Sep. 2022, 日本海洋学会賞・岡田賞, 沿岸域における混合過程と水理環境に関する研究
Japan society

Jan. 2021, 三陸海域研究論文知事表彰（岩手県知事賞）, 三陸沿岸域で発生する内部潮汐や関連する混合現象に関わる研究
Others

Jun. 2019, 第3回めぶきビジネスアワード 大学発イノベーション賞, 高精度海洋数値モデルと機械学習システムを用いた沿岸海域海況予測システムの提供, めぶきフィナンシャルグループ
増永英治
Publisher

Oct. 2018, Best Presentation Award (Oral), Mixing processes associated with hypoxia in Lake Kasumigaura, 17th World Lake Conference
Eiji Masunaga
International society

May 2017, 日本海洋学会奨励論文賞, 日本海洋学会
Official journal

〔Major achievements〕The Influence of Horizontal Dispersion on Residence Times in Shallow Lakes
Eiji Masunaga; Oliver B. Fringer; Tatsumi Kitamura; Takao Ouchi, Lead, Abstract

This study presents results of circulation and residence time in lakes influenced by wind‐induced mixing investigated with numerical simulations. The study area is Lake Kasumigaura, a continuous lake system primally consisting of two lakes, West Lake and North Lake. Although metrological conditions and depths are similar for both lakes, the surface area and shape of the lakes are very different. A numerical model resolves the primary features of the wind‐driven circulation in the lake system and is forced by observed river discharges and wind stress. A passive tracer released from the river mouths is used to estimate the residence time and evaluate mixing processes. Wind‐driven flow dominates the kinetic energy in the lakes and induces chaotic motions leading to tracer dispersion which is largely influenced by the shape of the lakes. Results indicate that the residence time is much longer in the well‐mixed middle basin of West Lake than North Lake. The estimated horizontal tracer diffusivity is approximately three times larger for the large West Lake than for the small‐narrow North Lake. This study suggests that the surface area and shape of lakes in which the flow is predominantly wind driven largely influences circulation, water exchange processes and residence times in lakes., American Geophysical Union (AGU)
Water Resources Research, 17 Feb. 2025, [Reviewed]

Turbulent mixing layers and associated diffusive fluxes across the epilimnion and metalimnion in stratified large Lake Biwa
Hikaru Homma; Eiji Masunaga; Ilia Ostrovsky; Hidekatsu Yamazaki, Abstract

Stratification and turbulent mixing have an immense impact on biogeochemical regimes and ecosystem dynamics in stratified large lakes. This study investigates the physical properties of the epi‐ and metalimnion of Lake Biwa (Japan), focusing on the persistent vertical diffusive fluxes due to turbulent mixing in the lower metalimnion and their effects on upward nitrate transport. We conducted 24‐h observations at an offshore station in the summer for three consecutive years to examine the temporal and vertical variations of stratification and turbulence. A mooring system provided long‐term data on stratification and current velocity, while thermal profiles along two offshore transects were collected to investigate lateral changes. Our findings revealed strong stratification in the upper metalimnion, where vertical diffusive fluxes were essentially suppressed. Distinct turbulent mixing layers were identified near the water surface and within the moderately stratified lower metalimnion. Field data and numerical model suggested that the turbulence in the lower metalimnion was driven by shear instability, straining, and/or wave–wave interactions linked with the persistent internal waves that occur even during weak winds. Vertical eddy diffusivity of > 10⁻⁵ m² s⁻¹ in the lower metalimnion was associated with rather strong turbulence, which has not been reported in other large lakes. The elevated turbulence resulted in an upward nitrate flux of 0.2 mmol N m⁻² d⁻¹ across the lower metalimnion, indicating that the upward nutrient transport could support primary productivity and play an important ecological role in deep stratified lakes., Wiley
Limnology and Oceanography, 2025, [Reviewed]

Eddy-covariance measurements of turbulent fluxes across the oxygen-depleted benthic layer in a shallow stratified lake
Yusuke Kawaguchi; Eiji Masunaga; Takao Ouchi; Tatsumi Kitamura; Eun Yae So
Limnology, Jan. 2025, [Reviewed]

遠州灘沿岸域における黒潮流路変動に伴う栄養塩輸送および表層一次生産の変 動特性について　　　　　　　　　　　　　　　
鯰江 岳; 内山雄介; 張 旭; 増永英治
土木学会論文集B2（海岸工学）, Nov. 2024, [Reviewed]

海岸地形に影響される浅水域における吹送流モニタリングと数値計算を用いた再現検証　　　　　　　　　　　　　　　
吉田 壮汰; 増永 英治; 北村 立実; 大内 孝雄, Corresponding
土木学会論文集(B2海岸工学), Nov. 2024, [Reviewed]

領域海洋モデル全域から放流した粒子追跡実験を用いた東日本南岸海域の物質輸送過程の評価　　　　　　　　　　　　　　　
佐近 淳平; 増永 英治; 内山 雄介, Corresponding
土木学会論文集(B2海岸工学), Nov. 2024, [Reviewed]

〔Major achievements〕Shoaling internal tides propagating from a shallow ridge modulated by the Kuroshio
Eiji Masuanga; Hitoshi Tamura; Yusuke Uchiyama, Lead
Journal of Geophysical Research: Oceans, Aug. 2024, [Reviewed]

〔Major achievements〕Numerical simulations of internal tide dynamics in a steep submarine canyon
Eiji Masunaga; Matthew H. Alford; Andrew J. Lucas; Andrea Rodriguez-Marin Freudmannb, Lead, American Meteorological Society
Journal of Physical Oceanography, Nov. 2023, [Reviewed]

粒子追跡モデルとドリフターデータを用いた日本海における物質輸送過程の研究　　　　　　　　　　　　　　　
原田 一宏,増永 英治,内山 雄介, Corresponding, 土木学会
土木学会論文集(B2海岸工学), Nov. 2023, [Reviewed]

傾圧と順圧的運動に関連する東京湾における運動エネルギーの評価　　　　　　　　　　　　　　　
渡邉 暦,到津 春樹,増永 英治, Corresponding, 土木学会
土木学会論文集（B2海岸工学）, Nov. 2023, [Reviewed]

沖合から伝播する内部潮汐の砕波による河川水の混合に関する研究　　　　　　　　　　　　　　　
門馬 宏典,増永 英治, Corresponding, 土木学会
土木学会論文集（B2海岸工学）, Nov. 2023, [Reviewed]

夏季の気象変化による成層の発達が及ぼす霞ヶ浦への影響の評価　　　　　　　　　　　　　　　
松本 大樹,増永 英治,横木 裕宗, Corresponding, 土木学会
土木学会論文集（G環境）, Sep. 2023, [Reviewed]

Effect of Oxygen Consumption by Bottom-Layer Water and Sediment on Formation of Hypoxic Water in Lake Kitaura　　　　　　　　　　　　　　　
北村 立実,増永 英治,鮎川和 泰,大内 孝雄,湯澤 美由紀,佐藤 和貴,清家 泰,福島 武彦, 水環境学会
水環境学会誌, Jul. 2023, [Reviewed]

〔Major achievements〕Vertical mixing and oxygen flux caused by daily sea breezes in a shallow stratified lake
Eiji Masunaga; Sachihiko Itoh; Tatsumi Kitamura, Lead
Limnology, Apr. 2023, [Reviewed]

沿岸域における混合過程と水理環境に関する研究：,内部潮汐と混合現象
増永英治, Lead, 日本海洋学会
海の研究（Oceanography in Japan）, Mar. 2023, [Reviewed], [Invited]

ASSESSMENT OF THE IMPACT OF STRATIFICATION DEVELOPMENT BY CLIMATE CHANGE DURING THE SUMMER SEASON IN LAKE KASUMIGAURA
Daiki MATSUMOTO; Eiji MASUNAGA; Hiromune YOKOKI, Japan Society of Civil Engineers
Japanese Journal of JSCE, 2023

領域海洋モデルを用いた洋上風力発電施設の適地選定システム開発に関する基礎的研究　　　　　　　　　　　　　　　
玉井 駿壮・内山 雄介・Xu Zhang・増永 英治・辻 一洋・山崎 秀勝
土木学会論文集（B2海岸工学）, Nov. 2022, [Reviewed]

複数定点観測データを用いた東京湾における水平物理構造と混合状態の評価　　　　　　　　　　　　　　　
到津 春樹・増永 英治, Last
土木学会論文集(B2海岸工学), Nov. 2022, [Reviewed]

沿岸地形が影響する風応力による鉛直混合の観測と評価　　　　　　　　　　　　　　　
佐藤 和貴・増永 英治・北村 立実, Corresponding
土木学会論文集(B2海岸工学), Nov. 2022, [Reviewed]

定常流，振動流及び密度成層を考慮した海洋構造物周辺の数値実験　　　　　　　　　　　　　　　
山﨑 彩花・増永 英治・内山 雄介・辻 一洋・山崎 秀勝, Corresponding
土木学会論文集（B1水工学）, Sep. 2022, [Reviewed]

Seasonal variability of upper ocean primary production along the Kuroshio off Japan: Roles of eddy-driven nutrient transport
Xu Zhang; Yusuke Uchiyama; Eiji Masunaga; Yota Suzue and Hidekatsu Yamazaki, We assessed spatial and seasonal variabilities of eddy-driven vertical nutrient fluxes, which are essential for maintaining primary production in the upper ocean. A climatological model based on a Regional Oceanic Modeling System (Regional Oceanic Modeling System) coupled with a Nutrient Phytoplankton Zooplankton and Detritus (NPZD) biogeochemical model at a submesoscale eddy-permitting resolution was used to investigate the mechanisms driving such variabilities around the Kuroshio, off the coast of Japan. The model realistically reproduced the spatial segmentations in primary production on both sides of the Kuroshio path with a higher chlorophyll-a concentration on the northern side than the southern side. In winter, downward eddy-induced nitrate flux is predominantly provoked in the upstream Kuroshio region (KR), while upward nitrate fluxes prevail in the downstream Kuroshio Extension (KE) region, due to both shear and baroclinic instabilities. Baroclinic instability plays a crucial role in inducing seasonal variability, leading to enhancement (reduction) of the eddy flux in winter (summer), particularly in regions away from the Kuroshio axis. Furthermore, we found that the influence of the Izu-Ogasawara Ridge, located in the KR, on regional dynamics and resultant spatial variability of the biogeochemical response are mostly confined in the KR. The Kuroshio is less turbulent in the upstream of the ridge, while it becomes unstable to shed mesoscale eddies in laterally wider and vertically deeper regions downstream. Consequently, although the near-surface nitrate concentration is lower downstream, the upward eddy-driven nitrate flux is more effective in maintaining active primary production due to the shear and baroclinic instabilities in winter., Frontiers Media SA
Frontiers in Marine Science, Aug. 2022, [Reviewed]

Seasonal cycle of the confluence of the Tsugaru Warm, Oyashio, and Kuroshio currents east of Japan
S. Itoh; E. Tsutsumi; E. Masunaga; T. T. Sakamoto; K. Ishikawa; D. Yanagimoto; Y.; Hoshiba; H. Kaneko; D. Hasegawa; K. Tanaka; H. Fukuda and T. Nagata, American Geophysical Union (AGU)
Journal of Geophysical Research: Oceans, Aug. 2022, [Reviewed]

〔Major achievements〕Modulation of submesoscale motions due to tides and a shallow ridge along the Kuroshio
Eiji Masunaga; Yusuke Uchiyama; Xu Zhang; Waku Kimura and Taichi Kosako, Lead, This study investigated submesoscale motions (SMs) and transport over the Izu-Ogasawara Ridge, located off mainland Japan, using a double-nested Regional Oceanic Modeling System (ROMS). Both the Kuroshio and tides largely influence physical processes in this area. The mean and submesoscale kinetic energies (MKE and SKE, respectively) were calculated using a horizontal Gaussian filter. Tidal forcing enhances SKE through Reynolds stress due to mean velocity shear (barotropic conversion); meanwhile, tides suppress the MKE and total kinetic energy. This implies that tidal forcing contributes to energy transfer from large-scale motions to smaller scales, which results in accelerated kinetic energy dissipation. Energy conversion from submesoscale potential energy to SKE (baroclinic conversion) is reduced by tidal forcing. In the summer, SKE is generated by barotropic conversion and suppressed by negative baroclinic conversion. On the other hand, in winter, SKE is enhanced by both barotropic and baroclinic conversions.
Deep Sea Research: Part I, Aug. 2022, [Reviewed]

自動昇降装置を用いた夏季における北浦の水温成層と貧酸素水塊の形成・消失およびリン溶出過程の検討　　　　　　　　　　　　　　　
北村 立実; 鮎川 和泰; 増永 英治; 小室 俊輔; 大内 孝雄; 湯澤 美由紀; 浅岡 大輝; 三上 育英; 清家 泰; 福島 武彦
水環境学会誌, Jun. 2022

〔Major achievements〕Variability of the diapycnal mixing coefficient in coastal oceans investigated with direct,microstructure measurements
Eiji Masunaga; Subhas K. Venayagamoorthy; Koyo Wada; Hidekatsu Yamazaki, Lead
Journal of Marine Systems, Mar. 2022, [Reviewed]

DEVELOPMENT OF AN EVALUATION SYSTEM FOR SUITABILITY OF OFFSHORE WIND FARM SITES AROUND JAPAN BASED ON A REGIONAL OCEAN CIRCULATION–BIOGEOCHEMICAL MODEL
Toshitake TAMAI; Yusuke UCHIYAMA; Xu ZHANG; Eiji MASUNAGA; Kazuhiro TSUJI; Hidekatsu YAMAZAKI, Japan Society of Civil Engineers
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 2022

粒子追跡モデルを用いた相模湾及び駿河湾周辺の物質輸送過程の解析　　　　　　　　　　　　　　　
井上孝義・増永英治・小硲大地・Xu Xhang・内山雄介, Corresponding
土木学会論文集(B2海岸工学), Nov. 2021, [Reviewed]

東京湾湾奥部における貧酸素水塊に関わる物理構造と混合状態　　　　　　　　　　　　　　　
到津春樹・増永英治, Last
土木学会論文集(B2海岸工学), Nov. 2021, [Reviewed]

領域海洋モデルを用いた黒潮・親潮混合水域における水塊分布に関する研究　　　　　　　　　　　　　　　
池田雅・増永英治・鈴江洋太・伊藤幸彦・内山雄介, Corresponding
土木学会論文集(B2海岸工学), Nov. 2021, [Reviewed]

北浦における貧酸素水塊の詳細分布と貧酸素水域面積の推計　　　　　　　　　　　　　　　
小室俊輔,北村立実,大内孝雄,増永英治,浅岡大輝,鮎川和泰,三上育英,清家泰,湯澤美由紀,福島武彦, 水環境学会
水環境学会誌, Sep. 2021, [Reviewed]

Diel vertical migration promotes zooplankton horizontal patchiness　　　　　　　　　　　　　　　
Bingzhang Chen; Eiji Masunaga; S. Lan Smith; Hidekatsu Yamazaki
Journal of Oceanography, Feb. 2021, [Reviewed]

MASS TRANSPORT TOWARD COASTAL REGIONS FROM THE KUROSHIO INVESTIGATED WITH A PARTICLE TRACKING MODEL
増永 英治; 木村 和久; 小硲 大地; 張 旭; 内山 雄介, Lead
土木学会論文集(B2海岸工学), Nov. 2020, [Reviewed]

TIME-SCALES OF WIND-INDUCED MIXING PROCESSES ASSOCIATED WITH THE TOPOGRAPHY AND STRATIFICATION　　　　　　　　　　　　　　　
浅岡 大輝; 増永 英治; 小室 俊輔; 北村 立実, Corresponding
土木学会論文集(B2海岸工学), Nov. 2020, [Reviewed]

〔Major achievements〕Baroclinic Residual Circulation and Mass Transport Due to Internal Tides
Eiji Masunaga; Robert S. Arthur; Hidekatsu Yamazaki, Lead
Journal of Geophysical Research: Oceans, Apr. 2020, [Reviewed]

〔Major achievements〕Stratification and mixing processes associated with hypoxia in a shallow lake (Lake Kasumigaura, Japan)　　　　　　　　　　　　　　　
Eiji Masunaga; Shunsuke Komuro, Lead
Limnology, Apr. 2020, [Reviewed]

MASS TRANSPORT TOWARD COASTAL REGIONS FROM THE KUROSHIO INVESTIGATED WITH A PARTICLE TRACKING MODEL
Eiji MASUNAGA; Waku KIMURA; Taichi KOSAKO; Xu ZHANG; Yusuke UCHIYAMA, Japan Society of Civil Engineers
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 2020, [Reviewed]

沿岸地形と風応力が形成する複雑な密度構造と混合状態の高精度計測　　　　　　　　　　　　　　　
増永英治; 浅岡 大輝; 小室 俊輔; 松本 俊一; 小野 正人; 番場 泰彰, Lead
土木学会論文集B2(海岸工学), Nov. 2019, [Reviewed]

Lagrange粒子追跡モデルを用いた伊豆諸島周辺海域の物質輸送及び拡散の評価
木村和久; 増永英治; 小硲大地; 内山雄介, Corresponding
土木学会論文集B2(海岸工学), Nov. 2019, [Reviewed]

TRANSPORT PROCESSES AROUND THE IZU-CHAIN ISLANDS INVESTIGATED WITH A LAGRANGIAN PARTICLE TRACKING MODEL
Waku KIMURA; Eiji MASUNAGA; Taichi KOSAKO; Yusuke UCHIYAMA, Japan Society of Civil Engineers
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 2019, [Reviewed]

Observation of three dimensional flow structures and effluent transport around fish cages using a towed ADCCP and free-fall multi-parameter profiler
Hidekatsu Yamazaki; Wataru Aoyama; Eiji Masunaga; Mamoru Tanaka
Aquaculture Research, 2019, [Reviewed]

〔Major achievements〕Strong internal waves generated by the interaction of the kuroshio and tides over a shallow ridge
Eiji Masunaga; Yusuke Uchiyama; Hidekatsu Yamazaki, © 2019 American Meteorological Society. The Kuroshio and tides significantly influence the oceanic environment off the Japanese mainland and promote mass/heat transport. However, the interaction between the Kuroshio and tides/internal waves has not been examined in previous works. To investigate this phenomenon, the two-dimensional high-resolution nonhydrostatic oceanic Stanford Unstructured Nonhydrostatic Terrain-Following Adaptive Navier–Stokes Simulator (SUNTANS) model was employed. The results show that strong internal tides propagating upstream in the Kuroshio are generated at a near-critical internal Froude number (Fri = 0.91). The upstream internal wave energy flux reaches a magnitude of 12 kW m-1, which is approximately 3 times higher than that of internal waves without the Kuroshio. On the other hand, under supercritical conditions, the Kuroshio suppresses the internal wave energy flux. The interaction of internal tides and the Kuroshio also generates upstream propagating high-frequency internal waves and solitary wave packets. The high-frequency internal waves contribute to the increase in the total internal wave energy flux up to 40% at the near-critical Fri value. The results of this study suggest that the interaction of internal tides and the Kuroshio enhances the upstream propagating internal tides under the specified conditions (Fri ~ 1), which may lead to deep ocean mixing and transport at significant distances from the internal wave generation sites.
Journal of Physical Oceanography, 2019, [Reviewed]

Mixing processes associated with hypoxia in Lake Kasumigaura　　　　　　　　　　　　　　　
Eiji Masunaga; Tomoko Ozawa., Lead
7th World Lake Conference proceedings, Oct. 2018, [Reviewed]

〔Major achievements〕Dynamics of Internal Tides Over a Shallow Ridge Investigated With a High-Resolution Downscaling Regional Ocean Model
Eiji Masunaga; Yusuke Uchiyama; Yota Suzue; Hidekatsu Yamazaki, ©2018. American Geophysical Union. All Rights Reserved. This study investigates the dynamics of tidally induced internal waves over a shallow ridge, the Izu-Ogasawara Ridge off the Japanese mainland, using a downscaled high-resolution regional ocean numerical model. Both the Kuroshio and tides contribute to the field of currents in the study area. The model results show strong internal tidal energy fluxes over the ridge, exceeding 3.5 kW m−1, which are higher than the fluxes along the Japanese mainland. The flux in the upstream side of the Kuroshio is enhanced by an interaction of internal waves and currents. The tidal forcing induces 92% of the total internal wave energy flux, exhibiting the considerable dominance of tides in internal waves. The tidal forcing enhances the kinetic energy, particularly in the northern area of the ridge where the Kuroshio Current is not a direct influence. The tidal forcing contributes to roughly 30% of the total kinetic energy in the study area.
Geophysical Research Letters, Apr. 2018, [Reviewed]

A three-dimensional numerical study of river plume mixing processes in Otsuchi Bay, Japan　　　　　　　　　　　　　　　
Sasmal; K.; Masunaga; E.; Webb; A.; Fringer; O. B.; Gross; E. S.; Rayson; M. D.; & Yamazaki; H.
Journal of Oceanography, 2018, [Reviewed]

Impacts of two super typhoons on the Kuroshio and marginal seas off the Pacific coast of Japan
HIroaki Tada; Yusuke Uchiyama; Eiji Masunaga, © 2017 Elsevier Ltd High-resolution downscaling ocean modeling was conducted to investigate the impacts of two super typhoons on the Kuroshio in the fall of 2014 off the Kyushu and Shikoku Islands, Japan. The model result was compared with field observations and satellite altimetry. The synoptic and mesoscale oceanic structures around the Kuroshio exhibit a good reproducibility. The typhoons generated near-inertial oscillations (NIOs) and near-inertial internal waves (NIIWs) around the Kuroshio path, particularly on the right side of the typhoon tracks. The NIOs developed in the mixed layer to alter the direction of the Kuroshio by ~30°. The associated velocity off the Shikoku and Kyushu Islands was significantly decelerated by ~0.2 ms−1. The velocity almost vanished off Kyushu Island and thus induced an unstable fluctuating path shortly after both typhoons passed over that region. The NIIWs were also excited at the thermocline, resulting in the oscillation of the Kuroshio path occurred in the entire water column. In contrast, off Shikoku Island, the typhoons shifted the Kuroshio path northward to enhance the interactions with the topographies. This shift caused considerable eddy shedding from the capes that resulted in mesoscale counterclockwise circulations as cyclonic quasi-standing eddies with a shedding period of ~3 days in the north of the Kuroshio path. The magnitude, direction, and meridional location of the path of the Kuroshio prominently fluctuated with the propagation of these eddies, manifested off Shikoku Island. Furthermore, these eddies induced sporadic northward intrusions of the Kuroshio warm water through the Kii Channel into the Seto Inland Sea (SIS), where a weak but persisting southward outflow prevails under normal conditions. Therefore, the process could collectively be called the “typhoon-Kuroshio-eddy interaction” which conceptually differs from the “typhoon-eddy-Kuroshio interaction” in the previous studies, where the Kuroshio was modulated by eddy collision. The wind stress curl and intrusions associated with the typhoons jointly provoked the inversion of the counterclockwise SIS residual circulation. The resultant spatially averaged volume flux was ~8 times as high as that under normal conditions.
Deep-Sea Res. Part I, 2018, [Reviewed]

複数気候モデルによる海面上昇に伴う浸水影響の不確実性評価　　　　　　　　　　　　　　　
土田 晃次郎; 田村 誠; 熊野 直子; 増永 英治; 横木 裕宗
土木学会論文集G（環境）, 2018, [Reviewed]

高解像度数値計算技術を用いた東京湾湾奥の物理構造の解明　　　　　　　　　　　　　　　
増永英治; 木村和久; 鯉渕幸夫, Lead
土木学会論文集B2（海岸工学）, 2018, [Reviewed]

珊瑚環礁内における流動構造と物質輸送過程の解明　　　　　　　　　　　　　　　
小池海; 増永英治; 横木裕宗, Corresponding
土木学会論文集B2(海岸工学), 2018, [Reviewed]

内部潮汐を考慮した伊豆大島周辺海域における潮流予測システムの開発と運用　　　　　　　　　　　　　　　
増永英治; 山崎秀勝; 山口邦久, Lead
土木学会論文集B2(海岸工学), 2018, [Reviewed]

〔Major achievements〕Dynamics and Energetics of Trapped Diurnal Internal Kelvin Waves around a Midlatitude Island
Eiji Masunaga; Oliver B. Fringer; Yujiro Kitade; Hidekatsu Yamazaki; Scott M. Gallager, The generation of trapped and radiating internal tides around Izu-Oshima Island located off Sagami Bay, Japan, is investigated using the three-dimensional Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier-Stokes Simulator (SUNTANS) that is validated with observations of isotherm displacements in shallow water. The model is forced by barotropic tides, which generate strong baroclinic internal tides in the study region. Model results showed that when diurnal K-1 barotropic tides dominate, resonance of a trapped internal Kelvin wave leads to large-amplitude internal tides in shallow waters on the coast. This resonance produces diurnal motions that are much stronger than the semidiurnal motions. The weaker, freely propagating, semidiurnal internal tides are generated on the western side of the island, where the M-2 internal tide beam angle matches the topographic slope. The internal wave energy flux due to the diurnal internal tides is much higher than that of the semidiurnal tides in the study region. Although the diurnal internal tide energy is trapped, this study shows that steepening of the Kelvin waves produces high-frequency internal tides that radiate from the island, thus acting as a mechanism to extract energy from the diurnal motions., AMER METEOROLOGICAL SOC
JOURNAL OF PHYSICAL OCEANOGRAPHY, Oct. 2017, [Reviewed]

〔Major achievements〕Sediment resuspension and the generation of intermediate nepheloid layers by shoaling internal bores　　　　　　　　　　　　　　　
Eiji Masunaga; Robert S. Arthur; Oliver B. Fringer and Hidekatsu Yamazaki, Lead
Journal of Marine Systems, Feb. 2017, [Reviewed]

日本における海面上昇への適応を目的とした防護費用の将来推計
熊野直子; 土田光次郎; 田村誠; 増永英治; 桑原祐史; 横木裕宗,  Sea level rise due to climate change may threaten those who live near the coastal area. It is important to examine the cost of coastal protection in the context of climate change and its adaptation. This paper constructed the database of installed cosatal protection around the world, and it tried to estimate the future cost of protection such as constructing new dykes and elevating them in Japan, baesd on SSP scenarios. It is feasble to install new dyke along the major coasts if the related budget keeps a certain level. However, the combination of constructing new dykes and elevating them enables us to cut down more protection cost., Japan Society of Civil Engineers
土木学会論文集B3（海洋開発）, 2017, [Reviewed]

RCP・SSPシナリオに基づく全球沿岸域での海面上昇による浸水影響評価
四栗瑞樹; 田村 誠; 熊野 直子; 増永 英治; 横木 裕宗, 土木学会
地球環境シンポジウム論文集, 2017, [Reviewed]

黒潮と内部波が影響する伊豆諸島周辺海域における流動場の解明
増永英治; 鈴江洋太; 内山雄介; 山崎秀勝, Lead,  Regional Oceanic Numerical simulations using ROMS with tidal forcing were conducted to investigate tidally induced internal waves (internal tides) in the vicinity of the Izu-chain Islands. The tides enhance the enrgy flux of internal waves by about 10 times as large around the islands. Therefore, in the study region, the internal waves are considerably enargized by the tidal forcing. Although the total and baroclinic components of kinetic eneygy increase due to the tides, the barotropic kinetic energy component decreased by the tidal forcing. The internal waves accompanied by strong baroclinic flows largely contribute to the flow compared to the currents due to winds and the Kuroshio. The numerical simulateons also revealed the enhanced eddy motiions due to the tidal forcing, suggesting that the tides contiribute to lateral mixing or transports via meso- and submesoscale eddies., 土木学会
土木学会論文集B2（海岸工学）, 2017, [Reviewed]

Coastal observation systems to monitor physical, chemical, and biological parameters
Hidekatsu Yamazaki; Eiji Masunaga; Scott Gallager; Mamoru Tanaka; Marika Takeuchi; Kazuo Amakasu; Hayato Kondo, We have developed a free-fall multi-parameter profiler (YODA Profiler) to measure various physical and biological parameters in coastal ocean. We found internal bores create a strong mixing event. Sediment resuspension is associated with the mixing event and also AZFP detected fish school at the front of bore. We have deployed a cable observatory system (Oshima Coastal Environment data Acquisition Network System, OCEANS) in a coastal area to monitor coastal ecosystem continuously. OCEANS can measure various physical, chemical and biological parameters simultaneously, and operates a plankton imaging system (Continuous Plankton Imaging and Classification System, CPICS). Based on acquired images of phytoplankton and zooplankton, we are investigating how planktonic biodiversity is affected by multi-scale physical processes, such as Kuroshio and internal waves. We are developing a technique to predict the biodiversity of plankton from three-dimensional hydrodynamic model using a newly developed plankton ecosystem model. We are also developing a AUV (MEMO-pen) that carries CPICS as well as microstructure profiler (TurboMAP) in order to simultaneously observe turbulence and plankton. We will introduce the most recent results from these observation systems., Acoustical Society of America (ASA)
Journal of the Acoustical Society of America, 01 Oct. 2016

〔Major achievements〕Strong turbulent mixing induced by internal bores interacting with internal tide-driven vertically sheared flow
Eiji Masunaga; Oliver B. Fringer; Hidekatsu Yamazaki; Kazuo Amakasu, We observed the formation of an internal bore interacting with the vertically sheared flow generated during the previous phase of the internal tide, which resulted in strong turbulent mixing. The rate of turbulent kinetic energy dissipation reached on the order of 10(-5)Wkg(-1) during the event. Numerical simulations reproduced the observed interaction of internal bores with the sheared flow and verified the hypothesized breaking and mixing mechanism. The numerical results indicated that the Iribarren number, or the ratio of the topographic slope to the internal wave slope, plays a major role in the mixing intensity and types of internal bores. It was found that waves with low Iribarren numbers lead to bores that interact with vertically sheared flows induced by the previous phase of the internal tide and are more likely to produce strong wave breaking and mixing., AMER GEOPHYSICAL UNION
GEOPHYSICAL RESEARCH LETTERS, Mar. 2016, [Reviewed]

〔Major achievements〕An observational and numerical study of river plume dynamics in Otsuchi Bay, Japan
Eiji Masunaga; Oliver B. Fringer; Hidekatsu Yamazaki, A newly developed tow-yo profiler (YODA Profiler) and a fully nonhydrostatic numerical model, SUNTANS, are used in this study to investigate river plume mixing in Otsuchi Bay, a ria estuary located in Iwate, Japan. Several field campaigns were conducted in the bay during early summer, late summer, and late winter. The YODA Profiler reveals fine features related to a shallow river plume that experiences rapid mixing events during the summer campaigns with a time scale of O(1) hour. These events coincide with strong baroclinic currents and large fluctuations in thermocline and pycnocline depths related to shoaling internal tides. The combined effects of wind stress and baroclinic flow appear to generate a strong shear near the surface layer and enhance mixing of the river plume, with typical eddy diffusivity values of O(10(-4)) m(2) s(-1). To investigate the physical mechanisms involved, numerical simulations are conducted with tidal and wind forcing. Analysis of tidal forcing mechanisms reveals that mixing near the river mouth (and upstream) is dominated by the barotropic tide, while turbulent mixing in the middle of the bay is significantly enhanced by the baroclinic internal tide. Wind forcing is also important for river plume dynamics; along-channel wind forcing mixes the river plume and transports it horizontally. Overall, this study suggests that all three forcing mechanisms (barotropic tide, baroclinic tide, and wind) are important for mixing processes of the river plume in Otsuchi Bay., SPRINGER
JOURNAL OF OCEANOGRAPHY, Feb. 2016

Development of Monitoring Technologies to Observe Plankton Ecosystem in Coastal Oceans　　　　　　　　　　　　　　　
Yamazaki; H.; E. Masunaga; H. Foloni-Neto; S. Gallager
Bulletin on Coastal Oceanography, Jan. 2016, [Reviewed]

〔Major achievements〕Mixing and sediment resuspension associated with internal bores in a shallow bay　　　　　　　　　　　　　　　
Masunaga; E.; H. Homma; H. Yamazaki; O. Fringer; T. Nagai; Y. Kitade and A. Okayasu, Lead
Continental Shelf Research, Sep. 2015, [Reviewed]

〔Major achievements〕A new tow-yo instrument to observe high-resolution coastal phenomena
Eiji Masunaga; Hidekatsu Yamazaki, Field observations in coastal and estuarine regions are important for studying physical and biological features. Recent studies have presented fine-scale physical features from numerical models and acoustic surveys. However, high spatial resolution data of physical structures are difficult to obtain, since the conventional CTD survey requires a stop-and-measure ship operation. To solve this issue, we have developed a new, portable tow-yo instrument, Yoing Ocean Data Acquisition Profiler (YODA Profiler), that continuously observes many vertical profiles of the fine-scale features in coastal regions. Using the YODA Profiler, we were able to rapidly obtain high-resolution data in a shallow estuary. The results showed fine-scale complicated internal wave features, upslope propagating fronts and a patchy distribution of phytoplankton. These observations are consistent with recent numerical models and acoustic surveys, as well as with the critical angle theory for internal wave reflections along a bottom slope. We have also developed a statistical technique to estimate the rate of turbulent kinetic energy dissipation, e, from the variance of dC/dz data. Using this technique we were able to estimate the turbulent kinetic energy dissipation rate associated with river outflow and internal waves in the river mouth. (C) 2013 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
JOURNAL OF MARINE SYSTEMS, Jan. 2014, [Reviewed]

Resuspension and lateral dispersal of sediments due to shoaling internal waves　　　　　　　　　　　　　　　
Masunaga; E.; H. Yamazaki; T. Nagai and O.; Fringer, Lead
IMBER newsletter, Dec. 2013, [Reviewed]

Internal Wave Breaking Dynamics and Associated Mixing in the Coastal Ocean, Encyclopedia of Ocean Science, Third Edition　　　　　　　　　　　　　　　
Eiji Masunaga; Robert S. Arthur; Oliver B. Fringer
Encyclopedia of Ocean Science, 3rd Edition, 2019, [Reviewed], [Invited]
Lead

Horizontal diffusion and resident time scale evaluated by a tracer dispersion model for Lake Kasumigaura　　　　　　　　　　　　　　　
Eiji Masunaga; Oliver B. Fringer
JpGU Meeting 2024, May 2024

Observations of vertical mixing structures in La Jolla Canyon off South California　　　　　　　　　　　　　　　
Eiji Masunaga; Matthew H. Alford
Ocean Science Meeting 2024, Feb. 2024

沿岸地形にトラップされた内部潮汐が引き起こす擬似的な M2順圧潮汐流(Quasi Barotropic Tides)　　　　　　　　　　　　　　　
増永 英治; Kevin Okun; Geno Pawlak
日本海洋学会 2023年度秋季大会, Sep. 2023

Dynamics of Internal Tides Generated by a Flow-tide Interaction Along the Kuroshio　　　　　　　　　　　　　　　
Eiji MASUNAGA; Hitoshi TAMURA; Yusuke UCHIYAMA
AOGS Meeting 2023, Aug. 2023

Internal tide dynamics and energy dissipation in La Jolla Canyon　　　　　　　　　　　　　　　
Eiji Masunaga; Matthew; H. Alford; Drew J. Lucas; Andrea RMF
JpGU Meeting 2023, May 2023

岡田賞受賞記念講演　　　　　　　　　　　　　　　
増永英治
2022年度日本海洋学会秋季大会, Sep. 2022, [Invited]

Observations of vertical mixing and associated transport in a shallow lake, Lake Kasumigaura, Japan　　　　　　　　　　　　　　　
Eiji Masunaga; Tastumi Kitamura; Sachihiko Itoh
JpGU Meeting 2022, May 2022, [Invited]

Circulation and water exchange in shallow lakes influenced by wind-induced mixing　　　　　　　　　　　　　　　
Eiji Masunaga Tatsumi Kitamura
JpGU Meeting 2022, May 2022

黒潮と潮汐が影響する伊豆小笠原海嶺北部における サブメソスケール渦と物質輸送　　　　　　　　　　　　　　　
増永英治,内山雄介,Xu Zhang,木村和久,小硲大地
2021年度日本海洋学会秋季大会, Sep. 2021, 日本海洋学会

Submeso-scale Eddies Generated in the Vicinity of the Izu-Ogasawara Ridge Investigated with aRegional Oceanic Simulator　　　　　　　　　　　　　　　
Eiji Masunaga; Xu Zhang; Yusuke Uchiyama
AOGS Meeting 2021, Aug. 2021

Vertical mixing and mass transport in a shallow lake, Lake Kasumigaura, Japan　　　　　　　　　　　　　　　
Eiji Masunaga; Tatsumi Kitamura; Sachihiko Itoh
JpGU Meeting 2021, Jun. 2021, JpGU

黒潮が影響する伊豆小笠原海嶺北部における　　　　　　　　　　　　　　　
増永 英治; 内山 雄介; 張 旭
日本海洋学会2020年度秋季大会, 26 Nov. 2020

霞ヶ浦での乱流混合過程について　　　　　　　　　　　　　　　
増永英治
海洋乱流に関する観測およびモデリング研究集会, 22 Oct. 2020

粒子追跡モデルを用いた黒潮から沿岸域への物質輸送過程の評価　　　　　　　　　　　　　　　
増永 英治; 木村 和久; 小硲 大地; 張 旭; 内山 雄介
海岸工学講演会, Oct. 2020

Observations of vertical mixing and sediment heat flux in a shallow lake　　　　　　　　　　　　　　　
Eiji Masunaga; Shunsuke Komuro; Tatsumi Kitamura
JpGU Meeting 2020, Jul. 2020

Uncertainty of the mixing coefficient investigated with microstructure surveys in coastal oceans　　　　　　　　　　　　　　　
Eiji Masunaga
Ocean Science Meeting 2020, Feb. 2020

三陸沿岸海域における多層水塊構造と乱流混合過程　　　　　　　　　　　　　　　
増永英治
日本海洋学会2019年度秋季大会, Sep. 2019

Mass and heat transport generated by the Kuroshio and tides investigated with a high resolution downscaled regional oceanic,model　　　　　　　　　　　　　　　
Eiji Masunaga
AOGS Meeting 2019, Aug. 2019

Mass and heat transport generated by the Kuroshio and tides investigated with a high resolution downscaled regional oceanic model　　　　　　　　　　　　　　　
Eiji Masunaga
AOGS Meeting 2019, Aug. 2019

Mixing and baroclinic structure in a stratified shallow lake, Lake Kasumigaura, Japan　　　　　　　　　　　　　　　
Eiji Masunaga
JpGU Meeting 2019, May 2019

Nonlinear Internal waves and mixing generated by an interaction of background flows and tides　　　　　　　　　　　　　　　
Eiji Masunaga; Yusuke Uchiyama; Hidekatsu Yamazaki
AGU Fall Meeting 2018, 12 Dec. 2018

内部潮汐を考慮した伊豆大島周辺海域における潮流予測システムの開発と運用　　　　　　　　　　　　　　　
増永英治; 山崎秀勝; 山口邦久
海岸工学講演会, 13 Nov. 2018

Mixing and sediment transport induced by nonlinear internal wave breaking in coastal regions　　　　　　　　　　　　　　　
Eiji Masunaga; Robert S. Arthur; Oliver B. Fringer; Hidekatsu Yamazaki
PICES Meeting 2018, 01 Nov. 2018

Mixing processes associated with hypoxia in Lake Kasumigaura　　　　　　　　　　　　　　　
Eiji Masunaga
17th World Lake Conference, 16 Oct. 2018

Nonlinear internal waves excited by an interaction of tides and Kuroshio　　　　　　　　　　　　　　　
Eiji Masunaga; Yusuke Uchiyama; Hidekatsu Yamazaki
JpGU-meeting 2018, 20 May 2018

Numerical simulations and observations of nonlinear internal tides in shallow coastal regions.　　　　　　　　　　　　　　　
Eiji Masunaga; Robert S. Arthur; Oliver B. Fringer; Hidekatsu Yamazaki
Ocean Science Meeting 2018, Feb. 2018, AGU

黒潮と内部波が影響する伊豆諸島周辺海域における流動場の解明　　　　　　　　　　　　　　　
増永英治; 鈴江洋太; 内山雄介; 山崎秀勝
海岸工学講演会, Oct. 2017

非構造格子を用いた東京湾奥における底質輸送過程の高解像度数値シミュレーション　　　　　　　　　　　　　　　
増永英治; 鯉渕幸雄
日本海洋学会2017年度秋季大会, Oct. 2017

Nonlinear internal wave dynamics and sediment transport processes investigated with the SUNTANS models
Eiji Masunaga
IMUM2017, Aug. 2017, Oliver. B Fringer

Numerical simulations of the interaction between internal waves and the Kuroshio Current over the Izu-Ogasawara Ridge　　　　　　　　　　　　　　　
Eiji Masunaga; Guillaume Auger; Matthew Rayson; Oliver Fringer; Hidekatsu Yamazaki
14th Annual Meeting Asia Oceania Geoscience Society, Aug. 2017, AOGS

Numerical simulations of internal wave dynamics in the vicinity of Izu-Oshima Island, off Sagami Bay, Japan　　　　　　　　　　　　　　　
Eiji Masunaga; Yota Suzue; Yusuke Uchiyama; Hidekatsu Yamazaki
JpGU-AGU joint meeting, May 2017

Internal wave-driven sediment transports over contineltal slopes　　　　　　　　　　　　　　　
Eiji MAsunaga; Robert S. Arthur; Oliver B. Fringer; Yusuke Uchiyama
ALSO meegting 2017, Mar. 2017

伊豆大島周辺の内部潮汐発生機構　　　　　　　　　　　　　　　
増永英治; Oliver Fringer; 北出裕二郎; 山崎秀勝
2016年度日本海洋学会春季大会, Mar. 2016

Generation mechanism and energetics of internalk waves around an island　　　　　　　　　　　　　　　
Masunaga; E.; O.B. Fringer; Y. Kitade and H. Yamazaki
Ocean Science Meeting 2016, 26 Feb. 2016

浅海域における河川水の混合拡散の観測とモデル化　　　　　　　　　　　　　　　
増永英治; Kaushik Sasmal; Adrean Webb; Oliver Fringer; 山崎秀勝
2015年度日本海洋学会春季大会, Mar. 2015

YODA Profilerを用いた沿岸海域のおける観測　　　　　　　　　　　　　　　
増永英治
2015年度日本海洋学会春季大会シンポジウムS6海洋乱流測定技術の変遷, Mar. 2015

Resuspnesion and turbulent mixing due to nonlinear internal bores along a shallow slope　　　　　　　　　　　　　　　
Masunaga; E.; H. Yamazaki and T. Nagai
Ocean Science Meeting 2014, 28 Feb. 2014

Multiple mixing layers and stratification observed in the upper water of Lake Biwa during summer　　　　　　　　　　　　　　　
Homma; H.; H. Yamazaki; T. Nagai; E. Masunaga and M Kumagai
Ocean Science meeting 2014, Feb. 2014

Resuspension and lateral dispersal of sediments due to shoaling internal waves　　　　　　　　　　　　　　　
Masunaga; E.; H. Yamazaki; T. Nagai and O.; Fringer
2013 6th China-Japan-Korea IMBER Symposium, Oct. 2013

斜面上を伝搬する内部波の構造について　　　　　　　　　　　　　　　
増永英治; 山崎秀勝; 長井健容; 本間光
2013年度日本海洋学会春季大会, Mar. 2013

Development of a new tow-yo instrument to observe detailed river plume structures　　　　　　　　　　　　　　　
Masunaga; E.; H. Yamazaki and T. Nagai
20212 AGU Fall Meeting, Dec. 2012

Development of a new tow-yo instrument to observe detailed river plume structures　　　　　　　　　　　　　　　
Masunaga; E.; H. Yamazaki and T. Nagai
2012 ASLO Summer meeting, Jul. 2012

東京湾北部における内部波と海底傾斜に関する研究　　　　　　　　　　　　　　　
増永英治; 山崎秀勝; 長井健容
2012年度日本海洋学会春季大会, Mar. 2012

新型曳航式観測装置を用いた沿岸の観測に関する研究　　　　　　　　　　　　　　　
増永英治; 山崎秀勝; 長井健容
2011年度水産海洋学会, Nov. 2011

自由落下式CTD(SBPro)による乱流混合強度の推定　　　　　　　　　　　　　　　
増永英治; 山崎秀勝; 岡田知也; 柏俊行
2011年度日本海洋学会春季大会, Mar. 2011

曳航式観測装置Sailing Boat Profiler (SBPro) の開発とその応用例　　　　　　　　　　　　　　　
増永英治; 山崎秀勝; 柏俊行; 長井健容; 野田明; 濱田浩明
2010年度日本海洋学会春季大会, Mar. 2010

2017 - Present, Asia Oceania Geosciences Society

日本海洋学会

土木学会

American Geophysical Union

沿岸域学会