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Byline: Tetsuo Yanagi (1), Goh Onitsuka (2), Naoki Hirose (1), John-Hwan Yoon (1) Keywords: Spring bloom; Sea of Japan; numerical ecosystem model Abstract: The northward migration of spring bloom was observed in the Sea of Japan from April to May 1997 by the Ocean Color and Temperature Scanner (OCTS) on board the Advanced Earth Observing Satellite (ADEOS). This phenomenon is well simulated with a numerical ecosystem model coupled with a hydrodynamic model. The hydrodynamic model is the Geophysical Fluid Dynamics Laboratory (GFDL) Modular Ocean Model (MOM). The ecosystem model consists of five components: dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), phytoplankton, zooplankton and detritus. Results of the numerical ecosystem model suggest that the mesoscale development of the spring bloom in the Sea of Japan is related to that of sea water temperature, and that the bloom is limited by the depletion of DIN. Author Affiliation: (1) Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan (2) Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, 816-8580, Japan Article History: Registration Date: 08/10/2004

Byline: Naoki Hirose (1), Ichiro Fukumori (2), Jong-Hwan Yoon (3) Keywords: Data assimilation; Kalman filter; TOPEX/POSEIDON; sea level; Japan Sea; reduced-gravity model Abstract: Sea level data measured by TOPEX/POSEIDON over the Japan Sea from 1993 to 1994 is analyzed by assimilation using an approximate Kalman filter with a 1.5 layer (reduced-gravity) shallow water model. The study aims to extract signals associated with the first baroclinic mode and to determine the extent of its significance. The assimilation dramatically improves the model south of the Polar Front where as much as 20 cm.sup.2 of the observed sea level variance can be accounted for. In comparison, little variability in the northern cold water region is found consistent with the model dynamics, possibly due to significant differences in stratification. Author Affiliation: (1) Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, 816-8580, Japan (2) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, U.S.A (3) Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan Article History: Registration Date: 01/10/2004

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. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) can be influenced by both physical and biogeochemical conditions of the ocean and is hence an important index for predicting changes in ocean environments. However, the relationship between biogeochemical activities and the DO concentration has not been quantified clearly in the Japan Sea (JS). In this study, we developed a coupled physical-biogeochemical model and clarified the contributions of biological processes to the DO content in the upper JS. We conducted two numerical experiments: with and without the biogeochemical compartments. Taking the biogeochemical factors into account gave better estimations for the spring-to-autumn seasonal migration of the subsurface DO maximum. In the euphotic zone, high photosynthetic production increases the DO concentration from spring to autumn. The strongest positive effect of biological processes on DO concentrations appears in summer at a depth of 30 m and is more than 0.5 ml l−1. As summer progresses to autumn, the vertical pattern of DO concentration in the Tsushima Warm Current (TWC) region shows minima at depths between 50 and 100 m, which is caused by the intrusion of low DO water from the East China Sea. The strongest negative effect on DO concentrations mainly due to the decomposition of detritus occurs in the TWC region below 150 m depth because the water is poorly ventilated by the relatively weak winter convection. [ABSTRACT FROM AUTHOR]

In the coastal areas of Wakasa Bay, the Japan Sea—an observation network for fisheries and a simulation system of coastal currents with a high-resolution numerical model—revealed intensification of current in summer around Cape Echizen. The 2012-2014 current data collected by mooring observations off Takasu, near Cape Echizen, showed that the current's speed exceeded 40 cm s−1 for more than 5 days around July and August each year. In addition, the 2014 current data collected by a research vessel indicated that the first branch of the Tsushima Warm Current (FBTWC) flowed near the coast when the strong current with an increase of water temperature occurred in the upper layer of coastal waters off Takasu. Similarly, the simulation results revealed that the FBTWC variability caused intensification of the current in coastal waters near Cape Echizen. In addition, they showed that when the strong current was generated in coastal waters off Takasu, cold water accompanied by strong current expanded to coastal seas around Cape Echizen in the subsurface layer. From these results of the observations and the simulation, it was considered that the strong current in the coastal waters off Takasu in summer was attributed to the acceleration of the FBTC, which is accompanied by cold water expansion in the subsurface layer to the vicinity of the coast and contact of the FBTWC along the cold water edge with the coast. [ABSTRACT FROM AUTHOR]

A sudden strong coastal current called a 'kyucho' occurred in August 2013 in the eastern coastal waters of Wakasa Bay, Japan. This study examined its characteristics based on both observational data collected by intensive field investigations and the simulation results of a numerical model. The field investigations comprised moored buoy observations near the coast and voyages by a research vessels and fishing boats. The mooring observations indicated that a current speed exceeding 50 cm s occurred abruptly near the eastern coast of the bay, in association with a synchronous change in the current direction. Data collected by acoustic Doppler current profilers (ACDPs) mounted on the vessels showed that a clockwise eddy existed in the bay and that the current on the east side of the eddy generated the kyucho near the coast. Based on the results of the numerical model and the analysis of the ADCP data, it was considered that the clockwise eddy was generated by a strong current at the tip of the Tango Peninsula, in the western part of the bay. As the eddy propagated from west to east across the bay, it induced the kyucho in the coastal waters in the east of the bay. [ABSTRACT FROM AUTHOR]

A simple effective method of inverse estimation provided by model Green's functions is examined to calibrate tides in a regional circulation model for the East Asian marginal seas. The Green's function optimization derived by perturbing the model parameters significantly improves the estimate relative to observation as compared with baseline integration. Among the optimized model parameters, the largest effects on cost function reduction come first from the harmonic constant of M along the open boundaries with the optimized values of 89.7 ± 0.8% for amplitude, and second from the bottom friction with the optimized value of (3.06 ± 0.08) × 10. [ABSTRACT FROM AUTHOR]

Recent investigation suggests that volume transport through the Tsushima/Korea Strait often has double peaks during the summer to autumn period with decreasing transport in September. The satellite-observed wind changes from weak northwestward (across-strait) in summer to strong southwestward (along-strait) in early autumn (September) in the strait. Such a strong along-strait wind is related to tropical cyclones, which frequently pass through the East China Sea in September. The effect of the along-strait wind component on the transport variation is examined using a three-dimensional numerical model. The simulated volume transport through the Tsushima/Korea Strait shows realistic seasonal and intra-seasonal variations. According to sensitivity experiments on local winds, the transport variations in September are mainly generated by strong along-strait (southwestward) wind rather than weak across-strait wind. The strait transport responds to the along-strait wind (southeastward), which produces a sea level increase along the Korean coast, resulting in the geostrophic balance across the strait. The transport minimum through the Tsushima/Korea Strait in September can be determined by the combination of the across-strait geostrophic and along-strait ageostrophic balances. [ABSTRACT FROM AUTHOR]

A list of reviewers including Stephen Bakan, Ryo Furue and Akio Ishida who reviewed articles of the periodical from January 1, 2015 to December 31, 2015 is presented.

The article lists the reviewers of the periodical including Susan Allen, Gualtiero Badin, and David Mackas.

A list of reviewers for manuscripts submitted to the "Journal of Oceanography" during 2010 is presented.