Full text - terrapub

Transcription

Full text - terrapub
Journal of Oceanography
Vol. 49, pp. 443 to 458. 1993
The Northward Intruding Eddy along the East Coast of Korea
YUTAKA ISODA1 and SEI-ICHI SAITOH2 *
1Department
of Civil and Ocean Engineering, Ehime University, Matsuyama 790, Japan
Institute, Japan Weather Association, Kaiji Center Bldg., 5,
4-chome, Kojimachi, Chiyoda-ku, Tokyo 102, Japan
2Research
(Received 3 September 1992; in revised form 22 January 1993; accepted 25 January 1993)
The current structures and their seasonal variations in the East Korean Warm
Current (EKWC) region, which plays a significant role in the northward transport
of warm and saline waters, were described by combining the sea surface temperature
(SST) data of consecutive satellite inferred (IR) images and hydrographic data.
The SST patterns in winter–spring clearly showed that the small meander of
thermal front originating from the Tsushima/Korea Strait formed close to the
Korean coast and grew an isolated warm eddy with horizontal dimension of order
100 km. Such warm eddy began to intrude slowly northward from spring to
summer. At that time, interactions with neighboring synoptic warm eddy [Ks]
around the Ulleung Basin were found to have strongly influence the movement of
the intruding eddy and its structural change. In autumn, after the northward
movement stopped at the north of eddy [Ks], the relative stable northward current
along the Korean coast were formed. The evidence from observational results does
not support a persistent branching of the EKWC from the Tsushima/Korea Strait,
but a seasonal episodic supply of warm and saline waters due to the northward
intruding eddy process described above.
1. Introduction
It was proposed by Suda and Hidaka (1932), Uda (1934) and Kawabe (1982a) that the
Tsushima Current formed three branches just after it enters the Japan Sea through the Tsushima/
Korea Strait as schematically shown in Fig. 1. The 1st (nearshore) branch is the extension flow
along the Japanese coast, which enters the Japan Sea through the eastern channel of the strait. The
2nd (offshore) branch and the 3rd branch (the East Korean Warm Current; referred to as the
EKWC) enters the Japan Sea through the western channel of the strait and they are separated from
each other northeast of the strait. The EKWC may be particularly significant, since it carries heat
and water mass northward and creates the warm surface layer throughout the basin south of the
oceanic thermal front, i.e. the polar front in the Japan Sea.
The dynamical process has been reported regarding the formation of this EKWC using the
numerical experiments, e.g. Yoon (1982a, b), Kawabe (1982b) and Sekine (1986). These
experiments have explained the EKWC as the steady western boundary current generated by the
external forcing of outflow at the Tsugaru Strait. Namely, the EKWC extends northward until
it reaches the latitudes of the Tsugaru Strait located at 41°N and becomes an eastward zonal
current to flow out through the outlet. However, the observations as discussed below show some
serious discrepancies of model results.
*Now at Faculty of Fisheries, Hokkaido University, 3-1-1, Minato-cho, Hakodate 041, Japan.
444
Y. Isoda and S. Saitoh
Fig. 1. Bathymetric chart in the Japan Sea. Three branches of the Tsushima Current near the Tsushima/
Korea Strait are schematically shown. Broken thick outline is the area covered by a consecutive
satellite IR images in 1987 utilized in this study.
Figure 2(a) shows the monthly isotherms of 100 m depth from the climatological mean from
1906 to 1987 for February and August (Japan Maritime Safety Agency, 1992). It is important to
note that there may be two or three fronts with the synoptic meanders in the EKWC region. These
meanders are taken to be accompanied by warm and cold eddies. Recently, statistical studies
were made on the existing frequency distributions in terms of the synoptic warm eddies with
horizontal dimension of order a few hundred km as shown in Fig. 2(b) (Isoda and Nishihara,
1992). This map implies that the movements of synoptic warm eddies are not turbulence, which
transfers heat northward steadily (Toba et al., 1984), but rather stable at the following five areas,
i.e. [Kn], [Ks], [Y], [O] and [N] in Fig. 2(b). From Figs. 2(a) and (b), it is found that the actual
separation of the EKWC occurs south of 38°N at the depth of 100 m and the local northern limit
of the polar front corresponds with the location of eddy [Y] on the Yamato Rise at 40°N.
Furthermore, a cold water region may be always situated to the northwest of the Oki spur (see
Fig. 2(a)), which is corresponding well to the low frequency area less than 10–20% in Fig. 2(b).
It is likely that warm eddies do not enter into this area. In fact, the Shimane Cold Water might
be frequently formed there, e.g. Tanioka (1962).
The existence of such eddies causes a large meandering paths in the EKWC region. Besides,
the recent observations have shown that the EKWC is highly energetic and characterized by
The Northward Intruding Eddy along the East Coast of Korea
445
Fig. 2. (a) Monthly isotherms of 100 m depth from the climatological mean from 1906 to 1987 for
February and August (Japan Maritime Safety Agency, 1992). (b) The existing frequency of synoptic
warm eddies during the statistical period from 1980 to 1990 (Isoda and Nishihara, 1992). [Y], [O], [N],
[Kn] and [Ks] indicate the sea areas with a local maximum value and suggest the stable existence areas
of synoptic warm eddies.
mesoscale features. In particular, satellite IR images off the Korean coast have shown some warm
filaments extending seaward or mesoscale warm eddies with horizontal dimension of order less
than 100 km, e.g. Tameishi (1987) and Kim and Legeckis (1986). We infer that these
observations provide evidence for synoptic or mesoscale warm eddies as an important role for
the current structures in the EKWC region.
446
Y. Isoda and S. Saitoh
In the present study, relatively cloud-free satellite IR images over the EKWC region were
obtained in spring and autumn from 1985 to 1989. In particular, based on a consecutive images
in 1987, we investigated the shapes and trajectories of the mesoscale warm eddies. The results
derived from these images were compared with the shallower and deeper hydrographic structures
in 1987. We clarified the relation between the synoptic processes of the ocean and mesoscale ones
in the EKWC region and their seasonal variability.
2. Data
Plate 1 shows the satellite IR images in the western part of the Japan Sea from 1985 to 1989,
which were processed by the Japan Weather Association. They are typical SST patterns of
enhanced images in spring (a: March–April) and autumn (b: October–December), in which
darker (brighter) tones enhanced warmer (colder) waters.
To investigate the temporal and spatial evolution of the mesoscale features in detail, the
consecutive satellite IR images over the EKWC region were collected in 1987. Study area of
these images is shown by the broken thick outline in Fig. 1. Figures 3 and 6 show the selected
images as the SST contour maps revealing the evolution of mesoscale warm eddies in winter–
spring (from 8 January to 17 April) and the northward flow close to the Korean coast in autumn
(4 October and 16 December) 1987, respectively.
Routine hydrographic survey were conducted in 1987, by the Fisheries Research and
Development Agency, Korea (1988) and the Shimane Prefectural Fisheries Experimental
Stations (Fisheries Agency Japan, 1990) in Japan. It has been considered that the 100 m isotherms
well represent the streamlines of the Tsushima Current. However, the trouble was that the quasisynoptic patterns of 100 m isotherms denoted the very complicated streamlines as for the
presence of the EKWC at each observation. There are examples of both absence and presence of
the northward branch from the Tsushima/Korea Strait (Kim and Legeckis, 1984) and the
existence of an isolated warm eddy or a simple one-mean-dering current off the Korean coast
(Tanioka, 1968). The fact is that such drastic changes at the middle layer, i.e. 100 m depth, occurs
due to the couple with mesoscale feature with the shallower depths and synoptic scale feature
with the deeper ones, as will be described in the present study. Therefore, we depicted the
temperature distributions of near-surface layer (75 m depth) which indicate the spatial structure
of mesoscale eddies and those of 200 m depth which clearly indicate synoptic warm eddies [Kn]
and [Ks] (Fig. 4). Furthermore, the structural changes of the Tsushima Current can be estimated
on the results from the distributions of high salinity water which flows into the Japan Sea through
the Tsushima/Korea Strait in spring every year. Figure 7 shows the temporal changes of the
salinity distributions of 100 m depth in 1987. To indicate the vertical features of synoptic warm
eddies, i.e. [Ks] and [Kn], and the offshore branch, the vertical sections of water temperature and
salinity observed along 103 and 105 lines off the Korean coast and the seaward line off Hamada
in Japan are shown in Fig. 5. Their locations are shown as the thick solid lines in Fig. 4.
3. Typical SST Patterns of the Enhanced Images in Spring and Autumn
It is apparent that the spring SST patterns of surface water system in the EKWC region differ
from the autumn SST patterns. The SST in spring is reflected by the spatial structure and location
of some thermal fronts, while the SST gradients in autumn are relatively small and it is impossible
to detect such thermal fronts. Therefore, it is noticed that a strong contrast of enhanced images
in autumn does not necessarily coincide with a sharp SST front.
Satellite IR images taken in spring (Plate 1(a)) indicated that the narrow-belt of warmest
The Northward Intruding Eddy along the East Coast of Korea
447
waters, about 50 km width, was formed close to the Korean coast, accompanied by some warm
filaments. Such filaments suggested the complex eddy-like structures or the existence of a few
turning flows from the Korean coast. So, it is difficult that the northern end of the EKWC is
clearly detected from the satellite SST patterns. Thus, the EKWC in spring does not appear to be
a stationary current but flows in a very turbulent way.
On the other hand, the satellite SST images in autumn (Plate 1(b)) showed the relative stable
flow pattern every year. The northward EKWC was clearly seen as the warm belt close to the
Korean coast, which was somewhat broader 50 km to 100 km width. It turned at 38°–39°N
sharply eastward, where the existence of a warm eddy can be inferred from the anticyclonic
rotation pattern of warm filament. Thus, in autumn, the sharp SST fronts accompanied by eddies
could not be seen except for the northern end of the EKWC.
SST features commonly observed in both seasons could be also detected. First, since we refer
to the warm belt as the trajectory of northward current, axis of the EKWC seems to approach near
the Korean coast in the upper oceans. Second, not only the southward counter-current flowing
along the eastern side of northward current close to the Korean coast, but also the eastward zonalcurrent which was directly connected to warm water on the Yamato Rise was not formed. Isoda
et al. (1992) studied the spatial structures around the warm eddy [Y] and their seasonal variations.
They suggested a possibility that warm water in eddy [Y] was not transported from an extension
of the EKWC, but composed of water flowing northeastward from the Oki spur. Presumably, the
EKWC cross-exchange as “leakage” or “diffusivity” process might play an important role in heat
and water mass transport to the interior region of the Tsushima Current.
Thus, the SST distributions of the upper oceans in the EKWC region have a seasonal
variability. The mesoscale features may dominate in spring, but not in autumn. Namely, the
mesoscale eddies will evolve rapidly in spring, and their drastic structural changes will occur
during spring to autumn. In the following analysis, we focus the discussion on their temporal and
spatial variations using the satellite and hydrographic data in 1987.
4. Northward Intruding Eddy along the Korean Coast
4.1 Formation process in winter to spring
The northward intruding eddy was born and evolved from January to April 1987. The
process of this formation can be seen in the satellite SST contour maps (Fig. 3). The SST from
the IR image on 8 January was higher than the SST on 5 March by about 4°C in most parts of the
EKWC region, which presumably indicates a uniform sea surface cooling due to wintertime
convection. On 8 January the sharp thermal fronts A, B, C and D–E appeared roughly
perpendicular to the Korean coast. Each front from A to C seems to be formed at the northern end
of mesoscale anticyclonic eddy. Concerning the thermal front B and C situated around 37°–38°N,
we find that on the following days these fronts near the Korean coast decreased in the horizontal
temperature gradient and amount of warm water in the southern mesoscale eddy engulfed into
the northern mesoscale eddy as the warm filament. Then, on 5 March the thermal front A and B
disappeared and the front C moved northward until around 39°N.
Another thermal front D–E originated near the southeastern part of the Korean Peninsula and
extended eastward on 8 January. This front corresponds to the offshore branch of the Tsushima
Current flowing along the shelf edge off the Japanese coast. On 28 January the thermal front at
side D started to form as the small meander moved northward along the Korean coast. On 27
March this meander grew as an isolated mesoscale warm eddy in size about 100 km in diameter.
Plate 1(a). The enhanced satellite IR images in spring from 1985 to 1989.
448
Y. Isoda and S. Saitoh
Plate 1(b). The enhanced satellite IR images in autumn from 1985 to 1989.
The Northward Intruding Eddy along the East Coast of Korea
449
450
Y. Isoda and S. Saitoh
On 17 April the thermal front at side D had separated from the offshore branch of the Tsushima
Current and can no longer be connected to the thermal front at side E.
Thus, a consecutive satellite IR images showed the northward migration of the southern
warm water wedge associated with the southern separation point. Although mesoscale eddies
with the thermal front A and B took the form of a fully developed warm filaments, they diffused
rapidly during a few months. On the other hand, similar fully developed mesoscale eddies with
the thermal front C and D were born from January to March and grew in size about 100 km in
diameter. After this, we could clearly see a tendency for these individual eddies to intrude
northward.
4.2 Northward movement from spring to autumn
After formation, the northward intrusion process of eddy can be seen in the near-surface
temperature maps of 75 m depth (the upper panels in Fig. 4). It is worth noticing that these patterns
entirely differ from those of 200 m depth (the lower panels in Fig. 4), particularly at the southern
part of the EKWC region. On February–March two synoptic warm eddies [Kn1] around the Korean
Plateau and [Ks] around the Ulleung Basin were clearly seen at the deeper hydrographic
distributions of 200 m depth, whereas two warm eddies [a] and [b] along the Korean coast were
seen at the shallower ones. Eddy [a] with an SST front C corresponded to the eddy [Kn1]. It moved
slowly northward at least by June. Eddy [b] with an SST front D also moved northward at the
western side of eddy [Ks] from February to August.
According to the hydrographic section on February 1987 in Fig. 5, the vertical features of
both eddies [Kn1] (or [a]) and [Ks] are characterized by about 5°C isotherm contour. The structure
of eddy [Ks] was evident to a depth of more than 300 m. This eddy [Ks] contained an intruding
eddy [b] at the western upper layer of itself, which could be characterized by the saline waters
more than 34.3 psu and about 10°C isotherm contour. This kind of superimposed eddies-structure
was also seen along 105 and 103 lines on June and along 103 line on October in Fig. 5, and has
been frequently observed as seen in Fig. 8 of Gong et al. (1985), Fig. 8 of Kim, K. et al. (1991)
and Fig. 4 of Kim, C. H. et al. (1991). The vertical distributions of saline water in an intruding
eddy [b] were almost the same as those conferring the shelf waters off Hamada throughout the
year in 1987 (see Fig. 5). This implies that the intruding eddy [b] is certainly separated from the
offshore branch with the shelf waters.
On June, eddy [Ks] formed a warm-water protrusion [Kn2] to the north and changed shape
to an ellipse when eddy [b] began to intrude along the northwest edge of eddy [Ks] (Fig. 4). At
that time, vertical section (along 105 line on June in Fig. 5) showed the superimposed eddiesstructure in an eddy [Kn2], accompanied by eddy [b]. Namely, the intrusion of eddy [b] has a
strong influence on the surface structure of eddy [Ks] shallower than 150–200 m, but not the core
structure. On August, the northward movement of eddy [b] (or [Kn2]) stopped at the north of eddy
[Ks] and, then, completely separated from the Korean coast (Fig. 4). After this, the superimposededdies structure in an eddy [Kn2] had disappeared and became to an isolated eddy, characterized
by about 5°C isotherm contour (along 105 line on October in Fig. 5).
Although the northward movement of eddy [a] (or [Kn1]) after August was not clear from
Fig. 4, we inferred that this eddy had to dissipate in the northern EKWC region during July to
October. From Fig. 6, the satellite SST contour maps on October and December capture a broader
warm belt close to the Korean coast, which are represented by the northward intruding SST
contour of 19°C and 13°C, respectively. Comparing with Fig. 4 and Fig. 6, it is found that there
is no warm eddy at the north of eddy [b]. Eddy [b] with the thermal front F was formed as the
Fig. 3. The consecutive SST contour maps over the EKWC region from 8 January to 17 April 1987
showing the northward movement of mesoscale eddies. Arrows A, B, C and D–E indicate the thermal
fronts in SST. Dashed arrow indicates the warm filament and its flow direction. Cross grid denotes the
cloud data, and the ship mark shows the period of the hydrographic survey.
The Northward Intruding Eddy along the East Coast of Korea
451
Fig. 4. Near-surface (75 m depth) temperature distributions showing the warm eddies [a], [b] and [c], and
temperature distributions at the depth of 200 m showing the synoptic warm eddies [Kn] (Kn1 , Kn2, Kn3)
and [Ks] in 1987. The solid lines on February, June and October indicate survey observation lines for
the vertical distributions of temperature and sanity in Fig. 5. Warm eddy [b] is the northward intruding
eddy along the Korean coast.
452
Y. Isoda and S. Saitoh
Fig. 5. Vertical temperature cross-sections of the offshore branch of the Tsushima Current off Hamada
in Japan and the synoptic warm eddies [Kn] and [Ks] along 103 and 105 lines on February, June and
October in 1987. Shadow areas show the saline waters more than 34.3 psu.
The Northward Intruding Eddy along the East Coast of Korea
453
454
Y. Isoda and S. Saitoh
northern end of the warm belt. However, the dissipation mechanism of eddy [a] could not be
clarified in the present study because it is difficult to observe off the north Korea and detect such
phenomena due to its rapid dissipation. On December, a significant offshore current flowing
along the shelf edge off Japanese coast was formed again as the thermal front (Fig. 4). This current
could be also seen at the SST maps in winter–spring (Fig. 3).
When we compared the two cross-sections of eddy [a] (or [Kn1]) and eddy [b] (or [Kn2]) in
Fig. 5, one finds that they are very similar structure. The saline waters could be found in the core
of both northern eddies [Kn1 ] and [Kn2 ], beyond the southern eddy [Ks]. These results suggest
that the formation of the northern synoptic eddy [Kn] might be due to the supplying of warm and
saline waters accompanied by the northward intruding eddy in the upper oceans.
4.3 Structural changes during the northward intruding
As mentioned in the previous sections, salinity maps of 100 m depth in 1987 (Fig. 7) reveal
a similar story, confirming the structural changes of intruding eddy [b]. Eddy [b] with a core of
saline waters moved slowly northward from February–March to June. On June, two developed
saline filaments appeared. The shape of these filaments shows that saline waters in eddy [b]
leaked outside of the northeast of eddy [Ks]. At that time, eddy [Ks] was elliptical in shape, and
accompanied by eddy [b] at the north rims itself. Such saline waters spread in all EKWC regions,
horizontally at the middle layer from 50 m to 150 m depth. From October to December, they were
detected in a core of eddy [b] and two patches along the rims of eddy [Ks]. Thus, the northward
intruding eddy in spring generally have sharp temperature gradients and well-defined patterns
of salinity in the upper oceans, while those in summer to autumn gradually obscured by warm
and saline waters engulfment into the southern synoptic eddy [Ks].
5. Discussion
Satellite IR images in 1987 with concurrent hydrographic data provide that the warm and
saline waters in the EKWC region are episodically intruded northward by the mesoscale eddylike plumes of the shelf waters near the Tsushima/Korea Strait. Seasonal variability of such flow
patterns is schematically represented in Fig. 8.
In winter to spring, the small meander of thermal front originating from the Tsushima/Korea
Strait forms close to the Korean coast and grows an isolated mesoscale warm eddy. In summer
to autumn, this mesoscale warm eddy intrudes slowly northward along the Korean coast around
36°–37°N and gradually leaks outside of the synoptic eddy [Ks] around 37°–38°N. At that time,
the density structure of intruding eddy is found at the depth shallower than 150–200 m. Below
this depth, the structures are superimposed on the synoptic eddy [Ks], suggesting the intruding
eddy may be driven by the deep of eddy [Ks]. After the movement of the intruding eddy, the
relative stable flow along the Korean coast and the warm eddy [Kn] as the northern end of the
EKWC are formed, but may be temporary only in autumn. As the results of wintertime
convection and diffusive process of saline waters, some mesoscale-size water patches will be
formed during winter, as seen in the satellite IR images in Plate 1(a) and Fig. 3. The present
observation suggests that the intruding eddy process occurs regularly with one-year cycle from
winter to autumn. Therefore, the seasonal difference of current structure in the EKWC region can
be explained by a series of intruding eddy process described above, with the addition of structural
changes during winter.
The existence of the southern synoptic eddy [Ks] is so important as the dynamical process
of the intruding eddy. From Fig. 2(b), eddy [Ks] is always in existence and its location is almost
The Northward Intruding Eddy along the East Coast of Korea
455
Fig. 6. The two SST contour maps over the EKWC region on 4 October and 16 December 1987 showing
the warm belt close to the Korean coast. Arrow F indicates the thermal front in SST. Cross grid denotes
the cloud data.
Fig. 7. Salinity distributions of 100 m depth showing the structural changes of the Tsushima Current in
1987. Shadow and black areas show the saline waters more than 34.3 psu and 34.6 psu, respectively.
456
Y. Isoda and S. Saitoh
Fig. 8. Schematic illustration of the intruding eddy process in the EKWC region, showing that the
northward movement of intruding eddy through the interaction with the southern synoptic eddy [Ks]
and the formation of the northern synoptic warm eddy [Kn], which was due to the supplying of warm
and saline waters accompanied by the northward intruding eddy. Shadow water mass shows the warm
and saline shelf waters which are intruded from the exit of the Tsushima/Korea Strait.
constant around the Ulleung Basin. Kim, K. et al. (1991) suggested that the stationary eddy [Ks]
was generated by the topographic control on the movement of the abyssal waters, but such
phenomena as the interaction with neighboring currents have not been well investigated. To
confirm the hypothesis that northward intruding eddy indicate the interaction with eddy [Ks], it
would be necessary in future to make an additional quantitative study of the velocity structure
of eddy [Ks] and to make concurrent measurements of northward current structure along the shelf
off the Korean coast.
Finally, we consider that the intruding eddy process mentioned above may occur due to the
following reasons. Outflows from the strait can be treated from the law of potential vorticity
conservation, e.g. Ichiye (1991). Namely, the flow just after leaving the Tsushima/Korea Strait
may conserve the potential vorticity near the strait. Furthermore, it can be assumed that near the
Tsushima/Korea Strait the relative vorticity, i.e. O(10–6 s–1) from (the horizontal shear/the width
of the strait) = 40 cm s–1/200 km referred to Isoda and Yamaoka (1991), is very small compared
to the local Coriolis parameter, i.e. O(10–4 s–1). Therefore, the amount of potential vorticity
largely depends on the distributions of local water depth. Most of the outflow waters from the
The Northward Intruding Eddy along the East Coast of Korea
457
Tsushima/Korea Strait, where the mean depth is less than 150 m, are occupied by warm waters
more than 10°C throughout the year, e.g. Ogawa (1983) and Isoda and Yamaoka (1991). On the
other hand, the warm waters of the synoptic eddy [Ks], characterized by about 5°C isotherm
contour, were found at the depths deeper than 250–300 m. Then, it is inferred that the water
masses through the shallower strait cannot directly connect to those in the synoptic eddy [Ks]
because of a large difference in the potential vorticity between deep water columns and shallow
ones. The intruding eddy process, in which the potential vorticity can be conserved in a local
water mass, will be most available features for the supply mechanism of warm waters into the
EKWC region.
Acknowledgements
The authors greatly thank Prof. T. Yanagi for many useful discussions and encouragement
during this study. Thanks are also due to the two anonymous reviewers who read the manuscript
carefully and gave thoughtful comments. We are also much indebted to Dr. T. Takeoka for his
valuable discussion and helpful comments. Thanks are also extended to Mr. Isobe for providing
the Korean survey data. The data analysis was carried out on a FACOM M770 of Ehime
University.
References
Fisheries Agency, Japan (1990): The Results of Fisheries Oceanographical Observation in 1987.
Fisheries Research and Development Agency, Korea (1988): Annual report of oceanographic observations in 1987,
36.
Gong, Y., T. Hirano and C. I. Zhang (1985): A study on oceanic environmental conditions for Pacific Saury in
Korean waters. Bull. Jap. Soc. Fish. Oceanogr., 47, 48, 36–58.
Ichiye, T. (1991): Outflows from straits. p. 223–230. In Oceanography of Asian Marginal Seas, Vol. 54, ed. by K.
Takano, Elsevier, Amsterdam.
Isoda, Y. and M. Nishihara (1992): Behavior of warm eddies in the Japan Sea. Umi to Sora, 67, 53–65 (in Japanese).
Isoda, Y. and H. Yamaoka (1991): Flow structure of the Tsushima Warm Current passing through the Tsushima
Straits. Bull. Coastal Oceanogr., 28, 183–194 (in Japanese).
Isoda, Y., S. Saitoh and M. Mihara (1991): SST structure of the polar front in the Japan Sea. p. 103–112. In
Oceanography of Asian Marginal Seas, Vol. 54, ed. by K. Takano, Elsevier, Amsterdam.
Isoda, Y., M. Naganobu, H. Watanabe and K. Nukata (1992): Horizontal and vertical structures of a warm eddy
above the Yamato Rise. Umi no Kenkyu, 1, 141–151 (in Japanese).
Japan Maritime Safety Agency (1992): Monthly mean maps of 100 m isotherms from the climatological mean from
1906 to 1987, in the Quick Bulletin of Oceanic Condition.
Kawabe, M. (1982a): Branching of the Tsushima Current in the Japan Sea, Part I. Data analysis. J. Oceanogr. Soc.
Japan, 38, 95–107.
Kawabe, M. (1982b): Branching of the Tsushima Current in the Japan Sea, Part II. Numerical experiment. J. Oceanogr.
Soc. Japan, 38, 183–192.
Kim, C. H., H. J. Lie and K. S. Chu (1991): On the intermediate water in the southwestern East Sea (Sea of Japan).
p. 129–141. In Oceanography of Asian Marginal Seas, Vol. 54, ed. by K. Takano, Elsevier, Amsterdam.
Kim, K. and R. Legeckis (1986): Branching of the Tsushima Current in 1981–83. Prog. Oceanogr., 17, 265–276.
Kim, K., K. R. Kim, J. Y. Chung and H. S. Yoo (1991): Characteristics of physical properties in the Ulleung Basin.
J. Oceanogr. Soc. Korea, 26, 83–100.
Ogawa, Y. (1983): Seasonal changes in temperature and salinity of water flowing into the Japan Sea through the
Tsushima Straits. Bull. Japan. Soc. Fish. Oceanogr., 43, 1–8 (in Japanese).
Sekine, Y. (1986): Wind-driven circulation in the Japan Sea and its influence on the branching of the Tsushima
Current. Prog. Oceanogr., 17, 297–312.
Suda, K. and K. Hidaka (1932): The results of the oceanographical observations on board R. M. S. in the summer
of 1929, Part 1. J. Oceanogr. Imp. Mar. Observ., 3, 291–375 (in Japanese).
Tameishi, H. (1987): Application of the NOAA images for the fishery (Sea area around the Tsushima islands). Bull.
458
Y. Isoda and S. Saitoh
Jap. Soc. Fish. Oceanogr., 51, 238–244 (in Japanese).
Tanioka, K. (1962): Oceanographical conditions of the Japan Sea (II)—On the cold and the warm region and haline
water. Umi to Sora, 38, 9–22 (in Japanese).
Tanioka, K. (1966): Oceanographical conditions of the Japan Sea (IV)—On the vertical section across Tosen warm
current. Umi to Sora, 41, 50–57 (in Japanese).
Tanioka, K. (1968): On the East Korean Warm Current (Tosen Warm Current). Oceanogr. Mag., 20, 31–38.
Toba, Y., H. Kawamura, F. Yamashita and K. Hanawa (1984): Structure of horizontal turbulence in the Japan Sea.
p. 317–332. In Ocean Hydrodynamics of the Japan and East China Seas, Vol. 39, ed. by T. Ichiye, Elsevier,
Amsterdam.
Uda, M. (1934): The results of simultaneous oceanographical investigations in the Japan Sea and its adjacent waters
in May and June, 1932. J. Imp. Fisher. Exp. St., 5, 57–190 (in Japanese).
Yoon, J. H. (1982a): Numerical experiment on the circulation in the Japan Sea, Part I. Formation of the East Korean
Warm Current. J. Oceanogr. Soc. Japan, 38, 43–51.
Yoon, J. H. (1982b): Numerical experiment on the circulation in the Japan Sea, Part II. Influence of seasonal
variations in atmospheric conditions on the Tsushima Current. J. Oceanogr. Soc. Japan, 38, 81–94.