The sea surface dynamic topography (SSDT; sea surface height relative to the geoid) is approximately estimated by combining the temporal fluctuation of SSDT determined from altimetry data with the climatological mean SSDT calculated from hydrographic data. This approximated SSDT, or composite SSDT, is obtained in the area southeast of Japan for the first year (1986--1987) of the Geosat Exact Repeat Mission. Variations in the Kuroshio Current System are well described by the composite SSDT. In particular, a complete life history of a cyclonic ring is observed for the first time in this region, namely, westward propagation of a southward meander of the Kuroshio Extension, its pinching-off to form a cyclonic ring, the ring's westward movement, its coalescence with the Kuroshio, and its eastward advection. All available hydrographic data and cloud-free satellite infrared images support the existence of this series of phenomena. ¿ American Geophysical Union 1994