The Kuroshio

In the 1970s, the Sagami Chemical Research Center in Japan provided nutrient reference material for the Cooperative Study of the Kuroshio Current (the so-called CSK standards). These solutions were not prepared in seawater, which limits their general utility (see below), however they are still distributed and widely used as a common reference. French and British scientists have conducted some studies on nutrient reference material (Aminot and Keroul, 1991, 1996 Zhang et al., 1999) with limited success. 

Ocean. The former is estimated to have a surface area the size of Texas. The focusing effect of the Kuroshio Current on the density of plastics collected in plankton net tows is shown in Figure 28.35. In some locations, particle densities are greater than that of the local zooplankton. High concentrations have also been reported on the seabed near industrialized areas such as the Mediterranean and the North Seas. In 2000, the volume of litter estimated to be residing on the seabed of the North Sea was 600,000 m. ... 

Locations of stations sampied for piastic in 2000-2001. (a) Distribution and abundance (pieces/km ) of totai piastics in the Kuroshio Current area, (b) Sampies were coiiected by a surface tow using a neuston net (mouth opening 50 x 50cm side iength 3m mesh size 330. m). The numericaiiy dominant size class (62%) was 1-3 mm. Broken iine in (b) denotes the Kuroshio flow path during the study period. Source From Yamashita, R., and A. Tanimura (2007). Marine Pollution Bulletin 54, 464-488. 

Hama, T. 1992. Primary productivity and photosynthetic products around the Kuroshio warm-core ring. Deep Sea Research 39 279-293. 

Marumo, R., and Nagasawa, S. (1976). Seasonal variation of the standing crop of the pelagic blue-green alga, Trichodesmium in the Kuroshio water. Bull. Plankton Soc. Jpn. 23, 19—25. 

Gomez et al. (2005) observed the Chaetoceros-Richelia (note these authors use an alternative nomenclature) symbioses was restricted to the transition zones between the slope waters and the Kuroshio Current in the western Pacific Ocean. They proposed that their distribution was related to local mixing of the Kuroshio Current with the coastal waters, where Chaetoceros is a dominant member of the neritic phytoplankton population. 

Okinawa is Japan s southernmost prefecture, and consists of hundreds of islands known as the Ryukyus, in an island chain over 1000 km long, which extends southwest from Kyusyu (the southwestemmost of Japan s main four islands) to Taiwan. The warm waters of the Kuroshio Current have developed and sustained the coral reefs of Okinawa, which are among biologically the most diverse and the richest coral reefs in the world. 

The variable surface currents, which are typical of the Kuroshio area (Hsu et al. 1997, 1998 Mitnik et al. 1996), produced the displacement of a spill of different scales relative to its initial position. The high spatial resolution of SAR data allowed us to detect both the mesoscale and small-scale disturbances of a spill s shape, interpreting them as current-induced. 

Fig. 3. Map of bathymetry of the Kuroshio area east of southern Taiwan. Isobaths are shown for 2000 m, 1000 m and 200 m. Solid and dashed rectangles note the boundaries of the SAR images acquired on May 20, 1994 and December 29, 1997, respectively, and arrow AB shows the location of ship course...

The step-like features in area 15 can also be interpreted as current-induced. The arrows in Figure lb show the directions of surface currents in a small-scale elliptical eddy. These currents were responsible for the westward and eastward displacements of the spill band. This cyclonic eddy has a low radar contrast without distinct boundaries similar to the current shift lines 7 and 8. The different scaled eddy-like structures and also the eddy streets were earlier detected in ERS SAR images of the Kuroshio east of Taiwan (Hsu et al. 1997 1998, Mitnik et al. 1996, Mitnik and Hsu 1998). 

A light (with increased a° values) band 6 crosses the image from north to south. The band divides the warmer surface Kuroshio waters 7 from the colder waters 8 bordering the Taiwan coast. The difference in sea surface temperature between the Kuroshio and coastal waters is indicated by their brightness (the values of the NRCS). The higher NRCS values of the Kuroshio waters can be explained by the joint influence of two factors. The... 

Fig. 4. ERS-2 SAR image of the Kuroshio east of Taiwan acquired on December 29, 1997, at 02 29 UTC (copyright European Space Agency). Dashed square marks the boundaries of fragment shown in Figure 6...

The maximum displacement from line AB was observed in area C, east of Lutao (Figure lb). This displacement was most likely caused by an eastward component of the Kuroshio Current. The shape of the spill in area C is similar to the shape of feature 4. The interaction of the Kuroshio flow with Lutao and underwater rising around it were responsible for the appearance of both feature 4 and the eastward component of the current. The change in velocity of this component with distance manifested itself as the shape of departure y(x). The maximum displacement was found at a dis-... 

The cyclonic eddy-like structures, similar to eddies 10 and 15 (Figure la) and 9-11 (Figure 4), are typical of the Kuroshio Current area east of Taiwan. They have been detected on many ERS-1/2 SAR images however, their position is variable. These eddies were observed due to their radar contrast against the background and/or the presence of definite structures (narrow spiral lines), resulting from the modulation of surface roughness by variable currents. Filamentary slicks were much less common here to favour their detection. Estimates of the current velocity for two eddies obtained by the analysis of the oil spill displacements were found to be 0.07-0.08 ms"1 and 0.3 ms"1. 

Ogura, N., 1972a. Dissolved organic matter in the sea, its production, utilization and decomposition. In K. Sugawara (Editor), The Kuroshio, II. Saigon Publ. Co., Tokyo, pp. 201—205. 

The Yellow Sea is affected by warm and saline oceanic currents and less saline coastal currents in a basin-wide scheme of a cyclonic gyre. In general, the former flow northward whilst the latter flow southward. On the east side of the Yellow Sea, the Kuroshio and Tsushima Warm Currents and the Yellow Sea... 

The East China Sea circulation is dominated by the northward flow of two loops of the Kuroshio Current (KC) the Taiwan Warm Water (TWW) in the west and the Yellow Sea Warm Water (YSWW) in the east. Both water masses are characterized by high salinity and warm water temperatures. In contrast, a southward flow in close to sea bottom water occurs from the flow of the Changjiang (CJCW) and Jiangsu Coastal Waters (JCW) along the Chinese coast, the Korean Coastal Waters (KCW) in the east, and the Yellow Sea Cold Waters (YSCW) in the north (Fig. 1.30, Lee and Chao, 2003). The coastal currents in particular appear as seasonally cold and brackish water masses. 

To the east of ECS, the Kuroshio Current, a strong western boundary current, flowing along the Pacific Margin of northeastern Asia, borders the shelf slope of the East China Sea. When passing through the ECS, it has... 

Fig. 1.37 shows the seasonal variation in the vertical temperature distribution at four different sites shown in Fig. 1.36. The temperature variation in the SCS mainly occurs in the upper eight layers, 0 400 m. The thermal structure to the west of Luzon, station C, and in the southern SCS, station F, shows distinct seasonal variations, cold in winter and warm in summer. The seasonal change in the temperature on the continental slope to the southwest of Taiwan, station D, has quite a different pattern. The Kuroshio intrusion across the Luzon Strait in October increases the upper layer temperature at station D. The water temperature in this slope area shows a major drop only when the cyclonic eddy to the west of Luzon extends into this area after February...

Yuan et al. (2005) pointed out that the Kuroshio intrudes into the SCS to flow northwestward through the Luzon Strait at 200 m and 500 m levels, but the flow direction at the 800 m level differs very much from that at the 200 m and 500 m levels. Model representations show that Luzon Strait Transport (LST) displays a maximum in winter (6.1x10 m /s, westward) and a minimum in summer (0.9x10 m /s, eastward). On the interannual time scale, LST tends to be larger during El Nino years and smaller during La Nina years. The results from many numerical models show that the intruded Kuroshio forms an anticyclonic current loop or a Kuroshio branch. 

Chen CTA, Liu CT, Pal SC (1994) Transport of oxygen, nutrients and carbonates by the Kuroshio current. Chin J Oceanol Linrnol 12(3) 220-227... 

Chen L, Yang X, Tang R, Yu Q (1992) The chemical characteristics of aerosols over the Kuroshio area. Essays Invest Kmoshio 4 295-302 (in Chinese with English abstract)... 

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