86 results on '"Takeshi Matsuno"'
Search Results
2. Vertical fluxes of nutrients enhanced by strong turbulence and phytoplankton bloom around the ocean ridge in the Luzon Strait
- Author
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Eisuke Tsutsumi, Takeshi Matsuno, Sachihiko Itoh, Jing Zhang, Tomoharu Senjyu, Akie Sakai, Keunjong Lee, Daigo Yanagimoto, Ichiro Yasuda, Hiroshi Ogawa, and Cesar Villanoy
- Subjects
Medicine ,Science - Abstract
Abstract 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 Hakuho Maru cruise, KH-17-5-2, in November 2017. We found a turbulent kinetic energy dissipation rate exceeding O(10−7) W kg−1 and vertical eddy diffusivity exceeding O(10−3) m2 s−1, 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 a 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−2 d−1) and phosphate (0.33 mmol P m−2 d−1) fluxes estimated near the base of the surface chlorophyll a 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 a bloom north of Itbayat Island on the eastern ridge.
- Published
- 2020
- Full Text
- View/download PDF
3. High-Resolution Vertical Observations of Phytoplankton Groups Derived From an in-situ Fluorometer in the East China Sea and Tsushima Strait
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Qian Xu, Shengqiang Wang, Chiho Sukigara, Joaquim I. Goes, Helga do Rosario Gomes, Takeshi Matsuno, Yuanli Zhu, Yongjiu Xu, Jutarak Luang-on, Yuji Watanabe, Sinjae Yoo, and Joji Ishizaka
- Subjects
phytoplankton community ,in-situ fluorometer ,East China Sea ,Changjiang River diluted water ,Kuroshio ,Tsushima Strait ,Science ,General. Including nature conservation, geographical distribution ,QH1-199.5 - Abstract
Vertical distribution of phytoplankton composition in the East China Sea (ECS) and Tsushima Strait (TS) was highly variable in the region where the Changjiang River diluted water (CDW), Kuroshio water (KW), and Tsushima water (TW) intersected. An in-situ multiple excitation fluorometer was used to obtain the high-resolution phytoplankton groups data from every meter of the water column. Sharp differences were noted in the distribution of phytoplankton groups in the CDW, KW, and TW. In the CDW, brown algae were generally present ~60% of all depths with exception of subsurface chlorophyll-a maximum (SCM), whereas cyanobacteria (>40%) and green algae plus cryptophytes (>40%) were found above and below the SCM, respectively. In TW, where chlorophyll a (CHL) was lower than in the CDW, brown algae predominated the water column (>60%) and SCM (>80%), except the surface layer where cyanobacteria dominated. In KW, a high fraction of cyanobacteria (>40%) extended up to 40 m, while brown and green algae dominated (>60%) the deeper waters below 40 m at western and eastern stations, respectively. These results can be further related to water property and nutrient concentration of the water masses in each region. This new data show that the in-situ multiple excitation fluorometer can be a powerful tool to estimate high-resolution vertical profiles of phytoplankton groups on a large scale in marine environments.
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- 2022
- Full Text
- View/download PDF
4. Internal Hydraulic Transition and Turbulent Mixing Observed in the Kuroshio over the I-Lan Ridge off Northeastern Taiwan
- Author
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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, and Xinyu Guo
- Subjects
Oceanography - 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−1) and unsteady (±0.5 m s−1) 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 Kρ is concentrated from O(10−4) to O(10−3) m2 s−1 and has a maximum value of 10 m2 s−1. The sill on the western flank of the Kuroshio is a hotspot for energetic mixing of Kuroshio waters and South China Sea waters.
- Published
- 2022
5. Interannual changes in summer phytoplankton community composition in relation to water mass variability in the East China Sea
- Author
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Qian Xu, Chiho Sukigara, Joaquim I. Goes, Helga do Rosario Gomes, Yuanli Zhu, Shengqiang Wang, Anglu Shen, Elígio de Raús Maúre, Takeshi Matsuno, Watanabe Yuji, Sinjae Yoo, and Joji Ishizaka
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- 2018
- Full Text
- View/download PDF
6. 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
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Siteng Justin Zhu, Jing Zhang, Takeshi Matsuno, Eisuke Tsutsumi, Shota Kambayashi, Keiji Horikawa, Katsumi Takayama, Mutsuo Inoue, and Seiya Nagao
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Geophysics ,Space and Planetary Science ,Geochemistry and Petrology ,Earth and Planetary Sciences (miscellaneous) ,Oceanography - Published
- 2023
7. Cutaneous adenomyoepithelioma with histopathological heterogeneity: A case report
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Hirotake Nishimura, Takuya Moriya, Takeshi Matsuno, and Tatsushi Shiomi
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Mixed tumor ,Pathology ,medicine.medical_specialty ,Myoepithelioma ,business.industry ,Adenomyoepithelioma ,Adenoid cystic carcinoma ,Myoepithelial cell ,General Medicine ,medicine.disease ,Pathology and Forensic Medicine ,Metastasis ,medicine ,Atypia ,business ,Apocrine Hidrocystoma - Abstract
Some skin adnexal tumors display both epithelial and myoepithelial cell populations and can be broadly categorized as biphasic tumors. These include apocrine hidrocystoma, mixed tumor, adenomyoepithelioma (AME), and adenoid cystic carcinoma (ACC). Myoepithelioma is the myoepithelial cell-predominant type in this category. Cutaneous AME is exceedingly rare and usually has a benign prognosis, but it is considered to have the potential for local recurrence and metastasis. We report the case of a 57-year-old man with a 1-year history of an ulcerated nodule on his scalp. Microscopically, it was a defined cutaneous nodule with a focal lobulated architecture, composed of epithelial cells forming ducts and myoepithelial cells distributed around the ducts. In addition to these findings of typical AME, the present case focally revealed atypical features, such as increased mitotic activity (7/10 high power fields), invasive growth, and necrosis. However, cytological atypia was not significant. We conclusively diagnosed cutaneous AME with atypical features, suggesting malignant potential. Moreover, areas showing appearances similar to apocrine hidrocystoma, mixed tumor, myoepithelioma, and ACC were focally observed. We present a unique case of cutaneous AME exhibiting histopathological heterogeneity. The recognition of morphological variation could be helpful in appropriately diagnosing and treating AME of the skin.
- Published
- 2021
8. Internal waves with high vertical wavenumber structure generated by diurnal tidal flow over the eastern ridge of Luzon Strait
- Author
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Takahiro Endoh, Akie Sakai, Tomoharu Senjyu, Eisuke Tsutsumi, and Takeshi Matsuno
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Physics::Fluid Dynamics ,Superposition principle ,Acoustic Doppler current profiler ,Zonal flow ,Flow (psychology) ,Ridge (meteorology) ,Wavenumber ,Zonal and meridional ,Geophysics ,Internal wave ,Oceanography ,Geology ,Physics::Geophysics - Abstract
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 ~ 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.
- Published
- 2021
9. The Kuroshio flowing over seamounts and associated submesoscale flows drive 100-km-wide 100-1000-fold enhancement of turbulence
- Author
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Ayako Nishina, Daisuke Hasegawa, Takeyoshi Nagai, Tomoharu Senjyu, Amit Tandon, Takeshi Matsuno, Eisuke Tsutsumi, Hirohiko Nakamura, Takahiro Endoh, and Ryuichiro Inoue
- Subjects
沖縄トラフ・トカラ海峡で高鉛直波数近慣性波シアと乱流が卓越するメカニズム ,geography ,二台同時自由落下曳航観測手法を用いたマルチスケール混合現象とその影響に関する研究 ,QE1-996.5 ,geography.geographical_feature_category ,Resolving multi-scale mixing processes and their impacts using a twin tow-yo microstructure profiling system ,Turbulence ,Seamount ,Geology ,Fold (geology) ,Dissipation ,Vorticity ,科学研究費研究成果 ,黒潮源流が陸棚縁で生成する近慣性内部波と躍層における鉛直混合メカニズムの解明 ,Atmospheric sciences ,Environmental sciences ,Orders of magnitude (time) ,Mechanisms of dominant vertical high wavenumber near inertial shear and strong turbulence in the Okinawa Trough and the Tokara Strait ,Negative potential ,General Earth and Planetary Sciences ,GE1-350 ,Near-inertial wave generations and diapycnal mixing in the Kuroshio origin regions near the continental shelf ,Mixing (physics) ,General Environmental Science - Abstract
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.
- Published
- 2021
10. Phytoplankton growth and consumption by microzooplankton stimulated by turbulent nitrate flux suggest rapid trophic transfer in the oligotrophic Kuroshio
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Eisuke Tsutsumi, Gen Kume, Taiga Honma, Takeyoshi Nagai, Toru Kobari, Fukutaro Karu, Takahiro Tanaka, Naoki Yoshie, Xinyu Guo, Koji Suzuki, Ayako Nishina, Takeru Kanayama, Daisuke Hasegawa, Hirohiko Nakamura, and Takeshi Matsuno
- Subjects
0106 biological sciences ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,fungi ,lcsh:QE1-996.5 ,Foraging ,lcsh:Life ,Plankton ,01 natural sciences ,lcsh:Geology ,lcsh:QH501-531 ,Oceanography ,Nutrient ,Productivity (ecology) ,Eddy ,lcsh:QH540-549.5 ,Phytoplankton ,Environmental science ,Photic zone ,lcsh:Ecology ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Trophic level - 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.
- Published
- 2020
11. Significance of nutrients in oxygen-depleted bottom waters via various origins on the mid-outer shelf of the East China Sea during summer
- Author
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Qian Liu, Jing Zhang, Huijun He, Li Ma, Huanxin Li, Siteng Zhu, and Takeshi Matsuno
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Oxygen ,China ,Environmental Engineering ,Rivers ,Water ,Environmental Chemistry ,Nutrients ,Estuaries ,Pollution ,Waste Management and Disposal - Abstract
East China Sea (ECS) is considered one of the largest dissolved oxygen (DO) depleted areas in the world's oceans. To assess the relative importance of water sources and biological processes to modulate low DO water over the ECS shelf, we conducted 7 cruises in the summers between 2004 and 2015. To cover a broad study area, observations were taken by both Chinese and Japanese research vessels in 2013, the consistent DO values were obtained in the intercalibration station from China and Japan. The subsurface/bottom water DO depletion was observed over both the inner and mid-outer shelves. In 2009 and 2013, the low DO (3-4.2 mg L
- Published
- 2022
12. Intrusion of Kuroshio water onto the continental shelf of the East China Sea
- Author
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Lee, Joon-Soo and Takeshi, Matsuno
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- 2007
- Full Text
- View/download PDF
13. Vertical fluxes of nutrients enhanced by strong turbulence and phytoplankton bloom around the ocean ridge in the Luzon Strait
- Author
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Sachihiko Itoh, Ichiro Yasuda, Cesar L. Villanoy, Keunjong Lee, Tomoharu Senjyu, Takeshi Matsuno, Jing Zhang, Eisuke Tsutsumi, Akie Sakai, Daigo Yanagimoto, and Hiroshi Ogawa
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Chlorophyll a ,010504 meteorology & atmospheric sciences ,Science ,01 natural sciences ,Article ,chemistry.chemical_compound ,Photic zone ,Surface layer ,0105 earth and related environmental sciences ,Marine biology ,geography ,Multidisciplinary ,geography.geographical_feature_category ,010505 oceanography ,Physical oceanography ,Mid-ocean ridge ,New production ,Oceanography ,Ocean sciences ,chemistry ,Ridge ,Turbulence kinetic energy ,Environmental science ,Medicine ,Bloom - Abstract
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 Hakuho Maru cruise, KH-17-5-2, in November 2017. We found a turbulent kinetic energy dissipation rate exceeding O(10−7) W kg−1 and vertical eddy diffusivity exceeding O(10−3) m2 s−1, 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 a 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−2 d−1) and phosphate (0.33 mmol P m−2 d−1) fluxes estimated near the base of the surface chlorophyll a 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 a bloom north of Itbayat Island on the eastern ridge.
- Published
- 2020
14. The Changing East China Sea—A Physical View
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Takeshi Matsuno
- Subjects
Sea surface temperature ,Discharge ,Climatology ,Global warming ,Environmental science ,Surface water ,Sea level ,China sea - Abstract
Long-term trends, along with various time-scale variations in the physical properties, in the East China Sea (ECS) are summarized. Long-term variations in sea surface temperature (SST) shows a clear trend after the year 1900 with a 1.2 °C per century variation. However, it includes relatively shorter interannual to multi-decadal time-scale variations. The SST increase rate is more distinct in winter than in summer. The Kuroshio is the most dominant oceanographic feature in the ECS, and it exhibits long-term variations. The Kuroshio volume transport in the PN section located in the central ECS, is known to have a slight long-term increase in 55 years after 1955. The expansion of Changjiang Diluted Water also shows long-term variations associated with climate indices caused by not only the amount of river discharge but also the movement of surface water driven by wind fields in the ECS. One of the symbolic factors related to global warming is sea level, and clear long-term variations in the sea level are found in the ECS, whereas the vertical land motion is noted using tide-gauge data. The long-term variation in the sea level is significantly correlated with climate indices particularly with the relatively regional wind fields.
- Published
- 2020
15. Estimating propagation speed and direction, and vertical displacement of second-mode nonlinear internal waves from ADCP measurements
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Takahiro Endoh, Eisuke Tsutsumi, Chang-Su Hong, Gyu-Nam Baek, Ming-Huei Chang, Yiing Jang Yang, Takeshi Matsuno, and Jae Hak Lee
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Geology ,Aquatic Science ,Oceanography - Published
- 2022
16. Water mass analysis and contribution estimation using heavy rare earth elements: Significance of Kuroshio intermediate water to Central East China Sea shelf water
- Author
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Takeshi Matsuno, Jing Zhang, Qian Liu, and Li-li Bai
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Water mass ,010504 meteorology & atmospheric sciences ,Temperature salinity diagrams ,Soil science ,General Chemistry ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Bottom water ,Salinity ,Water column ,Environmental Chemistry ,Potential temperature ,Environmental science ,Hydrography ,Surface water ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
The East China Sea (ECS) has complicated water masses, in which it is difficult to clarify the various sources solely by estimating the potential temperature (PT) and salinity. High-nutrient bottom water was identified on the central ECS shelf. The pattern of heavy rare earth elements (HREEs) suggested the important contribution of Kuroshio intermediate water (KIW) in this bottom water. HREEs combined with hydrographic and chemical parameters indicated that the bottom water is a mixture of KIW, Kuroshio tropical water (KTW), and mixed shelf water (MSW). The mixing ratios of these three water sources estimated by four HREEs are comparable with the results calculated by PT and salinity. Then, PT and salinity are combined with HREEs to quantify the mixing of four water masses (KTW, MSW, KIW, and Kuroshio surface water) in the entire water column on the central shelf of the ECS. Our results indicate that the high amounts of nutrients at 130 m (bottom) on the ECS middle shelf mainly originate from the 400–600-m depth of KIW and the 150–300-m depth of KTW. The fractional nutrient concentration from the KIW in the bottom water yielded NO 3 + NO2: 63 ± 23% and P: 62 ± 22%, suggesting the significance of the KIW's material transport to the central ECS shelf. This study demonstrates that HREEs, in combination with conventional temperature and salinity, effectively increase the number of available tracers so that water mass analysis can be done with more robust results achieved.
- Published
- 2018
17. Interannual changes in summer phytoplankton community composition in relation to water mass variability in the East China Sea
- Author
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Yuanli Zhu, Qian Xu, Joji Ishizaka, Sinjae Yoo, Takeshi Matsuno, Eligio de Raus Maure, Shengqiang Wang, Joaquim I. Goes, Helga do Rosario Gomes, Chiho Sukigara, Watanabe Yuji, and Anglu Shen
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Water mass ,education.field_of_study ,010504 meteorology & atmospheric sciences ,010505 oceanography ,fungi ,Population ,Prochlorophytes ,Oceanography ,01 natural sciences ,Nutrient ,Phytoplankton ,Upwelling ,Environmental science ,Hydrography ,education ,Surface water ,0105 earth and related environmental sciences - Abstract
The surface distribution of the phytoplankton community was investigated in July 2009, 2010, 2011, and 2013 on the mid-shelf of the East China Sea (ECS), which is under the influence of Changjiang River Diluted Water (CDW) and the Kuroshio Current. This study, based on a CHEMTAX analysis of phytoplankton pigments, revealed a predominance of cyanobacteria and prochlorophytes in the eastern ECS, which is perennially under the influence of oligotrophic Kuroshio Surface Water. Towards the west, on the mid-shelf of the ECS, the composition of the phytoplankton community varied from year to year. Diatoms dominated in 2009 and 2013, when dissolved inorganic phosphate (DIP) concentrations were higher than during 2010 and 2011. During the latter two years, characterized as high-nitrate years, a mixed population of cyanobacteria, chlorophytes, and other groups was observed. Cluster analysis based on the phytoplankton community composition together with a PCA of shipboard hydrographic and nutrient data for all four years helped to confirm that the summer phytoplankton community structure of the ECS was regulated by the mixing of water masses and the variability of nutrient ratios within the CDW as it moved offshore. Our results show that elevated DIP concentrations in the CDW favor the growth of diatoms and dinoflagellates. The primary pathway for DIP inputs appears to be the upwelling of high-phosphate subsurface waters along the coast of China.
- Published
- 2018
18. Development of a thin diatom layer observed in a stratified embayment in Japan
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Goh Onitsuka, Katsunori Kimoto, Kei Yufu, Takeshi Matsuno, K. Abe, Takahisa Tokunaga, Yutaka Yoshikawa, and Tomoyuki Shikata
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0106 biological sciences ,Chlorophyll a ,education.field_of_study ,Pycnocline ,010504 meteorology & atmospheric sciences ,biology ,010604 marine biology & hydrobiology ,Population ,Chaetoceros ,Oceanography ,biology.organism_classification ,Atmospheric sciences ,01 natural sciences ,chemistry.chemical_compound ,Diatom ,chemistry ,Turbulence kinetic energy ,Phytoplankton ,Environmental science ,education ,Layer (electronics) ,0105 earth and related environmental sciences - Abstract
The temporal evolution of a thin phytoplankton layer was observed by field measurements using a research vessel and mooring instruments in the Yatsushiro Sea, a semi-enclosed narrow embayment in Japan, in early August 2013. The subsurface chlorophyll maximum developed into a thin layer within 2 days just below the pycnocline at around 10-m depth, where turbulent mixing (the dissipation rate of turbulent kinetic energy) was weak (low). The layer persisted for 1.5 to 2 days and declined after irradiance drastically decreased at the sea surface. At the peak period, the layer thickness, which is defined as the full-width at half-maximum of the peak in chlorophyll a concentration, ranged from 0.6 to 1.4 m, and the maximum concentration reached 42.3 mg m−3. The horizontal extent of the layer was approximately 10 km along the longitudinal axis of the bay. The phytoplankton population characterized by the layer was dominated by a chain-forming centric diatom, Chaetoceros spp. The formation mechanisms of the thin diatom layer were investigated using the observed data and a vertical one-dimensional model that includes physical and biological processes. The results suggest that the development of the thin layer was caused by in situ growth and aggregation due to nutrient-dependent sinking of the species under weak turbulence. The study highlights that continuous multidisciplinary observations and understanding species-specific physiological responses to environmental variations are necessary to elucidate drastically fluctuating phytoplankton dynamics in a coastal water.
- Published
- 2018
19. Impacts of the Changjiang diluted water on sinking processes of particulate organic matters in the East China Sea
- Author
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Joji Ishizaka, Yoshihisa Mino, Takeshi Matsuno, S. C. Tripathy, and Chiho Sukigara
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0106 biological sciences ,Chlorophyll a ,Pycnocline ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,chemistry.chemical_element ,Biological pump ,Geology ,Aquatic Science ,Particulates ,Oceanography ,01 natural sciences ,Nitrogen ,chemistry.chemical_compound ,chemistry ,Sediment trap ,Environmental science ,Photic zone ,Surface layer ,0105 earth and related environmental sciences - Abstract
Intensive surveys with repeated CTD and microstructure turbulent observations, water and sediments sampling as well as onboard incubation and sediment trap experiments were conducted to reveal the nitrogen budget in the center of the East China Sea (ECS) during July 2010 and 2011. Low salinity water (Changjiang Diluted Water, CDW) covered the study area in 2010, but not in 2011. Higher chlorophyll a (chl. a ) concentration, primary productivity, and downward particle flux in the upper layer were observed in 2010 than those in 2011. Existence of the CDW resulted in a steep pycnocline and an associated subsurface chl. a maximum (SCM) layer directly beneath the CDW. From chemical analyses of particulate carbon and nitrogen contents and isotope ratios, it became apparent that the particles sunk out the euphotic zone in 2010 was primarily originated in the CDW layer and secondly in the SCM layer. Whereas, in 2011, sinking particles were originated in the surface layer but a part of them were decomposed in the bottom of pycnocline. Our findings indicate that the CDW would supply particles into the deep layer and contribute to the downward transport of materials and the efficiency of biological pump in the ECS.
- Published
- 2017
20. Relationship between light, community composition and the electron requirement for carbon fixation in natural phytoplankton
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Joaquim I. Goes, Shengqiang Wang, Yuanli Zhu, S. C. Tripathy, Joji Ishizaka, Takeshi Matsuno, Chiho Sukigara, and David J. Suggett
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0106 biological sciences ,Electron transfer rate ,010504 meteorology & atmospheric sciences ,Ecology ,Quantum requirement ,010604 marine biology & hydrobiology ,Carbon fixation ,Aquatic Science ,Biology ,01 natural sciences ,Natural (archaeology) ,Marine Biology & Hydrobiology ,Community composition ,Phytoplankton composition ,Fast repetition rate fluorometry ,Phytoplankton ,Primary productivity ,ETR ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Fast repetition rate fluorometry (FRRF) provides a means to examine primary productivity at high resolution across broad scales, but must be coupled with independent knowledge of the electron requirement for carbon uptake (KC) to convert FRRF-measured electron transfer rate (ETR) to an inorganic carbon (C) uptake rate. Previous studies have demonstrated that variability of KC can be explained by key environmental factors (e.g. light, nutrients, temperature). However, how such reconciliation of KC reflects changes of phytoplankton physiological status versus that of community composition has not been well resolved. Therefore, using a dataset of coupled FRRF and C uptake measurements, we examined how the environmental dependency of KC potentially varied with parallel changes in phytoplankton community structure. Data were combined from 14 campaigns conducted during the summer season throughout 2007 to 2014 in the East China Sea (ECS) and Tsushima Strait (TS). KC varied considerably, but this variability was best explained by a linear relationship with light availability (R^2 = 0.66). Co-variability between KC and light availability was slightly improved by considering data as 2 clusters of physico-chemical conditions (R^2 = 0.74), but was best improved as 2 taxonomic clusters: samples dominated by micro-phytoplankton (>20 µm) versus small phytoplankton (nano + pico, ファイル公開:2018-09-29
- Published
- 2017
21. Turbulent mixing within the <scp>K</scp> uroshio in the <scp>T</scp> okara <scp>S</scp> trait
- Author
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Tomoharu Senjyu, Eisuke Tsutsumi, Xinyu Guo, Takeshi Matsuno, Hirohiko Nakamura, and Ren-Chieh Lien
- Subjects
geography ,Turbulent mixing ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,010505 oceanography ,Hydraulics ,Advection ,Seamount ,Geophysics ,Oceanography ,01 natural sciences ,law.invention ,Eddy diffusion ,Shear (geology) ,Space and Planetary Science ,Geochemistry and Petrology ,law ,Earth and Planetary Sciences (miscellaneous) ,Crest ,Diffusion (business) ,Geology ,0105 earth and related environmental sciences - Abstract
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 Kρ ∼ O(10−3)–O(10−2) m2 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) m2 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) m2 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.
- Published
- 2017
22. A role of vertical mixing on nutrient supply into the subsurface chlorophyll maximum in the shelf region of the East China Sea
- Author
-
Chiho Sukigara, Takeshi Matsuno, Keunjong Lee, Shigenobu Takeda, Yuanli Zhu, Joji Ishizaka, and Takahiro Endoh
- Subjects
0106 biological sciences ,Pycnocline ,010504 meteorology & atmospheric sciences ,Turbulence ,010604 marine biology & hydrobiology ,Halocline ,Geology ,Soil science ,Aquatic Science ,Oceanography ,Saline water ,01 natural sciences ,Dilution ,chemistry.chemical_compound ,Nutrient ,chemistry ,Chlorophyll ,Environmental science ,Photic zone ,0105 earth and related environmental sciences - Abstract
In summer, Changjiang Diluted Water (CDW) expands over the shelf region of the northern East China Sea. Dilution of the low salinity water could be caused by vertical mixing through the halocline. Vertical mixing through the pycnocline can transport not only saline water, but also high nutrient water from deeper layers to the surface euphotic zone. It is therefore very important to quantitatively evaluate the vertical mixing to understand the process of primary production in the CDW region. We conducted extensive measurements in the region during the period 2009–2011. Detailed investigations of the relative relationship between the subsurface chlorophyll maximum (SCM) and the nitracline suggested that there were two patterns relating to the N/P ratio. Comparing the depths of the nitracline and SCM, it was found that the SCM was usually located from 20 to 40 m and just above the nitracline, where the N/P ratio within the nitracline was below 15, whereas it was located from 10 to 30 m and within the nitracline, where the N/P ratio was above 20. The large value of the N/P ratio in the latter case suggests the influence of CDW. Turbulence measurements showed that the vertical flux of nutrients with vertical mixing was large (small) where the N/P ratio was small (large). A comparison with a time series of primary production revealed a consistency with the pattern of snapshot measurements, suggesting that the nutrient supply from the lower layer contributes considerably to the maintenance of SCM.
- Published
- 2017
23. Synaptic distribution of individually labeled mitral cells in the external plexiform layer of the mouse olfactory bulb
- Author
-
Kazunori Toida, Takeshi Matsuno, and Emi Kiyokage
- Subjects
0301 basic medicine ,Olfactory system ,biology ,Gephyrin ,General Neuroscience ,Dendrite ,law.invention ,Olfactory bulb ,Synapse ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,medicine.anatomical_structure ,nervous system ,law ,Postsynaptic potential ,biology.protein ,Biophysics ,medicine ,Electron microscope ,Neuroscience ,030217 neurology & neurosurgery ,Parvalbumin - Abstract
Mitral cells are the major projection neurons of the olfactory bulb. They receive olfactory inputs, regulate information, and project their axons to the olfactory cortex. To understand output regulation of mitral cells better, we established a method to visualize individual projection neurons and quantitatively examined their synaptic distribution. Individual mitral cells were labeled by viral injection, reconstructed three dimensionally with light microscopy, and serial sectioned for electron microscopy. Synaptic distributions were analyzed in electron microscopically reconstructed cell bodies, two regions of secondary dendrites (near the somata and ∼200 μm from the somata), and primary dendrites. The ratio of presynaptic sites (60%) and reciprocal synapses (60% presynaptic and 80% postsynaptic sites) were similar in each region. Characteristically, primary dendrite synapses were distributed mainly within the inner half of the external plexiform layer (EPL). For comparison, tufted cells were also examined, and the synaptic distribution in two secondary dendrite regions, which corresponded with mitral cells, was analyzed. The results showed that the ratio of reciprocal synapses (80% presynaptic and 90% postsynaptic sites) was greater than in mitral cells. The distribution of symmetrical synapses was also analyzed with synaptic and neuronal markers, such as parvalbumin, vesicular gamma-aminobutyric acid transporter, and gephyrin. Parvalbumin-expressing neurons tended to form synapses on secondary dendrites near the somata and were more uniformly distributed on primary dendrites of mitral cells. These results indicate that local mitral cell synaptic circuits are formed in accordance with their functional roles and restricted to the inner half of the EPL. J. Comp. Neurol. 525:1633-1648, 2017. © 2016 Wiley Periodicals, Inc.
- Published
- 2017
24. Supplementary material to 'Phytoplankton productivity and rapid trophic transfer to microzooplankton stimulated by turbulent nitrate flux in oligotrophic Kuroshio Current'
- Author
-
Toru Kobari, Taiga Honma, Daisuke Hasegawa, Naoki Yoshie, Eisuke Tsutumi, Takeshi Matsuno, Takeyoshi Nagai, Takeru Kanayama, Fukutaro Karu, Koji Suzuki, Takahiro Tanaka, Xinyu Guo, Gen Kume, Ayako Nishina, and Hirohiko Nakamura
- Published
- 2019
25. Phytoplankton productivity and rapid trophic transfer to microzooplankton stimulated by turbulent nitrate flux in oligotrophic Kuroshio Current
- Author
-
Eisuke Tsutumi, Naoki Yoshie, Hirohiko Nakamura, Takeshi Matsuno, Daisuke Hasegawa, Xinyu Guo, Ayako Nishina, Takeru Kanayama, Takahiro Tanaka, Takeyoshi Nagai, Fukutaro Karu, Toru Kobari, Koji Suzuki, Gen Kume, and Taiga Honma
- Subjects
Oceanography ,010504 meteorology & atmospheric sciences ,Productivity (ecology) ,Eddy ,Advection ,Phytoplankton ,Front (oceanography) ,Environmental science ,Photic zone ,Plankton ,01 natural sciences ,0105 earth and related environmental sciences ,Trophic level - Abstract
The Kuroshio Current has been thought to be biologically unproductive due to oligotrophic conditions and low plankton standing stocks. Nevertheless, major foraging fishes are known to grow and recruit around the Kuroshio Current. While mixing and advection supplying nutrients to the euphotic zone are happened by eddies and meanders but limited at the Kuroshio front, there is a risk that survival of vulnerable life stages is encountered under the low food availability. Here we report that phytoplankton productivity is stimulated by turbulent nitrate flux amplified with the Kuroshio Current and rapidly transferred to microzooplankton through their grazing. Oceanographic observations demonstrate that the Kuroshio Current topographically enhances significant turbulent mixing and nitrate influx to the euphotic zone. Gradual nutrient enrichment experiments show growth rates of phytoplankton and microzooplankton communities stimulated within a range of the turbulent nitrate flux. Dilution experiments imply a significant microzooplankton grazing on phytoplankton. We propose that these rapid and systematic trophodynamics enhance invisible biological productivity in the Kuroshio.
- Published
- 2019
26. How a Small Reef in the Kuroshio Cultivates the Ocean
- Author
-
T. Tanaka, Tomoharu Senjyu, Toru Kobari, Daisuke Hasegawa, Ayako Nishina, Hirohiko Nakamura, Naoki Yoshie, Takeshi Matsuno, Takeyoshi Nagai, Eisuke Tsutsumi, Takahiro Endoh, and Xinyu Guo
- Subjects
geography ,geography.geographical_feature_category ,Turbulent mixing ,Nitrate flux ,the Kuroshio Current ,Kelvin Helmholtz instability ,Flow separation ,upwelling ,Geophysics ,Oceanography ,turbulent mixing ,flow separation ,General Earth and Planetary Sciences ,Upwelling ,Reef ,Geology ,nitrate flux - Abstract
[Abstract] / 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 m^2 s^−1), resulting in strong nitrate fluxes of O(1–10^3 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(10^2 mmol m^−2 day^−1) in the entire subsurface layer. / / [Plain Language Summary] / Vertical nitrate fluxes associated with flow-topography interactions around a small reef in the Kuroshio Current are quantified using state-of-the-art oceanographic instruments. When the flow passes over a shallow sill on the flank of the reef, the velocity differences between layers intensify, resulting in a substantial vertical overturning and mixing of the water column. This turbulent mixing causes the observed nitrate flux from deep water to reach a value among the highest observed worldwide. / / [Key Points] / • Flow separations and trains of Kelvin-Helmholtz billows mix the water column around a small reef in the Kuroshio / • Doming of isopycnals/nitraclines suggests strong upwelling in the lee of the reef / • Turbulent nitrate fluxes reach up to O(10^3 mmol m^−2 day^−1)
- Published
- 2021
27. Ocean Mixing.
- Author
-
Takeshi Matsuno, Hao Wei, Jae Hak Lee, and Chuanjie Wei
- Subjects
OCEANIC mixing ,OCEANOGRAPHY ,TURBULENT mixing ,ENERGY dissipation - Published
- 2021
28. Observational evidence for tidal straining over a sloping continental shelf
- Author
-
Takahiro Endoh, Takeshi Matsuno, Yutaka Yoshikawa, Keun Jong Lee, Yoshinobu Wakata, and Lars Umlauf
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Density gradient ,010505 oceanography ,Advection ,Turbulence ,Continental shelf ,Stratification (water) ,Geology ,Geophysics ,Aquatic Science ,Oceanography ,01 natural sciences ,Physics::Geophysics ,Boundary layer ,Acoustic Doppler current profiler ,Diurnal cycle ,Astrophysics::Earth and Planetary Astrophysics ,Geomorphology ,0105 earth and related environmental sciences - Abstract
Straining of a horizontal density gradient by tidal currents acts to periodically produce and destroy near-bottom stratification, which has been shown to modulate turbulence in the bottom boundary layer (BBL). Previous observations of such periodic variations have been limited to the coastal ocean and estuaries, where horizontal density gradients are maintained by river runoff or differential heating. In the present study, we show evidence for the existence of tidal straining over the continental shelf, outside any regions of freshwater influence, where horizontal density gradients are likely to result from the projection of the interior vertical stratification onto sloping topography. Based on microstructure data obtained in the East China Sea, we demonstrate that the tidal current shear interacting with the cross-isobath density gradient results in semidiurnal switching between unstable and stable stratification in the lower part of the BBL. The cycle of turbulent dissipation is quarter-diurnal, corresponding to the semidiurnal variation of tidal current shear. In addition, a noticeable diurnal modulation in stratification as well as a significant diurnal cycle of turbulent dissipation are observed in the upper part of the BBL, where the time evolution of stratification is dominated by tidal advection, rather than tidal straining.
- Published
- 2016
29. Temporal variations of volume transport through the Taiwan Strait, as identified by three-year measurements
- Author
-
Dong Jiing Doong, Kaoru Ichikawa, Yih Yang, Takeshi Matsuno, Ken-ichi Fukudome, Cho-Teng Liu, Hsien Wen Chen, and Wei Ling Tsai
- Subjects
0106 biological sciences ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,Wind stress ,Geology ,Aquatic Science ,Seasonality ,Oceanography ,medicine.disease ,01 natural sciences ,Current (stream) ,Acoustic Doppler current profiler ,Volume (thermodynamics) ,Climatology ,Typhoon ,medicine ,Sea level ,0105 earth and related environmental sciences ,China sea - Abstract
The water characteristics of the East China Sea depend on influxes from river run-off, the Kuroshio, and the Taiwan Strait. A three-year observation using an acoustic Doppler current profiler (ADCP) operated on a ferry provides the first nearly continuous data set concerning the seasonal flow pattern and the volume transport from the Taiwan Strait to the East China Sea. The observed volume transport shows strong seasonality and linkage to the along-strait wind stress. An empirical regression formula between the volume transport and wind was derived to fill the gaps of observation so as to obtain a continuous data set. Based on this unique data set, the three-year mean of monthly volume transport is northeastward throughout the year, large (nearly 3 Sv) in summer and low (nearly zero) in winter. The China Coastal Current flows southward in winter, while the northward-flowing Taiwan Strait Current may reverse direction during severe northeasterly winds in the winter or under typhoons. The sea level difference across Taiwan Strait is closely correlated to the transport through the strait, and their relation is found seasonally nearly stable.
- Published
- 2016
30. Development of Disk Type Underwater Glider for Virtual Mooring
- Author
-
Yasuhiro Morii, Yuzuru Ito, Kenichi Shimizu, Masahiko Nakamura, Nobuhiro Yamawaki, Wataru Koterayama, Takeshi Matsuno, and Joshiro Noda
- Subjects
Engineering ,business.industry ,business - Published
- 2016
31. Mesoscale Eddies Control the Timing of Spring Phytoplankton Blooms: A Case Study in the Japan Sea
- Author
-
Hidenori Aiki, Chiho Sukigara, Eligio de Raus Maure, Joji Ishizaka, Hiroyuki Tomita, Yoshihisa Mino, Helga do Rosario Gomes, Takeshi Matsuno, and Joaquim I. Goes
- Subjects
0106 biological sciences ,Chlorophyll a ,010504 meteorology & atmospheric sciences ,010604 marine biology & hydrobiology ,Mesoscale meteorology ,Spring bloom ,01 natural sciences ,Algal bloom ,chemistry.chemical_compound ,Geophysics ,Oceanography ,Eddy ,chemistry ,Anticyclone ,Phytoplankton ,General Earth and Planetary Sciences ,Bloom ,Geology ,0105 earth and related environmental sciences - Abstract
Satellite Chlorophyll a (CHL) data was used to investigate the influence of mesoscale anticyclonic eddies (AEs) and cyclonic eddies (CEs) on the timing of spring phytoplankton bloom initiation around the Yamato Basin (133-139° E and 35-39.5° N) in the Japan Sea, for the period 2002-2011. The results showed significant differences between AEs and CEs in the timing and initiation mechanism of the spring phytoplankton bloom. Blooms were initiated earlier in CEs which were characterized by shallow mixed-layer depths ( 100 m) but close to the commencement of positive Q0. This suggests that the relaxation of turbulent mixing is crucial for the bloom initiation in AEs.
- Published
- 2017
32. Formation of the well-mixed homogeneous layer in the bottom water of the Japan Sea
- Author
-
Takeshi Matsuno, Takahiro Endoh, Toshiyuki Hibiya, Tomoharu Senjyu, and Michio Watanabe
- Subjects
Bottom water ,Oceanography ,Turbulence ,Geothermal heating ,Stratification (water) ,Potential temperature ,Mineralogy ,Structural basin ,Microstructure ,Geology ,Seabed - Abstract
The deep and bottom waters of the Japan Sea (depth ≳ 1000 m) are characterized by low temperature and weak stratification. In the Japan Basin, especially, the bottom water (depth ≳ 2500 m), called the Japan Sea bottom water (JSBW), with a thickness of over 1000 m, is mostly homogeneous. Several studies in recent decades have suggested that the potential temperature of the JSBW is gradually increasing, even though the thick homogeneous vertical structure is being maintained. Although downward mixing of heat from the upper layer was believed to be responsible for this characteristic feature, our microstructure measurements found that the intensity of turbulence in the JSBW is too weak to explain the formation of the gradually warming thick homogeneous layer. By use of a one-dimensional numerical model we demonstrated that this characteristic feature of the JSBW can be reasonably explained on the basis of a combination of geothermal heating from the seabed and an appropriate horizontal supply of cold water to the bottom layer.
- Published
- 2015
33. Japanese research activities for Asian marine science - 25 years of WESTPAC
- Author
-
Kentaro Ando, Akihiko Morimoto, Akihiro Seta, Shuhei Nishida, Kazuhiro Kitazawa, Yutaka Michida, Teruhisa Komatsu, Toshiyuki Suzuki, Takeshi Matsuno, Hiroshi Ohno, Yasuwo Fukuyo, Mitsuo Uematsu, and Mitsunori Iwataki
- Subjects
Oceanography ,Geography - Published
- 2015
34. Influence of the Changjiang River on the light absorption properties of phytoplankton from the East China Sea
- Author
-
S. C. Tripathy, H. Yamaguchi, Joji Ishizaka, Y. J. Xu, Takeshi Matsuno, Yoshihisa Mino, Sinjae Yoo, Y. Watanabe, Shengqiang Wang, and M. Hayashi
- Subjects
Chlorophyll a ,Chemistry ,lcsh:QE1-996.5 ,fungi ,lcsh:Life ,Pigment composition ,Plankton ,Cell size ,lcsh:Geology ,lcsh:QH501-531 ,chemistry.chemical_compound ,Oceanography ,lcsh:QH540-549.5 ,Environmental chemistry ,Phytoplankton ,lcsh:Ecology ,Absorption (electromagnetic radiation) ,Ecology, Evolution, Behavior and Systematics ,Changjiang river ,Earth-Surface Processes ,China sea - Abstract
Phytoplankton light absorption properties were investigated at the surface and subsurface chlorophyll a maximum (SCM) layer in the East China Sea (ECS), a marginal sea which is strongly influenced by the Changjiang discharge in summer. Results from ECS were compared with those from the Tsushima Strait (TS) where the influence of Changjiang discharge is less. The probable controlling factors, packaging effect (cell size) and pigment composition of total chlorophyll a (Tchl a)-specific absorption coefficient (aph*(λ)) were examined by the corresponding measurements of pigments identified by high-performance liquid chromatography. We observed distinct phytoplankton size structure and thereby absorption properties between ECS and TS. At the surface, mixed populations of micro-, nano- and pico-phytoplankton were recorded in ECS while pico-phytoplankton dominated in TS, generating a lower average aph*(λ) in ECS than in TS. Within SCM, average aph*(λ) was higher in ECS than in TS because of the dominance of nano- and micro-phytoplankton in ECS and TS, respectively. By pooling surface and SCM samples, we found regular trends in phytoplankton size-fraction versus Tchl a; and correlations between aph*(λ) and Tchl a consistent with previous observations for the global ocean in TS but not in ECS. In ECS phytoplankton size-fraction was not correlated with Tchl a, which consequently caused poor relationships between aph*(λ) and Tchl a. The abnormal values mainly originated from the surface low-salinity waters and SCM waters beneath them. At high Tchl a, aph*(λ) of these samples was substantially higher compared to the values in TS and from the global regressions, which was attributable to the lower micro-phytoplankton fraction, and higher nano- and/or pico-phytoplankton fractions in ECS. These observations indicated that the distinct light absorption properties of phytoplankton in ECS were possibly influenced by the Changjiang discharge. Our findings imply that general bio-optical algorithms proposed based on the correlations between aph*(λ) and Tchl a or the patterns in size-fraction versus Tchl a are not applicable in ECS, and need to be carefully considered when using these general algorithms in river-influenced regions.
- Published
- 2014
35. Observations of external, internal tidal currents and associated turbulent mixing around the Isahaya bay mouth, Ariake Sea
- Author
-
Eisuke Tsutsumi and Takeshi Matsuno
- Subjects
Turbulent mixing ,Oceanography ,Bay ,Tidal current ,Geology - Published
- 2014
36. Estimates of the turbulent kinetic energy budget in the oceanic convective boundary layer
- Author
-
Takahiro Endoh, Yutaka Yoshikawa, Eisuke Tsutsumi, and Takeshi Matsuno
- Subjects
geography ,geography.geographical_feature_category ,Meteorology ,Continental shelf ,Dissipation ,Oceanography ,Residual ,Atmospheric sciences ,Lower half ,Convective Boundary Layer ,Turbulence kinetic energy ,Physics::Atmospheric and Oceanic Physics ,Geology ,Vertical shear ,China sea - Abstract
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.
- Published
- 2014
37. Tidal and low-frequency currents along the CK Line (31 deg 45 min N) over the East China Sea shelf
- Author
-
Kou Nishiuchi, Yutaka Yoshikawa, Toru Hasegawa, Hiroshi Yoshimura, Taku Wagawa, Kazumaro Okamura, Takeshi Matsuno, and Yasuhiro Morii
- Subjects
Baroclinity ,Geology ,Aquatic Science ,Low frequency ,Oceanography ,Geodesy ,Current (stream) ,Amplitude ,Barotropic fluid ,Aquatic science ,Line (formation) ,China sea - Abstract
The bottom-mounted and ship-mounted ADCP velocities were analyzed to quantify tidal and low-frequency currents between 124.0 deg E and 128.5 deg E over the CK line (31 deg 45 min N) in the East China Sea shelf. The bottom-mounted ADCP, deployed in summer and autumn at station 1 (127 deg 25 min E) or station 2 (125 deg 30 min E), reveals relatively large ( ≃ 0.2 m s − 1 ) mean currents to the north or northwest at station 1 and a small ( ≤ 0.03 m s − 1 ) eastward current at station 2, as well as large tidal currents whose major axis amplitude amounts to 0.25 m s − 1 at station 1 and 0.5 m s − 1 at station 2. The bottom-mounted ADCP velocities were used to correct the tidal harmonic coefficients of the NAO.99Jb model under the assumption of uniform correction coefficients. The corrected coefficients were then used to remove the tidal currents in the ship-mounted ADCP velocity obtained over the whole CK-line. The detided ship-mounted ADCP velocities, which agree well with the bottom-mounted ADCP velocities at stations 1 and 2, show a more detailed spatial structure of the low-frequency current and its seasonal variations. The overall structure is characterized by a large northward/northwestward current in the eastern part and a small eastward current in the western part. The northward/northwestward current is largest ( 0.24 m s − 1 ) and most baroclinic in summer, while it becomes weakest ( 0.11 m s − 1 ) and most barotropic in winter. The zonal position of the boundary between the northward/northwestward current and the eastward current changes seasonally.
- Published
- 2012
38. Variation of the photosynthetic electron transfer rate and electron requirement for daily net carbon fixation in Ariake Bay, Japan
- Author
-
Shengqiang Wang, Joji Ishizaka, Yoshihisa Mino, S. C. Tripathy, Yuanli Zhu, David J. Suggett, and Takeshi Matsuno
- Subjects
0106 biological sciences ,010504 meteorology & atmospheric sciences ,Meteorology ,010604 marine biology & hydrobiology ,Carbon fixation ,Primary production ,FRR fluorometry ,Atmospheric sciences ,Photosynthesis ,Oceanography ,01 natural sciences ,13C-uptake ,Electron transfer rate ,Productivity (ecology) ,Photosynthetically active radiation ,Primary productivity ,Environmental science ,Quantum requirement for carbon fixation ,Bay ,ETR ,0105 earth and related environmental sciences - Abstract
Fast repetition rate fluorometry (FRRf) provides a potential means to examine marine primary productivity; however, FRRf-based productivity estimations require knowledge of the electron requirement (K) for carbon (C) uptake (K C) to scale an electron transfer rate (ETR) to the CO2 uptake rate. Most previous studies have derived K C from parallel measurements of ETR and CO2 uptake over relatively short incubations, with few from longer-term daily-integrated periods. Here we determined K C by comparing depth-specific, daily ETRs and CO2-uptake rates obtained from 24-h on-deck incubation experiments undertaken on seven cruises in Ariake Bay, Japan, from 2008 to 2010. The purpose of this study was to determine the extent of variability of K C and to what extent this variability could be reconciled with the prevailing environmental conditions and ultimately to develop a method for determining net primary productivity (NPP) based on FRRf measurements. Both daily ETR and K C of the upper layer varied considerably, from 0.5 to 115.7 mmol e− mg Chl-a −1 day−1 and 4.1–26.6 mol e− (mol C)−1, respectively, throughout the entire data set. Multivariate analysis revealed a strong correlation between daily photosynthetically active radiation (PAR) and K C (r 2 = 0.94). A simple PAR-dependent relationship derived from the data set was used for generating K C, and this relationship was validated by comparing the FRRf-predicted NPP with the 13C uptake measured in 2007. These new observations demonstrate the potential application of FRRf for estimating regional NPP from ETR.
- Published
- 2016
39. Observations of turbulence under weakly and highly stratified conditions in the Ariake Sea
- Author
-
Eisuke Tsutsumi and Takeshi Matsuno
- Subjects
Physics::Fluid Dynamics ,Boundary layer ,Acoustic Doppler current profiler ,Richardson number ,Turbulence ,Turbulence kinetic energy ,Shear stress ,Stratification (water) ,Geophysics ,Mechanics ,Oceanography ,Geology ,Law of the wall - Abstract
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), e, 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.
- Published
- 2012
40. Recent progress in Pacific-Asian Marginal Seas (PAMS) studies
- Author
-
Jing Zhang, Dongliang Yuan, Naoki Hirose, Dake Chen, Yang-Ki Cho, Sen Jan, Takeshi Matsuno, and Chin-Chang Hung
- Subjects
Geology ,Aquatic Science ,Oceanography - Published
- 2017
41. INFLUENCE OF INSTALLATION-DAMAGE LEVEL ON TENSILE CREEP PROPERTIES OF HDPE GEOGRID
- Author
-
Takeshi Matsuno, Daiki Hirakawa, and Yoshihisa Miyata
- Subjects
Materials science ,Creep ,Ultimate tensile strength ,Geotechnical engineering ,High-density polyethylene ,Geogrid - Published
- 2011
42. EFFECTS OF INSTALLATION-DAMAGE LEVEL ON TENSILE STRENGTH PROPERTIES OF HDPE GEOGRID
- Author
-
Daiki Hirakawa, Yoshihisa Miyata, and Takeshi Matsuno
- Subjects
Materials science ,Ultimate tensile strength ,High-density polyethylene ,Composite material ,Geogrid - Abstract
粒状土中にHDPEジオグリッドを配置し締固め荷重を与えることで準備した損傷供試体の引張り強度特性を調べた.損傷レベルをレーザ変位計で測定した供試体の表面粗度をもとに評価した.引張り試験における供試体のひずみ解析には画像解析技術を用いた.損傷レベルがHDPEジオグリッドの引張強度特性の及ぼす影響を統計的に考察した.本研究の成果はジオグリッドの設計引張強さの評価法の合理化に貢献する.
- Published
- 2010
43. Two-Way Particle-Tracking Model for Specifying Sources of Drifting Objects: Application to the East China Sea Shelf
- Author
-
Takeshi Matsuno, Shin'ichiro Kako, Atsuhiko Isobe, and Pil Hun Chang
- Subjects
Atmospheric Science ,Meteorology ,Position (vector) ,Ocean current ,Particle ,Ocean Engineering ,Point (geometry) ,Observer (special relativity) ,Hydrography ,Geodesy ,Ellipse ,Geology ,Standard deviation - Abstract
The two-way Lagrangian particle-tracking model (PTM) is proposed for specifying sources of objects drifting with random-walk processes on the sea surface. First, to determine object source candidates, modeled particles are released from the point (hereafter, “receptor”) where an observer finds the objects using a backward-in-time PTM with modeled ocean currents of which directions are reversed in sign. Second, the modeled particles are released from these source candidates in a forward-in-time PTM using ocean currents originally computed in hydrographic models. Third, the source candidates are considered to be reliable at a 5% significance level if the observed receptor is located inside the ellipse whose center is the mean position of the modeled particles at the time when the observer found the objects and whose axis length is twice the standard deviation computed using all modeled particle positions. The two-way PTM experiments are carried out in a realistic hydrographic model over the East China Sea shelf for the period from June through August 2004. Statistically significant sources are well specified close to the true source because 58%–90% of source candidates are rejected in the experiments.
- Published
- 2009
44. Short-term temperature and salinity variations in the Tsushima Strait in 2004: Behavior of the surface low-salinity water in the strait
- Author
-
Takeshi Matsuno, Tomoharu Senjyu, Kosuke Mori, In Seong Han, and Naoki Hirose
- Subjects
Current (stream) ,Salinity ,geography ,Water mass ,Acoustic Doppler current profiler ,Oceanography ,geography.geographical_feature_category ,Temperature salinity diagrams ,Environmental science ,Surface layer ,Saline water ,Channel (geography) - Abstract
Temporal variations in temperature and salinity observed in 2004 were investigated on a short time scale in the Tsushima Strait. The data were obtained by long-term in situ measurements at Mitsushima and Futaoi Island using an instrument equipped with a piston-type wiper to avoid biofouling. In addition, the temperature and salinity values of the surface layer obtained by a commercial ferryboat between Hakata and Busan were used to investigate their spatiotemporal variations. Temperature and salinity variations with a time scale of several days had a negative correlation in the summer. This evidence suggests that a warm and less saline water mass, which is considered to be mainly the Changjiang Diluted Water (CDW), flowed intermittently through the Tsushima Strait in summer. In late July 2004, a large low-salinity water mass was detected in the Tsushima Strait. At that time, the freshwater transport through the Tsushima Strait transiently reached about 12 × 104 m3s−1, which is estimated from observed acoustic Doppler current profiler (ADCP) data along a ferryboat line and inferred salinity profiles. This estimated value is more than double the maximum of the climatological monthly mean of the Changjiang discharge. Furthermore, salinity and surface current data obtained by high frequency ocean radar (HF radar) indicate that water properties at Mitsushima may occasionally represent part of the water flowing through the western channel via a countercurrent, although Mitsushima is geographically located in the eastern channel.
- Published
- 2009
45. Observations of wind-driven deepening of the surface mixing layer in the Tsushima strait
- Author
-
Yasuto Tatsuyama, Takeshi Matsuno, Joji Ishizaka, Takahiro Endoh, and Yutaka Yoshikawa
- Subjects
Drifter ,Acoustic Doppler current profiler ,Meteorology ,Advection ,Turbulence ,Turbulence kinetic energy ,Dissipation ,Oceanography ,Atmospheric sciences ,Potential energy ,Physics::Atmospheric and Oceanic Physics ,Linear equation ,Geology - Abstract
A detailed description of wind-driven deepening of the mixing layer in the Tsushima strait is given by combining current data from the acoustic Doppler current profiler (ADCP) attached to a satellite-tracked surface drifter, with microstructure data from the Turbulence Ocean Microstructure Acquisition Profiler (TurboMAP) deployed from a ship following the surface drifter. By collecting data in a Lagrangian manner we attempted to minimize the effect of horizontal advection. The dissipation rate of turbulent kinetic energy (TKE), ɛ, was measured directly using the TurboMAP, whereas the production rate of TKE, P, was estimated from horizontal velocities obtained using the ADCP based on the one-dimensional linear equation of motion. The TKE budget in the mixing layer is examined by applying the integrated TKE equation to the observed data. The sum of the temporal change of potential energy, shear production, dissipation, TKE flux, and the surface buoyancy flux terms changes dramatically with time, indicating the importance of the temporal change of TKE in the deepening process on a time scale shorter than one day, which is neglected in widely used bulk mixedlayer models.
- Published
- 2009
46. Intrusion of Kuroshio water onto the continental shelf of the East China Sea
- Author
-
Takeshi Matsuno and Joon Soo Lee
- Subjects
Fundamental study ,geography ,Intrusion ,geography.geographical_feature_category ,Oceanography ,Continental shelf ,Climatology ,Geology ,China sea - Abstract
As a fundamental study to evaluate the contribution of the Kuroshio to primary production in the East China Sea (ECS), we investigated the seasonal pattern of the intrusion from the Kuroshio onto the continental shelf of the ECS and the behavior of the intruded Kuroshio water, using the RIAM Ocean Model (RIAMOM). The total intruded volume transport across the 200m isobath line was evaluated as 2.74 Sv in winter and 2.47 Sv in summer, while the intruded transport below 80m was estimated to be 1.32 Sv in winter and 1.64 Sv in summer. Passive tracer experiments revealed that the main intrusion from the Kuroshio to the shelf area of the ECS, shallower than 80m, takes place through the lower layer northeast of Taiwan in summer, with a volume transport of 0.19 Sv. Comparative studies show several components affecting the intrusion of the Kuroshio across the 200 m isobath line. The Kuroshio water intruded less onto the shelf compared with a case without consideration of tide-induced bottom friction, especially northeast of Taiwan. The variations of the transport from the Taiwan Strait and the east of Taiwan have considerable effects on the intrusion of the Kuroshio onto the shelf.
- Published
- 2007
47. Interannual salinity variations in the Tsushima Strait and its relation to the Changjiang discharge
- Author
-
Sigeaki Matsui, Takeshi Matsuno, Hirofumi Enomoto, and Tomoharu Senjyu
- Subjects
Salinity ,Low salinity ,Oceanography ,Mode (statistics) ,Environmental science ,Wind stress ,Negative correlation ,Hydrography ,China sea ,Communication channel - Abstract
Interannual salinity variations in the Tsushima Strait are investigated on the basis of historical hydrographic data. The EOF analysis revealed that the most dominant mode is the in-phase salinity variation between the eastern and western channels. The time coefficients of the EOF first mode in summer show a negative correlation with the Changjiang discharge, which indicates that salinity in the Tsushima Strait tends to decrease over summer, related to a large discharge of the Changjiang. The eigenvectors of the first mode are larger in the eastern channel than those in the western channel, though the low salinity water mainly flows through the western channel. This is because the low salinity water spreads into the eastern channel as well as the western channel over summers with a large discharge of the Changjiang. The out-of-phase salinity variation between the channels is extracted as the EOF second mode; this is the predominant variation in the western channel. The time coefficients of the second mode in summer show no significant correlations to the volume transports through the western channel and the transport differences between channels. A relationship between the EOF second mode and variations in the wind stress over the East China Sea is suggested.
- Published
- 2006
48. Phytoplankton productivity and rapid trophic transfer to microzooplankton stimulated by turbulent nitrate flux in oligotrophic Kuroshio Current.
- Author
-
Toru Kobari, Taiga Honma, Daisuke Hasegawa, Naoki Yoshie, Eisuke Tsutumi, Takeshi Matsuno, Takeyoshi Nagai, Takeru Kanayama, Fukutaro Karu, Koji Suzuki, Takahiro Tanaka, Xinyu Guo, Gen Kume, Ayako Nishina, and Hirohiko Nakamura
- Subjects
EDDY flux ,KUROSHIO ,EUPHOTIC zone ,OCEANOGRAPHIC observations ,ZOOPLANKTON ,TURBULENT mixing ,MARINE zooplankton ,MESOSCALE eddies - Abstract
The Kuroshio Current has been thought to be biologically unproductive due to oligotrophic conditions and low plankton standing stocks. Nevertheless, major foraging fishes are known to grow and recruit around the Kuroshio Current. While mixing and advection supplying nutrients to the euphotic zone are happened by eddies and meanders but limited at the Kuroshio front, there is a risk that survival of vulnerable life stages is encountered under the low food availability. Here we report that phytoplankton productivity is stimulated by turbulent nitrate flux amplified with the Kuroshio Current and rapidly transferred to microzooplankton through their grazing. Oceanographic observations demonstrate that the Kuroshio Current topographically enhances significant turbulent mixing and nitrate influx to the euphotic zone. Gradual nutrient enrichment experiments show growth rates of phytoplankton and microzooplankton communities stimulated within a range of the turbulent nitrate flux. Dilution experiments imply a significant microzooplankton grazing on phytoplankton. We propose that these rapid and systematic trophodynamics enhance invisible biological productivity in the Kuroshio. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
49. Measurements of the Turbulent Energy Dissipation Rate around the Shelf Break in the East China Sea
- Author
-
Manabu Shimizu, Hideaki Nishida, Takeshi Matsuno, Yasuhiro Morii, and Yasuaki Takaki
- Subjects
geography ,Buoyancy ,geography.geographical_feature_category ,Mixed layer ,Continental shelf ,Internal wave ,engineering.material ,Oceanography ,Eddy diffusion ,Physics::Fluid Dynamics ,Shear (geology) ,engineering ,Maxima ,Geomorphology ,Thermocline ,Physics::Atmospheric and Oceanic Physics ,Geology - Abstract
Using the micro-structure profiler, TurboMAP, large values for the turbulent energy dissipation rate e were found just above the bottom of the shelf and around the thermocline near the continental shelf break in the East China Sea. The values found above the bottom are produced by the bottom stress due to tidal currents, resulting in a distinct bottom mixed layer where the vertical eddy diffusivity Kz is also large. Distinct maxima in the values of e detected around the thermocline are located at the depth of the fine-scale shear maxima detected with the moored ADCP. The vertical profiles of e were compared with those of the current velocity, and it was found that the maxima in e appear to correspond to those of the shear with fine scale. The magnitude of the observed e coincided approximately with the e calculated from the fine-scale shear and the buoyancy frequency according to the parameterization proposed by Gregg (1989), if the large-scale mean shear caused by the Kuroshio is subtracted. However, it is not clear whether the parameterization for the internal wave fields in the open ocean is applicable to the estimation of e in the shelf break. Whereas the most predominant value of e was found just above the bottom and around the thermocline, the maxima of e could be found in the internal area. They could have been caused by the propagation of the vertically high wave number internal tides along the characteristic ray.
- Published
- 2005
50. Seasonal/Spatial Variations of the Near-Inertial Oscillations in the Deep Water of the Japan Sea
- Author
-
Tomoharu Senjyu, Takeshi Matsuno, and Kosuke Mori
- Subjects
geography ,geography.geographical_feature_category ,Ocean current ,Wind stress ,Structural basin ,Oceanography ,Annual cycle ,Inertial wave ,Physics::Geophysics ,Current (stream) ,Spring (hydrology) ,Surface layer ,Physics::Atmospheric and Oceanic Physics ,Geology - Abstract
A general description of the near-inertial oscillations in the deep water of the Japan Sea has been found by analyzing observed current data accumulated over a period of ten years. The near-inertial oscillations were dominant in the deep water, and those in the southern Japan Sea, the Tsushima current region, were more energetic than those in the northern area. Their temporal variations have an annual cycle with wintertime intensifications corresponding to the windy season over the Japan Sea. In the Yamato Basin, however, the power of the near-inertial oscillations was small during spring and large during summer, in addition to the above seasonal variations. The results of a slab model showed that the wind stress could account for part of the long periodic variations such as the annual cycle of the near-inertial oscillations in the deep water, but this is not expected to be their only source. Since the surface currents in the southern Japan Sea, especially in the Yamato Basin, vary significantly both temporally and spatially, the surface layer itself also could be responsible for the generation of the near-inertial oscillations in the deep water.
- Published
- 2005
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