Generation and decay of Kuroshio warm-core rings

Abstract

Warm-core rings of the Kuroshio were tracked on monthly temperature contour maps from their generation to decay over the period of 1973–1982. Fourteen warm-core rings were found in this period, with 1–2 rings generated each year. A particularly large and warm ring was formed in 1979. According to Kimura's results (1970, 1974), a giant warm-core ring is generated at intervals of 6 years. When a warm-core ring drifts immediately north of the Kuroshio, it often coalesces with and separates again from the Kuroshio. After a warm-core ring passes a winter without coalescing into the Kuroshio, a homogeneous water mass with a temperature of 9–11°C is formed in the interior of the ring. The temperature of this ‘wintered water’ varies little before the following winter. The disappearance of each warm-core ring since 1973 was checked on the monthly temperature maps. Only one warm-core ring was tracked to the east of Hokkaido; two rings entered the Tsugaru Warm Current. Aside from these warm-core rings and those that coalesced with the Kuroshio, it was difficult to trace rings until their disappearance.