A brief history of recognition of the Kuroshio

Abstract

Since ancient times the Japanese and Asians have encountered the Kuroshio. For instance, records of long-distance driftings that must have been greatly influenced by the Kuroshio are found in official chronicles of Japan from before 833 and a biography of Ganjin, the Chinese Buddhist who arrived in Japan on a religious mission in 754 across the Kuroshio. In the seventh and eighth centuries, some of the ships of Japanese envoys to China during the Tang Dynasty crossed the Kuroshio in the East China Sea, despite frequent incidents of ship wrecks. In the Momoyama and early Edo periods (1592–1635) Japanese ships with the shogunate license for foreign trade crossed the Kuroshio east of Taiwan bound for Luzon. During those periods, however, no mention of the Kuroshio has been found, except for that of S. Vizcaı́no, the Spanish navigator who reported a segment of strong current east of the Boso Peninsula in 1614. After the National Isolation Policy was enforced in 1635, the building of large ships and navigation in waters beyond where the coast was visible were prohibited in Japan, and hence it seems unlikely that many early books from this period will mention the Kuroshio. However, by searching and deciphering early books, the author has found many important notes, descriptions and illustrations referring to the Kuroshio in maps and books from the Edo period (1603–1867). Terms “Luo-Ji” and “Wei-Lü”, Chinese equivalents of “Kuroshio”, were searched for in Chinese classics and were examined. The term “Luo-Ji” (Rakusai in Japanese) was cited by some Japanese books written in the Edo period referring to the Kuroshio in the East China Sea. Meanwhile, the term “Wei-Lü” (Biryo in Japanese) was considered to be too mythical to be used in Japan as indicating the Kuroshio, although Needham (1971) inferred that the “Wei-Lü” had been used since ancient times as the Chinese equivalent of “Kuroshio”. To clarify the evolution of types of image of the current recognized as the Kuroshio, early books were sought in which there was recognition by navigators from Western countries of the existence of the Kuroshio, although some of them were unavailable for reading. Examining and comparing synoptically these Japanese, Chinese and Western records, the author reached the following conclusions. The term “Kuroshio” (blackish stream or tide) originated as a local synonym for “Kurose Gawa” (a river over blackish shallows) among inhabitants of the Izu Islands. However, it really indicated only a branch of the actual Kuroshio that flows over shallows along the Izu Ridge. This type of image of the Kuroshio is called the “short concentrated stream”. Towards the end of the 18th century it came to refer to a somewhat longer (about 400 km) path of the Kuroshio, which had become better known among Japanese people, through the publishing of maps, local geographies, accounts of trips and novels. This type of image of the Kuroshio is called the “middle-distance concentrated stream”. However, the “conception of fragmented currents” prevalent at that period probably delayed the recognition that the Kuroshio is a long continuous stream. From the end of the 18th century to the mid-19th century, Westerners collected information about Japan's geography and carried out research and made surveys of the Kuroshio, when they sent naval vessels to Japan in order to establish commercial relations. Before the Meiji Restoration (1868), Westerners viewed the “Kuroshio” as a broadly dispersing stream along the Japanese Islands and Taiwan. This type of image of the Kuroshio is called the “long dispersed stream”, and it was predominant until the modern picture of the “long concentrated stream” was first recognized by the Japanese in about 1930. Ironically, written use of the term “Kuroshio” is found in documents that appeared after the Japanese had ceased oceanic activities under the National Isolation Policy. During these two hundred-plus years, the types of image of the Kuroshio underwent major changes, reflecting the turbulent national and international conditions encountered in Japan.