulics, the associated internal-wave processes, and turbulent mixing processes.

    DOI: 10.1002/2017JC013049

    Web of Science

  • Eisuke Tsutsumi, Xinyu Guo .  Climatology and linear trends of seasonal water temperature and heat budget in a semienclosed sea connected to the Kuroshio region .  JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS121 ( 7 ) 4649 - 4669   2016.7Climatology and linear trends of seasonal water temperature and heat budget in a semienclosed sea connected to the Kuroshio regionReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER GEOPHYSICAL UNION  

    The climatology and linear trend of seasonal water temperature and heat budget in a semienclosed sea connected to the Kuroshio region (Seto Inland Sea: SIS) are investigated by constructing and analyzing a gridded data set of water temperature, salinity, and air-sea heat fluxes. In the SIS, winter-time water temperature and ocean heat content (OHC) showed a significant increasing trend while those in summer-time exhibited no significant change. By analyzing the heat budget between the tendency of ocean heat content OHC/t and air-sea net heat flux Q(net), the driving factor of the winter-time warming trend in the SIS was identified as autumn Q(net), while the unchanged summer-time OHC is mainly due to decreased spring-time oceanic heat transport to the SIS from the Kuroshio region. In addition, we showed that the decreased spring-time heat transport could have been induced by upwelling due to wind curl and wind speed in the shelf-slope region, heat transport by the Kuroshio south of Shikoku Island, and freshwater input to the SIS from rivers. The importance of both oceanic and atmospheric forcing mechanisms for explaining variation in the water temperature in coastal areas is demonstrated.

    DOI: 10.1002/2016JC011748

    Web of Science

  • Measurements of Turbulent Energy Dissipation Rate towards Better Understanding of Physical Processes in Coastal Seas : Case Study in Ariake Sea .    53 ( 2 ) 135 - 140   2016.2Invited Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    CiNii Books

  • Eisuke Tsutsumi, Takeshi Matsuno, Center for Marine Environmental Studies Ehime University, Research Institute for Applied Mechanics Kyushu University .  Observations of external, internal tidal currents and associated turbulent mixing around the Isahaya bay mouth, Ariake Sea .    23 ( 2 ) 45 - 72   2014.3Reviewed

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    CiNii Books

    Other Link: http://id.nii.ac.jp/1141/00047208/

  • Takahiro Endoh, Takeshi Matsuno, Yutaka Yoshikawa, Eisuke Tsutsumi .  Estimates of the turbulent kinetic energy budget in the oceanic convective boundary layer .  JOURNAL OF OCEANOGRAPHY70 ( 1 ) 81 - 90   2014.2Estimates of the turbulent kinetic energy budget in the oceanic convective boundary layerReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    The terms of the steady-state turbulent kinetic energy (TKE) budget in the oceanic convective boundary layer (CBL) are estimated by use of microstructure data obtained over the continental shelf of the East China Sea. The dissipation term is calculated from the micro-scale vertical shear of horizontal velocity measured directly using a freely-falling microstructure profiler, whereas the buoyancy flux and shear production terms are estimated indirectly by integrating vertically the one-dimensional conservation equation of density and by applying similarity theory, respectively. The transport term, calculated as the residual of the other three terms, vertically redistributes the TKE from the upper half of the CBL to the lower half, consistent with the TKE budgets in the atmospheric CBL and in shear-free and slightly-sheared CBLs simulated by large eddy-simulation models. The relatively large contribution of the transport term to the TKE budget shows that a local equilibrium form of the TKE equation is not appropriate for the TKE budget in the oceanic CBL.

    DOI: 10.1007/s10872-013-0215-3

    Web of Science

  • Eisuke Tsutsumi, Takeshi Matsuno .  Observations of turbulence under weakly and highly stratified conditions in the Ariake Sea .  JOURNAL OF OCEANOGRAPHY68 ( 3 ) 369 - 386   2012.6Observations of turbulence under weakly and highly stratified conditions in the Ariake SeaReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    Observations of turbulence, stratification, and mean current were made using a microstructure profiler and an acoustic Doppler current profiler (ADCP) during four cruises at a central location in the Ariake Sea, under weakly and strongly stratified conditions. Continuous measurements of the dissipation rate of turbulent kinetic energy (TKE), epsilon, were made. These revealed that frictional bed turbulence with quarterdiurnal variation in the bottom boundary layer (BBL) was one of the most energetic sources of vertical mixing in the sea. Thickness of the BBL was strongly confined by the stable stratification. We investigate a relationship between the BBL height h and the Ozmidov scale. We present a systematic argument that describes the vertical structure and characteristic scales of velocity and turbulence inside the frictional BBL, where the stratification persisted. Considerable deviation of observed vertical shear from the law of the wall indicated a modification of turbulent scales by the stratification. Shear stress calculated from the velocity data using vertical integration of the equation of motion was found to decrease approximately linearly with height. The TKE production rate P, estimated using the shear stress, was highly correlated with the dissipation rate. The buoyancy contribution to TKE balance in the BBL was quantified in terms of the flux Richardson number R-f as R-f = 0.12.

    DOI: 10.1007/s10872-012-0103-2

    Web of Science

  • Y. Yoshikawa, T. Endoh, T. Matsuno, T. Wagawa, E. Tsutsumi, H. Yoshimura, Y. Morii .  Turbulent bottom Ekman boundary layer measured over a continental shelf .  GEOPHYSICAL RESEARCH LETTERS37 ( 15 )   2010.8Turbulent bottom Ekman boundary layer measured over a continental shelfReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER GEOPHYSICAL UNION  

    An acoustic Doppler current profiler was deployed in summer and autumn in 2007-2009 at two stations on the East China Sea shelf. Clear velocity spirals that basically correspond to theoretical Ekman spirals were identified for both mean and tidal currents. From these spirals and the corresponding Ekman equation, we estimated the time-averaged eddy viscosity (mu) profiles. The estimated mu was largest (2-3 x 10(-3) m(2) s(-1)) around 5 m from the bottom and decreased almost exponentially with height. A qualitatively similar profile of the eddy diffusivity was also inferred from the acoustic Doppler current profiler data and microstructure profiler data. The flux Richardson number was estimated as 0.11 +/- 0.10 similar to 0.46 +/- 0.17, indicating relatively large buoyancy contribution to the turbulent kinetic energy budget. Citation: Yoshikawa, Y., T. Endoh, T. Matsuno, T. Wagawa, E. Tsutsumi, H. Yoshimura, and Y. Morii (2010), Turbulent bottom Ekman boundary layer measured over a continental shelf, Geophys. Res. Lett., 37, L15605, doi: 10.1029/2010GL044156.

    DOI: 10.1029/2010GL044156

    Web of Science

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MISC

  • Enhanced vertical mixing along a shelf-slope front east of Japan

    ITOH Sachihiko, MASUNAGA Eiji, TSUTSUMI Eisuke, SAKAMOTO Takashi T, ISHIKAWA Kazuo, YANAGIMOTO Daigo, KANEKO Hitoshi, HOSHIBA Yasuhiro, HASEGAWA Daisuke, NAGATA Toshi

    日本地球惑星科学連合大会予稿集(Web)   2020   2020

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  • 三陸沿岸における水平微細構造の季節変動

    伊藤幸彦, 堤英輔, 増永英治, 坂本天, 柳本大吾, 干場康博, 金子仁, 永田俊, 長谷川大介, 田中潔

    日本海洋学会大会講演要旨集   2020   2020

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  • 三陸沿岸における水平微細構造の季節変動

    伊藤幸彦, 堤英輔, 坂本天, 石川和雄, 柳本大吾, 干場康博, 永田俊, 田中潔, 長谷川大介, 増永英治, 金子仁

    海と地球のシンポジウム発表課題一覧・要旨集(CD-ROM)   2020   2020

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  • Mixing over the eastern ridge in the Luzon Strait caused by high-mode internal waves

    SAKAI Akie, SENJYU Tomoharu, TSUTSUMI Eisuke, MATSUNO Takeshi, ENDO Takahiro, YASUDA Ichiro, YANAGIMOTO Daigo

    日本地球惑星科学連合大会予稿集(Web)   2019   2019

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Presentations

  • 堤 英輔   「かごしま丸」を用いた東シナ海における黒潮観測と国際連携   Invited

    日本海洋学会2024年度秋季大会 シンポジウム「⿊潮および周辺海域の海洋研究に関する国際連携の今後を考える」  2024.9 

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    Event date: 2024.9

    Language:Japanese   Presentation type:Symposium, workshop panel (nominated)  

  • 堤 英輔, 吉江 直樹, 郭 新宇, 森本 昭彦, 遠藤貴洋, 宮澤泰正, 美山 透   豊後水道における乱流混合の観測とその流れと成層との関係  

    日本地球惑星科学連合2024年大会  2024.5 

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    Event date: 2024.5

    Language:Japanese   Presentation type:Oral presentation (general)  

  • Eisuke Tsutsumi, Ryuichiro Inoue, Takeyoshi Nagai, Hirohiko Nakamura, Ayako Nishina, Takahiro Endoh, Anne Takahashi, Ren-Chieh Lien, Eric Kunze, Sachihiko Itoh, Daisuke Hasegawa   Seamount wake and turbulent mixing induced by the Kuroshio and tides in Tokara Strait  

    2nd UN Ocean Decade Regional Conference & 11th WESTPAC International Marine Science Conference  2024.4 

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    Event date: 2024.4

    Language:English   Presentation type:Oral presentation (general)  

  • 堤 英輔, 広瀬 直毅, 石川和雄, 中村啓彦   DREAMS_Epsilonで見た九州西岸から沖合の流動場について  

    九州大学応用力学研究所研究集会 「東アジア縁辺海の物質循環と生物・物理・化学過程」  2024.2 

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    Event date: 2024.2

    Language:Japanese   Presentation type:Oral presentation (general)  

  • 堤 英輔, 井上 龍一郎, 長井 健容, 中村 啓彦, 仁科 文子, 遠藤 貴洋, 高橋 杏, Ren-Chieh Lien, Eric Kunze, 伊藤 幸彦, 長谷川 大介   黒潮と潮汐流が生じる海山ウェークと乱流混合の観測  

    北海道大学低温科学研究所2023年度共同利用研究集会 「海洋乱流の観測およびモデリングに関する研究集会」  2023.12 

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    Event date: 2023.12

    Presentation type:Oral presentation (general)  

  • 堤 英輔, 久米 元, 仁科 文子, 中村 啓彦, 須本 祐史, 遠藤 光, 小玉 将史, 作野 裕司, 加古, 真一郎, 山城 徹, 小針 統   鹿児島県海域における流れ藻来遊予測に向けた鹿児島大学の取り組み  

    第77回西日本海洋調査技術連絡会  2023.12 

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    Event date: 2023.12

  • 堤 英輔, 吉江 直樹, 郭 新宇, 遠藤 貴洋, 宮澤 泰正, 美山 透   急潮予測に向けた豊後水道御五神島周辺海域における乱流混合の観測  

    愛媛大学沿岸環境科学研究センター共同利用・共同研究拠点研究集会「瀬戸内海水産環境研究集会」  2023.11 

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    Event date: 2023.11

    Presentation type:Oral presentation (general)  

  • 堤 英輔   トカラ海峡部での物理過程   Invited

    東京大学大気海洋研究所共同利用研究集会「黒潮における物理・化学・生物過程:乱流と熱・栄養塩・仔稚魚輸送」  2023.11 

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    Event date: 2023.11

    Presentation type:Oral presentation (general)  

  • Eisuke Tsutsumi   Turbulent mixing in the WBC region around Japan and its potential for nutrient transport  

    Seminar for comparative study on Western Boundary Current “Toward Comparative Study on Ecosystems of Kuroshio and Gulf Stream”  2023.7 

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    Event date: 2023.7

    Language:English   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  • Eisuke Tsutsumi   Topographic lee wake and turbulent mixing induced by geostrophic flow and tides: observations at Hirase Seamount within the Kuroshio in Tokara Strait  

    Workshop on turbulent mixing in and around the Kuroshio  2023.6 

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    Event date: 2023.6

    Language:English   Presentation type:Oral presentation (general)  

  • Eisuke Tsutsumi, Takeshi Matsuno, Sachihiko Itoh, Jing Zhang, Tomoharu Senjyu, Akie Sakai, Keunjong Lee, Daigo Yanagimoto, Ichiro Yasuda, Hiroshi Ogawa, Cesar Villanoy   Vertical fluxes of nutrients enhanced by strong turbulence and phytoplankton bloom around the ocean ridge in the Luzon Strait  

    JpGU Meeting 2023  2023.5 

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    Event date: 2023.5

    Language:English   Presentation type:Poster presentation  

  • Observation of flow and turbulent mixing around Oitsukami Island in the Bungo Channel for prediction of sudden coastal intrusion of Kuroshio water (Kyocho)  

    JpGU Meeting 2023  2023.5 

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    Event date: 2023.5

    Language:Japanese   Presentation type:Poster presentation  

  • Eisuke Tsutsumi, Sachihiko Itoh, Shinichi Ito, Ryota Shibano, Itsuka Yabe, Eiji Masunaga, Ryuichiro Inoue   Study on submesoscales, mixing, and transport off Sanriku coast, Japan  

    2023.3 

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    Event date: 2023.3

    Language:Japanese   Presentation type:Symposium, workshop panel (public)  

  • Eisuke Tsutsumi   Flow and mixing at the tidal front in Bungo Channel  

    The 44th LaMer Special Seminar  2023.1 

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    Event date: 2023.1

    Language:English   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  • 堤英輔, 井上龍一郎, 長井健容, 中村啓彦, 仁科文子, 長谷川大介, 松野健, 遠藤貴洋, 千手智晴, 郭新宇   黒潮、潮汐及び海山が生じる鉛直混合 -トカラ海峡の平瀬における現場観測と数値シミュレーション-  

    東京大学大気海洋研究所共同利用研究集会「黒潮生態系とその変動を駆動する物理・化学・生物過程」  2022.12 

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    Event date: 2022.12

    Presentation type:Symposium, workshop panel (nominated)  

  • 堤英輔, 伊藤幸彦, 伊藤進一, 柴野良太, 矢部いつか, 増永英治, 井上龍一郎   夏季~秋季の三陸沿岸における津軽暖流と内部波、乱流混合(新青丸KS-22-11航海の結果速報)  

    北海道大学低温科学研究所共同利用研究集会「海洋乱流の観測およびモデリングに関する研究集会」  2022.11 

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    Event date: 2022.11

    Language:Japanese   Presentation type:Symposium, workshop panel (public)  

  • Eisuke Tsutsumi   Observation of the wake and energy dissipation of the Kuroshio flowing over Hirase in autumn  

    Seminar for “Kuroshio Interaction with the Tokara Strait Topography (KITTY)”  2022.11 

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    Event date: 2022.11

    Language:English   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  • 堤 英輔   黒潮中の流れ・地形間相互作用と乱流混合過程に関する研究   Invited

    九州大学応用力学研究所RIAMフォーラム2022  2022.7 

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    Event date: 2022.7

    Language:Japanese   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

  • 堤 英輔, 郭 新宇, 吉江 直樹, 董 孟洪, 遠藤 貴洋, 伊藤 幸彦   沿岸ー外洋移行帯として見た豊後水道の流動と混合  

    日本地球惑星科学連合2022年大会  2022.6 

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    Event date: 2022.5 - 2022.6

    Language:Japanese   Presentation type:Poster presentation  

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Research Projects

  • 黒潮流域で乱流混合によって有光層に供給される栄養塩の変遷過程と生物生産への寄与

    Grant number:24K03061  2024.4 - 2027.3

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    張 勁, 郭 新宇, 堤 英輔, 小林 英貴

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    Grant amount:\18330000 ( Direct Cost: \14100000 、 Indirect Cost:\4230000 )

  • 鹿児島県海域における漁場予測技術の開発

    2023.7 - 2026.3

    鹿児島県水産技術開発センター  共同研究 

    堤 英輔, 加古 真一郎, 湯ノ口 亮

  • Submesoscale Mixing Processes caused by Northward Shifted Kuroshio near the Yakushima and Tanegashima Islands and their chemical and biological impacts

    Grant number:23H01244  2023.4 - 2027.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Grant amount:\18980000 ( Direct Cost: \14600000 、 Indirect Cost:\4380000 )

  • Submesoscale Mixing Processes caused by Northward Shifted Kuroshio near the Yakushima and Tanegashima Islands and their chemical and biological impacts

    Grant number:23K25940  2023.4 - 2027.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Grant amount:\18980000 ( Direct Cost: \14600000 、 Indirect Cost:\4380000 )

  • Investigation of coastal upwelling induced by western boundary currents

    Grant number:23H01242  2023.4 - 2026.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Grant amount:\18720000 ( Direct Cost: \14400000 、 Indirect Cost:\4320000 )

  • Investigation of coastal upwelling induced by western boundary currents

    Grant number:23K25938  2023.4 - 2026.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Grant amount:\18720000 ( Direct Cost: \14400000 、 Indirect Cost:\4320000 )

  • 三陸沖のサブメソスケール流動に伴う水塊混合と物質輸送・生物環境に関する研究(KS-22-11次研究航海)

    2022.8

    東京大学大気海洋研究所  令和4年度研究船共同利用(新青丸単一課題航海) 

  • Flow variability and material diffusion processes from estuaries to continental shelves

    Grant number:22H05201  2022.6 - 2027.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Transformative Research Areas (A)  Grant-in-Aid for Transformative Research Areas (A)

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    Grant amount:\124410000 ( Direct Cost: \95700000 、 Indirect Cost:\28710000 )

  • 三陸沖のサブメソスケール流動に伴う水塊混合と物質輸送・生物環境に関する研究(KS-21-24次研究航海)

    2021.10

    東京大学大気海洋研究所  2021年度研究船共同利用(新青丸単一課題航海) 

  • Prediction and Understanding of Sudden Kuroshio Coastal Intrusion Processes by Integrating New Generation Satellites and Responsive Field Observations

    Grant number:21H01444  2021.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

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    Grant amount:\16900000 ( Direct Cost: \13000000 、 Indirect Cost:\3900000 )

  • Multiple time-scale Kuroshio variations driven by the East Asian Monsson

    Grant number:21H01157  2021.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

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    Grant amount:\18070000 ( Direct Cost: \13900000 、 Indirect Cost:\4170000 )

  • Long-term decrease in the M2 tide on the west coast of the Kyushu Island and its relation to changes in the tidal amplification of the Bohai, Yellow and East China Seas

    Grant number:18K13613  2018.4 - 2021.3

    Japan Society for the Promotion of Science  Grant-in-Aid for Early-Career Scientists  Grant-in-Aid for Early-Career Scientists

    Eisuke Tsutsumi

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    Authorship:Principal investigator  Grant type:Competitive

    Semi-diurnal tide along the west coast of the Kyushu Island, Japan has been decreasing in recent years, especially in the Ariake Sea. The mechanism and cause of the decreasing tide have been unknown. In this study, I conducted tide gauge data analysis and numerical model experiments using a three-dimensional general circulation model, and found that in the Ariake Sea about 90% of the decrease originated from that in the East China Sea, and 10% originated from the combined effect of the weakening of the bay-resonance due to the coastline modification and the strengthening of the resonance due to the weakening of the frictional drag of the seabed within the Ariake Sea. The results of numerical model experiments suggested that stratification changes over the northwestern Pacific region may have affected the changes in tidal amplitude along the east coast of the East China Sea through internal-tide generation and propagation, but the definitive cause of the changes could not be identified.

  • Mixing processes, nutrient transport, fundamental structure of ecosystem in the Kuroshio and its origin area

    Grant number:15H05821  2015.6 - 2020.3

    Japan Society for the Promotion Science  Grant-in-Aid for Scientific Research on Innovative Areas  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Xinyu Guo

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    Grant type:Competitive

    The purpose of this study is to clarify the role of boundary mixing in the material transport and ecosystem along the Kuroshio main current region including its origin area. The method is mainly based on field observations including physical and biogeochemical aspects. Specifically, we chose 4 areas (Luzon Strait, East of Taiwan, shelf edge of East China Sea, and Tokara Strait) along the Kuroshio main current and finished a total number of 14 field observations, in which we observed the vertical turbulent mixing and biogeochemical variables at selected stations and kept some mooring stations for ocean current. As a general fact, these observations demonstrated strong vertical mixing and upwelling around the islands and seamounts that are caused by the interaction between the strong Kuroshio current and the topographic obstacles. The upward nutrient flux due to the strong vertical mixing and upwelling likely plays an important role in maintaining the rich ecosystem along the Kuroshio.

  • Generation and propagation of internal tides in the Ariake Sea

    2013.4 - 2014.2

    The Japan Science Society  Sasagawa Scientific Research Grant 

    Eisuke Tsutsumi

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    Authorship:Principal investigator  Grant type:Competitive

  • Vertical mixing and internal tides in Ariake Sea

    2009.4 - 2010.2

    The Japan Science Society  Sasagawa Scientific Research Grant 

    Eisuke Tsutsumi

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    Authorship:Principal investigator  Grant type:Competitive

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Teaching Experience

  • On-board Training of Oceanographic Observation

    2023.11
    Institution:Kagoshima University

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    Level:Postgraduate 

  • Scientific English in Fisheries (Aquatic Science)

    2023.10
    Institution:Kagoshima University

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    Level:Undergraduate (specialized) 

  • Onboard Training of Oceanography I

    2023.6
    Institution:Kagoshima University

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    Level:Undergraduate (specialized) 

  • Basic Mathematics for Fisheries

    2023.4
    -
    2023.9
    Institution:Kagoshima University

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    Level:Undergraduate (specialized) 

  • Basic Mathematics

    2023.4
    -
    2023.9
    Institution:Kagoshima University

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    Level:Undergraduate (liberal arts) 

  • Basic Laboratory on Aquatic Science

    2023.4
    -
    2023.9
    Institution:Kagoshima University

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    Level:Undergraduate (specialized) 

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