Eutrophication mechanisms of narrow and deep Dokai Bay and wide and shallow Hakata Bay are compared on the basis of observed salinity, TP and TN data. Nutrients assimilated to phytoplankton in the euphotic layer sink to the aphotic layer and they are advected to the bayhead by the developed estuarine circulation in narrow and deep Dokai Bay. Therefore, the average residence times of TP and TN in Dokai Bay are two times as that of freshwater, while the average residence times of TP and TN are nearly the same as that of freshwater in wide and shallow Hakata Bay. Therefore, narrow and deep Dokai Bay is easy to eutrophicate although the average residence time of freshwater is short.

View full abstract

Although the paths and scales of typhoons T9119 and T9918 were similar, a severe storm surge was excited in the Yatsushiro Sea only by T9918. In order to examine the reasons for this, numerical experiments on the storm surges caused by T9119 and T9918 are performed. Results of the numerical experiments reveal that tidal anomalies induced by the wind and by depression of the sea surface pressure of T9918 were larger than those of T9119. An analysis of the meteorological data shows that the wind speed of T9918 was locally greater than that of T9119. It is suggested that the locally strong wind of T9918 caused the large tidal anomaly. The contribution of the sea surface pressure of T9918 to the storm surge was greater than that of T9119. The results of the numerical experiments show that the volume transport induced by T9918 toward the head was greater than that by 9119, since the pressure gradient of T9918 along the bay axis was stronger than that of T9119. It is indicated that the large volume transport induced by T9918 caused the large tidal anomaly at the head compared with that by T9119.

View full abstract

The purification abilities for nitrogen(N), phosphorus(P) and for particulate organic nitrogen(PON) were estimated in the Honjo District in Lake Nakaumi. Nitrogen and phosphorus were estimated to be eliminated mainly by sedimentation, fisheries, and denitirification at 161 kg N year^-1 and 11.1 kg P year^-1, respectively. The purification abilities of the Honjo District have been reported to be 250 kg N year^-1 and 11.4 kg P year^-1 by calculation of the water exchange between the Honjo District and Lake Nakaumi. Nitrogen and phosphorus eliminations estimated in this work are 64% and 97% of those previously reported. The discrepancy in the N budget was considered to be due to the underestimation of denitrification in this study. The filter-feeding bivalve Musculista senhousia which was dominant in the Honjo District was estimated to remove 0.74 t PON year^-1 (3.62 t COD year^-1); this rate was estimated to be about half of the whole removal rate in the Honjo Distirct. Finally, the importance of the activity of diving ducks predating the bivalve Musculista senhousia in the Honjo District and the possibility for increasing the number of useful bivalves are discussed.

View full abstract

A new method of CTD data processing is developed to improve precision in measurements of vertical microstructure of temperature and salinity profiles. Fluctuation of conductivity of sea water is affected by that of temperature quite sensitively, using this physical property, temperatures acquired by CTD are corrected by CTD conductivities in the new method, named the Temperature-Conductivity Combined method (TCC method). The TCC method drastically reduces the salinity/density spike and density inversion as shown in Figure 10 and Figure 11 independently of the descending speed of the CTD probe. Fluctuations of temperature, conductivity, salinity and density derived from the TCC method coincide with one another over a broad frequency range.

View full abstract

The East Korean Warm Current and North Korean Cold Current have been referred to historically by several names in the Japanese language literature, but To-Sen-Dan-Ryu and Hoku-Sen-Kan-Ryu, respectively, have come to be used frequently. "Sen", which literally means "fresh" or "clear", is abbreviated from "Chosen", a traditional name for Korea which literally means "land of the morning dawn". Although the literal meaning of "Sen" is benign, its use in abbreviated form in place of "Chosen" resembles, perhaps by coincidence, the similar use of the abbreviated "Sen" in place of "Chosen" in such terms as "Senjin", an abbreviated form of "Chosenjin" meaning Korean person or Korean people, which came into frequent use in Japanese newspapers soon after Japan colonized the Korean Peninsula in 1910, and according to Utsumi et al. (1986) was used with racially derogatory intent. I have reviewed about 30 Japanese language research papers on these currents published from 1897 through 1951. I found the first uses of "Sen" as abbreviation for "Chosen" in Nomitsu (1931), who used "Sei-Sen-Kai-Ryu" for the West Korean Current in charts but not in his text; Uda (1934), who was the first to use the above-mentioned names "To-Sen-Dan-Ryu" and "Hoku-Sen-Kan-Ryu"; and Hidaka (1943), who used "Hoku-Sen-Dan-Ryu" for the North Korean Warm Current. These usages occurred during the historical period when the racially derogatory "Senjin" was in wide use in the newspapers, but this in itself hardly proves a causal connection. This was also the first time that these currents became the subject of extensive published research, thus providing opportunities for naming them in print. Nomitsu used the abbreviated term in his chart but not in his text, suggesting that economy of chart space was a factor. Those of us who had the privilege of knowing Michitaka Uda and the other authors personally find it impossible to believe that they had racist motives for using these terms. However, the fact remains that any use of "Sen" as an abbreviation For "Chosen" revives harsh memories among at least some Koreans. In addition, the continuing series of well publicized, racially insensitive remarks by some Japanese politicians forces us to be extra-perhaps even excessively-cautious in these matters. Following a 1991 protest by a Korean anti-discrimination committee, in 1992 the Japanese Ministry of Education, Science and Culture ordered the offending terms removed from future editions of its Japanese-English technical dictionary of oceanographic terms. There is now a need for alternative terms. Keisuke Taira, past president of the Oceanographic Society of Japan, suggested in a previous edition of this publication (Taira, 2000) that the full "Chosen" be used in place of the abbreviated "Sen" in current names. I agree that such a change is necessary at this time; but given the economy of both chart space and of syllables in pronunciation that can be achieved by using the abbreviated form, I hope that in the future, perhaps by the 22nd century or later, people will become less sensitive to use of "Sen" in contexts unrelated to actual racist intent, permitting a more objective decision to be made on resuming its use.

View full abstract

In United Nations Conferences on Place Name Standardization in recent years, both nations in the Korean Peninsula proposed that the name "Japan Sea" is a heritage of Japan's colonial policy and should be changed. I have researched this question and found the claim to be groundless. Of the eleven marginal seas on Earth, five, the Andaman Sea, Gulf of California, Irish Sea, English Channel and Japan Sea, are named after the island or peninsula which separate the sea from the surrounding ocean and thus in a sense are responsible for its existence. Thus, the name "Japan Sea" is quite natural from a geographic point of view. Next I mention the background of the history how A. J. von Krusenstern had been blindly believed, among many Japanese encyclopedists, as the person who drew the earliest map that used the name "Japan Sea". Finally, using map data shown by Aoyama (1997) and early current charts (1837-1887), my research has confirmed the following historical facts. In both of Western-made and Japanese-made maps, the name "Japan Sea" was frequently used since about 1800, and was firmly established around the Meiji Restoration (1868), as Aoyama (1997) suggested. The name "Japan Sea" came into use obviously before the year 1910, when Japanese colonization of Korea began. Japan's military aggression against neighboring countries during the first half of the 20th century is a grave and great crime, but it has nothing to do with the international spread of the name "Japan Sea".

View full abstract

A term "Shiwo-Sakahi" ( ?? ?? ?? ), used in the Seto Inland Sea, Japan in the middle Edo Period (Mori, 1754), is interpreted to mean a boundary zone, on both sides of which the current direction from the low tide to the high tide becomes opposite. This term must have spread, because such information on tidal currents was useful for the practical aspect, related to the waiting in port until the tidal current shifts to a favorable direction. Kitahara (1912, 1921) used terms "Shio-Ai" ( ?? ?? ) and "Shio^Ai-Sen" ( ?? ?? ?? ) to mean a boundary between warm and cold currents, but actually warm and cold water-masses. While Nagatsuka (1906) used a term "Shio-Me" ( ?? ??, current-rip) to mean a boundary between cold river water and warm seawater in his traditional Japanese poem, Uda (1929a) used this term to mean a line of accumulation of drifting matter accompanied by a thermal front in his scientific report. Uda (1931) also used a term "Shio-Zakai" ( ?? ?? ) for the first time to mean a line of current convergence or a boundary between two water-masses with different colors. However, the motive for Uda, an ardent admirer of Kitahara, to have started using "Shio-Zakai" instead of "Shio-Ai-Sen" used by Kitahara, is still mysterious. Possibly "Shio-Zakai" might have already spread among fishermen in open seas. The terms "Shio-Ai" and "Shio-Zakai" were not used by Shigematsu and Kishindo of the Hydrographic Office, Japanese navy, but were used by Kitahara and Uda of fisheries experimental organizations. This is probably because these terms were useful for the practical aspect of the fisheries oceanography.

View full abstract