| 1. |
Decadal vision in oceanography 2021: Coastal oceans. |
| 2. |
Shinichiro Kida, Katsumi Takayama, Yoshi N. Sasaki, Hiromi Matsuura, Naoki Hirose, Increasing trend in Japan Sea Throughflow transport, Journal of Oceanography, 10.1007/s10872-020-00563-5, 2021.02, A long-term increasing trend in the transport of the Japan Sea Throughflow is observed from sea-level differences across the Tsushima Strait. Tidal gauge observations show sea level at Hakata, Japan, increasing at a higher rate than that at Busan, Korea. Numerical modeling results suggest that this increasing trend is forced by a northward shift in the Kuroshio axis. As the Kuroshio axis moves northward, sea level along the southern coast of Japan increases. The signal then propagates anticyclonically along the coast as topographic Rossby waves and Kelvin waves, raising sea level and, thus, increasing transport through the Tsushima Strait..  |
| 3. |
Shinichiro Kida, Katsumi Takayama, Yoshi N. Sasaki, Hiromi Matsuura, Naoki Hirose, Increasing trend in Japan Sea Throughflow transport, Journal of Oceanography, 10.1007/s10872-020-00563-5, 77, 1, 145-153, 2020.09, A long-term increasing trend in the transport of the Japan Sea Throughflow is observed from sea-level differences across the Tsushima Strait. Tidal gauge observations show sea level at Hakata, Japan, increasing at a higher rate than that at Busan, Korea. Numerical modeling results suggest that this increasing trend is forced by a northward shift in the Kuroshio axis. As the Kuroshio axis moves northward, sea level along the southern coast of Japan increases. The signal then propagates anticyclonically along the coast as topographic Rossby waves and Kelvin waves, raising sea level and, thus, increasing transport through the Tsushima Strait.. |
| 4. |
Hideharu Sasaki, Shinichiro Kida, Ryo Furue, Hidenori Aiki, Nobumasa Komori, Yukio Masumoto, Toru Miyama, Masami Nonaka, Yoshikazu Sasai, Bunmei Taguchi, A global eddying hindcast ocean simulation with OFES2, Geoscientific Model Development, 10.5194/gmd-13-3319-2020, 13, 7, 3319-3336, 2020.07, A quasi-global eddying ocean hindcast simulation using a new version of our model, called OFES2 (Ocean General Circulation Model for the Earth Simulator version 2), was conducted to overcome several issues with unrealistic properties in its previous version, OFES. This paper describes the model and the simulated oceanic fields in OFES2 compared with OFES and also observed data. OFES2 includes a sea-ice model and a tidal mixing scheme, is forced by a newly created surface atmospheric dataset called JRA55-do, and simulated the oceanic fields from 1958 to 2016. We found several improvements in OFES2 over OFES: smaller biases in the global sea surface temperature and sea surface salinity as well as the water mass properties in the Indonesian and Arabian seas. The time series of the Niño3.4 and Indian Ocean Dipole (IOD) indexes are somewhat better in OFES2 than in OFES. Unlike the previous version, OFES2 reproduces more realistic anomalously low sea surface temperatures during a positive IOD event. One possible cause of these improvements in El Niño and IOD events is the replacement of the atmospheric dataset. On the other hand, several issues remained unrealistic, such as the pathways of the Kuroshio and Gulf Stream and the unrealistic spreading of salty Mediterranean overflow. Given the worldwide use of the previous version and the improvements presented here, the output from OFES2 will be useful in studying various oceanic phenomena with broad spatiotemporal scales.. |
| 5. |
Hideharu Sasaki, Shinichiro Kida, Ryo Furue, Hidenori Aiki, Nobumasa Komori, Yukio Masumoto, Toru Miyama, Masami Nonaka, Yoshikazu Sasai, Bunmei Taguchi, A global eddying hindcast ocean simulation with OFES2, Geoscientific Model Development, 10.5194/gmd-13-3319-2020, 13, 7, 3319-3336, 2020.07, A quasi-global eddying ocean hindcast simulation using a new version of our model, called OFES2 (Ocean General Circulation Model for the Earth Simulator version 2), was conducted to overcome several issues with unrealistic properties in its previous version, OFES. This paper describes the model and the simulated oceanic fields in OFES2 compared with OFES and also observed data. OFES2 includes a sea-ice model and a tidal mixing scheme, is forced by a newly created surface atmospheric dataset called JRA55-do, and simulated the oceanic fields from 1958 to 2016. We found several improvements in OFES2 over OFES: smaller biases in the global sea surface temperature and sea surface salinity as well as the water mass properties in the Indonesian and Arabian seas. The time series of the Nino3.4 and Indian Ocean Dipole (IOD) indexes are somewhat better in OFES2 than in OFES. Unlike the previous version, OFES2 reproduces more realistic anomalously low sea surface temperatures during a positive IOD event. One possible cause of these improvements in El Nino and IOD events is the replacement of the atmospheric dataset. On the other hand, several issues remained unrealistic, such as the pathways of the Kuroshio and Gulf Stream and the unrealistic spreading of salty Mediterranean overflow. Given the worldwide use of the previous version and the improvements presented here, the output from OFES2 will be useful in studying various oceanic phenomena with broad spatiotemporal scales.. |
| 6. |
Shinichiro Kida, Dai Yamazaki, The Mechanism of the Freshwater Outflow Through the Ganges‐Brahmaputra‐Meghna Delta, Water Resources Research, 10.1029/2019WR026412, 2020.05. |
| 7. |
Naokazu Taniguchi, Shinichiro Kida, Yuji Sakuno, Hidemi Mutsuda, Fadli Syamsudin, Short-term variation of the surface flow pattern south of Lombok Strait observed from the Himawari-8 sea surface temperature, Remote Sensing, 10.3390/rs11121491, 11, 12, 2019.06, Spatial and temporal information on oceanic flow is fundamental to oceanography and crucial for marine-related social activities. This study attempts to describe the short-term surface flow variation in the area south of the Lombok Strait in the northern summer using the hourly Himawari-8 sea surface temperature (SST). Although the uncertainty of this temperature is relatively high (about 0.6 °C), it could be used to discuss the flow variation with high spatial resolution because sufficient SST differences are found between the areas north and south of the strait. The maximum cross-correlation (MCC) method is used to estimate the surface velocity. The Himawari-8 SST clearly shows Flores Sea water intruding into the Indian Ocean with the high-SST water forming a warm thermal plume on a tidal cycle. This thermal plume flows southward at a speed of about 2 m/s. The Himawari-8 SST indicates a southward flow from the Lombok Strait to the Indian Ocean, which blocks the South Java Current flowing eastward along the southern coast of Nusa Tenggara. Although the satellite data is limited to the surface, we found it useful for understanding the spatial and temporal variations in the surface flow field.. |
| 8. |
Shinichiro Kida, Kelvin J. Richards, Hideharu Sasaki, The Fate of Surface Freshwater Entering the Indonesian Seas, Journal of Geophysical Research: Oceans, 10.1029/2018JC014707, 2019.04, The Indonesian Seas receive one of the largest amounts of rainfall around the globe. Part of this freshwater disperses to the Indian Ocean through the Indonesian Throughflow (ITF), the Pacific and Indian interocean exchange flow, making the Indonesian Seas a major source of freshwater, and plays an important part of the global hydrological cycle. By using a Lagrangian particle tracking model, we examine the pathways behind the dispersion of freshwater that the Indonesian Seas receive through precipitation. The model suggests that the dispersion from the near-surface water of the Indonesian Seas occurs in about 6 months, primarily through advection to the surrounding seas, followed by evaporation, entrainment, and vertical mixing. The Lombok Strait and the Timor Strait are the major outflowing straits, and the freshwater exiting through these straits are found to originate from limited areas and seasons. The sources for the Lombok Strait outflow are the Java Sea precipitated freshwater during boreal fall and winter, while the sources for the Timor Strait outflow are the Flores-Banda Seas and Arafura Sea precipitated freshwater during winter and spring. Mixing with the thermocline water is found to occur when the monsoonal winds induce upwelling events in winter and summer, along the shelf breaks and steep coastlines surrounding the Flores-Banda Seas. Vertical mixing provides a pathway for the surface freshwater to enter the ITF thermocline, and our model suggests that it is the Java Sea precipitated freshwater during winter that is entering the ITF thermocline along its main pathway.. |
| 9. |
H. Sasaki, Shinichiro Kida, R. Furue, M. Nonaka, Y. Masumoto, An Increase of the Indonesian Throughflow by Internal Tidal Mixing in a High-Resolution Quasi-Global Ocean Simulation, Geophysical Research Letters, 10.1029/2018GL078040, 45, 16, 8416-8424, 2018.08, The impact of internal tidal mixing on the volume transport of the Indonesian Throughflow (ITF) is examined by a comparison of high-resolution quasi-global ocean simulations with and without a tidal mixing scheme. The ITF transport is found to be increased in the presence of tidal mixing. This is because tidal mixing decreases the density within and below the lower thermocline and increases the buoyancy of the water column. As a result, the surface pressure and the sea surface height (SSH) are raised. The magnitude of the SSH increase is larger for the tropical Pacific Ocean than for the other basins, possibly because many islands exist in the tropical Pacific and tidal mixing is effective around their shallow and rough topographies. Since SSH increases more in the tropical Pacific than in the Indian Ocean, the pressure difference between the two basins is enhanced and thus the ITF transport is strengthened.. |
| 10. |
Sooyeon Han, Naoki Hirose, Shinichiro Kida, The Role of Topographically Induced Form Drag on the Channel Flows Through the East/Japan Sea, Journal of Geophysical Research, 10.1029/2018JC013903, 2018.08, The dynamics responsible for the East/Japan Sea throughflow are examined using the Finite Volume Coastal Ocean Model. Existing ocean data assimilation models (Δx ~10 km) present overestimates of the volume transport through the Tsugaru Strait, and the outflow partitioning between the Tsugaru and Soya/La Perouse Straits also differs depending on the models. We find that this overestimate occurs when the form drag that is induced by detailed bottom topographic features in the Tsugaru Strait is not adequately resolved. A range of experiments with different horizontal resolutions in the Korea/Tsushima, Tsugaru, and Soya/La Perouse Straits were conducted to examine how detailed bottom topographic features in these three straits may affect the throughflow. We find that the volume transport is highly sensitive to the spatial resolution at the Tsugaru Strait but not at the Korea/Tsushima and Soya/La Perouse Straits. The high-resolution experiment showed a decreased outflow through the Tsugaru Strait and a reduction in the model bias. The outflow through the Soya/La Perouse Strait increased, while the inflow through the Korea/Tsushima Strait remained relatively unchanged. Additional experiments with modified topography further indicated that the abrupt change of the topography located at the upstream side of the Tsugaru Strait plays an important role in the outflow partitioning of the East/Japan Sea throughflow.. |
| 11. |
Sooyeon Han, Naoki Hirose, Shinichiro Kida, The role of topographically induced form drag on the channel flows through the East/Japan Sea, Journal of Geophysical Research: Oceans, 10.1029/2018JC013903, 2018.08. |
| 12. |
H. Sasaki, S. Kida, R. Furue, M. Nonaka, Y. Masumoto, An Increase of the Indonesian Throughflow by Internal Tidal Mixing in a High‐Resolution Quasi‐Global Ocean Simulation, Geophysical Research Letter, 10.1029/2018GL078040, 45, 16, 8416-8424, 2018.07. |
| 13. |
Shinichiro Kida, Takamitsu Ito, A Lagrangian View of Phytoplankton blooms, Journal of Geophysical Research Oceans, 10.1002/2017JC013383, 2017.11. |
| 14. |
Shinichiro Kida, Takamitsu Ito, A Lagrangian View of Spring Phytoplankton Blooms, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 10.1002/2017JC013383, 122, 11, 9160-9175, 2017.11, The mechanisms of spring phytoplankton blooms are investigated from a Lagrangian framework by using a Lagrangian NPZD model that can track the movement and transfers of nutrient parcels in a turbulent environment. The model reveals that the onset of spring blooms depends on the cumulative euphotic age, which is the total time that inorganic nutrient is exposed to light before the photosynthetic conversion to phytoplankton biomass. A spring bloom, defined as a tenfold increase of near-surface phytoplankton, occurs when this cumulative euphotic age is approximately mu(-1)(eff).ln?10, where mu(eff) is the effective growth rate in the euphotic layer, regardless of the underlying mechanism. If the turbulent layer depth is shallower than the critical depth and turbulence is strong, nutrient parcels accumulate enough light exposure through multiple entries to the sun-lit zone near the surface. If turbulence is weak, as that considered in the critical turbulence theory, the accumulation of the light exposure depends on the residence time of the nutrients parcels near the surface. The spectral shape of the cumulative euphotic age can clearly distinguish these two modes of spring blooms. The spectrum shows a peak at the theoretical growth timescale when multiple entries become important, while it shows a maximum near age zero that decays with age when the near-surface residence time becomes important. Mortality increases the cumulative euphotic age necessary for a bloom but does not affect the spectral shape, suggesting that it does not alter the primary mechanism behind the accumulation of cumulative euphotic age.. |
| 15. |
A numerical model for the marginal seas. |
| 16. |
Tangdong Qu, Tomoki Tozuka, Shinichiro Kida, Xinyu Guo, Yasumasa Miyazawa, Qinyu Liu, Western pacific and marginal sea processes, World Scientific Series on Asia-Pacific Weather and Climate, 10.1142/9789814696623_0006, 7, 151-186, 2016.02, This article focuses on the physical and dynamical processes of the marginal seas of the Western Pacific. The nature of the circulation regimes and their interconnectivity are discussed in detail, with emphasis on individual basins. In addition to the Kuroshio and its variability in the North Pacific, the circulation regimes in the South China Sea and Indonesian Seas are presented for an overall view of the circulation system. These circulations play important roles in regional ocean dynamics and global climate variations such as the El Niño/Southern Oscillation.. |
| 17. |
Shinichiro Kida, The Annual Cycle of the Japan Sea Throughflow, JOURNAL OF PHYSICAL OCEANOGRAPHY, 10.1175/JPO-D-15-0075.1, 46, 1, 23-39, 2016.01. |
| 18. |
Tangdong Qu, Tomoki Tozuka, Shinichiro Kida, Xinyu Guo, Yasumasa Miyazawa, Qinyu Liu, Western pacific and marginal sea processes, World Scientific Series on Asia-Pacific Weather and Climate, 10.1142/9789814696623_0006, 7, 151-186, 2016.01, This article focuses on the physical and dynamical processes of the marginal seas of the Western Pacific. The nature of the circulation regimes and their interconnectivity are discussed in detail, with emphasis on individual basins. In addition to the Kuroshio and its variability in the North Pacific, the circulation regimes in the South China Sea and Indonesian Seas are presented for an overall view of the circulation system. These circulations play important roles in regional ocean dynamics and global climate variations such as the El Niño/Southern Oscillation.. |
| 19. |
Shinichiro Kida, Humio Mitsudera, Shigeru Aoki, Xinyu Guo, Shin Ichi Ito, Fumiaki Kobashi, Nobumasa Komori, Atsushi Kubokawa, Toru Miyama, Ryosuke Morie, Hisashi Nakamura, Tomohiro Nakamura, Hideyuki Nakano, Hajime Nishigaki, Masami Nonaka, Hideharu Sasaki, Yoshi N. Sasaki, Toshio Suga, Shusaku Sugimoto, Bunmei Taguchi, Koutarou Takaya, Tomoki Tozuka, Hiroyuki Tsujino, Norihisa Usui, Oceanic fronts and jets around Japan
A review, Hot Spots in the Climate System
New Developments in the Extratropical Ocean-Atmosphere Interaction Research, 10.1007/978-4-431-56053-1_1, 1-30, 2016.01, This article reviews progress in our understanding of oceanic fronts around Japan and their roles in air–sea interaction. Fronts associated with the Kuroshio and its extension, fronts within the area of the Kuroshio-Oyashio confluence, and the subtropical fronts are described with particular emphasis on their structure, variability, and role in air–sea interaction. The discussion also extends to the fronts in the coastal and marginal seas, the Seto Inland Sea and Japan Sea. Studies on oceanic fronts have progressed significantly during the past decade, but many of these studies focus on processes at individual fronts and do not provide a comprehensive view. Hence, one of the goals of this article is to review the oceanic fronts around Japan by describing the processes based on common metrics. These metrics focus primarily on surface properties to obtain insights into air–sea interactions that occur along oceanic fronts. The basic characteristics derived for each front (i.e., metrics) are then presented as a table. We envision that many of the coupled ocean-atmosphere global circulation models in the coming decade will represent oceanic fronts reasonably well, and it is hoped that this review along with the table of metrics will provide a useful benchmark for evaluating these models.. |
| 20. |
Oceanic fronts and jets around Japan: A review
© The Oceanographic Society of Japan and Springer Japan 2016. This article reviews progress in our understanding of oceanic fronts around Japan and their roles in air–sea interaction. Fronts associated with the Kuroshio and its extension, fronts within the area of the Kuroshio-Oyashio confluence, and the subtropical fronts are described with particular emphasis on their structure, variability, and role in air–sea interaction. The discussion also extends to the fronts in the coastal and marginal seas, the Seto Inland Sea and Japan Sea. Studies on oceanic fronts have progressed significantly during the past decade, but many of these studies focus on processes at individual fronts and do not provide a comprehensive view. Hence, one of the goals of this article is to review the oceanic fronts around Japan by describing the processes based on common metrics. These metrics focus primarily on surface properties to obtain insights into air–sea interactions that occur along oceanic fronts. The basic characteristics derived for each front (i.e., metrics) are then presented as a table. We envision that many of the coupled ocean-atmosphere global circulation models in the coming decade will represent oceanic fronts reasonably well, and it is hoped that this review along with the table of metrics will provide a useful benchmark for evaluating these models.. |
| 21. |
Shinichiro Kida, Bo Qiu, Jiayan Yang, Xiaopei Lin, The Annual Cycle of the Japan Sea Throughflow, JOURNAL OF PHYSICAL OCEANOGRAPHY, 10.1175/JPO-D-15-0075.1, 46, 1, 23-39, 2016.01, The mechanism responsible for the annual cycle of the flow through the straits of the Japan Sea is investigated using a two-layer model. Observations show maximum throughflow from summer to fall and minimum in winter, occurring synchronously at the three major straits: Tsushima, Tsugaru, and Soya Straits. This study finds the subpolar winds located to the north of Japan as the leading forcing agent, which first affects the Soya Strait rather than the Tsushima or Tsugaru Straits. The subpolar winds generate baroclinic Kelvin waves along the coastlines of the subpolar gyre, affect the sea surface height at the Soya Strait, and modify the flow through the strait. This causes barotropic adjustment to occur inside the Japan Sea and thus affect the flow at the Tsugaru and Tsushima Straits almost synchronously. The barotropic adjustment mechanism explains well why the observations show a similar annual cycle at the three straits. The annual cycle at the Tsugaru Strait is further shown to be weaker than that in the other two straits based on frictional balance around islands, that is, frictional stresses exerted around an island integrate to zero. In the Tsugaru Strait, the flows induced by the frictional integrals around the northern (Hokkaido) and southern (Honshu) islands are in opposite directions and tend to cancel out. Frictional balance also suggests that the annual cycle at the Tsugaru Strait is likely in phase with that at the Soya Strait because the length scale of the northern island is much shorter than that of the southern island.. |
| 22. |
Shinichiro Kida, H. Mitsudera, S. Aoki, X. Gu, S. Ito, F. Kobashi, N. Komori, A. Kubokawa, T. Miyama, R. Morie, H. Nakamura,, T. Nakamura, H. Nakano, H. Nishigaki, M. Nonaka,, H. Sasaki, Y.N. Sasaki, T. Suga, S. Sugimoto, B. Taguchi, K. Takaya, T. Tozuka, H. Tsujino, N. Usui, Oceanic fronts and jets around Japan: a review, JOURNAL OF OCEANOGRAPHY, 10.1007/s10872-015-0283-7, 71, 5, 469-497, 2015.10. |
| 23. |
Shinichiro Kida, Humio Mitsudera, Shigeru Aoki, Xinyu Guo, Shin-ichi Ito, Fumiaki Kobashi, Nobumasa Komori, Atsushi Kubokawa, Toru Miyama, Ryosuke Morie, Hisashi Nakamura, Tomohiro Nakamura, Hideyuki Nakano, Hajime Nishigaki, Masami Nonaka, Hideharu Sasaki, Yoshi N. Sasaki, Toshio Suga, Shusaku Sugimoto, Bunmei Taguchi, Koutarou Takaya, Tomoki Tozuka, Hiroyuki Tsujino, Norihisa Usui, Oceanic fronts and jets around Japan: a review, JOURNAL OF OCEANOGRAPHY, 10.1007/s10872-015-0283-7, 71, 5, 469-497, 2015.10, This article reviews progress in our understanding of oceanic fronts around Japan and their roles in air-sea interaction. Fronts associated with the Kuroshio and its extension, fronts within the area of the Kuroshio-Oyashio confluence, and the subtropical fronts are described with particular emphasis on their structure, variability, and role in air-sea interaction. The discussion also extends to the fronts in the coastal and marginal seas, the Seto Inland Sea and Japan Sea. Studies on oceanic fronts have progressed significantly during the past decade, but many of these studies focus on processes at individual fronts and do not provide a comprehensive view. Hence, one of the goals of this article is to review the oceanic fronts around Japan by describing the processes based on common metrics. These metrics focus primarily on surface properties to obtain insights into air-sea interactions that occur along oceanic fronts. The basic characteristics derived for each front (i.e., metrics) are then presented as a table. We envision that many of the coupled ocean-atmosphere global circulation models in the coming decade will represent oceanic fronts reasonably well, and it is hoped that this review along with the table of metrics will provide a useful benchmark for evaluating these models.. |
| 24. |
Bo Qiu, Shuming Chen, Lixin Wu, Shinichiro Kida, Wind- versus Eddy-Forced Regional Sea Level Trends and Variability in the North Pacific Ocean, JOURNAL OF CLIMATE, 10.1175/JCLI-D-14-00479.1, 28, 4, 1561-1577, 2015.02. |
| 25. |
Shinichiro Kida, Yosuke Yamashiki, A layered model approach for simulating high river discharge events from land to the ocean, Journal of Oceanography, 10.1007/s10872-014-0254-4, 71, 1, 125-132, 2015.02. |
| 26. |
Shinichiro Kida, Yosuke A. Yamashiki, A layered model approach for simulating high river discharge events from land to the ocean, JOURNAL OF OCEANOGRAPHY, 10.1007/s10872-014-0254-4, 71, 1, 125-132, 2015.02, This study presents a new approach for simulating surface runoff, river flow, and oceanic flow. Hydrological-ocean coupled models often stitch the two models at the river mouth because they typically differ in formulation, dynamically and dimensionally. An isopycnal-layered model is shown to naturally couple hydrological and oceanic processes seamlessly with the use of a single dynamical core. Numerical experiments show the high discharge event of the Abukuma River in Japan during Typhoon Roke with realistic river flows and freshwater plumes in the ocean. The time series of the river discharge rates also match well with observations from upstream to downstream.. |
| 27. |
Bo Qiu, Shuiming Chen, Lixin Wu, Shinichiro Kida, Wind- versus Eddy-Forced Regional Sea Level Trends and Variability in the North Pacific Ocean, JOURNAL OF CLIMATE, 10.1175/JCLI-D-14-00479.1, 28, 4, 1561-1577, 2015.02, Regional sea level trend and variability in the Pacific Ocean have often been considered to be induced by low-frequency surface wind changes. This study demonstrates that significant sea level trend and variability can also be generated by eddy momentum flux forcing due to time-varying instability of the background oceanic circulation. Compared to the broad gyre-scale wind-forced variability, the eddy-forced sea level changes tend to have subgyre scales and, in the North Pacific Ocean, they are largely confined to the Kuroshio Extension region (30 degrees-40 degrees N, 140 degrees-175 degrees E) and the Subtropical Countercurrent (STCC) region (18 degrees-28 degrees N, 130 degrees-175 degrees E). Using a two-layer primitive equation model driven by the ECMWF wind stress data and the eddy momentum fluxes specified by the AVISO sea surface height anomaly data, the relative importance of the wind-and eddy-forced regional sea level trends in the past two decades is quantified. It is found that the increasing (decreasing) trend south (north) of the Kuroshio Extension is due to strengthening of the regional eddy forcing over the past two decades. On the other hand, the decreasing (increasing) sea level trend south (north) of the STCC is caused by the decadal weakening of the regional eddy momentum flux forcing. These decadal eddy momentum flux changes are caused by the background Kuroshio Extension and STCC changes in connection with the Pacific decadal oscillation (PDO) wind pattern shifting from a positive to a negative phase over the past two decades.. |
| 28. |
Shinichiro Kida, Bo Qiu, An exchange flow between the Okhotsk Sea and the North Pacific driven by the East Kamchatka Current, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 10.1002/2013JC009464, 118, 12, 6747-6758, 2013.12, A new mechanism for driving the water mass exchange between the Okhotsk Sea and the North Pacific is presented. This exchange flow originates from the East Kamchatka Current (EKC), a western boundary current of the subpolar gyre, and occurs through the two deepest straits of the Kuril island chain, the Kruzenshtern and Bussol straits. An inflow toward the Okhotsk Sea occurs at the northern Kruzenshtern strait and an outflow toward the North Pacific occurs at the southern Bussol strait. By using the Kelvin's Circulation theorem around the island between the two straits, we show that the transport of the exchange flow entering the Okhotsk Sea is determined such that the frictional stresses around the island exerted by the bifurcated EKC integrate to zero. This forcing mechanism is different from the dynamical framework of the widely used Island rule. Both an analytical analysis and 1.5-layer model experiments demonstrate that the strait width, lateral viscosity, and island geometry are controlling parameters for the exchange flow transport because they affect the magnitude and length scales of the frictional stresses. Inertia of the EKC decreases the exchange flow by enhancing the frictional stress along the northern coast of the Kuril island. Model experiments with realistic topography further reveal that while the steep continental slopes have minor impact on the exchange flow transport, the subsurface peninsula located east of the Kuril island works to decrease the exchange flow by altering the length scale of the frictional stresses and enabling the EKC to flow past the island.. |
| 29. |
Shinichiro Kida, Bo Qiu, An exchange flow between the Okhotsk Sea and the North Pacific driven by the East Kamchatka Current, Journal of Geophysical Research, Ocean, 10.1002/2013JC009464, 118, 2013.11. |
| 30. |
Shinichiro Kida, Choi, Takahashi, The impact of oceanic circulation and phase transfer on the dispersion of radionuclides released from the Fukushima Dai-ichi Nuclear Power Plant, BIOGEOSCIENCES, 10.5194/bg-10-4911-2013, 10, 7, 4911-4925, 2013.07. |
| 31. |
Y. Choi, S. Kida, K. Takahashi, The impact of oceanic circulation and phase transfer on the dispersion of radionuclides released from the Fukushima Dai-ichi Nuclear Power Plant, Biogeosciences, 10.5194/bg-10-4911-2013, 10, 7, 4911-4925, 2013.07, The mechanism behind the dispersion of radionuclides released from the Fukushima Dai-ichi Nuclear Power Plant on March 2011 is investigated using a numerical model. This model is a Lagrangian particle tracking-ocean circulation coupled model that is capable of solving the movement and migration of radionuclides between seawater, particulates, and bottom sediments. Model simulations show the radionuclides dispersing rapidly into the interior of the North Pacific once they enter a meso-scale eddy. However, some radionuclides also remain near the coast, with spatial distribution depending strongly on the oceanic circulation during the first month after the release. Major adsorption to bottom sediments occurs during this first month and many of these radionuclides remain on the sea floor once they are adsorbed. Model results suggest that weak offshore advection during the first month will increase the adsorption of radionuclides to bottom sediments and decelerate the dispersion to the open ocean. If vertical mixing is weak, however, fewer radionuclides reach the sea floor and adsorb to bottom sediments. More radionuclides will then quickly disperse to the open ocean. © Author(s) 2013.. |
| 32. |
ODaisuke Matsuoka, Fumiaki Araki, Shinichiro Kida, Hideharu Sasaki, Bunmei Taguchi, VISUALIZATION FOR HIGH-RESOLUTION OCEAN GENERAL CIRCULATION MODEL VIA MULTI-DIMENSIONAL TRANSFER FUNCTION AND MULTIVARIATE ANALYSIS, 2012 SC COMPANION: HIGH PERFORMANCE COMPUTING, NETWORKING, STORAGE AND ANALYSIS (SCC), 1466-1466, 2012.11. |
| 33. |
Shinichiro Kida, Susan Wijffels, The impact of the Indonesian Throughflow and tidal mixing on the summertime sea surface temperature in the western Indonesian Seas, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 10.1029/2012JC008162, 117, 2012.09. |
| 34. |
Shinichiro Kida, Susan Wijffels, The impact of the Indonesian Throughflow and tidal mixing on the summertime sea surface temperature in the western Indonesian Seas, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 10.1029/2012JC008162, 117, 9, 2012.09, A numerical model is used to investigate how the Indonesian Throughflow and tidal mixing are affecting the seasonal cycle of the sea surface temperature (SST) in the Indonesian Seas. The SST in these seas is considered to play a major role on the development of the Australian Summer Monsoon. Based on a quantitative assessment of the heat budget, the Indonesian Throughflow is found to affect the SST in the western Indonesian Seas primarily during Austral summer. The Throughflow advects the warm water from the Pacific and maintains the warm SST when the Northwestern Monsoonal wind induces coastal upwelling along the northern side of the Nusa Tenggara and cools the SST. Such balance is supported by observations. The hydrographic sections show the isotherms tilting upward toward the northern coast of the Nusa Tenggara when satellite observations show slight decrease of the SST in the region. Tidal mixing is found to cool the SST during summer the most. This is because the Northwest Monsoonal wind induces coastal upwelling near where strong tidal mixing above seamount occurs and brings the tidally well-mixed upper thermocline water to the surface. The surface Ekman flow also spreads this cool water around the Banda Sea where tidal mixing does not occur. The impact of tidal mixing on the SST is also found to come largely from that occurring above seamounts. The impact of tidal mixing on the continental shelves is limited to shelf-breaks because cold subsurface water is necessary for enhanced vertical mixing to cool the SST.. |
| 35. |
Daisuke Matsuoka, Fumiaki Araki, Shinichiro Kida, Hideharu Sasaki, Bunmei Taguchi, Visualization for high-resolution ocean general circulation model via multi-dimensional transfer function and multivariate analysis, 2012 SC Companion: High Performance Computing, Networking Storage and Analysis, SCC 2012
Proceedings - 2012 SC Companion: High Performance Computing, Networking Storage and Analysis, SCC 2012, 10.1109/SC.Companion.2012.263, 1466, 2012, Ocean currents and vortices play an important role in transferring heat, salt or carbon as well as atmospheric circulation. With advances in supercomputing technology, high-resolution large-scale simulation study has been focused in the field of ocean science. However, it is difficult to intuitively understand characteristic features defined as multivariable hiding in the high-resolution dataset. In order to obtain scientific knowledge from large-scale simulation data, it is important to effectively extract and to efficiently express the characteristic feature. The aim of this study is how to efficiently extract and how to effectively visualize ocean currents which affect the heat transportation. In this research, new multi-dimensional transfer function to emphasis the ocean currents and vortices is proposed. Furthermore, multivariate analyses to extract such features are developed. This presentation describes the methodologies and experimental results of these methods. Evaluation of visualization results and feedback to the parameter optimization will be also reported.. |
| 36. |
Shinichiro Kida, The Impact of Open Oceanic Processes on the Antarctic Bottom Water Outflows, JOURNAL OF PHYSICAL OCEANOGRAPHY, 10.1175/2011JPO4571.1, 41, 10, 1941-1957, 2011.10. |
| 37. |
Shinichiro Kida, The Impact of Open Oceanic Processes on the Antarctic Bottom Water Outflows, JOURNAL OF PHYSICAL OCEANOGRAPHY, 10.1175/2011JPO4571.1, 41, 10, 1941-1957, 2011.10, The impact of open oceanic processes on the Antarctic Bottom Water (AABW) outflows is investigated using a numerical model with a focus on outflows that occur through deep channels. A major branch of the AABW outflow is known to occur as an overflow from the Filchner Depression to the Weddell Sea through a deep channel a few hundred kilometers wide and a sill roughly 500 m deep. When this overflow enters the Weddell Sea, it encounters the Antarctic Slope Front (ASF) at the shelf break, a density front commonly found along the Antarctic continental shelf break. The presence of an AABW outflow and the ASF create a v-shaped isopycnal structure across the shelf break, indicating an interaction between the overflow and oceanic processes. Model experiments show the overflow transport to increase significantly when an oceanic wind stress increases the depth of the ASF. This enhancement of overflow transport occurs because the channel walls allow a pressure gradient in the along-slope direction to exist and the overflow transport is geostrophically controlled with its ambient oceanic water at the shelf break. Because the ASF is associated with a lighter water mass that reaches the depth close to that of the channel, an increase in its depth increases the density gradient across the shelf break and therefore the geostrophic overflow transport. The enhancement of overflow transport is also likely to result in a lighter overflow water mass, although such an adjustment of density likely occurs on a much longer time scale than the adjustment of transport.. |
| 38. |
Daria Halkides, Tong Lee, Shinichiro Kida, Mechanisms controlling the seasonal mixed-layer temperature and salinity of the Indonesian seas, OCEAN DYNAMICS, 10.1007/s10236-010-0374-3, 61, 4, 481-495, 2011.04, We examine the seasonal mixed-layer temperature (MLT) and salinity (MLS) budgets in the Banda-Arafura Seas region (120-138A degrees E, 8-3A degrees S) using an ECCO ocean-state estimation product. MLT in these seas is relatively high during November-May (austral spring through fall) and relatively low during June-September (austral winter and the period associated with the Asian summer monsoon). Surface heat flux makes the largest contribution to the seasonal MLT tendency, with significant reinforcement by subsurface processes, especially turbulent vertical mixing. Temperature declines (the MLT tendency is negative) in May-August when seasonal insolation is smallest and local winds are strong due to the southeast monsoon, which causes surface heat loss and cooling by vertical processes. In particular, Ekman suction induced by local wind stress curl raises the thermocline in the Arafura Sea, bringing cooler subsurface water closer to the base of the mixed layer where it is subsequently incorporated into the mixed layer through turbulent vertical mixing; this has a cooling effect. The MLT budget also has a small, but non-negligible, semi-annual component since insolation increases and winds weaken during the spring and fall monsoon transitions near the equator. This causes warming via solar heating, reduced surface heat loss, and weakened turbulent mixing compared to austral winter and, to a lesser extent, compared to austral summer. Seasonal MLS is dominated by ocean processes rather than by local freshwater flux. The contributions by horizontal advection and subsurface processes have comparable magnitudes. The results suggest that ocean dynamics play a significant part in determining both seasonal MLT and MLS in the region, such that coupled model studies of the region should use a full ocean model rather than a slab ocean mixed-layer model.. |
| 39. |
D.J. Halkides, T. Lee, Shinichiro Kida, The mechanism controlling seasonal mixed layer temperature of the Indonesian Seas in an ECCO assimilation product, Ocean Dynamics, 10.1007/s10236-010-0374-3, 61, 481, 2011.02. |
| 40. |
H. Annamalai, Shinichiro Kida, Jan Hafner, Potential impact of the tropical Indian Ocean-Indonesian seas on El Niño characteristics, Journal of Climate, 10.1175/2010JCLI3396.1, 23, 14, 3933-3952, 2010.07, Diagnostics performed with twentieth-century (1861-2000) ensemble integrations of the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (CM2.1) suggest that, during the developing phase, El Niño events that co-occur with the Indian Ocean Dipole Zonal Mode (IODZM; class 1) are stronger than those without (class 2). Also, during class 1 events coherent sea surface temperature (SST) anomalies develop in the Indonesian seas that closely follow the life cycle of IODZM. This study investigates the effect of these regional SST anomalies (equatorial Indian Ocean and Indonesian seas) on the amplitude of the developing El Niño. An examination of class 1 minus class 2 composites suggests two conditions that could lead to a strong El Niño in class 1 events: (i) during January, ocean-atmosphere conditions internal to the equatorial Pacific are favorable for the development of a stronger El Niño and (ii) during May-June, coinciding with the development of regional SST anomalies, an abrupt increase in westerly wind anomalies is noticeable over the equatorial western Pacific with a subsequent increase in thermocline and SST anomalies over the eastern equatorial Pacific. This paper posits the hypothesis that, under favorable conditions in the equatorial Pacific, regional SST anomalies may enable the development of a stronger El Niño. Owing to a wealth of feedbacks in CM2.1, solutions from a linear atmosphere model forced with May-June anomalous precipitation and anomalous SST from selected areas over the equatorial Indo-Pacific are examined. Consistent with our earlier study, the net Kelvin wave response to contrasting tropical Indian Ocean heating anomalies cancels over the equatorial western Pacific. In contrast, Indonesian seas SST anomalies account for about 60%-80% of the westerly wind anomalies over the equatorial western Pacific and also induce anomalous precipitation over the equatorial central Pacific. It is argued that the feedback between the precipitation and circulation anomalies results in an abrupt increase in zonal wind anomalies over the equatorial western Pacific. Encouraged by these results, the authors further examined the processes that cause cold SST anomalies over the Indonesian seas using an ocean model. Sensitivity experiments suggest that local wind anomalies, through stronger surface heat loss and evaporation, and subsurface upwelling are the primary causes. The present results imply that in coupled models, a proper representation of regional air-sea interactions over the equatorial Indo-Pacific warm pool may be important to understand and predict the amplitude of El Niño.. |
| 41. |
H. Annamalai, Shinichiro Kida, Jan Hafner, Potential Impact of the Tropical Indian Ocean-Indonesian Seas on El Nino Characteristics, JOURNAL OF CLIMATE, 10.1175/2010JCLI3396.1, 23, 14, 3933-3952, 2010.07, Diagnostics performed with twentieth-century (1861-2000) ensemble integrations of the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (CM2.1) suggest that, during the developing phase, El Nino events that co-occur with the Indian Ocean Dipole Zonal Mode (IODZM; class 1) are stronger than those without (class 2). Also, during class 1 events coherent sea surface temperature (SST) anomalies develop in the Indonesian seas that closely follow the life cycle of IODZM. This study investigates the effect of these regional SST anomalies (equatorial Indian Ocean and Indonesian seas) on the amplitude of the developing El Nino.
An examination of class 1 minus class 2 composites suggests two conditions that could lead to a strong El Nino in class 1 events: (i) during January, ocean-atmosphere conditions internal to the equatorial Pacific are favorable for the development of a stronger El Nino and (ii) during May-June, coinciding with the development of regional SST anomalies, an abrupt increase in westerly wind anomalies is noticeable over the equatorial western Pacific with a subsequent increase in thermocline and SST anomalies over the eastern equatorial Pacific. This paper posits the hypothesis that, under favorable conditions in the equatorial Pacific, regional SST anomalies may enable the development of a stronger El Nino.
Owing to a wealth of feedbacks in CM2.1, solutions from a linear atmosphere model forced with May-June anomalous precipitation and anomalous SST from selected areas over the equatorial Indo-Pacific are examined. Consistent with our earlier study, the net Kelvin wave response to contrasting tropical Indian Ocean heating anomalies cancels over the equatorial western Pacific. In contrast, Indonesian seas SST anomalies account for about 60%-80% of the westerly wind anomalies over the equatorial western Pacific and also induce anomalous precipitation over the equatorial central Pacific. It is argued that the feedback between the precipitation and circulation anomalies results in an abrupt increase in zonal wind anomalies over the equatorial western Pacific.
Encouraged by these results, the authors further examined the processes that cause cold SST anomalies over the Indonesian seas using an ocean model. Sensitivity experiments suggest that local wind anomalies, through stronger surface heat loss and evaporation, and subsurface upwelling are the primary causes. The present results imply that in coupled models, a proper representation of regional air-sea interactions over the equatorial Indo-Pacific warm pool may be important to understand and predict the amplitude of El Nino.. |
| 42. |
Shinichiro Kida, K. J. Richards, Seasonal sea surface temperature variability in the Indonesian Seas, Journal of Geophysical Research, 10.1029/2008JC005150, 114, 6, 2009.06. |
| 43. |
S. Kida, K. J. Richards, Seasonal sea surface temperature variability in the Indonesian Seas, Journal of Geophysical Research: Oceans, 10.1029/2008JC005150, 114, 6, 2009.06, The response of the Indonesian Seas to the monsoonal winds is investigated using a regional ocean model with an emphasis on understanding the mechanisms behind the observed seasonal sea surface temperature (SST) variability. Understanding the seasonal SST variability in the Indonesian Seas is crucial for understanding tropical climate variability since atmospheric deep convection is located directly above these seas. Our model results suggest that the monsoonal winds play a dominant role in creating the spatial SST variability and are responsible for inducing about half of the basin-averaged SST variability. The remaining half is found to be caused by conditions in surface heating, which is brought about by radiation and atmospheric temperature and humidity. The northwesterly wind during Austral summer is roughly uniform over the basin so wind mixing occurs roughly uniformly and no significant spatial SST variability is forced. The southeasterly wind during Austral winter, on the other hand, has a significant spatial variation with a maximum wind speed located in the middle of the basin. This spatial variability causes Ekman upwelling and downwelling in the north and south of the Indonesian Seas, respectively, and establishes a cold SST region in the northeast. The presence of the shallow shelf region in the east is also found critical to the formation of this cold SST event. Without the shelf, lateral advection of warm water from the west will trap the cold SST region to the eastern boundary. Copyright 2009 by the American Geophysical Union.. |
| 44. |
S. Kida, K. J. Richards, Seasonal sea surface temperature variability in the Indonesian Seas, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 10.1029/2008JC005150, 114, 2009.06, The response of the Indonesian Seas to the monsoonal winds is investigated using a regional ocean model with an emphasis on understanding the mechanisms behind the observed seasonal sea surface temperature (SST) variability. Understanding the seasonal SST variability in the Indonesian Seas is crucial for understanding tropical climate variability since atmospheric deep convection is located directly above these seas. Our model results suggest that the monsoonal winds play a dominant role in creating the spatial SST variability and are responsible for inducing about half of the basin-averaged SST variability. The remaining half is found to be caused by conditions in surface heating, which is brought about by radiation and atmospheric temperature and humidity. The northwesterly wind during Austral summer is roughly uniform over the basin so wind mixing occurs roughly uniformly and no significant spatial SST variability is forced. The southeasterly wind during Austral winter, on the other hand, has a significant spatial variation with a maximum wind speed located in the middle of the basin. This spatial variability causes Ekman upwelling and downwelling in the north and south of the Indonesian Seas, respectively, and establishes a cold SST region in the northeast. The presence of the shallow shelf region in the east is also found critical to the formation of this cold SST event. Without the shelf, lateral advection of warm water from the west will trap the cold SST region to the eastern boundary.. |
| 45. |
Shinichiro Kida, Jiayan Yang, James F. Price, Marginal Sea Overflows and the Upper Ocean Interaction, JOURNAL OF PHYSICAL OCEANOGRAPHY, 10.1175/2008JPO3934.1, 39, 2, 387-403, 2009.02, Marginal sea overflows and the overlying upper ocean are coupled in the vertical by two distinct mechanisms by an interfacial mass flux from the upper ocean to the overflow layer that accompanies entrainment and by a divergent eddy flux associated with baroclinic instability. Because both mechanisms tend to be localized in space, the resulting upper ocean circulation can be characterized as a beta plume for which the relevant background potential vorticity is set by the slope of the topography, that is, a topographic beta plume.
The entrainment-driven topographic beta plume consists of a single gyre that is aligned along isobaths. The circulation is cyclonic within the upper ocean (water columns are stretched). The transport within one branch of the topographic beta plume may exceed the entrainment flux by a factor of 2 or more.
Overflows are likely to be baroclinically unstable, especially near the strait. This creates eddy variability in both the upper ocean and overflow layers and a flux of momentum and energy in the vertical. In the time mean, the eddies accompanying baroclinic instability set up a double-gyre circulation in the upper ocean, an eddy-driven topographic beta plume. In regions where baroclinic instability is growing, the momentum flux from the overflow into the upper ocean acts as a drag on the overflow and causes the overflow to descend the slope at a steeper angle than what would arise from bottom friction alone.
Numerical model experiments suggest that the Faroe Bank Channel overflow should be the most prominent example of an eddy-driven topographic beta plume and that the resulting upper-layer transport should be comparable to that of the overflow. The overflow-layer eddies that accompany baroclinic instability are analogous to those observed in moored array data. In contrast, the upper layer of the Mediterranean overflow is likely to be dominated more by an entrainment-driven topographic beta plume. The difference arises because entrainment occurs at a much shallower location for the Mediterranean case and the background potential vorticity gradient of the upper ocean is much larger.. |
| 46. |
Shinichiro Kida, Jiayan Yang, James F. Price, Marginal sea overflows and the upper ocean interaction, Journal of Physical Oceanography, 10.1175/2008JPO3934.1, 39, 2, 387-403, 2009, Marginal sea overflows and the overlying upper ocean are coupled in the vertical by two distinct mechanisms by an interfacial mass flux from the upper ocean to the overflow layer that accompanies entrainment and by a divergent eddy flux associated with baroclinic instability. Because both mechanisms tend to be localized in space, the resulting upper ocean circulation can be characterized as a b plume for which the relevant background potential vorticity is set by the slope of the topography, that is, a topographic b plume. The entrainment-driven topographic b plume consists of a single gyre that is aligned along isobaths. The circulation is cyclonic within the upper ocean (water columns are stretched). The transport within one branch of the topographic b plume may exceed the entrainment flux by a factor of 2 or more. Overflows are likely to be baroclinically unstable, especially near the strait. This creates eddy variability in both the upper ocean and overflow layers and a flux of momentum and energy in the vertical. In the time mean, the eddies accompanying baroclinic instability set up a double-gyre circulation in the upper ocean, an eddy-driven topographic b plume. In regions where baroclinic instability is growing, the momentumflux from the overflow into the upper ocean acts as a drag on the overflow and causes the overflow to descend the slope at a steeper angle than what would arise from bottom friction alone. Numerical model experiments suggest that the Faroe Bank Channel overflow should be the most prominent example of an eddy-driven topographic b plume and that the resulting upper-layer transport should be comparable to that of the overflow. The overflow-layer eddies that accompany baroclinic instability are analogous to those observed in moored array data. In contrast, the upper layer of the Mediterranean overflow is likely to be dominated more by an entrainment-driven topographic b plume. The difference arises because entrainment occurs at a much shallower location for the Mediterranean case and the background potential vorticity gradient of the upper ocean is much larger.. |
| 47. |
Shinichiro Kida, James F. Price, Jiayan Yang, The upper-oceanic response to overflows
A mechanism for the Azores current, Journal of Physical Oceanography, 10.1175/2007JPO3750.1, 38, 4, 880-895, 2008.04. |
| 48. |
Shinichiro Kida, James F. Price, Jiayan Yang, The upper-oceanic response to overflows: A mechanism for the Azores Current, JOURNAL OF PHYSICAL OCEANOGRAPHY, 10.1175/2007JPO3750.1, 38, 4, 880-895, 2008.04, The oceanic response to overflows is explored using a two-layer isopycnal model. Overflows enter the open ocean as dense gravity currents that flow along and down the continental slope. While descending the slope, overflows typically double their volume transport by entraining upper oceanic water. The upper oceanic layer must balance this loss of mass, and the resulting convergent flow produces significant vortex stretching. Overflows thus represent an intense and localized mass and vorticity forcing for the upper ocean. In this study, simulations show that the upper ocean responds to the overflow-induced forcing by establishing topographic beta plumes that are aligned more or less along isobaths and that have a transport that is typically a few times larger than that of the overflows. For the topographic beta plume driven by the Mediterranean overflow, the occurrence of eddies near Cape St. Vincent, Portugal, allows the topographic beta plume to flow across isobaths. The modeled topographic beta-plume circulation forms two transatlantic zonal jets that are analogous to the Azores Current and the Azores Countercurrent. In other cases ( e. g., the Denmark Strait overflow), the same kind of circulation remains trapped along the western boundary and hence would not be readily detected.. |
