570 



Basic Principles of the General Oceanic Circulation 



current has been regarded by Hidaka (1927-28) from experimental evidence as due 

 to the change in direction of the north-east coast of Japan, but Wiist believed that 

 topographical factors south of the Boso Peninsula were responsible. The Kuroshio 

 extends out into the open ocean as a relatively strong current along 34-36° N. as far 

 as 175° E. a distance of about 1,600 miles. Only for a short distance along the coast 

 the current keeps the north-east direction. Figure 260 shows a schematic representation 

 of the main current cores of the Kuroshio system during the summer as given by 

 Wiist. Table 148 gives a comparison with the Gulf Stream system. 



Table 148. Comparison between Kuroshio and Gulf Stream 

 (Mean values for summer, according to Wiist) 



* After separation of the Tsusima Current. 



t 400 km east of the Japanese Coast. 



1 After confluence with the Antilles Current. 



The Oyashio flows south-west to south-south-west in the dead angle between the 

 north-west coast of Japan and the north-western branch of the Kuroshio as far as 

 37° N. It is a relatively cold current with a very low salinity (33-5"/oo). It does not reach 

 as far south in summer as in winter. According to Uda the boundary between the 

 Kuroshio and the Oyashio as a convergence region consists of numerous vortices 

 similar as at the boundary between Labrador Current and Gulf Stream. Differences 

 in temperature and salinity across this convergence line in winter will be at least as 

 large as those off the Newfoundland Banks. Driven by the strong northerly and 

 northwesterly winds the Oyashio takes its cold water supply from the Sea of Okhotsk 

 near the Kuriles and in part also from the Bering Sea. 



The water is mostly in slow motion between the cold boundary which runs east- 

 wards a little north of 40° N. and gradually fades away and the subtropical conver- 

 gence which begins in the west at 20° N. and turns northward, at first only slowly, 

 to reach 35° N., remaining in this latitude until about 138° W. This continuation of 

 Kuroshio is termed the North Pacific Current. It main part turns southward between 

 150° and 135° W., part joining the California Current and part mixing with the water 

 from the North Equatorial Current along the subtropical convergence. 



